[12]Preparation and thermoelectric properties of A8

-可编辑材料科学专业学术翻译必备词汇编号中文英文1合金alloy 2材料material 3复合材料properties 4制备preparation 5强度strength 6力学mechanical 7力学性能mechanical 8复合composite 9薄膜films 10基体matrix 11增强reinforced 12非晶amorphous 13基复合材料composites14纤维fiber 15纳米nanometer 16金属metal 17合成synthesis 18界面interface 19颗粒particles 20法制备prepared 21尺寸size 22形状shape 23烧结sintering 24磁性magnetic 25断裂fracture 26聚合物polymer 27衍射diffraction 28记忆memory 29陶瓷ceramic 30磨损wear 31表征characterization 32拉伸tensile 33形状记忆memory 34摩擦friction 35碳纤维carbon36粉末powder 37溶胶sol-gel 38凝胶sol-gel 39应变strain 40性能研究properties 41晶粒grain 42粒径size 43硬度hardness 44粒子particles 45涂层coating 46氧化oxidation 47疲劳fatigue 48组织microstructure49石墨graphite 50机械mechanical 51相变phase 52冲击impact 53形貌morphology 54有机organic 55损伤damage 56有限finite 57粉体powder 58无机inorganic 59电化学electrochemical 60梯度gradient 61多孔porous 62树脂resin 63扫描电镜sem 64晶化crystallization 65记忆合金memory 66玻璃glass 67退火annealing 68非晶态amorphous 69溶胶-凝胶sol-gel 70蒙脱土montmorillonite 71样品samples 72粒度size73耐磨wear 74韧性toughness 75介电dielectric 76颗粒增强reinforced 77溅射sputtering 78环氧树脂epoxy 79纳米tio tio 80掺杂doped 81拉伸强度strength 82阻尼damping 83微观结构microstructure84合金化alloying 85制备方法preparation 86沉积deposition87透射电镜tem 88模量modulus 89水热hydrothermal90磨损性wear 91凝固solidification 92贮氢hydrogen 93磨损性能wear 94球磨milling 95分数fraction 96剪切shear 97氧化物oxide 98直径diameter 99蠕变creep 100弹性模量modulus 101储氢hydrogen 102压电piezoelectric 103电阻resistivity 104纤维增强composites 105纳米复合材料preparation 106制备出prepared 107磁性能magnetic 108导电conductive109晶粒尺寸size 110弯曲bending 111光催化tio-可编辑112非晶合金amorphous 113铝基复合材料composites 114金刚石diamond 115沉淀precipitation 116分散dispersion 117电阻率resistivity 118显微组织microstructure119sic 复合材料sic 120硬质合金cemented 121摩擦系数friction 122吸波absorbing 123杂化hybrid 124模板template 125催化剂catalyst 126塑性plastic 127晶体crystal 128sic 颗粒sic 129功能材料materials 130铝合金alloy 131表面积surface 132填充filled 133电导率conductivity 134控溅射sputtering 135金属基复合材料composites 136磁控溅射sputtering 137结晶crystallization 138磁控magnetron 139均匀uniform 140弯曲强度strength 141纳米碳carbon 142偶联coupling 143电化学性能electrochemical 144及性能properties 145al 复合材料composite 146高分子polymer 147本构constitutive148晶格lattice 149编织braided150断裂韧性toughness 151尼龙nylon 152摩擦磨损性friction 153耐磨性wear 154摩擦学tribological 155共晶eutectic 156聚丙烯polypropylene 157半导体semiconductor158偶联剂coupling 159泡沫foam 160前驱precursor 161高温合金superalloy 162显微结构microstructure163氧化铝alumina 164扫描电子显微镜sem 165时效aging 166熔体melt 167凝胶法sol-gel 168橡胶rubber 169微结构microstructure170铸造casting 171铝基aluminum 172抗拉强度strength 173导热thermal 174透射电子显微镜tem 175插层intercalation 176冲击强度impact 177超导superconducting 178记忆效应memory 179固化curing 180晶须whisker 181溶胶-凝胶法制sol-gel 182催化catalytic 183导电性conductivity184环氧epoxy 185晶界grain 186前驱体precursor 187机械性能mechanical188抗弯strength 189粘度viscosity 190热力学thermodynamic 191溶胶-凝胶法制备sol-gel 192块体bulk 193抗弯强度strength 194粘土clay 195微观组织microstructure196孔径pore 197玻璃纤维glass 198压缩compression199摩擦磨损wear 200马氏体martensitic 201制得prepared 202复合材料性能composites 203气氛atmosphere 204制备工艺preparation205平均粒径size 206衬底substrate 207相组成phase 208表面处理surface 209杂化材料hybrid 210材料中materials 211断口fracture 212增强复合材料composites 213马氏体相变transformation214球形spherical 215混杂hybrid 216聚氨酯polyurethane 217纳米材料nanometer 218位错dislocation 219纳米粒子particles 220表面形貌surface 221试样samples 222电学properties 223有序ordered 224电压voltage-可编辑225析出phase 226拉伸性tensile 227大块bulk 228立方cubic 229聚苯胺polyaniline 230抗氧化性oxidation 231增韧toughening232物相phase 233表面改性modification234拉伸性能tensile 235相结构phase 236优异excellent 237介电常数dielectric 238铁电ferroelectric 239复合材料力学性能composites240碳化硅sic 241共混blends 242炭纤维carbon 243复合材料层composite 244挤压extrusion 245表面活性剂surfactant 246阵列arrays 247高分子材料polymer 248应变率strain 249短纤维fiber 250摩擦学性能tribological 251浸渗infiltration 252阻尼性能damping 253室温下room 254复合材料层合板composite 255剪切强度strength 256流变rheological257磨损率wear 258化学气相沉积deposition 259热膨胀thermal 260屏蔽shielding 261发光luminescence 262功能梯度functionally263层合板laminates 264器件devices 265铁氧体ferrite 266刚度stiffness 267介电性能dielectric268xrd 分析xrd 269锐钛矿anatase 270炭黑carbon 271热应力thermal 272材料性能properties 273溶胶-凝胶法sol-gel 274单向unidirectional275衍射仪xrd 276吸氢hydrogen 277水泥cement 278退火温度annealing 279粉末冶金powder 280溶胶凝胶sol-gel 281熔融melt 282钛酸titanate 283磁合金magnetic 284脆性brittle 285金属间化合物intermetallic 286非晶态合金amorphous 287超细ultrafine 288羟基磷灰石hydroxyapatite 289各向异性anisotropy 290镀层coating 291颗粒尺寸size 292拉曼raman 293新材料materials294tic 颗粒tic 295孔隙率porosity 296制备技术preparation 297屈服强度strength 298金红石rutile 299采用溶胶-凝胶sol-gel 300电容量capacity 301热电thermoelectric302抗菌antibacterial 303聚酰亚胺polyimide 304二氧化硅silica 305放电容量capacity 306层板laminates 307微球microspheres 308熔点melting 309屈曲buckling 310包覆coated 311致密化densification 312磁化强度magnetization313疲劳寿命fatigue 314本构关系constitutive 315组织结构microstructure 316综合性能properties 317热塑性thermoplastic 318形核nucleation 319复合粒子composite 320材料制备preparation 321晶化过程crystallization 322层间interlaminar 323陶瓷基ceramic 324多晶polycrystalline 325纳米结构nanostructures 326纳米复合composite 327热导率conductivity 328空心hollow 329致密度density 330x 射线衍射仪xrd 331层状layered 332矫顽力coercivity 333纳米粉体powder 334界面结合interface 335超导体superconductor 336衍射分析diffraction 337纳米粉powders 338磨损机理wear 339泡沫铝aluminum-可编辑340进行表征characterized 341梯度功能gradient 342耐磨性能wear 343平均粒particle 344聚苯乙烯polystyrene 345陶瓷基复合材料composites 346陶瓷材料ceramics 347石墨化graphitization348摩擦材料friction 349熔化melting 350多层multilayer 351及其性能properties 352酚醛树脂resin 353电沉积electrodeposition 354分散剂dispersant 355相图phase 356复合材料界面interface 357壳聚糖chitosan 358抗氧化性能oxidation 359钙钛矿perovskite 360分层delamination 361热循环thermal 362氢量hydrogen 363蒙脱石montmorillonite 364接枝grafting 365导率conductivity 366放氢hydrogen 367微粒particles 368伸长率elongation 369延伸率elongation 370烧结工艺sintering 371层合laminated 372纳米级nanometer 373莫来石mullite 374磁导率permeability375填料filler 376热电材料thermoelectric377射线衍射ray 378铸造法casting 379粒度分布size 380原子力afm381共沉淀coprecipitation 382水解hydrolysis 383抗热thermal 384高能球ball 385干摩擦friction 386聚合物基polymer 387疲劳裂纹fatigue 388分散性dispersion 389硅烷silane 390弛豫relaxation 391物理性能properties 392晶相phase 393饱和磁化强度magnetization 394凝固过程solidification 395共聚物copolymer 396光致发光photoluminescence 397薄膜材料films 398导热系数conductivity399居里curie 400第二相phase 401复合材料制备composites 402多孔材料porous 403水热法hydrothermal404原子力显微镜afm 405压电复合材料piezoelectric406尼龙6nylon 407高能球磨milling 408显微硬度microhardness 409基片substrate 410纳米技术nanotechnology 411直径为diameter 412织构texture 413氮化nitride414热性能properties 415磁致伸缩magnetostriction 416成核nucleation 417老化aging 418细化grain 419压电材料piezoelectric 420纳米晶amorphous421si 合金si 422复合镀层composite 423缠绕winding 424抗氧化oxidation 425表观apparent 426环氧复合材料epoxy 427甲基methyl 428聚乙烯polyethylene 429复合膜composite 430表面修饰surface 431大块非晶amorphous 432结构材料materials 433表面能surface 434材料表面surface 435疲劳性能fatigue 436粘弹性viscoelastic437基体合金alloy 438单相phase 439梯度材料material 440六方hexagonal 441四方tetragonal 442蜂窝honeycomb 443阳极氧化anodic 444塑料plastics 445超塑性superplastic446sem 观察sem 447烧蚀ablation 448复合薄膜films 449树脂基resin 450高聚物polymer 451气相vapor-可编辑452电子能谱xps 453硅烷偶联coupling 454团聚particles 455基底substrate 456断口形貌fracture 457抗压强度strength 458储能storage 459松弛relaxation 460拉曼光谱raman 461孔率porosity 462沸石zeolite 463熔炼melting 464磁体magnet 465sem 分析sem 466润湿性wettability 467电磁屏蔽shielding 468升温heating 469致密dense 470沉淀法precipitation471差热分析dta 472成功制备prepared 473复合体系composites 474浸渍impregnation 475力学行为behavior 476复合粉体powders 477沥青pitch 478磁电阻magnetoresistance 479导电性能conductivity480光电子能谱xps 481材料力学mechanical 482夹层sandwich 483玻璃化glass 484衬底上substrates 485原位复合材料composites 486智能材料materials 