衬底温度对钇稳定氧化锆薄膜择优生长的影响

使用脉冲激光沉积(PLD)技术在Si(100)衬底上沉积钇稳定的氧化锆(YSZ)薄膜,用XRD分析薄膜的结晶取向,SEM和AFM观测薄膜表面形貌,研究了在200-650℃的不同衬底温度下薄膜的择优生长.结果表明:衬底温度较低的YSZ薄膜为非晶组织,衬底温度为300-500℃时YSZ晶粒以表面能低的(111)面首先择优生长,衬底温度超过550℃后晶粒活化能提高而使表面能较高的(100)晶粒择优生长.YSZ薄膜是典型的岛状三维生长模式,较高的衬底温度有利于原子在衬底表面迁移和重排结晶长大.同其它沉积技术相比,用PLD技术能在比较低的衬底温度下在Si(100)表面原位外延生长出较高质量的YSZ薄膜.     

高分子辅助沉积法制备LaNiO3外延导电薄膜

近年来LaNiO₃(LNO)作为铁电超晶格、超导异质结和催化剂材料引起了广泛关注。本研究采用简便、低成本的高分子辅助沉积法(Polymer Assisted Deposition, PAD), 在(001)取向的SrTiO₃(STO)单晶衬底上制备了导电性能优异的LNO外延薄膜, 并对其进行各种结构和电学表征。摇摆曲线半高宽为0.38°, 表明LNO薄膜结晶度良好。高分辨XRD的φ扫描进一步证实LNO薄膜在STO衬底上异质外延生长。原位变温XRD测试进一步表征了LNO薄膜的外延生长过程。结果表明, 聚合物分解之后金属阳离子在单晶基体上有序释放并外延结晶。XPS结果表明, 采用PAD制备的LaNiO₃薄膜不存在氧空位。薄膜表面光滑, 粗糙度为0.67 nm。在10~300 K温度区间内的变温电阻率表明LNO薄膜具有良好的导电性能。上述结果表明：PAD制备的LaNiO₃薄膜具有较好的综合性能, PAD在制备外延功能薄膜材料方面具有很大的潜力。     

残余应力对SrRuO3薄膜磁学及电输运性能的影响

采用射频磁控溅射法在单晶SrTiO₃ (STO)衬底和硅(Si)衬底上制备出不同取向的SrRuO₃ (SRO)薄膜, 对薄膜的残余应力进行了分析, 并研究了应力对不同取向SRO薄膜磁学性能与电输运特性的影响。根据X射线衍射(XRD)结果分析可知, Si基SRO薄膜为多晶单轴取向薄膜, 且应力来源主要为热失配拉应力; STO基SRO薄膜为外延薄膜, 其应力主要为热失配压应力和外延压应力; 磁学性能测试表明, (001)取向SRO薄膜比(110)取向薄膜拥有更高的居里温度T_C; 压应力提高了(001)取向SRO薄膜的T_C, 却降低了(110)取向薄膜的T_C。电阻性能测试表明, 对于在同种类型衬底上沉积的SRO薄膜, (001)取向的薄膜的剩余表面电阻比(RRR)高于(110)取向的薄膜。另外, 拉应力引起了薄膜微结构的无序度增加, 弱化了表面电阻率的温度依赖性, 提高了金属绝缘体转变温度(T_MI)。     

Si(111)衬底上3C-SiC的固源MBE异质外延生长

国内首次利用固源分子束外延(MBE)技术,在衬底温度为1100℃时,以Si(111)为衬底成功地外延生长出了3C-SiC单晶薄膜。通过X射线衍射(XRD)、拉曼光谱(Raman)以及原位反射高能电子衍射(RHEED)等手段研究了外延薄膜的晶型、结晶质量、外延膜与衬底的外延取向关系,并考察了薄膜制备过程中衬底的碳化对薄膜质量的影响。结果表明,外延膜与衬底晶格取向完全一致;碳化可以减小SiC和衬底Si之间的晶格失配、释放应力、引入成核中心,有利于薄膜单晶质量的提高;碳化温度存在最佳值,这一现象与成核过程有关。     

