Native defect properties and p-type doping ef?ciency in group-IIA doped wurtzite AlN
Yong Zhang,1,2Wen Liu,2and Hanben Niu2,*
1Institute of Optoelectronics Science and Engineering,Huazhong University of Science and Technology,Wuhan430074,China
2Institute of Optoelectronics and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education,Shenzhen University,
Shenzhen518060,China
?Received18April2007;published2January2008?
Using the?rst-principles full-potential linearized augmented plane-wave?FPLAPW?method based on den-
sity functional theory?DFT?,we have investigated the native defect properties and p-type doping ef?ciency in
AlN doped with group-IIA elements such as Be,Mg,and Ca.It is shown that nitrogen vacancies?V N?have low
formation energies and introduce deep donor levels in wurtzite AlN,while in zinc blende AlN and GaN,these
levels are reported to be shallow.The calculated acceptor levels??0/??for substitutional Be?Be Al?,Mg
?Mg Al?,and Ca?Ca Al?are0.48,0.58,and0.95eV,respectively.In p-type AlN,Be interstitials?Be i?,which act
as donors,have low formation energies,making them a likely compensating center in the case of acceptor
doping.Whereas,when N-rich growth conditions are applied,Be i are energetically not favorable.It is found
that p-type doping ef?ciency of substitutional Be,Mg,and Ca impurities in w-AlN is affected by atomic size
and electronegativity of dopants.Among the three dopants,Be may be the best candidate for p-type w-AlN.
N-rich growth conditions help us to increase the concentration of Be Al,Mg Al,and Ca Al.
DOI:10.1103/PhysRevB.77.035201PACS number?s?:61.72.Bb,61.72.J?,61.72.uj,71.15.Nc
I.INTRODUCTION
Group-III nitrides?III-N,III=Ga,Al,and In?are wide-gap semiconductors and have attracted researcher’s attention for more than two decades due to their promising applica-tions for the blue-ultraviolet?UV?optoelectronics.1–5Among all III-V nitrides,wurtzite AlN has the widest direct gap?var-ies from6.28eV at5K to6.2eV at room temperature?.6 Thus,to push the optical emission and/or detection wave-length to the deep UV region???200nm?,AlN is of great interest.
In spite of the recognition of the importance of AlN,the report of light emitting directly from AlN is rare due to the lack of high-quality?lms.Recently,Taniyasu et al.have re-ported a light emitter with210nm made of AlN doped with Si and Mg,which is the shortest wavelength emitted by light-emitting diode at present,7whereas the internal quan-tum ef?ciency is still low due to low p-type doping ef?-ciency.So the fabrication of p-type doped layers is essential for all of these devices.However,similar to GaN,the growth of highly conductive p-type AlN layers has so far proven to be dif?cult.The main reasons have been proposed to be the formation of donor defects,such as nitrogen vacancies,lim-ited dopant solubility,and deep acceptor energy levels.Fol-lowing the“doping limit rule,”8it will be much more dif?-cult to achieve p-type AlN than to achieve p-type GaN.
To exploit fully the potential of AlN,systematic studies of native defects and impurities in AlN are required.While there have been several theoretical and experimental studies of crystal defects in GaN,9–11little work has been done on AlN.Magnesium is commonly used as p-type dopant for nitride semiconductors,but the Mg low doping ef?ciency is due to the deep acceptor level introduced by Mg.It would be desirable to?nd an alternative dopant that would exhibit higher solubility and lower ionization energy.In Ref.7, group-II and-IV elements have been proposed to be poten-tial candidates for Mg.However,group-IV elements are likely to become donors when incorporated in the cation sites,which will result in severe self-compensation.12Thus, group-II elements may be better candidates than group-IV elements for p-type AlN doping.In GaN,it has been reported that the acceptor level of Be Ga is shallower than that of Mg Ga.However,the behavior of doping Be in w-AlN is still unclear.To improve p-type doping ef?ciency,systemic stud-ies of doping properties of group-IIA elements in AlN are important.
In this work,theoretical studies are performed to under-stand the con?gurations of native defects and substitutional Be,Mg,and Ca impurities in wurtzite AlN.By comparing the formation energies and transition levels of Be-,Mg-,and Ca-related defects,the p-type doping ef?ciency of these dop-ants is examined.The organization of this paper is as fol-lows.In Sec.II,the computational methods are introduced. Section III gives some discussion and results.Section IV summarizes the paper and contains some suggestions for fu-ture experimental work.
II.METHODS
The calculations are performed using the FPLAPW method implemented in WIEN2K package.13The generalized gradient approximation of Perdew-Burke-Ernzerhof96?Ref. 14?is employed for the exchange-correlation potential.Cal-culations were done with R MT K max=9?where R MT is the av-erage radius of the muf?n-tin spheres and K max is the maxi-mum modulus for the reciprocal lattice vector?.The iteration process was repeated until the calculated total energy differ-ence between succeeding iterations is less than0.1mRy and the force on each atom is less than1.0mRy/a.u.To simulate isolated defects,a72-atom AlN supercell consisting of 3?3?2primitive wurtzite cells is used as it was found to be adequate in earlier work on similar systems.15The 4?4?3k-point mesh produces converged results.The lat-tice parameters of supercell are?xed and are described by
PHYSICAL REVIEW B77,035201?2008?
the theoretical value of pure AlN.The theoretical band gap
derived from the band structure is?4.1eV and about2.0eV
below the experimental gap.To?nd a realistic description of
both defect levels and band edges,we obtain them both from
electron addition and removal calculations.The theoretical
band gap evaluated from E??R????+E+?R?+???2E0?R?0???Ref.16?is5.98eV,in acceptable agreement with the ex-perimental value of6.12eV.17
At equilibrium and in the dilute limit,the concentration of
a defect in a crystal depends upon its formation energy E f.
Following Van de Walle and Neugebauer,18the formation
energy of a defect or impurity X?X=Be,Mg,and Ca in
present work?in charge state q is calculated from
E f?X q?=E tot?X q??E tot?AlN,bulk?
??n i?i+q?E F+E V+?V?,?1?where E tot?X q?is the total energy of the defect-containing AlN supercell and E tot?AlN,bulk?is the total energy of the equivalent supercell of AlN containing no defects.Here,n i indicates the number of atoms that have been added to ?n i?0?or removed from?n i?0?the supercell and?i are the corresponding chemical potentials of these species.E F is the Fermi level,referenced to the valence-band maximum E V in the bulk.A correction term?V is used to align the reference potential in our defect supercell with that in the bulk.
The chemical potentials?depend on growth process.19 To determine the bound of?Al and?X,we compute the enthalpy of formation of AlN and X3N2assuming the formation from metallic Al,X,and gaseous N2??H f?AlN?=?2.06eV,?H f?X3N2?=?5.0,?3.36,and ?2.63eV for X=Be,Mg,and Ca,respectively?.Chemical potentials are calculated using the following relationships:?Al+?N=?AlN=?Al?bulk?+?N?N
2
?+?H f?AlN?,?2?
