Growth process conditions of vertically aligned carbon nanotubes using PECVD
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2024学年江苏睢宁中学高三4月考-英语试题试卷注意事项:1.答卷前,考生务必将自己的姓名、准考证号填写在答题卡上。
2.回答选择题时,选出每小题答案后,用铅笔把答题卡上对应题目的答案标号涂黑,如需改动,用橡皮擦干净后,再选涂其它答案标号。
回答非选择题时,将答案写在答题卡上,写在本试卷上无效。
3.考试结束后,将本试卷和答题卡一并交回。
第一部分(共20小题,每小题1.5分,满分30分)1.Although values may be ____, it’s helpful to share the m with your partner for additional support.A.terminal B.personalC.crucial D.practical2.It’s impossible for all the people to get jobs because ______of them is not fit for them.A.every one B.allC.not all D.none3.I have no doubt that Anna will ________ it, but I wonder whether she is really ready enough.A.dig B.hit C.make D.lift4.---Can those___________ at the back of the classroom hear me?---No problem.A.seat B.sitC.seated D.sat5.--- How often do you work out?--- _________, but usually once a week.A.Have no idea. B.It depends. C.As usual. D.Generally speaking.6.The girl is sure to become a good actress __________ she gets the right training.A.until B.if C.although D.unless7.—Tony _______ what I did annoying though he didn’t say anything.—So you think you will have to make an apology?A.could find B.should have foundC.might find D.must have found8.Tom looked at Jenny, with tears _______ his eyes, and shouted out the words _______ in his heart for years. A.filling; having been hidden B.filled; hiddenC.filling; hidden D.filled; hiding9.Due to large investment in housing, many cities can ________ the flow of new arrivals, improving the quality of their life.A.give rise to B.make way for C.take part in D.keep pace with10.—I’m tired out. I can’t run any further, Tom.—________! Mike. I’m sure you can do it.A.Come on B.No hurryC.No problem D.Well done11.It is obvious to the students _____________they should get well prepared for their future.A.as B.thatC.which D.whether12.Abraham set himself up in front of his daughter, hands ________ her hair, and was close to tears, reluctant to tear himself from her.A.to toy with B.toyed with C.toying with D.being toyed with13.________ blood if you can and many lives will be saved.A.Giving B.GivenC.To give D.Give14.________ to her own work,she spent little time with her familyA.Devoting B.To be devotedC.Devoted D.Having devoted15.Sometimes smiles around the world ___________ be false, hiding other feelings like anger, fear or worry.A.can B.wouldC.should D.must16.---I saw no more than one motorcar in the shop. Will you go and buy ?---No, I’d rather find in other shops.A.it; oneB.one; itC.it; the oneD.the one; it17.To tell the truth, I didn’t expect that there were so many people ______ the idea.A.supported B.supporting C.to support D.having supported18.The project is far behind schedule. It’s impossible for you to ______ it in a week.A.catch upon B.live up toC.add up to D.hold on to19.What is your main reason for choosing one restaurant another?A.over B.ofC.from D.for20.Andrew lives alone and enjoys the company of a pet cat _______ he’s grown so fond.A.which B.in whichC.of which D.when第二部分阅读理解(满分40分)阅读下列短文,从每题所给的A、B、C、D四个选项中,选出最佳选项。
1 Vertical farming involves growingplants indoors, which is why it s some⁃times also known as indoor farming.Instead of sunlight and rain, vertical farms use LED lighting and controlled growing and nutrition systems. Plants are stacked (放成整齐的一堆) vertically in layers, somany of the farms look like warehouses filled with large shelving units.2 Vertical farming is considered a highly efficient and sustainable way of producing food. For instance, it uses 250 times less water than a traditional farm would need. Automa⁃tion is the key to this efficiency. Software, robotics and data science are some of the tech⁃nologies used in vertical farms to monitor crops and create best growing conditions.3 Controlled environment agriculture like this helps to reduce the vertical farms envi⁃ronmental impact, getting rid of the need for pesticides for example. Vertical farms also don t rely on the weather, so fresh produce can be grown all year round.4Instead of growing fruit and vegetables on big farms and then transporting them overlong distances in trucks and planes, vertical farming can supply local produce from neigh⁃bourhood buildings. This means less fuel is used and the food is fresher.5 Vertical farms also tend to produce more than traditional farms. Experts say plants can be harvested 15 times a year. In a traditional field, harvesting is twice a year.6 By precisely controlling the growing environment, products can last for 13 to14Vertical farming垂 直 农 业山东 孙启禄主题语境:农业 篇幅:350词 关键词:vertical farmingdays, against three to four days for the equivalent products from traditional agriculture.7 However, cost is a big hurdle for vertical farming. Sunlight and rain are free. Powering LED lights, software and complex growing systems aren t.8While some facilities run on electricity from wind turbines, vertical farms running on fossil fuels may be adding to the problem of climate change rather than making it better. Buying urban real estate to build vertical farms can also be expensive. 9“It s our mission to cultivate a sustainable future to meet global demands for fresh and local food, and this new farm is the manifestation (表明) of that commitment. This new facility serves as a model for what s possible around the globe,” says an expert.ReadingCheck1. What does paragraph 1 mainly tell us?A. What vertical farming is.B. How vertical farming originated.C. What the benefits of vertical farming are.D. How vertical farming will change agriculture.2. What can we infer from paragraphs 2 and 3?A. Vertical farming does harm to climate.B. It needs high technology to open a vertical farm.C. Vertical farming is very popular around the world.D. It costs more to open a traditional farm than a vertical farm.3. What does the underlined word “hurdle” in paragraph 7 most probably mean?A. Puzzle.B. Problem.C. Advantage.D. Convenience.4. What is the expert s attitude towards the future of vertical farming?A. Positive.B. Negative.C. Uncertain.D. Suspicious.Ø语篇解码本文是一篇说明文,主要介绍了垂直农业的定义、好处及影响,并说明了垂直农业不是一个全球性的种植方案的原因。
2020-2021学年山东省聊城市高二(下)期末英语试卷一、阅读理解(本大题共11小题,共27.5分)AIf you are tired of staying at home,now make the most out of the weekend by getting stuck into the best things going on this Friday,Saturday and Sunday.Kew GardensIf you are ready to fully put yourself into nature,get yourself down to Kew Gardens.The Royal Botanic Gardens is famous for its plant collections from around the world.Recently,everyone visiting the garden,including members,has to book tickets online for the time range before they set foot in the garden.This is the first time that Kew has adopted this policy in its history. Lambeth Country ShowThis year the countryside festival won't be going ahead in its usual home of Brockwell Park.But all your favourite aspects of the fair will be part of the virtual (虚拟的)edition,including the highly expected Vegetable Sculpture Competition,the usual flower show competitions,and local-themed talks.Walthamstow Garden Party in the AirThe free two-day festival in E17 will be held this weekend.You can enjoy online music and dance performances.Don't miss the most wonderful part of the weekend:East London Radio's first-ever online show taking place across the weekend with behind-the scenes chats with local musicians.Columbia Road Flower MarketAs the largest flower market in East London,this market is located in Bethnal Green.It opens on Sundays.Every Sunday morning the quiet street of Columbia Road fills up with stalls (摊位)selling fresh flowers and plants.Personally,it is wise to go there between 8:00 am and 10:00 am so that you can walk at your own pace and won't be pushed by the crowds.1.What is the recent change in Kew Gardens?