Ge基GaAs薄膜和InAs量子点MBE生长研究

采用分子束外延(MBE)法,在优化Ge衬底退火工艺的基础上,通过对比在(001)面偏<111>方向分别为0°、2°、4°和6°的Ge衬底上生长的GaAs薄膜,发现当Ge衬底的偏角为6°时有利于高质量GaAs薄膜的生长;通过改变迁移增强外延(MEE)的生长温度,发现在GaAs成核温度为375℃时,可在6°偏角的Ge衬底上获得质量最好的GaAs薄膜。通过摸索GaAs/Ge衬底上InAs量子点的生长工艺,实现了高效的InAs量子点光致发光,其性能接近GaAs衬底上直接生长的InAs量子点的水平。     

脉冲激光沉积法在Si(111)衬底上生长高c轴取向LiNbO3薄膜

在氧压20Pa,衬底温度600℃,靶材与衬底距离4cm的最优化条件下,利用脉冲激光沉积(PLD)技术首次在无诱导电压和任何缓冲层的情况下,在单晶Si(111)衬底上生长具有优良结晶品质和高c轴取向的LiNbO3晶体薄膜.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)对LiNbO3薄膜的结晶品质,择优取向性以及表面形貌进行了系统的分析.结果表明生长出了具有优异晶体质量的c轴取向LiNbO3薄膜,表面光滑平整且无裂纹产生,表面粗糙度约4.8nm,有利于硅基光电子器件的制备和利用.     

GaN/Al_2O_3(0001)上Ge薄膜的CVD外延生长

本工作采用化学气相淀积方法,以GcH4为反应气源,以InN/CaN/Al2O3(0001)复合衬底作陪片,在CaN/Al2O3(0001)复合衬底上外延生长了Ge薄膜,并对生长机理进行了探讨.研究结果表明直接在N2气氛下外延得到了多晶Ge薄膜,表面较平整,由吸收光谱得出其带隙宽度为0.78 eV;经过H2预处理,CaN/Al2O3复合衬底表面出现金属In的沉积,外延Ge薄膜沿(111)方向择优生长,晶体质量较高.     

Si(100)衬底上PLD法制备高取向度AlN薄膜

采用脉冲激光沉积法(PLD),以KrF准分子为脉冲激光源,Si(100)为衬底,同时引 入缓冲层TiN和Ti_0.8Al_0.2N,制备了结晶质量优异的A1N薄膜,X射线衍射(XRD)及反射 式高能电子衍射(RHEED)分析表明A1N薄膜呈(001)取向、二维层状生长.研究发现,薄膜 的生长模式依赖于缓冲层种类,直接在Si衬底上或MgO／Si衬底上的A1N薄膜呈三维岛状生 长;而同时引入缓冲层TiN和Ti_0.8Al_0.2N时,A1N薄膜呈二维层状生长.此外,激光能量密 度大小对A1N薄膜的结晶性有显著的影响,激光能量密度过大,薄膜表面粗糙,有颗粒状沉积 物生成.在氮气气氛中沉积,能使薄膜的取向由(001)改变为(100).     

钙钛矿型氧化物SrTiO3/BaTiO3多层膜的激光分子束外延生长研究

用激光分子束外延技术在SrTiO3(001)衬底上外延生长SrTiO3/BaTiO3多层膜,通过反射式高能电子衍射(RHEED)原位实时监测并结合原子力显微镜(AFM),研究了不同基片温度下所生长薄膜的表面平整度,利用X射线衍射(XRD)对外延薄膜进行了结构分析,结果表明薄膜具有二维生长模式,在基片温度为380～470℃之间生长的薄膜具有原子级光滑,并且具有完全C轴取向.同时运用X射线光电子能谱(XPS)研究了薄膜界面的互扩散,结果表明降低制备薄膜时的基片温度有利于减少互扩散.     

衬底温度对Si(111)衬底上MBE异质外延3C-SiC薄膜的影响

利用固源分子束外延(SSMBE)技术, 在Si(111)衬底上异质外延生长3C-SiC单晶薄膜, 通过RHEED、XRD、AFM、XPS等实验方法研究了衬底温度对薄膜结构、形貌和化学组分的影响. 研究结果表明, 1000℃生长的样品具有好的结晶质量和单晶性. 在更高的衬底温度下生长, 会导致大的孔洞形成, 衬底和薄膜间大的热失配使降温过程中薄膜内形成更多位错, 从而使晶体质量变差. 在低衬底温度下生长, 由于偏离理想的化学配比也会导致薄膜的晶体质量降低.     