487碳化物carbide 488复相composite 489氧化锆zirconia490基体材料matrix 491渗透infiltration 492退火处理annealing 493磨粒wear 494氧化行为oxidation 495细小fine 496基合金alloy 497粒径分布size 498润滑lubrication 499定向凝固solidification500晶格常数lattice 501晶粒度size 502颗粒表面surface 503吸收峰absorption504磨损特性wear 505水热合成hydrothermal506薄膜表面films 507性质研究properties 508试件specimen 509结晶度crystallinity510聚四氟乙烯ptfe 511硅烷偶联剂silane 512碳化carbide 513试验机tester 514结合强度bonding 515薄膜结构films 516晶型crystal 517介电损耗dielectric 518复合涂层coating 519压电陶瓷piezoelectric520磨损量wear 521组织与性能microstructure 522合成法synthesis 523烧结过程sintering 524金属材料materials 525引发剂initiator 526有机蒙脱土montmorillonite527水热法制hydrothermal528再结晶recrystallization 529沉积速率deposition 530非晶相amorphous531尖端tip 532淬火quenching 533亚稳metastable 534穆斯mossbauer 535穆斯堡尔mossbauer 536偏析segregation 537种材料materials 538先驱precursor 539物性properties 540石墨化度graphitization541中空hollow 542弥散particles 543淀粉starch 544水热法制备hydrothermal545涂料coating 546复合粉末powder 547晶粒长大grain 548sem 等sem 549复合材料组织microstructure550界面结构interface 551煅烧calcined 552共混物blends 553结晶行为crystallization554混杂复合材料hybrid 555laves 相laves 556摩擦因数friction 557钛基titanium 558磁性材料magnetic 559制备纳米nanometer 560界面上interface 561晶粒大小size 562阻尼材料damping 563热分析thermal 564复合材料层板laminates 565二氧化钛titanium-可编辑566沉积法deposition567光催化剂tio 568余辉afterglow 569断裂行为fracture 570颗粒大小size 571合金组织alloy 572非晶形成amorphous 573杨氏模量modulus 574前驱物precursor 575过冷alloy 576尖晶石spinel 577化学镀electroless 578溶胶凝胶法制备sol-gel 579本构方程constitutive 580磁学magnetic 581气氛下atmosphere 582钛合金titanium 583微粉powder 584压电性piezoelectric585sic 晶须sic 586应力应变strain 587石英quartz 588热电性thermoelectric589相转变phase 590合成方法synthesis 591热学thermal 592气孔率porosity 593永磁magnetic 594流变性能rheological 595压痕indentation 596热压烧结sintering 597正硅酸乙酯teos 598点阵lattice 599梯度功能材料fgm 600带材tapes 601磨粒磨损wear 602碳含量carbon 603仿生biomimetic 604快速凝固solidification605预制preform 606差示dsc 607发泡foaming 608疲劳损伤fatigue 609尺度size 610镍基高温合金superalloy 611透过率transmittance 612溅射法制sputtering 613结构表征characterization 614差示扫描dsc 615通过sem sem 616水泥基cement 617木材wood 618tem 分析tem 619量热calorimetry 620复合物composites 621铁电薄膜ferroelectric 622共混体系blends 623先驱体precursor 624晶态crystalline 625冲击性能impact 626离心centrifugal 627断裂伸长率elongation 628有机-无机organic-inorganic 629块状bulk 630相沉淀precipitation631织物fabric 632因数coefficient 633合成与表征synthesis 634缺口notch 635靶材target 636弹性体elastomer 637金属氧化物oxide 638均匀化homogenization 639吸收光谱absorption640磨损行为wear 641高岭土kaolin642功能梯度材料fgm 643滞后hysteresis 644气凝胶aerogel 645记忆性memory 646磁流体magnetic 647铁磁ferromagnetic648合金成分alloy 649微米micron 650蠕变性能creep 651聚氯乙烯pvc 652湮没annihilation 653断裂力学fracture 654滑移slip 655差示扫描量热dsc 656等温结晶crystallization 657树脂基复合材料composite 658阳极anodic 659退火后annealing 660发光性properties 661木粉wood 662交联crosslinking 663过渡金属transition 664无定形amorphous 665拉伸试验tensile 666溅射法sputtering 667硅橡胶rubber 668明胶gelatin 669生物相容性biocompatibility 670界面处interface 671陶瓷复合材料composite 672共沉淀法制coprecipitation 673本构模型constitutive674合金材料alloy 675磁矩magnetic 676隐身stealth 677比强度strength 678改性研究modification 679采用粉末powder-可编辑680晶粒细化grain 681抗磨wear 682元合金alloy 683剪切变形shear 684高温超导superconducting 685金红石型rutile 686晶化行为crystallization 687催化性能catalytic 688热挤压extrusion 689微观microstructure690tem 观察tem 691缺口冲击impact 692生物材料biomaterials 693涂覆coating 694纳米氧化nanometer695x 射线光电子能谱xps 696硅灰石wollastonite 697摩擦条件friction 698衍射峰diffraction699块体材料bulk 700溶质solute 701冲击韧性impact 702锐钛矿型anatase 703凝固组织microstructure704磨损试验机tester 705丙烯酸甲酯pmma 706raman 光谱raman 707减振damping 708聚酯polyester 709体材料materials 710航空aerospace 711光吸收absorption 712韧化toughening 713疲劳裂纹扩展fatigue 714超塑superplastic715凝胶法制备gel716半导体材料semiconductor717剪应力shear 718发光材料luminescence719凝胶法制gel 720甲基丙烯酸甲酯pmma 721硬质hard 722摩擦性能friction 723电致变色electrochromic724超细粉powder 725增强相reinforced 726薄带ribbons 727结构弛豫relaxation 728光学材料materials729sic 陶瓷sic 730纤维含量fiber 731高阻尼damping 732镍基nickel 733热导thermal 734奥氏体austenite 735单轴uniaxial 736超导电性superconductivity 737高温氧化oxidation 738树脂基体matrix 739含能energetic 740粘着adhesion 741穆斯堡尔谱mossbauer 742脱层delamination 743反射率reflectivity 744单晶高温合金superalloy 745粘结bonded 746快淬quenching 747熔融插层intercalation 748外加applied 749钙钛矿结构perovskite 750减摩friction 751复合氧化物oxide 752苯乙烯styrene 753合金表面alloy 754爆轰detonation755长余辉afterglow 756断裂过程fracture 757纺织textile。

fundamentals of thermoelectricityoxford 2015The fundamentals of thermoelectricity, as discussed in the Oxford 2015 book, are crucial for understanding the conversion of heat into electrical energy. This field combines principles from thermodynamics, solid-state physics, and materials science to explore the behavior and performance of thermoelectric devices. Thermoelectricity has gained significance in recent years due to its potential application in waste heat recovery, portable power generation, and energy-efficient cooling systems. Let's dive into some key concepts covered in this book.Thermoelectric phenomena arise from a temperature gradient across a material or device. The underlying principle is the Seebeck effect, which describes the generation of an electric voltage when there is a temperature difference between two points in a conductor or semiconductor. This voltage is proportional to the gradient in temperature and depends on the material properties.热电现象是在材料或器件中存在温度梯度时产生的。

二维纳米材料MXenes 的性质及应用研究进展王 剑，周榆力*（西华大学材料科学与工程学院，四川 成都 610039）摘 要：二维层状过渡金属碳/氮化物（MXenes ）以其独特的晶体特征和结构特性受到越来越多的关注，尤其是在能源、催化、环境等领域的应用中体现出优异的性能。

本文系统地综述MXenes 独特的稳定性、机械性能、电子性质、磁性质、光学性质、热电性能、铁电及压电性质，同时总结分析MXenes 在电池领域、电化学电容器领域及催化领域的应用所取得的最新进展及研究成果，最后对MXenes 及其复合材料的未来发展前景及面临的挑战进行探讨。

关键词：二维纳米材料；过渡金属碳/氮化物；MXenes ；物理化学性质；电化学储能领域；化学/光催化领域中图分类号：TB303 文献标志码：A 文章编号：1673–159X(2020)03 − 0076 − 14doi ：10.12198/j.issn.1673 − 159X.3615Research Progress of Characteristics and Applications ofTwo-dimensional Nanomaterial MXenesWANG Jian ，ZHOU Yuli *（School of Materials Science and Engineering , Xihua University , Chengdu 610039 China ）Abstract: Two-dimensional layered transition-metal carbonitrides (MXenes) have attracted increasing attention, and showed excellent performance in the field of energy, catalysis, environment due to the in-triguing crytal characteristics and structure properties. In this review, we systematically introduce the MXenes’ unique stability, mechanical properties, electronic properties, magnetic properties, optical proper-ties, thermoelectric properties, ferroelectric and piezoelectric properties . Meanwhile, we summarize and analyze the latest progress and research results on the application of MXenes in the field of batteries, elec-trochemical capacitors and catalysis. Finally, this review concludes with invigorating perspectives, out-looks and formidable challenges in the future development of MXenes and MXene-based composite materi-als.Keywords: two-dimensional nanomaterials ；transition-metal carbonitrides ；MXenes ；physi-cochemical properties ；electrochemical energy storage field ；chemistry/photocatalysis field收稿日期：2020 − 02 − 22基金项目：西华大学“西华学者”支持计划项目（DC1900007152)。