______A. The government opens it to the public for a shorter time.B. People are encouraged to appreciate the views online.C. Tickets are booked online for certain visiting hours.2.If you are interested in music,which of the following appeals to you?______A. Kew Gardens.B. Lambeth Country Show.C. Columbia Road Flower Market.D. Walthamstow Garden Party in the Air.3.Why does the author advise people to visit the flower market in the early morning?______A. To get a good deal.B. To get fresh flowers.C. To avoid the traffic jam there.D. To have a peaceful experience of buying flowers.BMore and more people around the world are living in city areas and the need for high-quality fresh food is rising.At the same time,new homes,apartment buildings,shopping centers and roads are taking the place of rich land near cities.That makes growing crops in tall buildings an interesting solution.In Dallas,Texas,a company called Green Habitat Hydroponics (GHH)sells vertical farming (垂直农业)supplies. "You can control anything and everything you want to with hydroponics—the process of growing plants in sand,small stones or water with added nutrients (营养物)but not soil," Kris Maxwell,a sales employee at GHH said. "For example,certain plants need certain nutrients and PH levels.But don't worry.You can change the hydroponics solutions (溶液)by adding or taking away nutrients,or by changing the PH level,or even by controlling the amount of water in a solution,so that plants get all the nutrients and water requirements they need.There are even different solutions for certain stages in the plants' growth."In this indoor environment,LED lights,which are environmentally friendly,replace thesun.Heaters,coolers,and special machines control the temperature and humidity.Up to 300 plants can grow in one container unit.GHH also sells aeroponics (气雾栽培)systems.With this system,plants are placed in huge containers where only the roots are put in a solution.Nutrient rich wastes from fish,for example,are filtered and sent through the system.all of the necessary nutrients.Another advantage of vertical farming is that no pests will damage your crops.What do you think?Does vertical farming have a bright future?4.Which of the following may not be the reason for vertical farming?______A. Many people nowadays are flowing into cities.B. The earth has to support more and more people.C. People show greater interest in eating fresh food.D. The fields for growing crops near cities are reducing day by day.5.As for vertical farming,what can be used to take the place of the sunshine?______A. Heaters.B. Coolers.C. Light from a kind of bulb.D. Air conditioning machines.6.The underlined word "filtered" in the fourth paragraph can be replaced by " ______ ".A. balancedB. removedC. destroyedD. created7.What is an advantage of aeroponics system used in vertical farming?______A. It can be easily operated.B. People can get delicious food.C. There is no need for chemical nutrients.D. It may bring about a good harvest.CMany rich parents drive their kids to special activities after school.Besides the trips to soccer practices and games or piano lessons,they increasingly make one more stop—a trip to their local after-school tutoring (辅导)center.It's becoming a more common activity within and outside of American schools.Parents pay tutoring around﹩200 per month for each child to get math,reading and other kinds of lessons once or twice a week with their own lessons and homework intended to be more challenging than what is offered by the schools.They aim at students not only struggling in school work but also those who are already ahead in courses.It seems that there no child is too young to start.They teach these little kids how to recognize letters,numbers,patterns and shapes. Children in after -school centers can get confused about which kind of learning matters more,but parents keep their kids in tutoring for years if they think it's getting results. "We justfourth-grade student mentioned that her regular teacher counted her private math center tasks as satisfying her school homework.Troublingly,educators believe that the growth of private tutoring in the U.S.is leading to a sense of pressure that can result in emotional problems. "The students who take classes outside of school make other kids feel bad,because they're brighter and they do more,and they can do it faster," a Boston- area elementary school headmaster told me.What's more frightening is happening.A growing education arms race is going among families.They feel pressured to make sure their kids learn enough to be above their grade level and ranked at or near the top of their classes.Many parents told me they keep their children in after-school education simply to keep up with those who do.Tutoring education is seriously changing what it means to go to school.8.What can we learn about tutoring centers from paragraph 2?______A. They serve children of different levels and ages.B. Their charges are relatively cheap.C. They mainly provide courses related with exams.D. Their teaching content keeps pace with that of schools.9.What does the author intend to tell us in paragraph 3?______A. Students benefit a lot from private tutoring.B. Tutoring is recognized by some parents and school teachers.C. Parents try to raise kids' interest in private tutoring.D. Tutoring takes up a lot of students' spare time.10.What is a problem caused by the growth of private tutoring?______A. Students are tired of schooling under great pressure.B. Parents pay little attention to their children's mental health.C. Parents are under the pressure of education arms race.D. The public become less satisfied with the school education system.11.Which of the following is a suitable tile for the text?______A. The Advantages of Private TutoringB. The Disadvantages of Private TutoringC. The Popularity of Private TutoringD. The Concerns about Private TutoringNo act of kindness,no matter how small,is ever wasted.Yesterday a salesman,working for a telecom company,(12)me to sell his phone plans.I was at work and unwilling to spend time on those conversations,so I made a(n)(13) that I couldn't talk yet and I(14) him to call back one hour later.However,he continued to explain his phone plans,which he said were better thanmy(15)one.While listening to him,sometimes I was lost in thought,giving "hmm" as a signof(16)or showing him that I was still there.Sometimes I felt a bit impatient.But I tried to be(17) during the conversation.At the end of the conversation,he said:"Thank you for listening to me.(18),people treat us as thieves or(19) at us.Today,I haven't had a conversation without offense (侮辱).I know you could have been(20) after work or done something else had I not(21) your time.So I am really touched."I thanked him for this statement.I(22)how much he could have been the subject of verbal (言语的)(23)all through his working days.I also admitted that those people showing bad(24)to him might have been me.But now I am delighted to allow him to feel treated(25) .In fact everyone should be(26) as a human being.12. A. forced B. invited C. called D. allowed13. A. choice B. promise C. decision D. excuse14. A. begged B. advised C. warned D. encouraged15. A. present B. common C. former D. extra16. A. impatience B. confusion C. agreement D. confidence17. A. polite B. proud C. excited D. annoyed18. A. Rarely B. Personally C. Recently D. Usually19. A. shout B. wave C. stare D. smile20. A. bored B. relaxed C. stressed D. amazed21. A. dealt with B. got through C. given back D. taken up22. A. argued B. appreciated C. realized D. accepted23. A. communication B. challenge C. attack D. ability24. A. impression B. character C. demand D. attitude25. A. seriously B. differently C. unfairly D. badly26. A. respected B. regarded C. explored D. trusted27.假定你是李华,你校网站准备开设"英语角"专栏,以便学生发表文章。