3?X+2?N=?X
3N2
=3?X?bulk?+2?N?N
2
?+?H f?X3N2?.
?3?
By combining Eqs.?2?and?3?,the chemical potential of Al and impurity X are therefore
?Al=?Al?bulk?,?4?
?X=?X?bulk?+1
3?H f?X3N2??2
3
?H f?AlN?,?5?
for Al-rich limit,and
?Al=?Al?bulk?+?H f?AlN?,?6?
?X=?X?bulk?+1
3
?H f?X3N2?,?7?for N-rich limit.
III.RESULTS AND DISCUSSION
A.Native defects
In order to?nd the possibility of compensation,we per-form a comprehensive study on the native point defects in AlN.Figure1shows the formation energies of native defects
in w-AlN as a function of the Fermi level under the two
extreme conditions:the Al-rich limit and the N-rich limit.
Here,E F spans the theoretical band gap?5.98eV?.
Moreover,V N behave as donors that can donate one,two, or three electrons,but only the V N+and V N3+charge states are stable.The V N2+state is unstable,thus presenting a
negative-U effect.The similar behavior of V N has been found in GaN.20The V N3+has very low formation energy under
p-type conditions?E F close to the top of the valence band?.
Taking no account of ionization level,nitrogen vacancies,
therefore,are likely to play an important role in compensat-
ing acceptors in p-type AlN.Under n-type conditions ?E F close to the bottom of the conduction band?,however, the formation energy of V N is actually quite high.In
thermodynamic equilibrium,the concentration of nitrogen
vacancies should therefore be quite low.On the other hand,
V N act as deep donors and the transition level locates at ??1+/0?=1.75eV blow the conduction-band minimum.This conclusion is different from what was reported about V N in zinc blend e AlN in Van de Walles’work,21where V N act as a shallow donor.Because of deep transition energy and high formation energy under n-type conditions,V N should not be responsible for the observed n-type conductivity in as-grown AlN.It is more possible that unintentional impurities lead to n-type conductivity other than native defects do.It has been reported that unintentional impurities such as oxygen and silicon are the cause of the observed unintentional n-type doping in GaN.22As shown in Fig.1,the formation energies of V N can be changed signi?cantly depending on growth conditions?Al rich or N rich?.
Our calculations reveal that V Al are the lowest-energy de-
fects in n-type AlN,where they behave as triple acceptors.
These defects are likely to act as compensating centers for
shallow donors.The calculated transition energy??0/??for V Al is0.95eV above the valence-band maximum?VBM?. Additionally,for p-type AlN,our results show that Al N3+has a low formation energy in Al rich,but in N rich,it is
very FIG.1.Defect formation energies for native point defects in wurtzite AlN as a function of the Fermi level?E F?under aluminum-rich?left panel?and nitrogen-rich?right panel?conditions.E F is de?ned to be zero at the valence-band edge.
ZHANG,LIU,AND NIU PHYSICAL REVIEW B77,035201?2008?
high,which indicate that Al N3+concentration is affected by growth conditions of AlN strongly.The other native defects, such as Al i and N Al,possess high formation energies both in Al rich and N rich,so they cannot be the dominant defects in w-AlN.
B.p-type doping
In this section,we study the doping behavior of Be,Mg, and Ca impurities in AlN.The main information about the geometry and stability of substitutional impurities is given in Table I.
1.Mg dopant in AlN
In wurtzite AlN,a substitutional impurity has four nearest neighbors.One of them located along the c axis relative to the impurity?forming X-N?I?bond?is nonequivalent by symmetry to the three remaining neighbors?forming X-N?II?bonds?.For substitutional Mg,we?nd that Mg atom is lo-cated very close to the lattice site of the Al atom that it https://www.doczj.com/doc/1a1210739.html,ttice relaxation increases the length of Mg-N bonds and releases elastic energies for both neutrally and negatively charged states?listed in Table I?.This outward relaxation can be attribute to that of the atomic radius of a substitutional impurity?Mg?which is larger than that of re-placed host atom?Al?.15Large relaxation of the surrounding host atoms will raise the formation energy.Very similar re-sults are obtained for substitutional Mg in zinc blend e AlN.21Magnesium on the Al site induces the acceptor level ??0/1??=0.58eV above the VBM,which is close to the experimental value of0.51eV.23The large acceptor level of Mg Al may has relation to the electronegativity of Mg atom
?for detailed analysis,see below Be dopant in AlN?.As can be seen in Fig.2,Mg Al has a high formation energy.This high formation energy stems from the strict solubility limit imposed by the formation of Mg3N2.The formation energy of Mg Al is affected by the growth conditions:by moving from Al-rich to N-rich conditions,the formation energy of
Mg Al decreases by1
3??H f?AlN??.
In contrast to the Mg Al,Mg N induces a deep donor level.
For Al rich,our calculations indicate that incorporation of
Mg on nitrogen site is energetically favorable in p-type con-
ditions,which can result in self-compensation effect,but this
is not true under N-rich conditions.Therefore,N-rich growth
conditions can restrict Mg N concentration in AlN.Mg on
interstitial site behaves as donor,but both in Al-and N-rich
conditions,Mg i is unfavorable due to the large atom size of
Mg.
2.Be dopant in AlN
For a substitutional Be Al acceptor,the Be-N bonds show
inward relaxation for both neutrally and negatively charged
states for Al atom that has larger atomic radius than that of
Be.A similar inward relaxation for this complex is also re-
ported in GaN,19but percentage change of Be-N bond length
is larger than that of Be impurity in AlN due to even larger
atomic radius?1.30???Ref.24?of Ga atom.The relaxation
energy E rel of Be Al is lower than that of Mg Al both in neu-
trally and negatively charged states,showing that Be re-
places Al in AlN with less perturbation of the lattice.Our
formation energy calculations reveal that Be occupying Al
site creates a single acceptor state above the VBM of AlN.
The calculated transition energy of Be Al is0.48eV which is
shallower than that of Mg Al by?0.1eV.By using effective-
mass theory,Mireles and Ulloa estimated this value to be
0.22–0.45eV,25but their computation is semiempirical and
results are affected by computational parameters strongly.In
GaN,Latham et al.had reported that the acceptor level of
Mg Ga was about0.09eV higher than that of Be Ga,19which is
in good agreement with our result.Different transition ener-
gies between Be Al and Mg Al can be understood as follows:
The acceptor level of Mg Al and Be Al consists mostly of p
https://www.doczj.com/doc/1a1210739.html,paring with Mg,Be atom has lower p orbital
energy for it is more electronegative;26thus,electron can be
excited from the VBM to acceptor level with less energy.As
can be seen from Fig.2,the formation energy of Be Al is
about0.2eV lower than that of Mg Al.So the concentration
TABLE I.Atomic radius R a of X and Al,Pauling electronega-tivity?of X,percentage change of bond lengths with respect to bulk AlN,lattice relaxation energy E rel,optimal formation energy ?N-rich conditions?for different charge states q,and ionization lev-els??0/?1?for substitutional Be,Mg,and Ca at Al site in AlN.