声子散射对载流子输运特性的影响吕英波【摘要】分析了晶格振动对固体材料中载流子输运特性的影响,重点阐述了长声学波对载流子的散射作用.使用玻尔兹曼输运理论描述了弱场下载流子的输运特性,给出了使用形变势散射和压电散射机制计算载流子迁移率的详细分析和具体公式.【期刊名称】《大学物理》【年(卷),期】2017(036)012【总页数】5页(P10-14)【关键词】迁移率;声子散射;形变势散射;压电散射【作者】吕英波【作者单位】山东大学(威海)空间科学与物理学院,山东威海264209【正文语种】中文【中图分类】O472+.4在固体材料包括各种半导体材料的研究中，载流子的输运特性一直是当前新型光电材料的一个热点研究问题.在半导体中带正电的空穴和带负电的电子在电场力的作用下会发生定向漂移，形成沿电场方向的电流 .载流子的迁移率μ用漂移速度和场强|E|表示载流子在导体或者半导体中传输时，除了受到电场力驱动的定向运动外，还受到持续的散射作用，使得载流子的运动方向不断改变.散射主要来源于晶界散射、杂质散射、缺陷散射和晶格振动散射等，它们在半导体材料的周期性势场之外引入附加势场ΔV，使得载流子在运动过程中遭遇散射.载流子在连续两次散射之间的时间平均值称为平均弛豫时间(〈τ〉).一般使用玻尔兹曼输运理论来描述弱场下载流子的输运特性，将弛豫时间近似和蒙特卡洛方法应用于玻尔兹曼输运方程的求解过程中，可得迁移率为[2]要提高载流子的迁移率，应该提高平均弛豫时间τ或者减小载流子的有效质量m*.传统的半导体材料如硅单晶的迁移率约为102～103cm2/V·s.目前人们希望获得迁移率更高的替代材料，如一维碳纳米管和二维石墨烯层状材料，因此就必须得清楚的了解载流子在材料中所遭受到的散射作用机制.目前学界研究较多且在固体材料中起到重要作用的散射机制为晶格振动/声子散射.因此声子散射是大学物理专业教学中非常重要的一个问题，本文给出声学声子散射的具体分析和计算方法.学生们如能对这个问题有清晰的认识，将非常有助于他们今后从事光电材料研发或者凝聚态物理相关领域的研究.晶格在平衡位置处的热振动使用格波表示.在三维晶格中，每一个格波的波矢q有3n个分支，其中频率最低的3支格波为声学波，频率高的3n-3支格波为光学波.每一支格波都含有1个纵波和2个横波.原胞中所有原子同向振动产生声学波，反向振动产生光学波.电子在晶体中被格波散射可视为电子与声子的碰撞.长声学波散射可近似看为弹性散射，而长光学波散射为非弹性散射.在长声学波中只有纵波在散射中起主要作用.长纵声学波会造成原子分布的疏密变化，使在一个波长中的原子中的一半处于压缩状态，另一半处于膨胀状态.半导体的禁带宽度会随着原子间距的变化而产生变化，如图1(c)所示.纵波引起的能带起伏产生了附加势场ΔE，这一附加势场破坏了原来势场的严格周期性，令电子从k状态散射到k′状态.声学波散射机制通过形变势散射和压电散射来主导迁移率.但是除非特别说明，一般声学声子散射就是指形变势散射.因为在氮化物中压电效应很明显，所以形变势散射和压电散射都必须考虑.一般来讲，在200 K以下形变势散射所占比重大于压电散射，但是在高温下压电效应变强.形变势散射在非极性半导体材料(如Si、Ge)中非常重要.声学声子振动引起晶格原子在平衡位置附近振动，这也意味着原子间距有轻微扰动，进而引起带宽的局域变化，如图1所示.因为带边能级位置的变化是由局域化的晶格形变引起的，所以称这种势能变化为形变势.它的大小就是单位体积变化导致的带边位置变化，通常用Edp或者Dac表示.载流子所遭遇到的形变势散射通常可由电子波动图像来解释[3].电子波遇到较高的势垒时，就会发生透射或者反射，这就是形变势散射的具体形式，如图1(d)所示.根据量子力学理论，在定量分析形变势散射的过程中：1) 不考虑横声学波的作用；2) 散射概率与电子态动量无关；3) 假设电荷输运方向平行于声子的传播方向.在弛豫时间近似下，将形变势理论和第一性原理能带计算以及玻尔兹曼输运理论结合起来，就可以很好的描述碳和有机系统等的输运特性.形变势散射的平均弛豫时间为因此由形变势散射决定的迁移率为[4-6]其中kB为玻尔兹曼常量，e为电子电荷的绝对值，T为温度，ћ为约化普朗克常量为态密度有效质量为电导有效质量，m*为能带有效质量，B为体弹性模量，Ξ为电子-声子耦合能量，由形变势来计算.Ξ代表了载流子和声子的作用，因此Ξ越小，表明载流子被声子散射的概率越小.ρ为材料的密度，s为声速.ΔEi为应力下带边能级的变化值，这里我们选择导带底和价带顶作为电子和空穴的能级.如果考虑载流子浓度的影响，则载流子浓度为f为费米狄拉克分布函数：ε为约化载流子能量，ξ=EF/kBT，为电子的约化化学势.NV为能带简并度(带边态密度方程的意义在于假设对输运性质有贡献的电子限制在费米能级10 kBT的范围之内.在三维晶体中，沿某个晶格方向的迁移率为其中β表示迁移率的方向(β=x, y, z).Cβ为β方向的弹性常数，纵声学波引起的Cβ可由下述公式表示：E0、V0和l0分别为平衡状态下晶体的能量、体积和β方向的晶格常数，而E、Δl 为沿着晶格β方向施加应力之后晶格的总能量和晶格常数的改变值.在这种情况下形变势的计算公式变为如果使用形变势散射模型来计算二维材料的迁移率，则[7，8]其中md=为状态密度平均有效质量.对于一维材料，迁移率公式变为[6]需要注意：在三维材料中Cβ的单位为J·m-3，而在二维材料中Cβ的单位为J·m-2，而在在一维材料中Cβ的单位为J·m-1.应力会使非中心对称的晶体材料中的正负电荷中心发生偏移，从而产生极化电场，这就是压电效应，如图2(a)所示.极化电场使得能带同时上升或下降，如图2(b)所示.这些能带的起伏变化同样会对载流子产生散射作用，形成压电散射.在这种散射作用中，横声学波和纵声学波都起到重要的作用.与形变势散射不同，压电散射中波矢q的方向也非常重要，而且q较小的声子散射中，压电散射的影响大于形变势散射的影响.在共价键为主的半导体中，波矢小的声子不能对载流子的动量进行有效的弛豫，所以在这种材料中形变势散射占主导地位.而在离子键为主或者压电效应比较明显的半导体(如GaN等)中，压电散射则居于主导地位.在低温下由压电散射来决定GaN或者GaN基二维电子气的载流子迁移率.压电散射的平均弛豫时间为[9-11]其中求和是针对纵波和横波模式进行求和，(K2)av的纵向分量和横向分量分别为其中el、et分别为纵向和横向压电应力常数，单位为分别为纵波和横波的球面平均值.cl和ct分别为纵波和横波的球面弹性常数，单位为GPa，m*的单位为me，εs为相对介电常量.1) 对于具有轴向对称性的晶格，如四方结构(4 mm)、纤锌矿和闪锌矿结构，压电应力常量e的纵向(沿r方向)分量[12，13]：而两个横向分量则分别为：他们的球面平均值则为[9]：(e31+2e15)2(e33-e31-e15)22) 对于正交晶格：对于三角晶系：横向弹性常数为Ct=ρ(vt)2=G，为剪切模量；纵向弹性常数为Cl=ρ(vl)2=B+(4/3)G，B为体弹性模量.1) 对于纤锌矿或闪锌矿[9]：2) 对于立方材料如RbCaX3(X= F和Cl)[15]3) 对于四方相晶体[16]：BR=[(2S11+S33)+2(S12+2S13)]-1BV= (2C11+C33)+(C12+2C13)B=GR=15[(4(2S11+S33)-4(S12+2S13)+3(2S44+S66)]-1GV= (2C11+C33-2C12-2C13)+(2C44+C66)G=其中S=1/C,称为弹性压缩系数，S13=[C13/C1]S33=[(C11+C12)/C1]S44=， S66=在固体材料中由于声学支格波具有与电子波动相同量级的波长，因此在载流子的输运过程中起到决定性的作用.声学支格波振动改变晶格点阵的位置，从而引入形变势散射和压电散射.本文根据玻尔兹曼输运理论详细分析了载流子的形变势散射和压电散射，并给出了迁移率的具体计算公式，这有助于应用物理专业的学生从事凝聚态物理的研究工作.【相关文献】[1] 黄昆，韩汝琦.固体物理[M].北京：高等教育出版社，1988: 292.[2] 刘恩科，朱秉生，罗晋升.半导体物理学[M].北京：电子工业出版社，2011：98.[3] Morkoç H. Devices Fundamentals and Applicat ions, in:Nitride Semiconductor Devices[M].Wiley-VCH Verlag GmbH & Co.KGaA, 2013:121.[4] Wang H, Pei Y, LaLonde A D, et al.Weak electron-phonon coupling contributing to high thermoelectric performance in n-type PbSe[J].PNAS,2012, 109: 9705.[5] Xi J, Long M, Tang L,et al. First-principles prediction of charge mobility in carbon and organic nanomaterials[J].2012, Nanoscale 4:4348.[6] Beleznay F B, Bogr F, Ladik J. Charge carrier mobility in quasi-one-dimensional systems: Application to a guanine stack[J].J Chem Phys, 2003, 119: 5690.[7] Bruzzone S, Fiori G. Ab-initio simulations of deformation potentials and electron mobility in chemically modified graphene and two-dimensional hexagonal boron-nitride[J].Appl Phys Lett, 2011, 99: 222108.[8] Qiao J, Kong X, Hu Z X, et al.High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus[J].Nature communications, 2014, 5: 4475.[9] Vitanov S, Nedjalkov M, Palankovski V. in:Proceedings of the 6th international conference on Numerical methods and applications[J].Springer-Verlag, Borovets, Bulgaria, 2007: 197.[10] Kang N L, Choi S D. Scattering effects of phonons in two polymorphic structures ofgallium nitride[J].J Appl Phys, 2009, 106: 063717.[11] Hutson A R. Piezoelectric Scattering and Phonon Drag in ZnO and CdS[J].J Appl Phys,1961, 322287.[12] Zook J D. Piezoelectric Scattering in Semiconductors[J].Phys Rev,1964, 136: A869.[13] Kholkin A L, Pertsev N A, Goltsev A V. Piezoelectricity and Crystal Symmetry, in:A.Safari, E.K. (Eds.) Piezoelectric and Acoustic Materials for TransducerApplications[M].Boston:Springer 2008:23.[14] Feng J. Mechanical properties ofhybrid organic-inorganic CH3NH3BX3 (B= Sn, Pb; X= Br, I) perovskites for solar cell absorbers[J].Apl Materials, 2014, 2: 081801.[15] Mubarak A A. The elastic, electronic and optical properties of RbCaX3 (X= F, Cl) compounds[J].Int.J.Mod.Phys.B, 2014, 28: 1450192.[16] 丁建刚，冯丽萍，刘其军，等.四方晶相SrHfO3弹性性质、电子结构和光学性质的第一性原理计算[J].应用物理, 2014, 1: 64.。

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Table of Contents GraphicA B50 nm Nd0.5Sr0.5CoO3 thin film “as deposited” (A) and “annealed” (B)Brief SummarySingle phase thin films of Nd1-x Sr x CoO3 (x=0, 0.2 and 0.5) perovskite with nanocrystalline morphology have been deposited on single crystalline substrates (SrTiO3 and LaAlO3) by means of rf-magnetron sputtering. Influence of the substrate nature, thickness and thermal treatments have been studied.RF Sputter Deposition of Epitaxial NanocrystallineNd1-x Sr x CoO3 Thin FilmsLorenzo Malavasi1,*, Eliana Quartarone1, Carla Sanna2, Nathascia Lampis2, Alessandra Geddo Lehmann2, Cristina Tealdi1, Maria Cristina Mozzati3, and Giorgio Flor11Dipartimento di Chimica Fisica “M. Rolla” and INSTM, Università di Pavia, Viale Taramelli 16,27100 Pavia, Italy.2Dipartimento di Fisica – Università di Cagliari - Cittadella Universitaria St. Pr.le Monserrato-Sestu km.0.700, I-09042 Monserrato (Ca), Italy.3CNISM, Unità di Pavia and Dipartimento di Fisica “A. Volta”, Università di Pavia, Via Bassi 6, I-27100, Pavia, Italy.RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to)*Corresponding Author: Dr. Lorenzo Malavasi, Dipartimento di Chimica Fisica “M. Rolla”, INSTM, Università di Pavia, V.le Taramelli 16, I-27100, Pavia, Italy. Tel: +39-(0)382-987921 - Fax: +39-(0)382-987575 - E-mail: lorenzo.malavasi@unipv.itABSTRACTIn this paper we report the deposition of epitaxial thin films of Nd1-x Sr x CoO3 with x=0, 0.2 and 0.5 on single crystalline substrates (SrTiO3 and LaAlO3) carried out by means of rf-magnetron sputtering. The deposited films are all completely oriented and epitaxial and characterized by a nanocrystalline morphology. As-deposited films have an average roughness around 1 nm while after the thermal treatment this increases up to 20 nm while preserving the nanocrystalline morphology. All the films deposited on SrTiO3 have shown to be under a certain degree of tensile strain while those on the LaAlO3 experience a compressive strain thus suggesting that at about 50 nm the films are not fully relaxed, even after the thermal treatment. For the x=0.2 composition three different thickness have been investigated revealing an increased strain for the thinner films.KEYWORDS: cobaltite, perovskite, thin films, rf-sputtering, x-ray diffraction.IntroductionCobalt-containing perovskite-type oxides, particularly La-rich oxides, have been the subject of intense research