小学上册英语第二单元测验卷(有答案)英语试题一、综合题(本题有100小题,每小题1分,共100分.每小题不选、错误,均不给分)1.I want to ________ (make) a difference.2.What do you call a person who collects stamps?A. PhilatelistB. NumismatistC. CollectorD. Archivist答案: A3.What is the value of 6 ÷ 2 + 3?A. 5B. 6C. 8D. 9答案:A4.The chemical symbol for mercury is _______.5.An __________ is a substance that donates protons in a reaction.6.The flowers are _____ and purple. (pink)7.The _____ (parrot) can talk.8.The ______ repairs cars for a living.9.I want to _______ (参加) a cooking class.10.The _______ (猪) will oink when happy.11.I think nature is beautiful. My favorite natural scenery is __________.12. (Civil) Rights Act was passed in 1964. The ____13.The ice cream is ______ (cold) and tasty.14.My favorite animal is a ______ (猫) because they are gentle.15.My dad inspires me to be a better __________ (人).16.I like to ______ (参与) in cooking competitions.17.The mountains are ________ (高).18.I think it’s essential to have goals in life. They give us direction and purpose. I set goals for myself by __________ and tracking my progress.19. A ____(green roof) supports biodiversity in urban areas.20.He is very ___. (happy)21.In which country is the Eiffel Tower located? __________. (法国)22.How many letters are in the English alphabet?A. 24B. 25C. 26D. 27答案:C.2623.The pelican dives into the _______ (水).24.I love going to the park with my __________. (家人)25._____ (宝贵的资源) like trees are crucial for our planet.26.I enjoy _____ (拍摄) videos.27.I can ________ (strategize) effectively.28.The _____ (果实) of the orange tree is juicy.29.The frog croaks at night in the ______.30. A solar eclipse happens when the moon blocks the ______ (sun).31.What is the capital of Malta?A. VallettaB. MdinaC. RabatD. Sliema答案:A.Valletta32.The ____ is small and collects nuts for the winter.33.What is the name of the famous clock tower in London?A. Big BenB. Eiffel TowerC. Leaning Tower of PisaD. Statue of Liberty答案: A34.We have a _____ (旅行) planned for the summer.35.Water freezes at ______ degrees Celsius.36.My mom is known for her __________ (耐心).37.My _____ (阳台) has colorful flowers.38.The smell of vinegar is due to acetic ______.39. A shark is a powerful ________________ (捕食者).40.I love to watch the ______ (星空) at night.41.The formula for water is ______.42. A cactus can survive in very _______ places.43.What is the main language spoken in Brazil?A. SpanishB. PortugueseC. EnglishD. French答案:B44.Which of these is a type of tree?A. RoseB. OakC. DaisyD. Tulip答案:B45.The candy is very ___. (colorful)46.What do we call a young dolphin?A. CalfB. KitC. PupD. Chick答案:A.Calf47.The _____ (泳池) is cool.48. A kitten loves to explore new ______ (地方).49.The __________ (奥林匹克运动会) originated in ancient Greece.50.The chemical formula for selenium dioxide is _____.51. A planet's orbit around a star is influenced by the star's ______.52.In winter, I wear ______ (靴子) to keep my feet warm.53. (Titanic) sank in 1912 after hitting an iceberg. The ____54.I ride my bike to _____ (学校).55.The __________ (气候) affects plant growth.56.In the summer, I go to the ________.57. A leopard can climb trees very ______ (轻松).58.The ________ (market) sells fresh fruit.59.Turtles can live for a ______ (很长的时间).60.My favorite hobby is ______ (读书).61. A ____ can fly high in the sky and has a sharp beak.62.The antelope hops quickly to escape _______.63.My family enjoys __________ together. (旅行)64.My sister enjoys __________ (艺术) and creating new pieces.65.I saw a _____ (小羊) in the grassy meadow.66.The garden is ________ (生机勃勃).67.The ________ loves to explore.68.The train goes _____ (fast/slow) on the tracks.69. A bison can weigh up to ______ (一吨) or more.70.What is 50 20?A. 30B. 25C. 20D. 15答案:a71.She has long _______ (hair).72.The process of ______ can reveal hidden geological structures.73.Frogs come in many different ________________ (颜色).74. A __________ (自然保护区) helps protect wildlife and plants.75.When I see a rainbow, it makes me feel _______ (情感). It is a sign of _______ (名词).76.__________ are used in the food industry for flavor enhancement.77.The frog's skin can absorb ______ (水).78.根据图片提示,选出正确的答案。
2.菜籽油精炼技术介绍(总3页) --本页仅作预览文档封面,使用时请删除本页--菜籽油精炼技术介绍菜籽油就是我们俗称的菜油,又叫香菜油,是以十字花科植物芸苔(即油菜)的种子榨制所得的透明或半透明状的液体。
菜籽油色泽金黄或棕黄,有一定的刺激气味,民间叫作“青气味”。
这种气体是其中含有一定量的芥子甙所致,但特优品种的油菜子则不含这种物质。
是中国主要食用油之一,主产于长江流域及西南、西北等地,产量居世界首位。
菜籽油营养分析:1. 人体对菜籽油的吸收率很高,可达99%。
因此它所含的亚油酸等不饱和脂肪酸和维生素E等营养成分能很好地被机体吸收,具有一定的软化血管、延缓衰老的功效;2. 由于榨油的原料是植物的种实,一般会含有一定的种子磷脂,对血管、神经、大脑的发育十分重要;3. 菜籽油的胆固醇很少或几乎不含,所以控制胆固醇摄入量的人可以放心食用;从营养价值方面看,人体对菜籽油消化吸收率可高达99%,并且有利胆功能。
在肝脏处于病理状态下,菜籽油也能被人体正常代谢。
菜籽油精炼经过半连续脱胶工艺,连续脱色工艺,连续脱色工艺三步完成。
首先说的是半连续脱胶工艺,2、精制菜籽色拉油精炼工艺流程(间歇)碱液富油皂脚—→盐析—→贫油皂脚↓↑过滤毛菜油—→预热—→中和—→静置沉降—→分离—→水洗←—软水↓过滤←—蒸馏脱臭←—过滤←—吸附脱色←—脱水↓↓↓↑↓精制菜油水蒸气废白土吸附剂废水操作条件:碱炼操作温度初温30~35℃,终温60~65℃,碱液浓度16°Bé,超量碱添加量为油量的%~%,另加占油量%的泡花碱(浓度为40°Bé),中和时间lh左右,沉降分离时间不小于6h。
碱炼油洗涤温度85~90℃,第一遍洗涤水为稀盐碱水(碱液浓度%,添加油量%的食盐),添加量为油量的15%。
以后再以热水洗涤数遍,洗涤至碱炼油含皂量不大于50 ppm。
脱色时先真空脱水30min,温度90℃,操作绝对压力,然后添加活性白土脱色,白土添加量为油量的%~3%,脱色温度90~95℃,脱色时间20min,然后冷却至70℃以下过滤。
Unit 1~2 Mercantilism重商主义Trade surplus 贸易顺差Quota and tariff配额和关税Zero-sum game零和博弈Positive-sum game常和博弈The theory of absolute advantage绝对优势理论The theory of comparative advantage 比较优势理论Factor endowments要素禀赋理论Product life cycle 产品生命周期Economies of scale 规模经济First mover advantage先占优势Barrier to entry进入(市场)壁垒Porter’s diamond theory波特的钻石理论National competitive advantage国家竞争优势The department of commerce 商务部Letter of credit信用证Draft /bill of exchange 汇票bill of lading B/L 提单Sight draft即期汇票Time draft 远期汇票Banker ‘s acceptance 银行承兑Trade acceptance商业承兑汇票Countertrade 对等贸易Barter 易货贸易Switch trading 转手贸易Offset 抵消Counter purchase 互购贸易Compensation trade 补偿贸易1.波特钻石理论的主要内容①Factor endowments ②Firm strategy, structure, and rivalry③ Demand conditions ④Relating and supporting industries2.对等贸易的主要类型和优缺点①Types of countertradeCountertrade has evolved into a diverse set of activities that can be categorized as five distinct types of trading arrangements: barter, counter purchase, offset, switch trading, and compensation or buyback②The pros and cons of countertrade优:① The main attraction of countertrade is that it can give a firm a way to finance an export deal when other means are not available.② Thus if a firm is unwilling to enter into a countertrade agreement, it may lose an export opportunity to a competitor that is willing to make a countertrade agreement.缺:① Countertrade contracts may involve the exchange of unusable or poor-quality goods that the firm cannot dispose of profitably② In addition, even if the goods it receives are of high quality, the firm still needs to dispose of them profitably.Unit 3Strategic alliance 战略联盟Licensing 许可证Joint venture 合资经营Contracting 承包经营Partnership 合资人Return on investment 投资回报率Franchising 特许经营Contract manufacturing 生产承包Management contracting 管理承包1.许可贸易的优缺点优:①The basic advantage in licensing as contrasted to other approaches is theease and low cost of entering a foreign market.②Licensing is also advantageous in that it can be used to test a foreignmarket without the risk of capital loss should the market not be receptive to the manufacturer’s product.缺:①The greatest disadvantages to the licensor are that a potential competitoris set up.②There is a lack of control over production and marketing.③There may be incomplete market exploration.Unit 4Foreign direct investment 外国直接投资Small and medium-sized firms 中小企业Horizontal FDI 横向外国直接投资Vertical FDI 纵向外国直接投资Product life cycle 产品生命周期Backward vertical FDI 后移纵向外国直接投资Forward vertical FDI 前移纵向外国直接投资Transportation costs 运输成本Market impediments 市场阻碍Market power 市场力量Oligopoly 寡头垄断Specialized assets 特殊资产1.影响横向对外投资的因素①Transportation costs ②Market imperfections④Following competitors ④The product life cycle2.What are the impediments to the sale of know-how?①Licensing may result in a firm’s giving away its technological know-how to a potential foreign competitor.②Licensing does not give a firm the tight control over manufacturing, marketing, and strategy in a foreign country that may be required to profitably exploit tis advantage in know-how.