AlN:X R a
????q
X-N?I?
?%?
X-N?II?
?%?
E rel
?eV?
E f
?eV?
?
?eV?
X=Be 1.05a 1.5b0?4.1?0.00.18 2.390.48
?1
?2.6?3.90.28?3.08
X=Mg 1.50a 1.2b0 6.88.40.68 2.560.58
?1 6.57.80.78?2.82
X=Ca 1.81a 1.0b013.512.0 3.44 3.730.95
?114.917.4 3.73?1.27
X=Al 1.25aˉˉˉˉˉˉˉ
See Ref.23.
b See Ref.25.
FIG.2.Formation energy as a function of Fermi level for Mg, Be and Ca in AlN under aluminum-rich?left panel?and nitrogen-rich?right panel?conditions.
NATIVE DEFECT PROPERTIES AND p-TYPE DOPING…PHYSICAL REVIEW B77,035201?2008?
of substitutional Be in AlN is expected to be higher than that
of Mg.Similarly to substitutional Mg,the formation energy
of Be Al is affected by growth conditions.
It is reported that Be Ga acceptor is strongly compensated
by interstitial defects,19so we pay more attention to Be i for
Be in AlN.According to total energy computation,we?nd
that the lowest-energy structure is that Be atom lies in the
center of the hexagonal channel as viewed along the c axis.
Be i behaves as donor and can occur in1+and2+charge
states,while only2+charge state is stable for Be i in GaN.19
This difference is due to the fact that AlN has larger band gap than GaN does.For N-rich conditions,Be i2+has a low
formation energy in p-type AlN,E f?0eV for E F at the VBM.So holes may be compensated by interstitial defects
Be i,which is consistent with Be i in GaN.However,under
N-rich conditions,Be i is energetically unfavorable due to a
positive formation energy?E f=1.30eV for E F=0?;it is pos-
sible to select N-rich growth conditions to restrict the com-
pensation by Be i in p-type AlN.
Since Be N defect has a high formation energy both in Al-
and N-rich conditions,and is thus unlikely to occur in sig-
ni?cant concentration,we do not discuss it in detail here.
3.Ca dopant in AlN
Finally,the behaviors of Ca in AlN are discussed.Cal-
cium has the largest atomic radius and is the least electrone-
gative among the three dopants,so it is expected that calcium
on a substitutional Al site will produce the most signi?cant
outward relaxation with large relaxation energy,highest for-
mation energy,and deepest acceptor level.Our calculations
con?rm these predictions perfectly.The surrounding N atoms
undergo a signi?cant outward relaxation,increasing the
Ca-N distance to2.16?.This distance is very close to the
Ca-N distance in the compound Ca3N2.27Similar to Be and
Mg,Ca Al behaves as a single acceptor,but the transition level between0and?1charge states occurs around0.95eV above the VBM,becoming a deep acceptor.The formation energy of Ca Al is higher than that of both Be Al and Mg Al.So the doping ef?ciency of Ca is lowest comparing with Be and Mg.
IV.CONCLUSIONS
DFT generalized gradient approximation is used to study the native and group-IIA elements related defects in wurtzite AlN.Both V N and Be i act as donor with a low formation energy,making them a likely compensating center in the case of acceptor doping.However,V N do not account for the observed n-type conductivity of as-grown AlN for its high ionization levels and high formation energy in n-type AlN. Under Al-rich growth conditions,Mg N and Be i will compen-sate hole severely,whereas this problem can be improved by N-rich growth conditions.Our calculations revealed that atomic size and electronegativity of group-IIA impurity are important factors for p-type doping ef?ciency:an impurity with similar atomic radius as Al atom can achieve a higher concentration;an impurity with more electronegative prop-erties can produce a lower ionization level.Among the three elements,Be may be the best candidate for producing p-type AlN.In order to achieve high doping ef?ciency,restricting the concentration of V N and Be i is essential and N-rich growth conditions are expected.
ACKNOWLEDGMENTS