mainly due to the possibility of optimizing their structural and physical properties by doping. The range of possible application for these oxides is wide, extending from components in solid oxides fuel cells (SOFCs), oxygen separation membranes and electrochemical reactors, to sensor devices based on their ability to catalytically oxidize CO and CH4 and reduce NO.1-6 In addition, perovskite cobaltites have received further attention after the observation of elevated Seebeck coefficients in related layered systems such as GdBaCo2O5+δ7-9 which suggest their possible application as thermoelectric materials (TE). Recent reports showed that doped perovskite cobaltites have relatively high figures of merit (Z) and this directly correlates to the different spin states available for the cobalt ions10-13. As a consequence, the TE materials research is the latest field where cobaltites appeared as promising and new compounds.Their magnetic and magnetoresistive properties are also of recent interest. In particular, a debate has been opened regarding the actual spin-state of Co in lanthanum cobaltites. In fact, it has been shown that in the range from 5 to 1000 K the Co ions pass through three different spin-states (low-spin LS, intermediate-spin IS, and high-spin HS) which are intimately connected to the structural as well as internal parameters such as the metal-oxygen bond lengths14. The spin state, in turn, affects the physical properties such as transport, magnetic and optical properties15-18 acting as a sort of “Jahn-Teller switch”, where for certain spin configurations the J-T distortion, for the same Co valence state, is suppressed. A general gradient approximation (GGA) study due to Knižek19 demonstrated that the relative stability of IS and LS depends on the Co-O distances and angles with longer bonds and more open Co-O-Co angle favouring the IS state. It is clear that the internal parameters, such as bond lengths and angles, play a major role in defining the cobaltites physical properties.Among RECoO3 (RE=rare earth) compounds, LaCoO3 and NdCoO3 have been object of previous investigation both as pure compounds and considering the role of divalent dopant (Sr) concentration20-23. Much of the previous work focussed on bulk or single crystalline materials and less on thin films preparation and characterization which, however, is the useful “physical form” for sensing and catalytic as well as TE micro-devices applications. Moreover, it would be desirable to make available nanocrystalline thin films where the high surface-to-volume ration can enhance the cobaltites physical properties.The current literature concerning with the synthesis of cobalt containing perovskite thin films is not rich and mainly devoted to the LaCoO3 and Sr-doped LaCoO3 whose preparation has been carried out by means of sol-gel24-26, screen-printing27, pulsed laser deposition (PLD)28, spray pyrolysis29 and hybrid CVD/sol-gel route30. Thin films of other phases with a different lanthanide on the A-site, such as the object of this work, have not been considered in the previous literature. However, other materials, such as the NdCoO3 perovskite, have already shown to be highly interesting materials for both magnetic18,20, sensing31-33, catalytic34,35, SOFC36,37 and thermoelectric properties38.In this paper we report the synthesis and structural and morphological investigation of oriented epitaxial thin films of Nd1-x Sr x CoO3 with x=0, 0.2 and 0.5 on single crystalline substrates (SrTiO3 and LaAlO3). The Sr-dopant has been chosen since it has shown to be one of the most soluble39 and one of the most favourable dopants in terms of structure distortion, with a tolerance factor close to 1. This leads to low-distorted phases where the Co-O-Co hole hopping is favoured. Increasing Sr-concentration gives origin to higher Co valence state and oxygen vacancies concentration, which are thought to be the active sites for gas adsorption. We stress that among the current literature, to the best of our knowledge, this is the first work reporting the deposition of a cobalt containing perovskites thin films by means of rf-sputtering and, in addition, the first paper reporting the preparation of oriented Nd1-x Sr x CoO3 thin films.Experimental SectionPowder samples of NdCoO3, Nd0.8Sr0.2CoO3 and Nd0.5Sr0.5CoO3 have been prepared by conventional solid state reaction from the proper stoichiometric amount of Nd2O3, Co3O4, and SrCO3 (all Aldrich ≥99,9%) by repeated grinding and firing for 24 h at 900-1050 °C.Thin films were deposited onto single-crystalline SrTiO3 (001), and LaAlO3 (100) (Mateck) by means of off-axis rf-magnetron sputtering (Rial Vacuum). The gas composition in the sputtering chamber was argon and oxygen (16:1) with a total pressure of 4x10-6 bar. The substrate was heated at 700°C and rotated during deposition. The rf-power was set to 150 W. After the deposition the films were annealed at 900°C in pure oxygen for 30 minutes. The chemical composition of starting powders and thin films was checked by means of electron microprobe analysis (EMPA) which confirmed their correct cation ratio.XRR data have been collected by using a Bruker D8 advance reflectometer equipped with a Göbel mirror. The Cu Kα line of a conventional X-ray source powered at 40 kV and 40mA was used for the experiment. The grazing incidence specular reflectivity curves were recorded with a θ-θscan in the 0–3°range. X-ray diffraction (XRD) patterns of starting powders were acquired on a Bruker D8 Discover diffractometer equipped with a Cu anode in a θ-2θgeometry. High resolution reciprocal space maps around symmetric and asymmetric reflections and ω-scans (rocking curves) on the epitaxial layers were performed on a 4-circles “Bruker D8 Discover” diffractometer (Cu anode) equipped with Goebel mirror for parallel beam geometry and pure Kα selection and with a 2-bounces (V-Groove) monochromator (Ge 022) for Kα2 elimination.AFM images (256×256 pixels) were obtained with an AutoProbe CP microscope (ThermoMicroscopes-VEECO), operating in contact mode (C-AFM), by means of sharpened silicon tips onto V-shaped cantilevers (resonance frequency: 15 kHz; force constant: 0.03 N/m). For each analysed film, scans of 5 µm × 5 µm and 2.0 µm × 2.0 µm have been carried out with a scan rate ranging from 1.0 to 1.5 Hz. A standard 2nd order flatten processing of the images has been performed in order to correct the scanner non-linearity.Results and DiscussionFigure 1 reports the refined X-ray diffraction pattern of the Nd 0.8Sr 0.2CoO 3 target material, chosen as a representative example. For all the three samples, namely NdCoO 3, Nd 0.8Sr 0.2CoO 3 and Nd 0.5Sr 0.5CoO 3, the X-ray diffraction patterns can be perfectly refined considering an orthorhombic unit cell (space group n. 62, Pnma ) with lattice constants reported in Table 1.Doping the Nd-site with of Sr induces a progressive expansion of the unit cell from 215.59(1) Å3 to 220.67(2) Å3. This relatively small expansion with respect to the difference in the ionic radii which, for the same coordination (12), are 1.27 Å for Nd 3+ and 1.44 Å for Sr 2+, is due to the concomitant oxidation of Co ions as the Sr-doping occurs. As a matter of fact, we expect that the Sr-doping will increase the hole concentration according to the following equilibria, which take into account the cation replacement and the (partial or