③A firm’s know-how may not be amenable to licensing.Unit 5Bretton Woods System 布雷顿森林体系Fixed exchange rate 固定汇率制OPEC 石油输出国组织Organization of the Petroleum Exporting Countries Floating exchange rate regime 浮动汇率制Plaza Accord 和平广场协议Louvre Accord 卢浮宫协议Foreign exchange market 外汇市场European Monetary System 欧洲货币体系EMSExchange Rate Mechanism 汇率机制ERMEuropean Currency Unit欧元 ECUTrade deficit贸易赤字Real interest 实际利息Balance of payment 收支平衡表Forward market 期货市场Swaps 掉期交易1. 布雷顿森林体系/固定汇率制瓦解的主要原因As the only currency that could be converted into gold, and as the currency that served as the reference point for all others①It was financed by an increase in the money supply, which, in turn, led to a rise in price inflation from less than 4percent in 1966 to dose to 9 percent by 1968②The rise in government spending had stimulated the economy③Gave rise to speculation in the foreign exchange market that the dollar would be devalued④Weakening dollars lose its credibility.2. What are the reasons for the unexpected rise in the dollar between 1980 and 1985, and what are the reasons for the rapid fall of the US dollar between 1985 and 1987?The reasons for the unexpected rise in the value of the dollar between 1980 and 1985:①Strong economic growth in the US attracted heavy inflows of capital from foreign investors seeking high returns on capital assets.②High real interest rate attracted foreign investors seeking high vellums on financial assets③Political turmoil in other parts of the world.The reasons for 1985 and 1987:The fall in the value of the dollar between 1985 and 198 was caused by a combination of government intervention and market forces.Unit 6Common law 普通法Code civil law 成文法Roman law 罗马法Industrial property right 工业产权Act of god 不可抗力Element forces of nature 天灾自然因素Arbitration 仲裁Conciliation 调节Litigation 诉讼World court at the Hague 海牙国际法庭Tribunals for arbitration 仲裁庭U.N. convention on the Recognition and Enforcement of ForeignArbitral/Awards 联合国承认和执行外国仲裁裁决公约International Chamber of commerce 国际商会1. What are the differences between two legal systems in solving commercial disputes?①Under common law, commercial disputes are subject to laws which may be applied to either civil or commercial disputes since there is no specific recognition of commercial problems as such.②Code law differs in that there is a separate code specifically designed for business2. What are the procedures used by formal arbitration organizations? The usual arbitration procedure is for the parties involved to select a disinterested and informed party or parties as referee to determine the merits of the case and make a judgment that both parties agree to honor.Unit 7Intellectual property rights 知识产权Trade mark copyright, patents, trade secrets 商标权,版权,专利权,商业秘密Intangible assets, tangible assets 无形资产,有形资产Trademark registration 商标注册Generic terms 通称Infringement 侵权GATT 关贸总协定General Agreement on Tariffs and Trade1. What does intellectual property right consist of?①It consists of the products of individual’s minds—products that result from intellectual, creative processes.②Trademarks, copyrights and patents are all forms of intellectual propertyUnit 8The TRIPS agreement 与贸易有关的知识产权协议Need Hierarchy 需求层次理论Self-reference criterion 自我参考标准The adoption process 接纳过程理论High-context cultures 高背景文化Low-context cultures 低背景文化Poly-chromic time 多元化时间观Mono-chromic time 单一性时间观Perception 观念1. What are the characteristics of culture?①It is not innate, but learned②The various facts of culture are interrelated-touch a culture in one place andeverything else is affected.③It is shared by the members of a group and defines the boundaries betweendifferent groups.2. What are the main contents of Need Hierarchy theory?①Self-actualization ②Esteem ③Social ④Safety ⑤Physiological3. What is the concept of adoption process? How many stages will a person undergo before he can finally purchase a new product?Adoption process─through which an individual passes from the time of his or her first knowledge of an innovation to the time of adopting or purchase of the innovation.These stages are as follows: ①awareness ②interest ③evaluation④trial ⑤adoption4. What are the adopter categories? What is the feature for early adopter?Adopter categories are classifications of individuals within a market on the basis of their innovativeness. They include innovators、early adopters, the early majority, the late majority and laggards.The future for early adopter: They tend to be younger, have higher social status and in a more favorable financial position than later adopter. They must be responsive to mass-media information sources and must learn about innovation form these sourcesbecause they cannot simply copy the behavior of earlier adopters.Unit 9Organizational behavior组织行为学Multinational Corporation 跨国公司Maquiladoras 马基拉朵拉工厂Parochialism 地方主义NAFTA 北美自由贸易协定North American Free Trade AgreementKluckhohn-Strudtbeck framework 克拉克洪─斯托特柏克构架Hofstede framework 霍夫斯诺德构架BRICS 金砖五国巴西俄罗斯印度中国南非APEC 亚太经合组织Asia-Pacific Economic Cooperation1. Identify the sic cultural dimensions in the Kluckhohn-strodtbeck framework.①Relationship to the environment ②time orientation③nature of people ④Activity orientation⑤focus of responsibility ⑥conception of space2. Explain the dimensions of national culture in Hofstede framework.①Individualism versus collectivism②power distance③uncertainty avoidance④masculinity versus femininity。
(京津鲁琼专用)2020版高考英语二轮复习40分钟阅读提速练1 阅读提速练(一)(含解析)编辑整理:尊敬的读者朋友们:这里是精品文档编辑中心,本文档内容是由我和我的同事精心编辑整理后发布的,发布之前我们对文中内容进行仔细校对,但是难免会有疏漏的地方,但是任然希望((京津鲁琼专用)2020版高考英语二轮复习40分钟阅读提速练1 阅读提速练(一)(含解析))的内容能够给您的工作和学习带来便利。
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阅读提速练(一)(建议用时:40分钟)阅读理解(共两节,满分40分)第一节(共15小题;每小题2分,满分30分)阅读下列短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。
A(2019·山西五地高三联考)Kirby Wildlife Park—Keeper ExperienceDue to the large number of inquiries from people interested in working with animals, Kirby Wildlife Park has set up the unique “Keeper Experience”package。
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山东省聊城市2020-2021学年高二英语下学期期末考试试题本试卷分四部分,共12页。
满分150分。
考试用时120分钟。
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第一节(共5小题;每小题1.5分,满分7.5分)听下面5段对话。
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1. What will the woman probably do after class?A. Go to dinner.B. Talk with a professor.C. Go to the theatre.2. What is the relationship between Jim and Bob?A. Classmates.B. Close friends.C. Twins.3. What does the woman mean?A. She will finish the photocopies in no time.B. She can’t make the photocopies now.C. She is too busy to make the photocopies.4. What does the woman suggest the man do?A. Give his ankle a good rest.B. Treat his injuries immediately.C. Continue his regular activities.5. What can we know about the woman’s roommate?A. She is always late.B. She is forgetful.C. She is bad-tempered.第二节(共15小题;每小题1.5分,满分22.5分)听下面5段对话或独白。