This work was supported by the National Natural Science Foundation of China under Project No.60532090.The au-thors would like to thank the Supercomputer Center of Shen-zhen University for the computation support.The authors also thank R.S.Zheng for useful discussions.
*hbniu@https://www.doczj.com/doc/1a1210739.html,
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中英文自荐信范文 第一篇：中英文-自荐信dear sir, professor kenneth h. chan, head of the department of metallurgy, has informed me that your agency is looking for an engineering graduate with the ability to write about technical subjects for non-technical readers. the four years at hong kong university have given me a thorough foundation in such fundamental sciences as physics, mathematics, and chemistry, in addition to specialized courses in metallurgy. i have also taken as many courses in english and psychology as possible with the expectation that i would enter the field of technical sales or editing following my graduation this summer. fortunately, as my resume shows, i now have a mature interest in finding a satisfying job. may i come in for an interview at your convenience? sincerely yours, 敬啟者: 冶金系主任陈教授告诉我,贵公司在物色有能力写专门性文章给一般读者阅读的工科毕业生。 在香港大学四年我奠定了冶金及物理、数学、化学基本科学的良好基础。我曾经选修许多门英语和心理学方面的课程,期望今年夏天
中英文自荐信范文 第1篇第2篇第3篇第4篇第5篇更多顶部 目录 第一篇：中英文-自荐信第二篇：中英文自荐信四第三篇：中英文自荐信五第四篇：个人简历中英文自荐信第五篇：医药学毕业中英文自荐信更多相关范文 正文第一篇：中英文-自荐信dear sir, professor kenneth h. chan, head of the department of metallurgy, has informed me that your agency is looking for an engineering graduate e a thorough foundation in such fundamental sciences as physics, mathematics, and chemistry, in addition to specialized courses in metallurgy. i have also taken as many courses in english and psychology as possible y graduation this summer. fortunately, as my resume shoature interest in finding a satisfying job. may i come in for an intervie the university of kansas asters degree in june of this year. my major is pharmacy and i am very interested in securing a position before i graduate, if possible. i am a hong kong chinese and my bachelor’s degree is
2011年全球半导体设备制造商发展概况 上海科学技术情报研究所董瑞青2013-01-28 关键字：全球半导体设备制造商发展概况浏览量：1601 半导体设备是半导体产业发展的基础，也是半导体产业价值链顶端的“皇冠”。从全球范围看，美国、日本、荷兰等国家是世界半导体装备制造的三大强国，全球知名的半导体设备制造商主要集中在上述国家。如表1所示，2011年世界前十六大半导体设备生产商中，有美国企业7家，日本企业6家，荷兰企业2家，德国企业1家，其中荷兰阿斯麦（ASML）以78.8亿美元的销售额位居全球第一，美国应用材料公司以74.4亿美元的销售额位居第二，日本东京电子销售额为62.0亿美元，位列第三；从企业主要的半导体设备产品看，美国主要控制等离子刻蚀设备、离子注入机、薄膜沉积设备、掩膜板制造设备、检测设备、测试设备、表面处理设备等，日本则主要控制光刻机、刻蚀设备、单晶圆沉积设备、晶圆清洗设备、涂胶机/显影机、退火设备、检测设备、测试设备、氧化设备等，而荷兰则在高端光刻机、外延反应器、垂直扩散炉等领域处于领导地位。从国内看，近年来，在国家科技重大专项支持下，我国集成电路装备产业发展取得了显著进展。上海中微半导体的90nm-65nm等离子体介质刻蚀机、45nm-32nm等离子体介质刻蚀机及北方微电子装备的65nm硅栅刻蚀机已通过12英寸片生产线的考核验证，并实现销售。上海微电子装备的先进封装光刻机进入江苏长电科技集团的集成电路封装生产线正式使用。七星华创的12英寸氧化炉也进入大线试用。中科信12英寸大角度离子注入机已完成3台样机组装，正在进行测试验证。盛美半导体的12英寸单晶圆兆声波清洗机已进入韩国海力士12英寸晶圆生产线的使用，并取得了韩国海力士本部的书面认证。
2009 半导体设备供应商电镀 电镀/电化学电镀/淀积系统应用材料（中国）有限公司 Applied Materials 诺发系统半导体设备（上海）有限公司 Novellus Systems 美国辛耘科技工程公司上海代表处（代理）
Semitool 淀积 CVD/PECVD/ALD 应用材料（中国）有限公司 Applied Materials 先晶半导体前工序设备（上海）有限公司ASM International 爱德万测试（苏州）有限公司上海分公司Advantest America,Inc Hitachi High Technologies Hitachi High Technologies
诺发系统半导体设备（上海）有限公司Novellus Systems 牛津仪器有限公司上海代表处 Oxford Instruments 东电电子（上海）有限公司 Tokyo Electron 优利讯（上海）有限公司 UNAXIS PVD 应用材料（中国）有限公司 Applied Materials 诺发系统半导体设备（上海）有限公司Novellus Systems
牛津仪器有限公司上海代表处 Oxford Instruments GermanTech Co. Ltd 上海办公室GermanTech Co. Ltd 优利讯（上海）有限公司 UNAXIS 海德汉（天津）光学电子有限公司北京办事处HEIDENHAIN Corporation 光刻 光刻曝光系统 阿斯麦-中国 ASML-China
三井信息电子（上海）有限公司（代理）Canon 上海乔治.费歇尔管路系统有限公司 上海尼康精机有限公司 Nikon Precision 上海微高精密机械工程有限公司 Shanghai Nanpre Mechanics Co.,Ltd 苏斯贸易（上海）有限公司 SUSS MicroTec AG 涂布/显影系统 迪恩士电子（上海）有限公司
应聘秘书的中英文求职信范文 Model Chinese and English application letter for Secreta ry