IF钢铁素体区热轧和退火过程中织构的演变

研究了一种Ti—IF（Interstitial—free）钢在铁素体区热轧和退火过程中织构的变化．由于轧制过程摩擦的影响,热轧织构和退火织构在厚度方向上都有很大的差异．在钢板的表层,热轧织构的主要组分是{110}（001）,退火后表层的铁素体晶粒没有发生再结晶,该组分转变为（001）（110）;在试样的中心和1／4面,热轧织构组分主要是较弱的（111）／／ND（板法向）织构和部分（110）／／RD且在{001}（110）处最强;退火后中心面上的晶粒发生了完全再结晶,{001}组分转变为（111）／／ND组分使（111）／／ND织构成为唯一织构组分且在{111}（112）处最强．     

Solid-phase crystallization of β-FeSi2 thin film in Fe/Si structure

Dependence of solid-phase growth of β-FeSi₂ thin films on the crystal orientation of Si substrates has been investigated by using a-Fe (thickness: 20 nm)/c-Si(100), (110) and (111) stacked structures. X-ray diffraction (XRD) measurements suggested that the substrate orientation dependence of the formation rate of β-FeSi₂ was as follows: (100)>(111)>(110). This dependence can be explained on the basis of the lattice mismatch between β-FeSi₂ and Si substrates, i.e., the lattice mismatch between β-FeSi₂(100) and Si(100), β-FeSi₂(110) or (101) and Si(111), and β-FeSi₂(010) or (001) and Si(110) of 1.4-2.0%, 5.3-5.5% and 9.2%, respectively. The substrate orientation dependence of solid-phase growth becomes relatively remarkable for very thin films.     

Study of electrochemically grown copper indium diselenide (CIS) thin films for photovoltaic applications

CIS thin films have been grown electrochemically from an aqueous electrolyte at room temperature on fluorine doped tin oxide coated glass substrate at different deposition potentials ranging from ?0.7 to ?1.0 V versus Ag/AgCl reference electrode. Cyclic voltammetry was studied at slow scan rate to optimize the deposition potential. The thin film samples were selenized in a tubular furnace at 400 °C for 20 min. X-ray diffraction and Raman analysis was used to study the structural properties. Optical absorption, scanning electron microscopy and energy dispersive X-ray analysis (EDAX) have been used to investigate the band-gap, surface morphology and compositional analysis. Electrical properties were studied with the help of current–voltage measurements. Conductivity type for CIS thin films was studied by using photo-electrochemical study. The prominent reflections (112), (204/220) and (312/116) of tetragonal chalcopyrite CIS have been revealed for all as-grown and selenized samples. The energy band gap of the selenized CIS thin film deposited at various deposition potentials was found to be ~1.03 to 1.24 eV. Granular, uniform and void free surface was observed in as-prepared sample, while large clusters were noticed in selenized samples. EDAX results reveal that the stoichiometric CIS thin film are deposited ?0.8 V, however, Cu-rich and In-rich CIS layers were grown at lower and higher cathodic deposition potentials, deviated from ?0.8 V. The values ideality factor (η) calculated from I–V measurements were found to be decreased upon selenization. The Raman spectra of stoichiometric CIS thin film shows dominant A1 mode with spectral features sensitive to the microcrystalline quality of the layers. A ordered defect compound layer and secondary phases of CuSe are observed in In-rich and Cu-rich CIS layers, respectively.     

Structure and magnetic properties of Fe epitaxial thin films prepared by UHV rf magnetron sputtering on GaAs single-crystal substrates

Fe thin films were prepared on GaAs single-crystal substrates of (100)_B3, (110)_B3, and (111)_B3 orientations by ultra high vacuum rf magnetron sputtering. The effects of substrate orientation and substrate temperature on the film growth, the structure, and the magnetic properties were investigated. On GaAs(100)_B3 substrates, Fe(100)_bcc single-crystal films are obtained at 300 °C, whereas Fe films consisting of bcc(100) and bcc(221) crystals epitaxially grow at room temperature (RT). Fe(110)_bcc and Fe(111)_bcc single-crystal films are respectively obtained on GaAs(110)_B3 and GaAs(111)_B3 substrates at RT-300 °C. The in-plane lattice spacings of these Fe epitaxial films are 0-9% larger than the out-of-plane lattice spacings due to accommodation of lattice mismatch between the films and the substrates. The film strain is decreased by employing an elevated substrate temperature of 300 °C. The in-plane magnetization properties are reflecting the magnetocrystalline anisotropy of bulk bcc-Fe crystal.     