口腔正畸学单词Orthodontics 口腔正畸学American Board Orthodontists 美国正畸学会Differentiation 分化Translocation 改位、易位Orthopedic devices 矫形治疗措施Functional jaw orthopedic 功能颌骨矫形Cephalocaudal gradient of growth生长的头尾增减率Pattern of growth 生长型Pattern of facial growth 面部生长型Average growth pattern 平均生长型Horizontal growth pattern 水平生长型Vertical growth pattern 垂直生长型Balanced growth 平衡生长Growth variability 生长变异Chronometry 颅测量术Cephalometic radiography 线头影测量术Displacement 骨移位Primary displacement 原发性骨移位Secondary displacement 继发性骨移位Premature hypostasis 骨缝早融Skeletal craniofacial developmentsyndrones颅面发育综合征Oxycephaly 尖头畸形Brachycephaly 短头畸形Scaphocephaly 舟状头畸形Chondrocranium 软骨性颅Desmocranium 头颅Cranial base 颅底Spheno-occipital synchondrosis 蝶枕软骨联合Inter-sphenoid synchondrosis蝶骨间软骨联合Spheno-ethmoid synchondrosis蝶筛软骨联合Growth of masomaxillary complex鼻上颌复合体的生长Masomaxillary complex 鼻上颌复合体Nasal septum 鼻中隔Frontal-maxillarysuture 额颌缝Eygomatic-maxillarysurure 颧颌缝Eygomatic-temporal suture 颧颞缝Pterygo-palatin suture 翼颌缝Mandible下颌骨Genial angle 下颌角External rotation 外旋转Internal rotation 内旋转T otal rotation 总旋转Intramatrix rotation 基质内旋转Hypertrophy 肥大Hyperplasia 增生Acceptable compromises 可接受的折中值T reatment goal individualized个体化治疗目标T otal discrepancy 上下牙弓总不调量Discrepancy 牙弓不调量Available space 可用间隙Requried space 必需间隙Relocation 复位Expansion 扩大牙弓Intermaxillary 颌间Extraction 拔牙supra- 表示[在上; 在远方]之义Visual treatment objective 治疗目标预测法Mesiofacial type 中间型Brachyfacial type 短面型Dalichofacial type 长面型Guadrilateral analysis 四边形分析法Sassauni analysis 正位片(后前位)的分析法Ritucci-Burston 颏顶位分析法Soft tissue facial angle 软组织面角Nose prominence 鼻突度Superior sulcus depth 上唇沟深H-line to subnasale 鼻下点至H线距Skeletal profile convexity 骨侧面突度Upper lip strain measurement 上唇紧张度Lower lip to H-line 下唇H线距Inferior sulcus to H-line 颏唇沟深度Soft tissue chin thickness 颏部软组织厚度Esthetic plane、E-Plane 审美平面Mesioversion 近中错位Distoversion 远中错位Linguoversion 舌向错位Labioversion 唇向错位Infraversion 低位(牙合下错位)Supraversion 高位(牙合上错位)T orsiversion 旋转Axisversion 斜轴Transversion 易位Ba-N 全颅底平面N-Pog 面平面Nba-PtGn 面轴角Pt-Gn 面轴FH-Npog 面角FH-MP 下颌平面角MP-NPg 颏角ANS-Xi-Pm 下面高角Dc-Xi-Pm 下颌弓角A-Npog A点突度L1-Apog 下中切牙突距,下中切牙倾斜度PTV-U1 上颌第一磨牙位置L1-EP 下唇位置N 鼻根点S 蝶鞍点Ba 颅底点Bo Bolton点Po 耳点Or 眶点ANS 前鼻棘点PNS 后鼻棘点Ptm 翼上颌裂点Pt 翼点B 下牙槽座点Pm Pm点,下颌前缘部B点到颏前点间,由凹至凸的移行交界点。
材料科学基础复习题第三章:晶体的范性形变(crystal plastic deformation)单晶体范性形变的两种基本⽅式:滑移(slip)和孪⽣(twinning)两者都为剪应变。
FCC的滑移⾯都是{111},滑移⽅向都是<110>,BCC的滑移⾯都有{110},滑移⽅向都是<111> 滑移⽅向都是最密排的⽅向,⽽滑移⾯则往往是密排⾯Schmid定律:当作⽤在滑移⾯上沿着滑移⽅向的分切应⼒达到某⼀临界值τc时,晶体便开始滑移。
P144.我们把只有⼀个滑移系统的滑移称为单滑移,具有两个或以上的滑移叫做双滑移或者多滑移。
晶粒和晶粒之间的过渡区域就称晶粒边界或称晶界。
晶粒越细,阻碍滑移的晶界便越多,屈服极限也就越⾼。
(细化晶粒不仅可以提⾼⾦属的强度,同时还可以提⾼其韧性)Hall 公式:拉伸应⼒变形(tensile stress deformation)晶体在外⼒作⽤下会发⽣形变,当外⼒较⼩时变形是弹性的,即卸载后变形也随之消失,这种可恢复的变形就称为,弹性变形(elastic deformation)当外⼒超过⼀定值后,应⼒和应变就不在成线性关系,卸载后变形也不能完全消失,⽽会留下⼀定的残余变形或者永久变形,这种不可恢复的变形就称为,塑性变形(plastic deformation)低碳钢的拉伸应⼒——应变曲线(图解计算题)延伸率(elongation):断裂前的最⼤相对伸长。
断⾯收缩率(reduction in cross-section):断裂前最⼤的相对⾯积缩减。
晶体的断裂(Crystal fracture)滑移系统(slip system):⼀个滑移⾯和位于该⾯上的⼀个滑移⽅向便组成了⼀个滑移系统。
孪⽣系统(twinning system):⼀个孪⽣⾯和该⾯上的⼀个孪⽣⽅向组成⼀个孪⽣系统。
加⼯硬化(work hardening):⾦属在冷加⼯过程中,要想不断地塑性变形,就需要不断增加外应⼒。
Growth process conditions of vertically aligned carbon nanotubes using plasma enhanced chemical vapor depositionM.Chhowalla,a)K.B.K.Teo,C.Ducati,N.L.Rupesinghe,G.A.J.Amaratunga,A.C.Ferrari,D.Roy,J.Robertson,and neEngineering Department,University of Cambridge,Cambridge CB21PZ,United Kingdom͑Received5March2001;accepted for publication13August2001͒The growth of vertically aligned carbon nanotubes using a direct current plasma enhanced chemicalvapor deposition system is reported.The growth properties are studied as a function of the Nicatalyst layer thickness,bias voltage,deposition temperature,C2H2:NH3ratio,and pressure.It wasfound that the diameter,growth rate,and areal density of the nanotubes are controlled by the initialthickness of the catalyst layer.The alignment of the nanotubes depends on the electricfield.Ourresults indicate that the growth occurs by diffusion of carbon through the Ni catalyst particle,whichrides on the top of the growing tube.©2001American Institute of Physics.͓DOI:10.1063/1.1410322͔I.INTRODUCTIONCarbon nanotubes are attracting great interest for their remarkable properties such as ballistic electron transport and large elastic moduli.The high surface area and chemical in-ertness of nanotubes grown directly onto desired substrates makes them attractive for demanding applications such as electrochemistry,electrodes for fuel cells and supercapaci-tors.1–6High quality single walled carbon nanotubes͑SWNTs͒and multiwalled carbon nanotubes͑MWNTs͒can be ob-tained using high pressure arcs,laser ablation,and high pres-sure chemical vapor deposition͑CVD͒.7–12Many applica-tions desire nanotubes with well defined diameters and lengths.MWNTs can be deposited using plasma enhanced chemical vapor deposition͑PECVD͒methods onto sub-strates coated with a suitable transition metal catalyst.13–19 The essential parameters involved in the growth of vertically aligned carbon nanotubes͑V ACNTs͒are the feed gas,the nature of the catalyst,and the substrate temperature.Free standing aligned nanotubes werefirst grown using a hotfila-ment plasma enhanced chemical vapor deposition method.14 Subsequently,various plasma methods have been used.16–20 There is presently great interest in V ACNTs forfield emission and vacuum microelectronic devices because car-bon nanotubes are among the bestfield emitters presently available.21–25Their excellentfield emission characteristics are attributed to the high aspect ratios,resulting in a large field enhancement factor.Carbon nanotubes are also me-chanically and chemically robust and can emit large current densities at low electricfields.24The ability to grow carbon nanotubes on conducting substrates over a large area is es-sential for uniform emission required for vacuum microelec-tronic devices.In this article,we report on the growth of vertically aligned nanotubes using a direct current͑dc͒glow discharge CVD system and a Ni or Co catalyst.We have performed a detailed parametric study of the various factors influencing the growth of aligned carbon nanotubes.Specifically,we in-vestigated the effects of catalyst layer thickness,the applied bias voltage,the deposition temperature,and the C2H2:NH3 gasflow ratio on the nanotube growth rate,diameter,density, and structure.It is believed that the nanotubes grow by the decomposition of the carbonaceous gas on the surface of a catalyst particle.The carbon dissolves in the catalyst,dif-fuses through it,and exits to form the nanotube.The role of the NH3is to etch by-products such as amorphous carbon. Our process consists of four stages;substrate pretreatment, catalyst deposition,catalyst annealing͑sintering͒,and then nanotube growth.The initial catalyst layer is formed into nanoparticles or islands by annealing or sintering at high temperature.This sintering depends on the annealing tem-perature and also on the interaction of the catalyst layer with the substrate.Therefore the initial condition of the substrate is important and we define it in a pretreatment step.The nanotubes are then characterized using scanning electron mi-croscopy͑SEM͒,high-resolution transmission electron mi-croscopy͑HREM͒,Raman spectroscopy and Auger spectros-copy.The results show that the catalyst thickness is important in controlling the nanotube diameter,length,and density,and their alignment is controlled by the electricfield. Deposition temperature and plasma characteristics are also important for the growth of uniform,well-aligned nanotubes with few defects.II.EXPERIMENTAL DETAILSThe V ACNTs were grown using a direct current͑dc͒PECVD system on a resistively heated graphite substrate stage capable of reaching a maximum temperature of 1000°C.The Si substrates were treated in several ways prior to the catalyst deposition.Untreated Si substrates with a thin native oxide,pristine Si͓cleaned with hydrofluoric͑HF͒acid͔,and Si with a layer of50nm SiO2grown using elec-tron cyclotron resonance͑ECR͒were used as the substrates.a͒Electronic mail:mc209@JOURNAL OF APPLIED PHYSICS VOLUME90,NUMBER1015NOVEMBER200153080021-8979/2001/90(10)/5308/10/$18.00©2001American Institute of PhysicsThinfilms͑0.5–20nm͒of Co or Ni catalyst are then depos-ited onto the Si substrates using magnetron sputtering or thermal evaporation.After depositing the catalyst layer,the substrates are transferred in air to the growth chamber.The bell jar cham-ber is pumped down to a base pressure of10Ϫ2Torr using a rotary pump.20–30Torr of high purity hydrogen or nitrogen is then introduced via a leak valve.The samples were also annealed in vacuum in some cases.The substrates were heated to750°C and held at this temperature for15min to sinter the catalyst layer,with the plasma off,prior to initiat-ing the deposition.The substrate