应聘秘书的中英文求职信范文 前言：个人简历是求职者给招聘单位发的一份简要介绍，包括个人的基本信息、过往实习工作经验以及求职目标对应聘工作的简要理解，在编写简历时，要强调工作目标和重点，语言精简，避免可能会使你被淘汰的不相关信息。写出一份出色的个人简历不光是对找工作很有用处，更是让陌生人对本人第一步了解和拉进关系的线。本文档根据个人简历内容要求和特点展开说明，具有实践指导意义，便于学习和使用，本文下载后内容可随意调整修改及打印。 英文版 personal details name: miss. liang xiaoyan nationality: china （mainland） current place: guangzhou height/weight: 163 cm marital status: married age: 27 years career objective
application type: jobseeker preferred job title: admin staff/assistant: assistant 、 shipping: 、 secretary/paper staff: working life: 3 title: no title job type: full time expected start date: in a day expected salary: ￥2，000--￥3，500 preferred working place: guangzhou work experience company's name: guangzhou sanny import and export co.， ltdbegin and end date: XX-01-XX-08 enterprise nature: private enterprisesindustry: mechnical follow all the business for old customers. 2> place new order to factory， follow producing process. 3> prepare paper work for custom declaration and inspection.
盘点全球十大半导体IP供应商 时间：2014-12-25 15:58 字体大小：小中大点击： 2013年全球半导体IP市场规模达24.5亿美元，较上一年增长11.5%，其中ARM以43.2%的市占率遥遥领先，稳居龙头地位，Synopsys与ImaginationTechnologies分别以13.9%与9%市占率占据二、三位。而Cadence由于在IP业务策略上改弦更张，并收购了Tensilica 与CosmicCircuits等公司，以163.7%的年增长率跃居排行榜第四位，表现十分抢眼。下面小编为大家一一介绍全球前十大半导体IP供应商们。 NO.10、Vivante Corporation(市占率1%) VivanteCorporation(图芯技术有限公司)是嵌入式图形处理器(GPU)设计领域中的技术先行者。公司总部位于加州森尼韦尔，为全球移动设备和家庭娱乐市场的尖端应用提供一套全面的图形处理器解决方案。种类繁多的2D和2D/3D图形处理器，能够提供高性能和低功耗消耗。 同时，用最小的硅印模为业界标准应用程序接口(OpenGL;ES2.0和 OpenGL;ES1.1OpenVG、DirectX9)提供强大支持。图芯芯片技术，将桌面质量的图象和性能带入位于您卧室、汽车和手掌中的屏幕。Vivante的嵌入式解决方案是可升级的，建立在业界标准之上，且优化功耗、性能和大小，因此，可以有效的区别其他产品。 NO.9、eMemory(市占率1.1%) eMemory(力旺电子)为全球最大的嵌入式非挥发性记忆体(eNVM)技术开发及矽智财供应厂商。力旺电子与全球主要的晶圆代工厂、整合元件制造商以及专业IC设计公司有紧密的合作关系，协助这些合作夥伴导入力旺电子独特开发之矽智财(IP)。
先进半导体设备制造技术及趋势 张云王志越 中国电子科技集团公司第四十五研究所 摘要：本文首先介绍了国内外半导体设备市场，认为市场虽有起伏，但前景良好。从晶圆处理和封装的典型设备入手介绍了当前最先进半导体设备技术，之后总结出半导体设备技术发展的四大趋势
。 １国内外半导体设备市场 根据ＳＥＭＩ的研究，２００６年全球半导体设备市场为３８８．１亿美元，较２００５年增长１８％，主要原因是各地区投资皆有一定程度的成长，少则２０％（日本），多则２２９％（中国大陆），整体设备订单成长率则较２００５年成长５１％，比２００５年底预测值多出２８．４亿美元。 ＳＥＭＩ在ＳＥＭＩＣＯＮＪａｐａｎ展会上发布了年终版半导体资本设备共识预测（ＳＥＭＩＣａｐｉｔａｌＥｑｕｉｐｍｅｎｔＣｏｎ－ｓｅｎｓｕｓＦｏｒｅｃａｓｔ），预计２００７年全球半导体制造设备市场销售增长减缓为３％，达到４１６．８亿美元；２００８年全球半导体设备市场将出现衰退，下滑１．５％；而到２００９年及２０１０年恢 长６％达到３０６．１亿美元，封装设备领域增长１１％至２７．２亿美元，而测试设备领域预计将出现１５％下滑 了１２．４％。表二为按地区划分的市场销售额，包括往年的实际销售额和未来的预测。
虽然半导体设备市场有一定的起伏，但是很明显，市场的前景非常好，总体一直是稳中有升。中国大陆２００６年半导体设备销售额超过２３亿美元，比２００５年增长了７４．４％，中国大陆的市场销售额一直呈上升趋势，国内半导体设备具有非常诱人的市场前景。这和中国半导体产业的快速发展有着直接关系，中国的市场也越来越引起国际半导体设备厂商的重视，投资的力度会越来越大，对我们国内半 复增长，预计实现高个位数增速，至５４．７亿美元。表一为按设备类型２０１０年销售额达到４７９．９亿美元。 ＳＥＭＩ总裁兼ＣＥＯＳｔａｎｌｅｙＴ．Ｍｙｅｒｓ表示，２００７年半导体制造、封 划分的市场销售额，包括往年的实际销售额和未来的预测。 从区域市场分析，北美、日本及 下降装及测试设备销售情况略高于去年，欧洲半导体设备市场出现下滑，成为业界历史上销售额第二高的一年。ＳＥＭＩ成员将继续推进半导体制造设备的强势增长，预计到２０１０年市场销售额达到４８０亿美元。 从设备类型分析，占有最大份额的晶圆处理设备领域２００７年将增 幅度分别为８．９％、３．１％及１１．７％；而台湾和中国大陆销售增长幅度最大，分别为２８．９％和２３．８％，台湾地区销售额达到９４．２亿美元，有史以来第二次超过日本；南韩市场略微增长５．２％，其余地区市场也下降 ４０半导体行业
中英文求职信 提要：随信附上我的简历，如有机会与您面谈，我将十分感谢。即使贵公司认为我还不符合你们的条件，我也将一如既往地关注贵公司的发展，并在此致以最诚挚的祝愿。 更多内容通告 DearSir, Twoyearsasaseniorclerkin*salesdepartmentof*theGreatwallcompanyhave,Ibelievegivenmetheexpe riencetoqualifyforthejobyouadvertisedin51jobwebsite. Since2000Ihavebeenresponsiblefor*allofficedetailsintheadministrationofsales,,Ihavebecomefamili arwiththevarioussalesterritories,andhavealsoinmysparetimeexperienceofhandlingbusinessproblems otherthanmypropersphere. TheyearsbeforeIwasemployedattheGreatwall,Iwasasecretaryfor*LongDragon, Iwasgraduatedat*wuhanUniversity,*twenty-sevenyearsofageandsingle. Iamleavingmypresentpositio mayIseeyouatyourofficetotellyoumoreaboutmyselfandshowyoujusthowwellIcandotheworkyourequ ire. yoursfaithfully, 参考译文: 敬启者: 在51job人才网站上,获悉贵公司招聘人才。本人曾担任长城公司*销售部高级职员两年,自信有充分工作经验,可担任贵公司所招聘的职务。 本人自二零零零年开始,一直担任*售货业务以及函件的撰写工作。在工作期间,除正式业务范围外,与各地区客户颇有来往,并利用公余时间,学会了很多有关商业问题的处理。 在长城公司任职前,我曾在*长龙会计公司担任过秘书工作。在任职期间,学会很多有关会计名词及会计作业程序。 本人*现年二十七岁,未婚,一九九七年毕业于*武汉大学,我希望有机会充分利用自己工作能力,从事更大范围工作之需要,这是我急于离开现职的主要原国。本人现任职的公司老板,对我的工作雄心颇为赞许,因此,愿协助找另谋他职。 如果方便的话,我愿亲赴贵公司办公室晋见阁下,以便详细说明。