total) compensation of oxygen vacancies with external oxygen:x O 32O 'Nd 3O 5O Nd V Sr 2SrO 22NdCoO +++⇔+••(1) x O 2O O 2h 4O 2V +⇔+•••(2)Starting from the pure and Sr-doped NdCoO 3 targets we deposited a series of thin films on single-crystalline substrates. We chose to grow the films on cubic SrTiO 3 (001) and LaAlO 3 (001). The choice has been done considering the lattice constants of the target materials with respect to the parameters of the substrate. In particular, the cubic axis for SrTiO 3 is 3.905 Å while for LaAlO 3 the pseudo-cubic axis is 3.785 Å. Considering a pseudo-cubic cell for the Sr-doped neodymium cobalt perovskites, we may expect an average parameter around 3.78 Å for the NdCoO 3, ~3.79 Å for the Nd 0.8Sr 0.2CoO 3 and ~3.81 Å for the Nd 0.5Sr 0.5CoO 3, respectively. So, in principle, we should be able to look at the role of substrate nature on the growth of the films and on the physical properties induced by possible modulation of the lattice parameters (i.e. strain).The deposited films have been, first of all, characterized through X-ray reflectivity (XRR) to determine their thickness. The estimated standard deviation in the determination of the film thickness by means of XRR is around 4-5%. Figure 2 reports, as an example, the XRR spectrum for the pure NdCoO3 thin film deposited on STO for about 30 minutes. In the inset it is highlighted a small part of the spectrum in order to put in evidence the Kiessig fringes which originate from the interference between successive layers of the film. The separation between two successive maxima in the curve is a direct and reliable measurement of the thin film thickness, t. However, the t value has been calculated from a fit of the experimental curve to a model curve by means of the LEPTOS software (Bruxer AXS). It turned out that the film thickness is around 50 nm, thus indicating a deposition rate of ~1.7 nm/min. For the three cobaltites, namely x=0, 0.2 and 0.5, we deposited 50 nm thin films on STO and LAO substrates. For the x=0.2 composition we also deposited thinner films, i.e. ~8.5 and 17 nm, in order to look at the role of film thickness. For all the deposited films the roughness estimated from the XRR are around or lower than 1 nm prior to oxygen annealing. After the thermal treatment the film roughness is significantly enhanced and reach, usually, values of few nm for the 50 nm thin films. Some more details about the samples roughness is given later in the text when discussing the AFM data. We note that in this work we were mainly interested in looking at thin films (< 100 nm), where the substrate-induced effects are more significant but the preparation route detailed here can be easily applied to the deposition of thicker films of hundreds of nanometers.A full x-ray diffraction characterization has been carried out on the as-deposited as well as annealed thin films of all the three compositions. In the following we will show some representative examples of the general behaviour shown by the samples.Let us look first at the role of post-deposition annealing treatment. Figure 3 reports the X-ray diffraction patterns for the Nd0.8Sr0.2CoO3 50 nm film (labelled as NSCO in Figure 3) measured immediately after the deposition (black line), and after the oxygen annealing (blue line), respectively; in addition, vertical red bars represent the STO peaks (also labelled in the Figure) while the green lines are relative to the orthorhombic Nd0.8Sr0.2CoO3 peaks.First of all we note that the thin films are highly oriented since in their X-ray patterns are clearly visible the only peaks related to those of the substrate. Before the annealing treatment the full-width-at-half-maximum (FWHM) of the peak centred around 48° is 0.352°; after the thermal treatment the peak width slightly reduces to 0.327°, thus suggesting the crystallinity of the films is not significantly improved by this relatively short treatment. From the X-ray patterns of Figure 3 we calculated the out-of-plane parameter for the 50 nm Nd0.8Sr0.2CoO3 thin film before and after the annealing treatment. In the first case the out-of-plane coordinate is 3.781(3) Å while after the heat treatment the parameter slightly contracts to 3.771(3) Å. This is most probably due to the partial oxidation of the cobalt ions with the creation of smaller oxidised species such as Co4+. This effect has been found to be a general trend for all the films.The role of the thermal treatment on thin film morphology was studied. Figure 4 shows the comparison between the morphology of the 50 nm thin film of Nd0.8Sr0.2CoO3 after the deposition (“as-deposited” sample) and after the thermal treatment (“annealed” sample). The as-deposited sample has a very low roughness of about 0.8 nm and is formed by nanocrystalline grains with an average size of about 10-15 nm characterized by a relatively narrow grain size distribution. The treatment at 900°C leads to a significant increase of both the grain size and the roughness, which is now around 5 nm. Peak in the grain size distribution after the thermal treatment is around 80 nm. Let us note, however, that the grains of the annealed sample are actually made of smaller grains of tents of nm; the high temperature treatment led to the formation of bigger island as a consequence of the coalescence of the previous, smaller, islands.Concerning the thin films orientation we can not be conclusive based on these XRD data. In fact, considering the pseudo-cubic cell parameters derived from the orthorhombic ones and assuming that the thin films adopt the Pnma crystal structure of the target material, two orientations of the films, with respect to the substrate, can be found: i) [010]-orientation, and thus the peaks in Figure 3 correspond to the (020) and (040) reflections of the cobaltite, and ii) [101]-orientation, with peaks in the pattern corresponding to the (101) and (202) cobaltite planes. This point is illustrated in more details in Figure1-SI available as Supporting Information, where, for a wider specular scan, the two sets of Miller indices for the two different epitaxial orientations of the Nd 0.8Sr 0.2CoO 3 film are indicated. Finally, we may not exclude that the substrate induced the growth of more symmetric films with respect to the target materials. In particular, cubic or more probable, tetragonal symmetry may not be ruled out based on these data. In the following we will use a pseudocubic approximation to evaluate the relaxation degree of the films.Let us now pass to discuss the role of Sr-doping on the thin films structure and morphology. Figure 5 shows the X-ray diffraction patterns for the three 50 nm thin films grown on STO (001) substrate for those two regions of the patterns where the (002) and (004) cubic diffraction peaks due to the perovskite are present. The out-of-plane lattice parameter for the three films is reported in Table 2. As can be seen, by increasing the Sr-concentration the parameter tends to expand, in accordance with the higher ionic radius of Sr with respect to Nd. We may note that the out of plane parameter for the three films is smaller than the pseudo-cubic parameter calculated from the bulk lattice constants. This is most probably directly connected to the tensile strain induced by the substrate, that is, a decreasing in the growth direction and expanding in the plane, which has an in-plane parameter of 3.90 Å. To