temperature is measured by attaching a thermocouple directly to the graphite heater.Af-ter the treatment step,the chamber was evacuated to base pressure and ammonia(NH3)was introduced immediately. The NH3flow was maintained by massflow controllers at 200sccm,achieving a pressure of3.5Torr.A dc discharge between the cathode͑sample͒and theanode͑2mm diameter by1cm length copper wire͒was initiated using an AE MDX1kW supply.The anode–cathode distance was2cm.The bias voltage(V b)was in-creased toϪ600V and the acetylene(C2H2)feed gas was introduced within a few seconds using a separate massflow controller.The C2H2flow ratio was varied from0to75%to investigate the effect of the C2H2:NH3ratio on growth.The total pressure after introducing C2H2depends on the ratio used.The depositions were carried out for15min in a stable discharge.The SEM studies were performed on a Hitachi S800-FE SEM operated at20kV.The HREM was performed on a JEOL4000EX operated at400kV.The HREM samples were prepared by scraping thefilms off the substrates,dispersing them in a ethanol ultrasonic bath,and placing them onto copper grids.The Auger chemical analysis was carried out using a Physical Electronic PHI680Auger nanoprobe with a 10–15nm electron beam probe with a multichannel plate detector.The structure of the nanotubes was studied by Ra-man spectroscopy.Unpolarized visible Raman spectra were obtained using a514.5nm Ar ion laser excitation and a Ren-ishaw spectrometer.UV Raman spectra were recorded on a UV-enhanced charge coupled device camera on a different Renishaw spectrometer modified for use at244nm with fused silica optics.The UV Raman used the244nm line of an inter-cavity frequency-doubled Ar ion laser.The laser power was always less than0.5mW/m2to avoid sample damage.The spectral resolution was3cmϪ1.In all cases,the spectra were obtained with the laser beam directed perpen-dicular to the samples and thus nominally parallel to the V ACNTs.III.RESULTSA.Influence of catalyst layer thicknessSEM observations of the Ni catalystfilms after sputter deposition onto ECR SiO2coated substrates showed that Ni films thicker than1nm were continuous with a few pinholes. Films thinner than1nm were found to be discontinuous in some regions.Figure1shows SEM photographs of Nifilms of varying thickness after annealing.It is seen that the Ni breaks into small islands due to surface tension,as well as the compressive stress due to the mismatch of the thermal expansion coefficients of Si and Ni.16,17The island size depends on the thickness of the initial Ni film,similar to the results of Bower et al.16Figure2shows that the average island size varies in proportion to the initial Ni layer thickness.The island diameter is much larger than the thickness,indicating that the islands have a low aspect ratio.In contrast to this,no islands form after annealing Ni films deposited on a Si surface cleaned with HF or with only native oxide.The lack of fragmentation of Nifilms on Si surfaces is attributed to the diffusion of Ni into the Si,lead-ing to the formation of a silicide,NiSi x,above300°C.26 Therefore a barrier layer such as SiO2is required to prevent silicide formation when using Ni as a catalyst.To study other potential barrier materials we also deposited Ni onto100nm Ti and W barrier layers.Postannealing results of Nifilms on metal layers showed poorer results.However,similar anneal-ing experiments with Co deposited on HF dipped Si and on Si with native oxide revealed significantly different results. The Co was found to form spherical islands similar to those in Fig.1even on a pristine Si surface,as seen in Fig.3.The corresponding nanotube growth on Co islands is shown in Fig.3͑b͒.Figure4shows the nanotubes grown on annealed Ni layers of different initial thickness,with a C2H2:NH3flow FIG.1.SEM photographs of Nifilms with varying thicknesses deposited using magnetron sputtering on50nm of ECR SiO2after annealing at750°C in20Torr of H2for15min.FIG.2.The average Ni island size after annealing versus initial Ni layer thickness.ratio of 75:200sccm at Ϫ600V and 700°C.All the results in Fig.4are for samples grown simultaneously in a single deposition.The thickness of the catalyst layer affects the tube diameter,the tube length,and the density of the tubes as seen in Fig.5.Indeed,Fig.6shows that the nanotube diam-eter approximately equals the Ni island size.In Fig.4a metal cap is observed predominantly at the top of the nanotubes for all our films grown using Ni or Co as the catalyst,as found by Ren et al.14and Merkulov et al.17but in contrast to Bower et al.16It can be seen that for cata-lyst thickness under 1.0nm,the tubes are very thin and long with diameters as low as 10nm and lengths up to 10m,similar to the results of Ren et al.14Figures 4͑a ͒and 4͑b ͒also show that the tubes are not perfectly aligned and appear distorted.As the catalyst layer thickness increases to 1.5–2.0nm,the tubes become more uniform in diameter and are almost perfectly aligned.As the catalyst layer becomes even thicker,however,the average diameter and the distribution of nanotube diameter both increase and they become much shorter.It is also worth noting that we did not observe any nanotube growth in the absence of a catalyst.The wider size distribution of the nanotubes for thick catalyst layers is at-tributed to the nonuniform fragmentation of the catalyst layer during annealing.In some reports,catalyst layers as thick as 15–20nm were used to grow nanotubes.17To investigate the growthmechanism on such thick catalyst layers we attempted to grow nanotubes on a 20nm Co layer.However,we find that thick catalyst films do not form islands.An additional NH 3etch for 15s was required to fragment the thick catalyst layer.The etching was performed by initiating a NH 3plasma at Ϫ600V,similar to that in Refs.14and 17.After this annealing and etching treatment,the Co film was found to form islands comparable to Fig.1͑f ͒,as shown in Fig.7͑a ͒.It may be that during the NH 3etching,the polycrystalline Co film is preferentially etched at the grain boundaries.Figure 7͑b ͒shows the corresponding nanotube growth for a 20nm Co layer.The growth is now substantially different to any seen in Fig.4.The nanotubes appear to grow preferentially at the edges of each island,resembling the grain boundary growth seen by Huang et al.27for nanotubes on thick ͑1mm ͒Ni substrates.We attribute this type of growth to the fact that the Co at the island edge is thinner than in the island middle,allowing the carbon to diffuse through and form nanotubes.The middle of the island effectively behaves like a continu-ous film where no nanotube growth canoccur.FIG.3.͑a ͒SEM photograph of a 2nm magnetron sputtered Co film on HF cleaned Si after annealing in 20Torr of H 2for 15min.