德州仪器(TI) LOGO： 德州仪器（Texas Instruments），简称TI，是全球领先的半导体公司，为现实世界的信号处理提供创新的数字信号处理(DSP)及模拟器件技术。除半导体业务外，还提供包括传感与控制、教育产品和数字光源处理解决方案。TI总部位于美国得克萨斯州的达拉斯，并在25多个国家设有制造、设计或销售机构。 德州仪器 (TI) 是全球领先的数字信号处理与模拟技术半导体供应商，亦是推动因特网时代不断发展的半导体引擎。 ----作为实时技术的领导者，TI正在快速发展，在无线与宽带接入等大型市场及数码相机和数字音频等新兴市场方面，TI凭借性能卓越的半导体解决方案不断推动着因特网时代前进的步伐！ ----TI预想未来世界的方方面面都渗透着 TI 产品的点点滴滴，您的每个电话、每次上网、拍的每张照片、听的每首歌都来自 TI 数字信号处理器 (DSP) 及模拟技术的神奇力量。 网址：https://www.doczj.com/doc/1a1210739.html, 意法半导体（ST） LOGO： 意法半导体（ST）集团于1987年6月成立，是由意大利的SGS微电子公司和法国Thomson半导体公司合并而成。1998年5月，SGS-THOMSON Microelectroni cs将公司名称改为意法半导体有限公司 意法半导体是世界最大的半导体公司之一，2006年全年收入98.5亿美元，2007年前半年公司收入46.9亿美元。 公司销售收入在半导体工业五大高速增长市场之间分布均衡（五大市场占2007年销售收入的百分比）：通信（35%），消费（17%），计算机（16%），汽车（16%），工业（16%）。 据最新的工业统计数据，意法半导体是全球第五大半导体厂商，在很多市场居世界领先水平。例如，意法半导体是世界第一大专用模拟芯片和电源转换芯片制造商，世界第一大工业半导体和机顶盒芯片供应商，而且在分立器件、手机相机模块和车用集成电路领域居世界前列。 网址：https://www.doczj.com/doc/1a1210739.html,
半导体制造行业产业链 研究报告 Standardization of sany group #QS8QHH-HHGX8Q8-GNHHJ8-HHMHGN#
半导体制造行业研究报告2017 1 对半导体制造设备行业的整体研究 通过对参加这次展会厂商的总体范围的了解，对半导体制造产业链的总体情况有了基本的认识，半导体制造涉及以下几个相关的细分行业。 晶圆加工设备 在半导体制造中专为晶圆加工的工序提供设备及相关服务的供应商，包括光刻设备、测量与检测设备、沉积设备、刻蚀设备、化学机械抛光(CMP)、清洗设备、热处理设备、离子注入设备等。 厂房设备 包括工厂自动化、工厂设施、电子气体和化学品输送系统、大宗气体输送系统等。晶圆加工材料 在半导体制造中提供原材料和相关服务的供应商，包括多晶硅、硅晶片、光掩膜、电子气体及化学、光阻材料和附属材料、CMP 料浆、低 K 材料等。 测试封装设备 在半导体测试和封装过程中提供设备及其他相关服务的供应商。主要涉及晶圆制程的后道工序，就是将制成的薄片“成品”加工为独立完整的集成电路。包括切割工具及材料、自动测试设备、探针卡、封装材料、引线键合、倒装片封装、烧焊测试、晶圆封装材料等。 测试封装材料 在半导体测试和封装过程中提供材料和相关服务的供应商，包括悍线、层压基板、引线框架、塑封料、贴片胶、上料板等。 子系统、零部件和间接耗材 为设备和系统制造提供子系统、零部件、间接材料及相关服务的厂商，包括质量流量控制、分流系统、石英、石墨和炭化硅等。 2 对电子气体和化学品输送系统行业的详细研究
电子气体和化学品输送系统涉及上游的电子气体产品提供商，半导体行业用阀门管件提供商，常规阀门管件提供商，气体供应设备提供商，气体输送系统设计、施工单位以及下游的后处理设备厂商。 电子气体 电子气体在半导体器件的生产过程中起着非常重要的作用，几乎每一步、每一个生产环节都离不开电子气体，并且电子气体的质量在很大程度上决定了半导体器件性能的好坏。 电子气体的纯度是一个非常重要的指标，其纯度每提高一个数量级,都会极大地推动半导体器件质的飞跃。同时，电子气体纯度也是区分气体厂商技术水平和生产能力的一个重要考量指标。 目前主要的气体产品公司多为欧美公司在中国的分公司，主要有法国液化空气公司，美国普莱克斯，德国林德公司，美国空气产品公司等。国内的品牌有苏州金宏气体，广东华特气体等。 半导体阀门管件 半导体阀门管件是气体输送系统和设备中重要的原材料，阀门管件的性能和质量水平也直接影响着气体输送系统的送气能力和运行稳定性，也会影响半导体产品的质量和性能。严重的情况下，一个阀门出现质量问题可能造成严重的生产事故。 半导体阀门管件的重要性也体现在其成本上，目前阀门管件等原材料的成本占据了气体输送系统和设备的大部分成本，但是，目前绝大部分供应要依赖进口品牌，并且是供不应求（货期较长），这造成了目前系统和设备厂商的运营成本居高不下。 此领域知名的厂商有APTECH,TESCOM,PARKER,SWAGELOK,KITZ，Valex等，但都为进口品牌，价格贵，交货期长（目前一般要2个月以上）。国产品牌目前主要的问题是半导体阀门管件产品种类少，并且产品并不成熟。通过和杰瑞，赛洛克等厂商的交流，了解到目前这些国内厂家公司规模多在一百人左右，新产品的研发能力和研发投入都十分有限，很难在短期内保质保量的供应市场上需求的半导体阀门管件。这也预示着电子气体输送系统和设备厂商在很长一段时间内还是要依赖进口品牌提供相应的材料，这种现状就要求系统和设备厂商有更好的成本和交货周期的管控能力，甚至在承接项目时做好提高其成本预算和延长交货期的准备。
求职信中英文对照范文 求职信是我们求职过程中的一个重要环节，你知道你的中文求职信怎么翻译成英文吗?下面由为你提供的求职信中英文对照范文，希望能帮到你。 求职信中英文对照范文(一)尊敬的先生/小姐： 您好!我从报纸上看到贵公司的招聘信息，我对网页兼职编辑一职很感兴趣。 我现在是出版社的在职编辑，从1998年获得硕士学位后至今，一直在出版社担任编辑工作。两年以来，对出版社编辑的工作已经有了相当的了解和熟悉。经过出版者工作协会的正规培训和两年的工作经验，我相信我有能力担当贵公司所要求的网页编辑任务。 我对计算机有着非常浓厚的兴趣。我能熟练使用FrontPage和DreamWeaver、PhoteShop等网页制作工具。本人自己做了一个个人主页，日访问量已经达到了100人左右。通过互联网，我不仅学到了很多在日常生活中学不到的东西，而且坐在电脑前轻点鼠标就能尽晓天下事的快乐更是别的任何活动所不及的。 由于编辑业务的性质，决定了我拥有灵活的工作时间安排和方便的办公条件，这一切也在客观上为我的兼职编辑的工作提供了必要的帮助。基于对互联网和编辑事务的精通和喜好，以及我自身的客观
条件和贵公司的要求，我相信贵公司能给我提供施展才能的另一片天空，而且我也相信我的努力能让贵公司的事业更上一层楼。 随信附上我的简历，如有机会与您面谈，我将十分感谢。即使贵公司认为我还不符合你们的条件，我也将一如既往地关注贵公司的发展，并在此致以最诚挚的祝愿。 此致 求职信人：xxx 20xx年xx月xx日 April 13,2000 P.O. Box 36 BIIT University Beijing,China 100000 Dear Sir/Madam: Are you searching for a telecommunications manager with expertise in project management and team leadership? I specialize in creating and implementing high-performance strategies that directly impact growth and profitability of large telecommunications companies. In addition to my knowledge of business processes, I also offer proficiency in telecom software development and cutting-edge technologies. I am relocating to Shenzhen and would be interested in