evaluate the in plane lattice parameters and the relaxation degree of the films substratebulk substrate strained a a a a R −−= - in pseudocubic (tetragonal) approximation - high resolution reciprocal space maps (RSM) have been performed around the asymmetric cubic reflection (103)+ (grazing exit). The results for the 50 nm thick Sr-doped films with x =0, 0.2, 0.5 are shown in Figure 6A-C. The estimated in-plane lattice parameters are a =3.847(6) Å, 3.836(4) Å and 3.820(3) Å, leading to a relaxation degree R of about 50%, 60% and 90% respectively for the three compositions. We note that even if the film of composition Nd 0.5Sr 0.5CoO 3 appears to be to most relaxed among the analyzed samples, its epitaxial quality is still high as shown by the narrow rocking curve on the (002) pseudocubic reflection (Figure 7a) and also by the RSM around the symmetric (002) cubic reflection (Figure 7b) which shows that the width of the Bragg diffusion along the L direction (which depends on the out of plane texture) is thesame for the film and of the oriented single crystalline substrate. We also note in the (002) map the absence of the film truncation rod intensity, which indicates a three dimensional growth in agreement with AFM results.The same structural investigation has been carried out for the three 50 nm films on LAO (001). Figure 8 reports the results for the undoped sample, i.e. NdCoO3. First we note that also with the LAO substrate the film growth is completely oriented. In this case the lattice parameters of the substrate and those of the cobalt perovskites are closer with respect to the STO substrate. The pattern in Figure 8 shows the presence of just two peaks exactly located at the position of the (001) and (002) reflections of the LAO substrate. In the inset of the Figure it is presented the comparison of the diffraction patterns of the NdCoO3 film on LAO (red line) and of the substrate (black line). As can be appreciated, the only difference between the two patterns is the lack, in the film pattern, of the clear Kα1/Kα2 separation which is clearly visible in the substrate pattern. This means that the film has grown with lattice constants so close to those of the LAO substrates that is not possible to discriminate between them. This is also due to the FWHM of the films being of the order of 0.3° with respect to the FWHM of the single crystal peaks whish is around 0.05°. Overall, this result means that the out-of-plane parameter for the NdCoO3 film on LAO is 3.785(5) Å and considering that the in-plane parameter for the LAO material is 3.785 Å this suggests that the perfect match of the lattice parameters between the film and substrate leads to the growth of a nearly cubic film.For the other two compositions (patterns not shown), i.e. x=0.2 and 0.5, the out-of-plane parameter is bigger. For x=0.2 it is about 3.816(3) Å, to be compared to the pseudo-cubic parameter of the bulk phase being ~3.79 Å. In this case the film grows under the effect of a compressive strain, that is, an expanding in the growth direction and a decreasing in the plane. For the x=0.5 sample the effect is even higher, with a out-of-plane parameter close to 3.820(2) Å.We also note that different Sr-dopings lead to different morphologies. Figure 9 shows, as an example, the AFM measurements carried out on the x=0.5 50 nm film deposited on STO (001). This has to be compared to Figure 4, which reports the same data for the x=0.2 composition. As can be seen, byincreasing the Sr-doping, the surface roughness increases from 0.8 nm (x=0.2) to 1.1 nm (x=0.5) and it is clearly composed by very tiny grains which are practically undetectable on the surface of the x=0.2 film. A greater difference between the two samples is found looking at the surfaces of the annealed samples. The difference in the surface roughness between the two compositions is now higher: ~4.6 nm for the x=0.2 film and ~23 nm for the x=0.5 film. Also the morphology is significantly different, with elongated island for lower Sr-doping with respect to the round-shaped found for x=0.5. This difference is interesting and is most probably correlated to the different growth properties (both adsorption and diffusion processes) of the two compositions induced by the presence of a higher doping level of Sr. More details about this topic are beyond the scope of the present paper and will be considered in the future. However, for practical applications in which surface properties are crucial, the knowledge of this doping-dependence of both roughness and morphology has to be taken into account.For the Nd0.8Sr0.2CoO3 sample grown on STO we tried to look at the role of film thickness on the structural properties. Figure 10 shows the X-ray diffraction pattern for three thicknesses: 8.5, 17 and 50 nm. The out-of-plane parameter for the thicker film is, as mentioned above, 3.771(3) Å, while for the other two films it is slightly reduced to about 3.753(5) Å. For both 8.5 and 17 nm the diffraction peaks looks also wider with respect to the 50 nm sample being the 8.5 nm the one with the highest FWHM (ca. 1.2°). The presence of a smaller lattice parameter for the 8.5 and 17 nm samples suggest a stronger effect of the substrate on the film which induces a higher degree of strain; in both cases the samples are less relaxed with respect to the 50 nm sample. The presence of broader diffraction peaks for the thinner samples may be the result of the presence of a relaxation gradient or/and of an interface substrate/film layer contribution where the chemical composition of this layer is different with respect to that of the film “bulk”.Finally, the influence of substrate temperature during thin film deposition is put in prominence through Figure 11. Here, it is reported the XRD pattern of a NdCoO3 thin film deposited while heating the substrate to 400°C instead of heating to 700°C, as done for the other films considered in this work; all the other deposition parameters were kept constant. As can be appreciated, beside the cobaltite phaseother intense peaks appear in the pattern (marked with an asterisk). At present we are not able to undoubtedly associate these peaks to a precise phase. The peak located at about 38° might be the (102) and (201) reflections of the orthorhombic cobaltite, thus indicating that in order to obtain full oriented films the deposition has to occur by heating the substrate to high temperatures. Anyway, peak at around 65.5° can not be related to the cobaltite structure. As a consequence, another possibility is that these peaks originate from a second phase of still uncertain composition (which is not, however, any of the simple metal oxides of Co or Nd). We also remark that the FWHM of the NdCoO3 peaks is around 0.55° which strongly indicates that higher deposition temperatures are effective in improving the thin film crystallinity.ConclusionIn this paper we report, to the best of our knowledge, the first deposition of epitaxial thin films of Nd1-x Sr x CoO3 with x=0, 0.2 and 0.5 on single crystalline substrates (SrTiO3 and LaAlO3) and also the first deposition by means of rf-sputtering of a cobalt perovskite film.Our investigation has shown that epitaxial single phase thin films can be successfully deposited by means of rf-magnetron sputtering if the substrates is heated at high temperatures (700°C); lower substrate temperature has shown to lead to