单靶磁控溅射制备铜铟硒和铜铟锌硒薄膜及其结构、光学性质研究

采用单靶磁控溅射法制备了铜铟硒(CIS)和铜铟锌硒(CIZS)薄膜。XRD表征发现CIZS-300出现了与其它薄膜不同的择优取向, 分析认为贫铜的状态和适宜温度可能促使薄膜择优取向从(112)向(220)转化; 拉曼光谱在171 cm^-1处出现的较强峰, 和206 cm^-1处出现的较弱峰, 分别为A₁和B₂振动模式, 而Zn的掺入导致A₁拉曼峰的宽化和蓝移; Zn的掺入使Cu含量改变进而使CIZS禁带宽度增大, 这是由于Se的p轨道和Cu的d轨道杂化引起的; SEM测试结果表明CIZS薄膜表面比CIS表面更为紧密、平滑。     

MBE方法在GaAs(001)衬底上外延生长GaSb膜

利用分子束外延方法(MBE)在GaAs(001)衬底上外延生长了GaSb薄膜,利用高分辨透射电子显微镜(HRTEM)、原子力显微镜(AFM)、Hall效应(HallEffect)和低温光荧光谱(LTPL)等手段对薄膜的晶体质量、电学性能和光学质量进行了研究。发现直接生长的GaSb膜表面平整,空穴迁移率较高。引入GaSb/AlSb超晶格可有效阻断进入GaSb外延层的穿通位错,对应的PL谱强度增强,材料的光学质量变好。     

CVD金刚石的晶体形态及界面位向关系

综述了CVD金刚石的晶体形态及界面位向关系.用SEM观察CVD金刚石晶粒形态主要有立方体、长方体、八面体、立方八面体、孪晶八面体、十面体和二十面体颗粒以及球形金刚石,讨论了晶粒的形成条件.用TEM观察则主要有单晶体、孪晶八面体和五重孪晶体形态.界面位向关系主要有:Si(001)//Diamond(001),Si<110>//Diamond<110(50078018);Si(111)//Diamond(111),Si<110>//Diamond<110>和Si(110)//Diamond(110),Si[110]//Diamond[111].     

Mechanisms of layer growth during molecular beam epitaxy of semiconductor films

This paper reviews our present understanding of particular aspects of the surface processes involved in the growth of epitaxial semiconductor films by molecular beam epitaxy. Emphasis is placed on adatom migration and incorporation on GaAs (001) substrates during the growth of GaAs, a comparison with equivalent growth effects on (110) and (111)A oriented substrates, and the influence of mismatch and substrate orientation on growth mode and strain relaxation in the InAs/GaAs system. A brief indication of surface segregation behaviour is also included.     

Contribution study of properties of copper indium diselenide thin films

Stoichiometric powder of CuInSe₂ (CIS) was prepared from molten stoichiometric quantities of the elements. The structure analyzed by X-ray diffraction powder (XRD), shows mainly the chalcopyrite phase. CIS polycrystalline thin films deposited from this powder have been grown on glass substrates in vacuum by thermal evaporation method. The structural and electrical properties of both as-deposited and annealed films were studied using X-ray diffraction and dark conductivity measurements respectively. As-prepared films at room temperature showed an amorphous structure. However, the chalcopyrite structure with (112) preferential orientation was observed after annealing in vacuum at 400 °C during 30 min. The influence of the annealing process on the dark conductivity of the films was also discussed.     

Structural studies of ZnS thin films grown on GaAs by RF magnetron sputtering

X-ray diffraction (XRD) studies of ZnS thin films grown on GaAs (001) substrates at different temperatures by rf magnetron sputtering have been carried out using CuKα radiation. XRD analysis reveals that deposited films below 335 °C, assumed the zinc blend structure. Samples annealed at above 335 °C showed mixed phases of the zinc blend and wurzite structures. Information about crystallite size is obtained from (001), (111) and (104) diffraction peaks. The average crystallite size of the film was determined to be ∼ 32 nm using the Scherrer formula.