全球半导体设备厂商名单及网站 全球半导体设备厂商名单及网站 A.E. ADVANCED ENGINEERING, LTD. https://www.doczj.com/doc/1a1210739.html, ABAKUS SOFTWARE GMBH www.abakus-soft.de AC SP. ZOO https://www.doczj.com/doc/1a1210739.html, ACCRETECH www.accretech.jp ACCRETECH/TOKYO SEIMITSU EUROPE GMBH www.accretech.jp ACE, INC. https://www.doczj.com/doc/1a1210739.html, ACECO PRECISION MANUFACTURING https://www.doczj.com/doc/1a1210739.html, ACP-IT AG https://www.doczj.com/doc/1a1210739.html, ACUID https://www.doczj.com/doc/1a1210739.html, ADE CORPORATION https://www.doczj.com/doc/1a1210739.html, ADTEC PLASMA TECHNOLOGY CO. LTD. https://www.doczj.com/doc/1a1210739.html, ADVANCE ELECTRIC CO., INC. https://www.doczj.com/doc/1a1210739.html, ADVANCED DICING TECHNOLOGIES https://www.doczj.com/doc/1a1210739.html, ADVANCED FLUID SYSTEMS LTD https://www.doczj.com/doc/1a1210739.html, ADVANTEK GMBH https://www.doczj.com/doc/1a1210739.html, AEM-EVERTECH https://www.doczj.com/doc/1a1210739.html, AES MOTOMATION GMBH https://www.doczj.com/doc/1a1210739.html, AGRU KUNSTSTOFFTECHNIK GMBH www.agru.at AIR PRODUCTS PLC https://www.doczj.com/doc/1a1210739.html, 全球半导体设备厂商名单及网站（二）
大学生兼职求职信（中英文） 献给兼职求职的大学生们： 尊敬的领导： 你好!! 本人是在校学生，对快速成长的贵公司非常感兴趣。从XX日报得知，贵公司提供暑期实习生的职位，在认真阅读了岗位说明之后，我认为本人完全符合贵公司的要求，特此递上这份求职信。 本人在学校学生会各部门中工作和学习，现已升为学生会主席。今年1月份在佛山做过电子产品销售，熟悉各部门业务，包括与客户关系、沟通、及微笑曲线原则。对市场营销、客服服务深有体会和丰厚的实践经验。本人与XX 年曾经到Xx公司参与实习，业绩斐然，获得公司领导的嘉奖，是个难得营销人才。 本人将在暑假放假到XX市兼职学习，如能蒙赐机会，使本人显示如何有助于贵公司达到目标则感激不尽。 我这次暑期实习工作的主要目的是发挥自己的优势为贵公司创造价值，同时继续提升自我能力，并且获得经济上的收益，为明年的上学、生活得到一定保障，望贵公司能给以成全。 我很希望能加盟贵公司，发挥我的潜力。随信附上我的简历。如有机会与您面谈，我将十分感谢。
[大学生兼职求职信] Dear Hiring Manager, I am interested in the part-time position at Sarasota Saddlery advertised in The Sarasotian. I have equine experience, as I have been around horses for over nine years. Not only have I showed and rode horses, but I have also had extensive experience assisting in a barn. Through working with horses, I have acquired a thorough knowle ge of horses, tack, and equine apparel for both horse and rider. While I have equine experience, I also have excellent communication skills and an aptitude for customer service. My past experience as a volunteer at Sarasota Hospital made it necessary for me to focus on providing quality customer service, and also enabled me to work with all types of people. I believe that my communication skills, partnered with my equine knowledge, would make me an asset to your company. Thank you for your consideration. I can be reached at 111-111-1111 or 222-222-2222.. I look forward to hearing from you soon. Sincerely, Your Signature Your Typed Name [大学生兼职求职信] directions: the summer vacation is drawing near. you, liming by name, want to find a part-time job. write an application letter of about 120-150 words within 30 minutes.
世界半导体公司排名———详细 25大半导体厂商排名（2006年统计数据）： 1. 英特尔，营收额313.59亿美元 2. 三星，营收额192.07亿美元 3. 德州仪器，营收额128.32亿美元 4. 东芝，营收额101.66亿美元 5. 意法半导体，营收99.31亿美元 6. Renesas科技，营收82.21亿美元 7. AMD，营收额74.71亿美元 8. Hynix，营收额73.65亿美元 9. NXP，营收额62.21亿美元 10.飞思卡尔，营收额60.59亿美元 11. NEC，营收额56.96亿美元 12. Qimonda，营收额55.49亿美元 13. Micron，营收额52.90亿美元 14. 英飞凌，营收额51.95亿美元 15. 索尼，营收额48.75亿美元 16. 高通，营收额44.66亿美元 17. 松下，营收额41.24亿美元 18. Broadcom，营收额36.57亿美元 19. 夏普，营收额34.76亿美元 20. Elpida，营收额33.54亿美元 21. IBM微电子，营收额31.51亿美元
22. Rohm，营收额29.64亿美元 23. Spansion，营收额26.17亿美元 24. Analog Device，营收额25.99亿美元 25. nVidia，营收额24.75亿美元 飞思卡尔介绍： 飞思卡尔半导体是全球领先的半导体公司，为汽车、消费、工业、网络和无线市场设计并制造嵌入式半导体产品。这家私营企业总部位于德州奥斯汀，在全球30多个国家和地区拥有设计、研发、制造和销售机构。 产品领域： 嵌入式处理器 汽车集成电路 集成通信处理器 适用于2.5G 和3G无线基础设施的射频功率晶体管 基于StarCore? 技术的数字信号处理器(DSP) 下列领域处于领先地位： 8位、16位和32位微控制器 可编程的DSP 无线手持设备射频微处理器 基于Power Architecture?技术的32位嵌入式产品 50多年来，飞思卡尔一直是摩托罗拉下属机构，2004年7月成为独立企业开始了新的生活。此后，公司在董事长兼首席执行官Michel Mayer的领导下，努力提高财务业绩，打造企业文化，构筑全球品牌。 意法半导体（ST）集团介绍