multi-phase materials with a low degree of crystallinity.All the deposited thin films posses a nanocrystalline morphology, even after the post-deposition annealing treatments with average grain size lower than 100 nm. This aspect is of significant interest, particularly when considering the possible applications of these materials as sensors and/or catalysts.Post-deposition annealing treatments in oxygen are efficient in increasing the oxygen content of the samples, as witnessed by the lattice constant reduction.All the films deposited on SrTiO3 have shown to be under a tensile strain while those on the LaAlO3 experience a compressive strain thus suggesting that at about 50 nm the films are not fully relaxed even after the thermal treatment. In addition, by reducing the film thickness more strained films have been found for the x=0.2 composition. This tuning of the film strain may lead to improved and unexpected magnetic and transport properties as well as induce positive effects on the catalytic/sensing activity of the film. Future work is planned in order to fully characterized the physical properties of the deposited films.AcknowledgementFinancial support from the Italian Ministry of Scientific Research (MIUR) by PRIN Projects (2004) is gratefully acknowledged. One of us (L.M.) gratefully acknowledges the financial support of the “Accademia Nazionale dei Lincei”. Dr. Oleg Gorbenko is gratefully acknowledged for useful discussion.“Supporting Information Available: Figure showing the two possible epitaxial orientations of the film with respect to the cubic substrate. This material is available free of charge via the Internet at .”References1.Tejuca L.G.; Fierro J.L.G.; Tascon J.M.D. Adv. Cat.1989, 36, 237-328.2.Steele B.C.H. Solid State Ionics1996, 86-88, 1223-1234.3.Doshi R.; Alcock C.B.; Carberry J.J. Catal. Lett. 1993,18, 337-343.4.Forni L.; Rossetti I. Appl. Catal. B-Environ. 2002, 38(1), 29-37.ne J.A.; Benson S.J.; Waller D.; Kilner J.A. 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第52卷第8期2023年8月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALSVol.52㊀No.8August,2023薄膜热电堆(Cu/Cu55Ni45)热流传感器的制备工艺及性能研究冯楠茗1,代㊀波1,王㊀勇2,李㊀伟1(1.西南科技大学环境友好能源材料国家重点实验室,绵阳㊀621000;2.山东大学空间科学与物理学院,威海㊀264200)摘要:本文首先通过磁控溅射技术在单晶Si和Al2O3陶瓷衬底上分别依次沉积厚度为600nm的Cu和Cu55Ni45薄膜,然后使用微加工技术在10mmˑ10mm的衬底区域内制备了200对串联的热电偶组成薄膜热电堆结构,最后采用反应溅射联合硬掩膜沉积了不同厚度的氧化铝热阻层,使串联的热电偶分别产生冷端和热端㊂根据Seebeck效应,在热流的作用下薄膜热电堆冷热两端的温差使传感器输出热电信号,实现对热流密度的测量㊂通过对薄膜热电堆的表征与标定,结果表明:沉积在Si衬底与Al2O3陶瓷衬底上的Cu/Cu55Ni45热电堆中,Cu膜粗糙度分别为20和60nm,Cu55Ni45膜粗糙度分别为15和20nm,电阻分别为38.2Ω和2.83kΩ,灵敏度分别为0.06945和0.02697mV/(kW㊃m-2)㊂具有不同表面粗糙度的单晶Si衬底与Al2O3陶瓷衬底会影响在其表面沉积的Cu/Cu55Ni45热电堆表面粗糙度,进而导致薄膜热电堆产生电阻大小差异,此外,Cu/Cu55Ni45热流传感器的输出热电势与热流密度呈现良好的线性关系㊂关键词:薄膜热电堆;磁控溅射;微加工;Seebeck效应;热流传感器;灵敏度中图分类号:TP212㊀㊀文献标志码:A㊀㊀文章编号:1000-985X(2023)08-1523-09 Preparation Process and Performance of Thin FilmThermopile(Cu/Cu55Ni45)Heat Flux SensorFENG Nanming1,DAI Bo1,WANG Yong2,LI Wei1(1.State Key Laboratory of Environment-friendly Energy Materials,Southwest University of Science and Technology,Mianyang621000,China;2.School of Space Science and Physics,Shandong University,Weihai264200,China)Abstract:In this work,Cu and Cu55Ni45thin films with a thickness of600nm were firstly deposited on single crystal Si and Al2O3ceramic substrates by magnetron sputtering respectively.Then,the thin film thermopiles composed of200pairs of in-series thermocouples were fabricated by microfabrication technology in10mmˑ10mm substrate area.Finally,aluminum oxide layers were deposited by reactive magnetron sputtering as thermal resistance layers,with the help of hard mask.The different thickness of the aluminum oxide layer produces the cold and hot ends in the thin film thermopile,giving rise to a voltage under the irradiation of heat flux by the Seebeck effect,realizing the measurement of heat flux.The thin film thermopiles were analyzed and calibrated.The results show that in the Cu/Cu55Ni45thermopiles deposited on the Si substrate and Al2O3ceramic substrate,the roughness of the Cu films are20and60nm,the roughness of Cu55Ni45films are15and 20nm,the electrical resistance of thermopiles are38.2Ωand2.83kΩ,the sensitivity of thermopiles are0.06945and 0.02697mV/(kW㊃m-2),respectively.The surface roughness of Cu/Cu55Ni45thermopiles deposited on single crystal Si substrate and Al2O3ceramic substrate with different surface roughness will be affected,resulting in the difference in electrical resistance of thin film thermopile.In addition,the output thermoelectric voltage exhibits a good linear relationship with heat flux.Key words:thin film thermopile;magnetron sputtering;microfabrication;Seebeck effect;heat flux sensor;sensitivity㊀㊀收稿日期:2023-02-27㊀㊀基金项目:环境友好能源材料国家重点实验室自主课题(20fksy23,21fksy27)㊀㊀作者简介:冯楠茗(1995 ),男,贵州省人,硕士研究生㊂E-mail:984050669@㊀㊀通信作者:代㊀波,博士,教授㊂E-mail:xdaibo@1524㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷0㊀引㊀㊀言热量传递是一种普遍的自然现象,一般以热传导㊁热对流和热辐射等形式进行㊂随着科学技术高速发展,只把温度作为热量传递的唯一信息是远远不够的[1]㊂温度是标量,热流是矢量,温度只反映能量作用的结果,不能反映能量传递的过程㊂为了更好地控制热过程,需要获得热流信息来预测系统能量的变化趋势㊂热流传感器(heat flux sensor,HFS)作为测量热量传递的关键元件,广泛应用于机械㊁能源㊁冶金㊁建筑㊁设备,以及航空航天等各个领域,主要类型包括同轴热电偶[2-3]㊁戈登计[4-5]和热电堆[6-7]等㊂伴随着薄膜制备技术的发展,薄膜型热流传感器也随之兴起,通过物理气相沉积(physical vapor deposition,PVD)或化学气相沉积(chemical vapor deposition,CVD)技术制备的薄膜热流传感器因为其器件尺寸非常小,对测试环境的热量流动干扰非常小;同时因为其厚度是纳米到微米数量级,可用于快速瞬态热通量测量,频率响应最高达1MHz [8-10]㊂基于Seebeck 效应的热流传感器灵敏度主要来源于冷热结点的温差,薄膜热流传感器因其热阻层厚度在纳米级到微米级间,冷热结点温差非常小㊂为了制备高灵敏度的热流传感器,将多组热电偶串联组成热电堆结构,从而达到放大输出热电势的目的,可用于监测微小的热流变化㊂热电堆式热流传感器是目前最常见的一类热流传感器之一[11]㊂最早通过将热电堆缠绕在热阻层上,测量垂直通过热阻层的热通量[12]㊂但缠绕式的热电堆传感器尺寸通常较大,应用场景有限㊂新型薄膜型热电堆(thin film thermopile,THTP)热流传感器将薄膜制备技术与微加工技术结合,传感器尺寸可控制在毫米级别,扩大了热流传感器的应用范围㊂2019年,Zhang 等[13]通过丝网印刷技术在Al 2O 3衬底上制备了厚度为20μm 的Pt-Pt /Rh 热电堆,在3~57kW/m 2热流范围内,传感器灵敏度为0.025~0.03mV /(kW㊃m -2),可在50~900ħ稳定工作㊂2020年,Tian 等[14]设计的微型热流传感器在0.12~1.10MW /m 2热流范围内,灵敏度为1.50ˑ10-6V /(W㊃m -2),并在能量密度为0.44MW /m 2的200个激光脉冲测试下表现出良好的重复性㊂Fu 等[15]使用磁控溅射在AlN 衬底上制备W-5Re /W-26Re 热电堆,设计了Al 2O 3-SiO 2-Al 2O 3三明治结构的热阻层,该热电堆在1000ħ高温环境下可工作1h,灵敏度为38μV /(W㊃cm -2)㊂2021年,Li 等[16]制备了ITO /In 2O 3陶瓷型薄膜热电堆,研究冷热节点以垂直㊁水平和阶梯三种分布方式对传感器灵敏度的影响,结果表明垂直分布时传感器灵敏度最高,达到280.8μV /(kW㊃m -2)㊂崔云先等[17]针对高温环境制作了PtRh30-PtRh6薄膜热电堆,传感器灵敏度为0.01μV /(W㊃m -2),可在1200ħ环境下稳定工作㊂2022年,Wang 等[18]在PCB 电路板上使用电镀的方式制备Cu /Ni 热电堆,在0~20kW /m 2的热流范围内,灵敏度为0.267μV /(W㊃m -2),响应时间为5s,传感器的微结构具有灵活嵌入电子产品中测量芯片热流分布的潜力㊂郭林琪等[19]研制的Pt /Pt-13Rh 薄膜热电堆在0~110kW /m 2热流范围内灵敏度达8.04ˑ10-6V /(kW㊃m -2),并且在1000ħ环境下保温3h 后灵敏度不受影响㊂热电偶的工作原理是基于Seebeck 效应,将串联的热电偶组成热电堆的结构从而达到增强传感器热电信号输出的目的,如公式(1)所示㊂结合一维傅里叶传热定律,如公式(2)与图1所示,可以根据传感器输出的热电信号得到热流信息㊂图1㊀傅里叶一维传热示意图Fig.1㊀Fourier one-dimensional heat transfer diagram 热电堆输出热电势V OUT 为V OUT =N ΔT (S A -S B )=N ΔTS AB (1)式中:N 为热电堆串联热电偶组数,ΔT 为热电偶冷热两端温差,S A 和S B 为组成热电偶材料的塞贝克系数,S AB 为两者塞贝克系数差值㊂热电堆对热流的测量基于傅里叶一维传热定律,公式为q =-λΔT Δx =-λT 1-T 2d x (2)式中:q 为热流,单位W /m 2;λ为热阻层热导率,单位W /(m㊃K);ΔT /Δx 表示垂直于等温面方向的温度梯度㊂㊀第8期冯楠茗等:薄膜热电堆(Cu /Cu55Ni45)热流传感器的制备工艺及性能研究1525㊀结合热电堆输出公式(1),可以得到q =λd x ㊃S AB ㊃N㊃V OUT =C ㊃V OUT (3)式中:C 为热流计系数,其物理意义是当传感器接收到的热流时输出1mV 的热电势㊂公式(4)中,将C 的倒数定义为灵敏度K ,K 越大,表明相同热流下传感器输出热电势越大,公式为K =d x ㊃S AB ㊃N λ=V OUT q(4)图2㊀热电偶原理示意图Fig.2㊀Schematic diagram of thermocouple principle 根据公式(1)~(4)可以推断,提高热电堆输出的方式包括串联更多的热电偶,提高冷热两端的温差以及选择Seebeck 系数相差较大的材料作为热电偶㊂如图2所示,通过增大热电偶两端覆盖的热阻层厚度差,使其产生更大的温差,以达到提高输出的目的最为便捷,然而保护层的厚度过大会使传感器响应时间过长,不利于瞬时测量㊂目前评价热流传感器的性能指标有:灵敏度㊁响应时间㊁工作温度范围㊁尺寸以及特殊环境下的力学强度等㊂因此,在设计热流传感器时,需要综合考虑热电堆材料㊁热阻层㊁基底材料以及厚度等因素对于传感器在不同工作环境下的性能影响㊂本文以Cu55Ni45㊁Cu 和Al 2O 3作为热电堆组成材料,旨在研究热电堆微加工工艺,解决热电堆制备过程中难导通,易短路等问题㊂并探究薄膜热电堆热流传感器输出信号与热流强度之间的关系,以及不同衬底上热电堆灵敏度的差异㊂1㊀实㊀㊀验选择中低温区常用的T 