͑b ͒Corresponding nanotube growth on Coparticles.FIG.4.SEM photographs of nanotubes grown on Ni layers of various initial thicknesses shown in Fig. 1.Standard growth conditions ͑bias voltage ϭϪ600V,C 2H 2:NH 3ϭ75:200,time ϭ15min ͒were used for all deposi-tions.FIG.5.Plot of average ͑a ͒nanotube density,͑b ͒nanotube length,and ͑c ͒tube diameter as a function of the Nithickness.FIG.6.The average nanotube diameter vs average Ni island size.B.Plasma properties of dc PECVDFor dc plasmas,the glow discharge is initiated by apply-ing a bias between the cathode and anode.The applied volt-age governs the plasma properties if conditions such as elec-trode gap and pressure are kept constant.In order to understand the growth mechanism of the nanotubes some basic plasma parameters were measured using the graphite substrate holder as a planar Langmuir probe with an area of about 10cm Ϫ2.The probe current is plotted against applied voltage in Fig.8.The breakdown voltage for plasma initia-tion in our system is about Ϫ300V,although this depends strongly on the substrate temperature.The plasma current density at Ϫ600V was about 9mA cm -2.The plasma poten-tial (V p )obtained using a much smaller 0.5mm ϫ0.5cm tungsten wire probe was found to be 3V .The plasma density (n )is derived from the current density to be 1010cm Ϫ3,tak-ing the ion energy as 30%of the bias voltage or 200eV .The electron temperature (T e )derived from the probe measurement was found to be 1.5eV .The Debye length,d ϭ(o T e /ne 2)1/2,of the plasma was derived from these data as Ϸ50–90m.The sheath width over which the bias voltage V d is dropped is calculated from d as 28ϭ0.47dͩ2e ͉V p ϪV d ͉kT eͪ3/4,where k is the Boltzmann constant.This gives a sheath width of about 4–6mm.Therefore the field across the sheath at Ϫ600V is Ϸ0.1–0.15V/m,similar to that found by Bower et al.29Note that when the voltage is reduced to Ϫ400V the field is only 0.07V/m,which is not enough to completely align the nanotubes as shown later.Returning to Fig.8,it can be seen that the probe currents measured at 750°C are significantly higher than those at 550°C.This indicates that heating of the graphite substrate holder contributes to additional excitation of gas species in the plasma.The additional ionization may be due to colli-sions between neutral species and electrons in the sheath.The electrons may result from secondary emissions and/or field emitted electrons emanating from fine protrusions on the graphite surface.Therefore the higher growth rate and better quality nanotubes generally observed at higher tem-peratures may be partly due to the presence of specific ex-cited or ionized C 2H 2*and NH 3*species rather than substrate temperature alone.The species required for nanotube growth is presently being studied and will be reported elsewhere.C.Influence of applied voltageFigure 9shows nanotubes grown at three different bias voltages while keeping all other parameters constant.At 0V bias,no plasma is present and the nanotubes grow only by thermal decomposition of C 2H 2.No electric field is present,and the nanotubes are randomly oriented or spaghetti-like,as shown in Fig.9͑a ͒.If a small bias voltage is applied,a weak plasma is generated,a weak electric field is present above the substrate,and some alignment begins to occur as observed in Fig.9͑b ͒.However,an electric field of about 0.07V/m (Ϫ400V)does not appear to be enough to completely align the nanotubes.In contrast,nanotubes deposited at Ϫ600V ͑electric field Ϸ0.15V/m ͒are perfectly aligned with uni-form diameter and length.Although Fig.9indicates the ef-fect of applied field on alignment,it must be noted that the plasma characteristics ͑such as the bias current,degree of ionization/excitation ͒at 0,Ϫ400,and Ϫ600V are expected to be significantly different in terms of the types and amount of species contributing to growth.The changes in plasma characteristics may also contribute to the degree of align-ment,though not for the nucleation of nanotubes.Figure 10shows the deposition rate as a function of the applied bias voltage.Here we use the deposition rate rather than the nanotube length,as thermally deposited tubes are not aligned and so it is difficult to estimate their length.Surprisingly,we found that the deposition rate decreases with increasing bias voltage.This rather unexpected result is attributed to greater etching by ionized or excited NH 3spe-cies.The NH 3etching is strongest when a plasma is initiated,as indicated by the sharp drop in the deposition rate when the bias voltage is above Ϫ300V.NH 3etching is animportantFIG.7.͑a ͒SEM photograph of a 20nm Co film after annealing in H 2for 15min and etching with NH 3͑3.5Torr ͒plasma for 15s at Ϫ600V.͑b ͒Corre-sponding nanotube growth on the 20nm Co film using standardconditions.FIG.8.Planar probe current versus the applied probe voltage characteristics taken at two different probe temperatures for the dc PECVD plasma used to grow alignednanotubes.FIG.9.SEM photographs of nanotubes grown at ͑a ͒0V ,͑b ͒Ϫ400V,and ͑c ͒Ϫ600V for a Ni catalyst thickness of 2nm.aspect of growing well-aligned nanotubes with uniform di-ameters from top to bottom ͑see below ͒.Figure 11͑a ͒shows the nanotube length ͑growth rate ͒as a function of the deposition time.We see that the length increases linearly with time,in contrast to the results of Bower et al.,who observe that the nanotube length saturates quickly after the first 3min.16This result,together with the fact that the catalyst particle remains at the top of the nano-tubes,indicates different growth mechanisms for the two cases.Note that our nanotube lengths are significantly less than those of other groups.14,16,17,27This is due to the relatively low pressure ͑4Torr compared to 20Torr ͒used here.Figure 11͑b ͒shows the nanotube length as a function of the total gas pressure,while keeping the C 2H 2:NH 3ratio constant.It is seen that the nanotube length increases with gas pressure.D.Influence of the C 2H 2:NH 3ratioFigure 12shows micrographs of nanotubes grown at dif-ferent C 2H 2:NH 3flow ratios.Note that the NH 3flow and the bias voltage were kept constant at 100sccm and Ϫ600V,respectively,while the C 2H 2flow is varied.Furthermore,the pressure was also kept constant by adjusting the pumping speed in order to maintain similar plasma properties.Figures 12͑a ͒and 12͑b ͒show that well-aligned nanotubes with a uniform diameter can be grown for C 2H 2concentrations of 20%and 30%.Indeed,we find that nanotubes similar to those in Figs.12͑a ͒and 12͑b ͒can be obtained for C 2H 2concentrations from 5%to 30%.Above 30%C 2H 2,the nano-tubes become obelisk-like as seen in Fig.12͑c ͒.For even higher C 2H 2flows the growth changes dramatically from nanotubes to tip structures,as in Fig.12͑d ͒.A pure carbon plasma yields films resembling amorphous carbon,with a cauliflower-like structure often reported in the literature.30,31Figure 11͑c ͒plots the nanotube length against the C 2H 2concentration.As C 2H 2concentration increases,the growth rate initially rises by 30%and then decreases again.The initial rise in nanotube length is expected,as a higher con-centration of feed gas in the plasma compensates for the etching by NH 3.The catalyst particles can be seen on top of all the structures,including the pyramids in Fig.12͑d ͒.This indicates that,even at high C 2H 2flows,the carbon diffuses through the metal particles and precipitates below it.How-ever,at concentrations over 50%,the vertical nanotube growth cannot keep pace with the amount of carbon extruded through the metal catalyst,so that the lateral growth below the metal cap dominates giving rise to pyramidal structures..Furthermore,since the relative amount of NH 3in the plasma is less,the etching rate is lower than the deposition rate,leading to a buildup of amorphous or poor quality carbon between the structures.E.Influence of the deposition temperatureNanotubes were grown at three different deposition tem-peratures while keeping all other parameters constant.Fig-FIG.10.Average deposition rate versus the applied bias voltage using a C 2H 2:NH 3ratio of 75:200and Ni thickness of 2nm.FIG.11.Average nanotube length as a function of ͑a ͒growth time,͑b ͒deposition pressure,and ͑c ͒C 2H 2concentration.FIG.12.SEM photographs of nanotubes grown at different concentrations of C 2H 2,͑a ͒20%,͑b ͒30%,͑c ͒50%,and ͑d ͒75%.Note that the NH 3flow was kept constant at 100sccm.ures 13͑a ͒–13͑c ͒show the nanotubes grown at 550,700and 900°C,respectively.The growth rate at 550°C is much less,with the nanotubes having a diameter of 50nm and a height of only 1m,similar to the results of Cui et al.19The results of Fig.13͑a ͒suggest that 550°C may not be sufficient for nucleating nanotubes.However,this is not supported by HREM observations,which reveal short nanotubes with a bamboo-like structure ͑see below ͒.The low growth rate ap-pears to be a direct consequence of the low