电气图形符号大全 时间：2015/10/09 11:44:44 电气图形符号大全比较详细的介绍电气符号,图标符号以及作用说明，电气符号在电气管理和应用中起到非常重要的作用。 图形符号的种类和组成 图表符号一般分为：限定符号、一般符号、方框符号、以及标记或字符。 限定符号不能单独使用，必须同其他符号组合使用，构成完整的图形符号。 如交流电动机的图表符号，由文字符号、交流的限定符号以及轮廓要素组成。 延时过流继电器图形符号，由测量继电器方框符号要素，特性量值大于整定值时动作和延时动作的限定符号以及电流符号组成。 方框符号一般用在使用单线表示法的图中，如系统图和框图中，由方框符号内带有限定符号以表示对象的功能和系统的组成，如整流器图表符号，由方框符号内带有交流和直流的限定符号以及可变性限定符号组成。 图形符号分类： 限定符号和常用的其他符号包括：电流和电压的种类，可变性，力或运动的方向，流动方向，特性量的动作相关性，效应或相关，性辐，射信号波形，机械控制，操作方法，非电量控制，接地和接机壳等。 导线和连接器件图形符号包括：导线，端子和导线的连接，连接器件，电缆附件等。 无源元件图形符号包括：电阻器，电感器，电容器等。 半导体和电子管图形符号包括：二极管，晶闸管，光电子，光敏器件等。 电能的发生和转换图形符号包括：绕组连接的限定符号，内部连接的绕组，电机部件及类型变压器，电抗器，消弧线圈，制动电阻，串并补电容，变流器，原电池等。 开关，控制和保护装置图形符号包括：触点开关，开关装置和起动器，有或无继电器，测量继电器，熔断器，间隙避雷器等。 测量仪表灯和信号器件图形符号包括：指示积算和记录仪表，遥测器件，电钟，灯，喇叭和电铃等。 电信图形符号包括：交换设备，电话机，传输信号发生器，变换器，放大器，光纤，光缆，光器件等。 电力照明和电信布置图形符号包括：发电厂和变电所，电信局局和机房设施，线路，配线，电什，配电箱，控制台，控制设备，用电设备，插座，开关和照明灯照明引出线等。
德州仪器 (TI LOGO ： 德州仪器（Texas Instruments），简称TI ，是全球领先的半导体公司，为现实世界的信号处理提供创新的数字信号处理(DSP及模拟器件技术。除半导体业务外，还提供包括传感与控制、教育产品和数字光源处理解决方案。TI 总部位于美国得克萨斯州的达拉斯，并在25多个国家设有制造、设计或销售机构。 德州仪器 (TI 是全球领先的数字信号处理与模拟技术半导体供应商，亦是推动因特网时代不断发展的半导体引擎。 ----作为实时技术的领导者，TI 正在快速发展，在无线与宽带接入等大型市场及数码相机和数字音频等新兴市场方面，TI 凭借性能卓越的半导体解决方案不断推动着因特网时代前进的步伐！ ----TI 预想未来世界的方方面面都渗透着 TI 产品的点点滴滴，您的每个电话、每次上网、拍的每张照片、听的每首歌都来自 TI 数字信号处理器 (DSP 及模拟技术的神奇力量。 网址：https://www.doczj.com/doc/1a1210739.html, 意法半导体（ST ）
LOGO ： 意法半导体（ST ）集团于1987年6月成立，是由意大利的SGS 微电子公司和法国Thomson 半导体公司合并而成。1998年5月，SGS-THOMSON Microelectronics 将公司名称改为意法半导体有限公司 意法半导体是世界最大的半导体公司之一，2006年全年收入98.5亿美元，2007年前半年公司收入46.9亿美元。 公司销售收入在半导体工业五大高速增长市场之间分布均衡（五大市场占2007年销售收入的百分比）：通信（35%），消费（17%），计算机（16%），汽车（16%），工业（16%）。 据最新的工业统计数据，意法半导体是全球第五大半导体厂商，在很多市场居世界领先水平。例如，意法半导体是世界第一大专用模拟芯片和电源转换芯片制造商，世界第一大工业半导体和机顶盒芯片供应商，而且在分立器件、手机相机模块和车用集成电路领域居世界前列。 网址：https://www.doczj.com/doc/1a1210739.html, 飞利浦半导体（PHILIPS ）
常考应用文 应用文主要指各种书信, 如求职信、投诉信、申请信、邀请信、推荐信和感谢信等。按文体,书信 可分为私人信件和事务信件 , 考试中涉及到的大都为事务信件。考生应注意书信的格式及重要书信体 的写法。 一、事务信件的格式 英文书信的格式, 尤其是正式的事务信件的格式与汉语的同类书信格式不同。就形式而言 , 英语 的事务信件可分为三种样式 : 现代常用格式 (modified form ) 、齐头式 (blocked form ) 和缩进式(indented form ) 。 1. 现代常用格式 : William Scott ( 写信人姓名 ) College of Education( 写信人地址 ) 5284University of Oregon U.S.A. March 20,2003( 写信日期 ) Mr.John Smith ( 收信人姓名 ) 235Wall Street ( 收信人地址 ) New York 5.N.Y. 16432 U.S.A. Dear Mr.John Smith:( 称呼 ) ( 正文 ) Yours truly,( 套语 ) Signature ( 手写签名 ) William Scott( 打字签名 ) Director of Admissions and Student Affairs ( 职务 ) Enclosure:( 附件 )
2. 齐头式 : William Scott( 写信人姓名 ) College of Education( 写信人地址 ) 5284 University of Oregon U.S.A. March 20,2003( 写信日期 ) Mr.John Smith ( 收信人姓名 ) 235Wall Street ( 收信人地址 ) New York 5.N.Y. 16432 U.S.A. Dear Mr. John Smith:( 称呼 ) ( 正文 ) Yours truly,( 套语 ) Signature ( 手写签名 ) DirectorofAdmissions and Student Affairs ( 职务 ) Enclosure:( 附件 ) 3. 缩进式 : William Sc 。 "( 写信人姓名 ) College of Education( 写信人地址 ) 5284University of Oregon U.S.A. March 20,2003( 写信日期 ) Mr.John Smith ( 收信人姓名 ) 235Wall Street ( 收信人地址 ) New York 5.N.Y. 16432 U.S.A. Dear Mr. John Smith:( 称呼 ) ( 正文 ) Yours sincerely,( 套语 ) Signature ( 手写签名 )
配电箱符号
配电箱符号
常用电气元件文字符号表
电缆型号 NH是耐火，YJV是交联聚乙烯绝缘，聚氯乙烯护套铜芯电缆 4*150是4芯150平方毫米 E70是接地用线为70平方毫米。 你学习一下下面的电缆基础知识就知道了！ 一、电缆型号由下面字母属性组成 （1）类别： H——市内通信电缆 HP——配线电缆 HJ——局用电缆 （2）绝缘： Y——实心聚烯烃绝缘 YF——泡沫聚烯烃绝缘 YP——泡沫／实心皮聚烯烃绝缘 （3）内护层：
A——涂塑铝带粘接屏蔽聚乙烯护套 S——铝，钢双层金属带屏蔽聚乙烯护套 V——聚氯乙烯护套 （4）特征： T——石油膏填充 G——高频隔离 C——自承式 （5）外护层： 23——双层防腐钢带绕包销装聚乙烯外被层 33——单层细钢丝铠装聚乙烯被层 43——单层粗钢丝铠装聚乙烯被层 53——单层钢带皱纹纵包铠装聚乙烯外被层 553——双层钢带皱纹纵包铠装聚乙烯外被层 常用电缆规格型号 一、铜(铝)芯聚氯乙烯绝缘聚氯乙烯绝缘及护套固定敷设用电缆(电线) BV -铜芯聚氯乙烯绝缘电缆（电线） BLV-铝芯聚氯乙烯绝缘电缆（电线） BVR-铜芯聚氯乙烯绝缘电缆（电线） BVV-铜芯聚氯乙烯绝缘聚氯乙烯护套圆形电缆（电线） BLVV-铝芯聚氯乙烯绝缘聚氯乙烯护套圆形电缆（电线） BVVB-铜芯聚氯乙烯绝缘聚氯乙烯护套平形电缆（电线） BLVVB-铝芯聚氯乙烯绝缘聚氯乙烯护套平形电缆（电线） BV-90-铜芯耐热90℃聚乙烯绝缘电线 本产品适用于交流额定电压U/U450/750V及以下的动力、照明、日用电器、仪器仪表及电信设备用铜芯或铝芯聚氯乙烯绝缘电缆（电线） 二、低烟无卤系列产品 低烟无卤阻燃系列电缆电线，WDZ-（加普通型号的电缆电线代号）注：阻燃一般分A、B、C、D四类, 例如：WDZD-VY WDZA-YJY WDZB-YJV23 WDZC-BY WDZ-BVY WDZB-KYJY WDZC-KVV23等供固定（软电缆为移动式）敷设在额定交流电压U0/U为35kV及以下的室内、电缆桥架、电缆管道等固定场合的输配电力线路用，主要应用于高层建筑、医院、剧场、电站、地铁、隧道、舰船、海上石油平台、广播电视中心、计算机中心等人员密集、空间封闭的场所，电缆的额定电压应不低于供电系统的标称电压。