型(Cu /Cu55Ni45)薄膜热电偶,这种热电偶的输出热电势较大,且材料成本低,在300ħ以下输出热电势与热流具有良好的线性关系㊂磁控溅射技术制备薄膜具有沉积速度快㊁致密度高以及结合力好等优点,制备的薄膜成分与靶材成分的一致性高㊂选择单晶Si 片和99Al 2O 3陶瓷片作为热电堆衬底,Si 表面有一层很薄的SiO 2,具备电绝缘性,Si 片尺寸为20mm ˑ20mm ˑ0.525mm,表面粗糙度小于1nm,99Al 2O 3陶瓷片尺寸为20mm ˑ20mm ˑ1mm,表面粗糙度小于200nm㊂结合微加工技术,在衬底上制备200对串联的Cu /Cu55Ni45薄膜热电偶组成热电堆结构㊂使用反应溅射在热电堆表面沉积Al 2O 3保护层,配合硬掩模板使保护层在热电堆连接处形成600nm 厚度差,连接导线与热沉后完成传感器制备,如图3所示㊂图3㊀薄膜热电堆热流传感器制备流程图Fig.3㊀Flow chart for fabrication of heat flow sensor of thin film thermopile 1.1㊀薄膜制备根据Chopra 等[20]研究结果,只有当Cu 和Cu55Ni45薄膜厚度超过250nm 时,才能获得较高的热电动势㊂陈皓帆等[21]研究Cu 膜的临界尺寸在600nm 左右,CuNi 的临界尺寸在400nm 左右㊂金属薄膜具有明显的尺寸效应,即薄膜的电学性能会因膜厚的不同而改变㊂通常金属薄膜的电阻率远大于块体金属,随着薄膜厚度的增加,电阻率逐渐趋近于块体,但随着薄膜厚度的增加,薄膜的内应力也随之增大,使得薄膜对基底的结合力下降㊂因此本试验为保证膜厚大于临界尺寸,设计的Cu 和Cu55Ni45薄膜厚度均为600nm㊂首先将Si 片与Al 2O 3陶瓷片分别使用丙酮㊁去离子水和无水乙醇超声清洗15min,再使用氮气吹干,得到干净清洁的衬底㊂采用JPG-450直流磁控溅射沉积系统制备薄膜,靶材为北京晶迈中科材料技术有限公司生产,Cu 靶纯度99.999%,Cu55Ni45靶的Cu 与Ni 质量比为55ʒ45㊂在溅射室真空度小于2.0ˑ10-4Pa1526㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷的真空环境内溅射薄膜,工作气压为0.5Pa㊂在Si 片上分别沉积Cu 和Cu55Ni45薄膜,使用台阶仪DektaXT 对样品厚度进行测量,根据溅射时间计算出Cu 膜生长速率约为42.3nm /min,Cu55Ni45膜生长速率约为35.2nm /min㊂确定生长速率后开始热电堆的制备,热电堆组成薄膜溅射的工艺参数如表1所示㊂沉积600nm 厚度的Cu55Ni45薄膜后,进行第一次光刻,再次沉积600nm 厚度的Cu 膜,对样品进行第二次光刻后得到串联的热电堆结构,最后通过反应溅射制备Al 2O 3保护层,热端保护层厚度为400nm,冷端保护层厚度为1000nm㊂研究[22-23]表明,覆盖了氧化铝保护层的热电偶能够有效防止金属在高温环境下蒸发导致的传感器失效,并保证传感器在高温下的热稳定性以延长使用寿命㊂反应溅射与射频溅射Al 2O 3相比,溅射速率更快,通过调节O 2的流量改变溅射过程中Al 的氧化程度,经过多次试验确定溅射工艺如表1中所示㊂表1㊀薄膜溅射工艺Table 1㊀Technology process of thin film sputteringThin film Current /mA Ar flow /(mL㊃min -1)O 2flow /(mL㊃min -1)Thickness /nm Cu55Ni4520065 600Cu 25065 600Al 2O 330080 3.41000(400)1.2㊀微加工将沉积了600nm 厚的Cu55Ni45薄膜的衬底放置在KW-4C 型台式匀胶机上甩胶,低速500r /min,9s;高速2000r /min,40s㊂旋涂厚度约为2μm 的NR9-1500P 光刻胶之后,在型号为MODELKW-4AH 平板加热台进行前烘,150ħ,120s㊂使用中国科学院光电技术研究所研制的URE-2000/35型深紫外深度光刻机,配合掩模板在光强为14mW /cm 2下曝光25s,将样品放置在平面加热台上后烘,100ħ,120s㊂在ZX-238显影液中浸泡25s 取出,此时样品如图4(a)所示㊂使用50ħ的FeCl 3溶液对薄膜图形化处理,FeCl 3与去离子水质量比为1ʒ2,对样品进行湿法刻蚀5s,使用丙酮去除线条表面光刻胶得到样品如图4(b)所示㊂在第一次光刻结束后获得长度为1mm,宽度为0.1mm 的Cu55Ni45线条㊂为了保证热电堆连接良好,因此为Cu55Ni45线段包裹一层长度为0.9mm,宽度为0.11mm 的光刻胶㊂这样做的目的是在保证第二次湿法刻图4㊀薄膜热电堆微加工流程图Fig.4㊀Microfabrication process of thin film thermopile 蚀时,Cu55Ni45线段不会出现侧腐蚀的情况,并且能够使串联的热电堆中出现一个接触良好的结点,结点面积为0.05mm ˑ0.1mm㊂对刻蚀好的线条进行第二次甩胶,得到如图4(c)所示的样品㊂对带有光刻胶的样品再次溅射沉积600nm 厚的Cu 膜,如图4(d)所示,重复第一次光刻的步骤,如图4(e)所示,获得长度为1mm,宽度为0.1mm 的Cu 线条,并且与康铜线条首尾相连,完成热电堆的制备,如图4(f)所示㊂1.3㊀表征与测试方法使用日本Rigaku 公司生产的Smart Lab 型X 射线衍射(X-ray diffraction,XRD)仪表征薄膜物相,工作电压40V,工作电流40mA,X 射线衍射实验所用入射源为波长为1.5406Å的Cu K α射线,扫描步长为10(ʎ)/min,在5ʎ~80ʎ对薄膜进行扫描测试㊂使用德国Carl Zeiss 公司生产的Sigma300型场发射扫描电子显微镜对薄膜表面进行X 射线能谱(energy dispersive spectrometer,EDS)扫描,表征薄膜组成元素以及各元素原子量百分比㊂使用SPA-300HV 原子力显微镜(atomic force microscope,AFM)表征薄膜的表面粗糙度,扫描区域为3μm ˑ3μm㊂使用KEITHLEY 4200-SCS 参数分析仪测试薄膜电阻值,将探针正负极与薄膜接触,设定起始输入电压㊁终止电压及电压步长,根据欧姆定律R =U /I ,计算得到不同电压下薄膜电阻值,将所有电压下的电阻值求和并取平均值,得到薄膜的电阻㊂使用实验室自主搭建的高温黑体平板炉对待测传感器灵敏度进行标定,该系统主要由电源控制系统㊁加㊀第8期冯楠茗等:薄膜热电堆(Cu /Cu55Ni45)热流传感器的制备工艺及性能研究1527㊀热腔与数据采集系统组成,其最大热流可达3MW /m 2,最大功率可达40kW㊂2㊀结果与讨论2.1㊀薄膜XRD 结果分析如图5所示,Cu 膜在2θ角为43.297ʎ㊁50.433ʎ㊁74.13ʎ时有明显的衍射峰,分别对应(111)㊁(200)㊁(220)晶面,其余衍射峰均为衬底峰㊂Cu 与Ni 均为面心立方结构,但Ni 原子半径较Cu 原子小,根据Bragg 定律,XRD 表征Cu55Ni45薄膜时,衍射峰相较Cu 膜向右偏移,衍射峰所对应的晶面与Cu 膜相同㊂XRD 测试结果表明,使用磁控溅射沉积的Cu55Ni45和Cu 膜结晶性好,呈现多晶结构,未出现金属氧化物杂相㊂2.2㊀保护层EDS 分析Al 2O 3保护层制备工艺如表1所示,使用此工艺在Si 片上沉积Al 2O 3薄膜,扫描电子显微镜对薄膜表面进行EDS 分析测试,测试结果图6所示,框线内为扫描面区域,其中O 元素占60.26%,Al 元素占39.17%,Si 元素占0.57%(原子数分数),由于Al 2O 3薄膜沉积在硅片上,硅片表面存在一层很薄的SiO 2,因此假设检测到的Si 元素全部来自于SiO 2,于是计算得到O 元素和Al 元素原子比约为1.51,接近标准值1.5㊂使用KEITHLEY 4200-SCS 参数分析仪测试薄膜导电性,结果表明薄膜绝缘,结合EDS 结果推断,Al 2O 3薄膜被成功制备㊂图5㊀Cu55Ni45和Cu 膜XRD 图谱Fig.5㊀XRD patterns of Cu55Ni45and Cu films 图6㊀Al 2O 3薄膜的EDSFig.6㊀EDS of Al 2O 3thin film 2.3㊀传感器电阻测试与分析使用KEITHLEY 4200-SCS 参数分析仪测量热电堆电阻,在显微镜下将两个探针与热电堆电极接触,起始电压为0V,终止电压为0.5V,步长为0.002V,在该测试条件下,测得在硅片上沉积的热电堆电阻为38.2Ω,Al 2O 3陶瓷片上沉积的热电堆电阻为2.83kΩ㊂在相同工艺以及相同结构下,Al 2O 3陶瓷片上的热电堆电阻远大于硅片,使用AFM 表征薄膜的表面粗糙度,如图7所示,沉积在Si 衬底上的Cu 和Cu55Ni45薄膜的粗糙度均小于沉积在Al 2O 3衬底上的薄膜㊂表面粗糙度的大小可以反映在溅射过程中薄膜的生长情况㊂镀膜后薄膜表面粗糙度受到衬底粗糙度的影响,在粗糙度较高的衬底上,薄膜粗糙度会有一定程度上的降低,在粗糙度很低的衬底上,溅射薄膜对表面的粗糙度影响很小,甚至会提高成膜表面的粗糙度[24]㊂金属薄膜电阻的形成来自自由电子的碰撞,失去了来自电场提供的定向速度,薄膜表面粗糙度的提高使得电子发生碰撞概率提高㊂在图7中可观察到,Cu㊁Cu55Ni45薄膜在Si 衬底上的粗糙度分别为20㊁15nm,在Al 2O 3衬底上的粗糙度分别为60㊁20nm,纵向不同高度的颗粒导致了不同的薄膜表面粗糙度,从而影响电子在薄膜中的输运,导致薄膜电阻率的变化[25],最终反映在沉积在Al 2O 3陶瓷片上的热电堆电阻远大于沉积在Si 片上的热电堆电阻㊂2.4㊀传感器灵敏度标定与分析通常传感器连接导线的方式有3种,分别是锡焊连接㊁导电银浆粘接,以及对电极位置打通孔穿Pt 丝,将导线引到传感器背面㊂锡的熔点较低,约为230ħ,随着温度上升锡逐渐液化,机械强度下降,不适用于较大热流下的实验㊂本实验采用在电极处打通孔穿Pt 丝,导电银浆涂在电极处固定Pt 丝㊂这种方式不论在机械强度还是在耐高温方面都较强㊂将连接好导线的传感器通过导热胶固定在圆形铜柱热沉上,避免测试1528㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷过程中传感器升温速度过快,如图8(a)所示㊂对于热流传感器的标定方式主要有直接标定和对比标定两种,热源主要是辐射和对流热源[26]㊂本文采用比较标定方法,该方法可适用的热场环境和温度范围大,在对流传热和辐射传热的环境中都有不错的适用性㊂用比较法标定热流传感器是根据在相同校准热源和校准位置下,由已校准的热流传感器测量热源输出的热流,以此作为已知条件,分析待校准热流传感器信号输出与热流的关系,并获得待校准热流传感器的响应特性[27]㊂图7㊀薄膜AFM 照片㊂(a)Si 衬底上的Cu 膜;(b)Si 衬底上的Cu55Ni45膜;(c)Al 2O 3衬底上的Cu 膜;(d)Al 2O 3衬底上的Cu55Ni45膜Fig.7㊀AFM images of films.(a)Cu film on the Si substrate;(b)Cu55Ni45film on the Si substrate;(c)Cu film on the Al 2O 3substrate;(d)Cu55Ni45film on the Al 2O 3substrate 图8㊀THTP 传感器的连接与测试㊂(a)待测热流传感器实物图;(b)对比标定示意图Fig.8㊀Connection and testing of THTP sensor.(a)Physical picture of developed heat flux sensor;(b)schematic diagram of comparison calibration principle 使用高温平板黑体炉对待测样品灵敏度进行标定,待测样品与标准戈登热流计(灵敏度:0.0228mV/(kW㊃m -2))等距分布在石墨板两侧,电流将石墨板加热向两侧辐射出相同能量密度的热流,由于样品与标准戈登热流计受热面距加热的石墨板距离相等,接收到相同能量密度的热流,如图8(b)所示㊂如图9(a)所示,左侧纵坐标表示被测传感器吸收石墨板释放热流后输出该热流密度下的热电势,单位㊀第8期冯楠茗等:薄膜热电堆(Cu /Cu55Ni45)热流传感器的制备工艺及性能研究1529㊀为mV,右侧纵坐标表示戈登计测量石墨板在该时刻释放的热流密度,单位为kW /m 2㊂在相同时刻下,以Si 为衬底的热流传感器在0~105kW /m 2的热流范围内与标准戈登计对比标定过程中的数据㊂可以明显看到传感器在热流逐渐上升过程中输出的热电势在时间尺度上与热流密度基本保持相同的变化趋势,当热流靠近100kW /m 2附近,传感器输出的热电势出现漂移,上升趋势减缓㊂对采集到的热电信号进行拟合,如图9(b)所示,该传感器的灵敏度为0.06945mV /(kW㊃m -2),优于标准戈登计的灵敏度[0.0228mV /(kW㊃m -2)]㊂待测传感器输出的热电势与热流密度呈线性关系,表明在该热流范围内传感器的测量结果准确度较高,R 2达到0.98588㊂图9㊀Si 衬底热流传感器的标定与拟合㊂(a)比标定数据;(b)数值拟合Fig.9㊀Calibration and fitting of Si substrate HFS.(a)Comparison and calibration data;(b)data fitting 图10(a)是以Al 2O 3陶瓷为衬底的热流传感器在0~160kW /m 2的范围内与标准戈登计对比标定过程中采集的数据,传感器的热电信号随着热流密度的上升而上升,且上升趋势与热流密度保持一致,当热流密度达到160kW /m 2后,输出热电势随热流密度的下降而下降㊂对采集到的热电信号进行拟合,如图10(b)所示,该传感器的灵敏度为0.02697mV /(kW㊃m -2),优于标准戈登热流计的灵敏度0.0228mV /(kW㊃m -2),同时R 2达到0.994㊂图10㊀Al 2O 3衬底HFS 的标定与拟合㊂(a)Al 2O 3衬底热流传感器对比标定数据;(b)Al 2O 3衬底热流传感器数据拟合Fig.10㊀Calibration and fitting of Al 2O 3substrate HFS.(a)Comparison and calibration data of Al 2O 3substrate HFS;(b)data fitting of Al 2O 3substrate HFS以Si 为衬底的传感器的灵敏度远大于以Al 2O 3为衬底的传感器,两者热电堆薄膜的材料㊁制备工艺㊁结构及几何尺寸均相同,仅由衬底不同引起薄膜热电堆电阻的差异㊂根据2.3小结分析可知,衬底粗糙度影响薄膜表面粗糙度,电阻的形成与薄膜自由电子输运有关,表面粗糙度大的薄膜会阻碍自由电子的定向运动,增加自由电子间的相互碰撞几率,从而使薄膜电阻率提高㊂根据电阻率与电阻的关系可知,相同几何尺寸的导体,其电阻随电阻率的增大而增大㊂Cattani 等[28]研究金属和合金材料电性能对其塞贝克系数的影响,如公式(5)所示㊂1530㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷S=π2k2B T3eE F d lnσ(E)d ln E[]E=E F(5)式中:k B为玻尔兹曼常数;T为绝对温度;e为电子电荷;E F为金属的费米能;σ(E)为电子能量为E时金属的电导率㊂由公式(5)可知,材料的塞贝克系数与材料电导率有关,根据公式(1),热电信号的输出与组成热电堆材料S AB有关㊂实际上,对于不同材料,电导率对塞贝克系数的影响程度不同,S AB需要通过实验确定,根据杨丽红等[29]研究表明T型热电偶的热电势率与金属电导率成正相关,电阻率是电导率的倒数,因此热电阻率越大的热电偶,其热电势率越小㊂本实验中,T型热电偶作为热电堆传感器组成单元,从而热电堆电阻率越大,传感器灵敏度越小㊂3㊀结㊀㊀论1)通过直流磁控溅射技术和微加工技术在单晶Si和99Al2O3衬底上制备出结晶度与导电性良好的薄膜热电堆结构;使用反应磁控溅射制备Al2O3薄膜,薄膜O原子与Al原子之比为1.51,同时具备电绝缘性㊂2)在单晶Si和Al2O3陶瓷衬底上制备Cu/Cu55Ni45薄膜热电堆热流传感器中,以表面粗糙度低的单晶Si作为衬底的热流传感器灵敏度为0.06945mV/(kW㊃m-2),高于以表面粗糙度高的Al2O3陶瓷作为衬底的热流传感器灵敏度0.02697mV/(kW㊃m-2)㊂3)热电堆电阻会对热流传感器的灵敏度产生影响,在由相同几何尺寸和材料组成的热电堆中,电阻小的传感器灵敏度更大㊂参考文献[1]㊀李㊀娟,张丛春,杨申勇,等.MEMS薄膜热流传感器研制[J].传感器与微系统,2019,38(5):71-73.LI J,ZHANG C C,YANG S Y,et al.Research and fabrication of MEMS thin-film heat 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