deposition tem-perature rather than a lack of plasma density,as thermal growth without a plasma occurs at 700°C.At 550°C,the temperature may be too low to decompose C 2H 2,hindering growth.Furthermore,the low temperature also limits the graphitization,which increases the condensation of a -C.The nanotubes grown at 700°C are well-aligned and uniform in size.However,as the deposition temperature is further in-creased to about 900°C,the nanotubes become disordered and less well aligned.The nanotube distortion at 900°C may be caused by ion damage.At this temperature,the ion current is Ϸ0.7A,indicating a higher plasma ionization.Figure 14shows the variation of growth rate with sub-strate temperature.It is seen that the growth rate initially increases with the substrate temperature and then decreases at higher temperatures.This trend is similar to that found by Cui et al.,19even though they used microwave PECVD in which ion bombardment effects are small.The trend is also quite similar to that in pyrolysis found by Baker,32–34which suggests a common mechanism,as discussed below.F.Transmission electron microscopyThe tubular structure of the nanotubes was verified using TEM.The nanotubes generally consisted of 20–30graphiticshells with a central hollow region of about 3–5nm.The Ni catalyst particle is always found at the top of the nanotubes.The HREM images reveal that the catalyst particle is mostly single crystal Ni completely encapsulated by carbon.Figures 15͑a ͒and 15͑c ͒show TEM images of nanotubes deposited using standard conditions but at substrate temperatures of 550and 900°C,respectively.The low and high temperature nanotubes have a more defective,bamboo-like structure,in contrast to nanotubes deposited at 700°C as shown in Fig.15͑b ͒.Their tube walls are also thinner (Ϸ2to 3nm).The smaller number of tube walls is consistent with a lower growth rate.The interrupted growth for the 550and 900°C nanotubes may be related to nonequilibrium extrusion of car-bon from the catalyst particle.Examination of the tube walls reveal that the graphene planes were not always parallel to the tube axis but often twisted and broken for low tempera-ture depositions while the graphite layers were found to be more defined for the high temperature case.The high reso-lution TEM image shown in Fig.15͑b ͒confirms the tubular nature of these nanotubes.Well-defined graphene planes par-allel to the tube axis are clearly visible in Fig.15͑b ͒.A simi-lar structure along with defects in the form of ‘‘cross-struts’’perpendicular to the tube axis are present in all PECVD grown nanotubes.A high magnification image of the catalyst particle for the 900°C nanotubes is shown in Fig.15͑d ͒.Carbon encap-sulation and the Ni fringes at the center of the particle can be readily observed.Note that the carbon surrounding the cata-lyst particle is graphitic in nature in this case due to the high deposition temperature.In contrast,the carbon layer sur-rounding the catalyst particles in the low temperature depo-sitions was found to resemble disordered carbon.Closer observation of Fig.15͑d ͒reveals three distinct regions in the image.The first is the Ni core of thecatalystFIG.13.SEM micrographs of nanotubes grown at ͑a ͒550°C,͑b ͒700°C,and ͑c ͒900°C under standardconditions.FIG.14.Average nanotube length versus inverse depositiontemperature.FIG.15.Transmission electron microscopy images of ͑a ͒nanotubes depos-ited at 550°C,͑b ͒700°C and ͑c ͒900°C.͑d ͒is a high magnification image of a catalyst particle from the 900°C material.particle ͑consistent with fringe spacing of cubic Ni ͒,the sec-ond is a shadowy interface region between the Ni particle and the carbon,and the third is the carbon encapsulation.The image indicates that carbon and Ni interact only near the edges of the catalyst and not with the entire particle.The spacing in the interface region appears to differ from that of pure Ni or graphite.The graphite phase also seems to be extruded outwards from this transition region.This appears to occur over the entire particle,consistent with the cap be-ing completely encapsulated in three dimensions.Further work on the nature of the transition region will be reported elsewhere.G.Raman spectroscopyRaman spectroscopy is a useful nondestructive method for the structural characterization of different carbon materials.35–37Most work on nanotubes has been performed on very pure SWNTs samples to determine their Raman sig-natures and correlate them to calculations.38–40In our case the samples contain some Ni and amorphous impurities which dilutes the nanotube signature.Nevertheless,struc-tural information can still be extracted.Figure 16͑a ͒shows the Raman spectra from nanotubes grown at varying C 2H 2:NH 3ratios.The two main features in the Raman spec-tra are the D and G peaks at about 1350and 1600cm Ϫ1and the corresponding second order peaks at around 2700and 2950cm Ϫ1.The first and second order Si peaks are also seen.The 15%spectrum shows some photoluminescence ͑PL ͒background along with the second order Si peak at 960cm Ϫ1,both consistent with the low growth rate of nano-tubes at this concentration,Fig.11͑c ͒.The second order D and G peaks become less prominent and the I (D )/I (G )ratio increases for higher C 2H 2concentrations.The Raman spectra of nanotubes shown in Fig.4are plotted in Fig.16͑b ͒.Again,there are no significant differ-ences among the spectra.However,the nanotubes grown on a 9.5nm Ni layer show a large photoluminescence ͑PL ͒background,attributed to the a-C between the short and less densely packed nanotubes.Figure 16͑c ͒shows the Raman spectra of nanotubes grown at 550,700and 900°C.The high temperature tubes have sharper D and G peaks,while the strong PL and the lack of second order D and G peaks in 550°C spectrum indicates disordered tubes and the presence of large amounts of a -C.In general,we find that more aligned and ordered samples correspond to lower I (D )/I (G )ratios and sharper first and second order D and G peaks.The effects of acetylene concentration,deposition temperature,and catalyst layer thickness on the Raman spectrum param-eters are summarized in Figs.17͑a ͒–17͑c ͒,respectively.The visible and UV Raman spectra from the nanotubes grown at 700°C are compared in Fig.18.The UV Raman spectrum shows only a very sharp G peak.The absence of a residual D peak is consistent with ordered graphitic bonding within the tubes.35H.Auger analysisA chemical analysis of the nanotube base,body,and tip was conducted using nano-Auger spectroscopy.By using a focused electron beam nanoprobe,the various portions of the nanotube were analyzed.Figure 19͑a ͒shows the Auger chemical analysis from different regions of the nanotubes ͑deposited using standard conditions and 700°C ͒.The re-sults show that the body of the nanotube is almost entirely carbon with only residual nitrogen and oxygen present in the form of adsorbed contaminants.Ni was never detected in the body of the nanotube for all our measurements.Ni catalyst together with carbon was readily detected at the top of the nanotube.The nature of the carbon in the body and tip of the nano-tube was derived from the Auger carbon signal.The carbon peak is shown in detail in Fig.19͑b ͒.The prepeak feature from 260to 270eV for both the tip and the body of the nanotube indicates that carbon is predominantly sp 2bonded.The better-defined features ͑crystalline graphite-like ͒of the spectrum from the body of the nanotube suggests thatthereFIG.16.Visible Raman spectra of nanotubes grown on ͑a ͒varying C 2H 2:NH 3ratios,͑b ͒different Ni thicknesses,and ͑c ͒varying depositiontemperatures.FIG.17.Variation of Raman G peak,I (D )/I (G )ration,and G peak width vs ͑a ͒acetylene concentration,͑b ͒deposition temperature,and ͑c ͒Ni layerthickness.FIG.18.UV and visible Raman spectra of nanotubes deposited at 700°C.。