PLZST单晶的弛豫结构相变

采用复合助熔剂技术,生长了完整、尺寸为2 mm× 2 mm× 2 mm的锆钛锡酸铅镧(简称PLZST)单晶.X射线衍射分析结果表明:晶体属四方晶系结构,晶格常数为:a=b=4.062 nm,c=4.106 nm.Raman光谱分析确定了PLZST单晶的结构相变温度为175℃,且其顺电-反铁电相变为可逆相变,具有弛豫特性.通过高分辨透射电镜(HRTEM)分析了晶体的微观结构,讨论了PLZST单晶的弛豫相变规律和相变行为.     

COHERENT GROWTH OF α-W FILM ON Si WAFER AND ITS THICKNESS DEPENDENT MECHANICAL AND ELECTRICAL PROPERTIES

以模板效应为手段,在单晶Si-(100)基片上借助预先沉积的Mo膜成功制备出共格生长的Pα-W薄膜.用X射线衍射、场发射扫描电镜和高分辨透射电镜分析薄膜微结构,用偏振相位移技术分析残余应力,用四点探针技术分析电阻率.结果表明:MO模板诱导下共格生长出的α-W膜为等轴晶,Si基底上则为亚稳态β-W的非等轴晶.两组样品的电阻率和残余应力均随膜厚降低而升高,但β-W膜归因于晶粒尺寸减小,即晶界的大量增加;而α-W/Mo双层膜归因于两者之间共格界面的约束作用,当膜厚减至数十纳米后尤其如此.     

六钛酸钾纳米线的结构分析

采用X射线粉末衍射Rietveld精修方法和高分辨电子显微方法分析了六钛酸钾纳米线的品体结构。X射线精修结果表明纳米线的晶体结构与六钛酸钾晶须结构相同。高分辨电子显微像模拟计算所得的像与高分辨像匹配良好，且与X射线结构精修所得结构模型相符。纳米线的生长方向平行于K2Ti6O13结构的[010]方向。     

TiN/Si3N4纳米多层膜硬度对Si3N4层厚敏感性的研究

通过反应磁控溅射制备了一系列不同Si3N4层厚的TiN/Si3N4纳米多层膜,利用X射线衍射仪、高分辨透射电子显微镜、扫描电子显微镜和微力学探针表征了多层膜的微结构和硬度,研究了其硬度随Si3N4层厚微小改变而显著变化的原因.结果表明,在TiN调制层晶体结构的模板作用下,溅射态以非晶存在的Si3N4层在其厚度小于0.7 nm时被强制晶化为NaCl结构的赝晶体,多层膜形成共格外延生长的{111}择优取向超晶格柱状晶,并相应产生硬度显著升高的超硬效应,最高硬度达到38.5GPa.Si3N4随自身层厚进一步的微小增加便转变为非晶态,多层膜的共格生长结构因而受到破坏,其硬度也随之降低.     

半导体异质结界面处Sb/As交换反应研究

利用分子束外延(MBE)技术,在GaAs衬底上生长了高质量的GaAs/GaAsSb超晶格,并通过高分辨X射线衍射(HRXRD)技术对Sb/As交换反应进行研究.实验表明,随着衬底温度的升高,Sb解吸附速度增加,在Sb束流作用下形成的GaAs/GaAsSb超晶格中的Sb含量下降.而Sb束流大小和暴露在Sb束流中的时间对GaAs/GaAsSb超晶格中的Sb含量影响很小.这说明Sb与GaAs中的As原子的交换反应仅发生在GaAs表层,Sb原子在GaAs中的扩散距离很短.     

MOCVD外延Al_2O_3基AlGaN/GaN超晶格的结构和光学特性

通过X射线衍射分析、透射电镜观察、红外透射光谱分析、紫外-可见吸收光谱分析和光致发光试验,研究了用金属有机物化学汽相沉积(MOCVD)的方法,在带有GaN缓冲层的蓝宝石(Al2O3)衬底上生长的AlGaN/GaN超晶格材料的微观结构、光吸收性质和发光特性。X射线衍射结果表明,GaN基材料均为纤锌矿六方结构,薄膜具有良好的结晶质量,薄膜生长沿c轴择优取向。透射电镜观察表明,超晶格试样的周期结构分布均匀,实际周期为13.3nm,且观察到高密度的位错存在于外延膜中。通过光学试验数据,确定了试样的光学吸收边都是在370nm附近,理论计算显示试样为直接跃迁型半导体,禁带宽度约为3.4eV。试样的折射率随光子能量的增加而增加、随波长的增加而减小,计算表明消光系数的极小值位于370nm处。光致发光测试分析表明,超晶格有很好的发光性能,并发现存在黄带发光。     

界面精细结构与界面反应产物结构

界面的原子结构特征对材料的性能有很重要的影响.本文介绍用选区电子衍射及高分辨电子显微术研究半导体超晶格、金属多层膜、陶瓷和复合材料相界面的精细结构及界面反应产物结构的结果.对两相之间的取向关系,界面的台阶、小面和粗糙度,界面的原子键合,界面的共格性,错配位错的性质及界面附近弹性应变松弛度,界面附近缺陷结构,电子束辐照或制备工艺条件引起的界面固态化学反应动力学和反应机制以及界面反应产物结构进行了分析和讨论。     

磁控溅射铱薄膜的表面形态与取向演变的控制优化

目的 研究磁控溅射制备金属Ir膜的过程中溅射参数对Ir膜表面微结构和晶体质量的影响,制备高质量(100)取向的外延Ir膜,为单晶金刚石的异质外延生长奠定重要基础。方法 通过磁控溅射技术在单一改变参数(溅射功率、溅射厚度)的条件下制备金属Ir膜,通过分析原子力显微镜、扫描电子显微镜、X射线衍射、电子背散射衍射等测试结果,研究了各条件对所制备Ir膜粗糙度、表面形貌、晶体结构和取向的影响,并通过摇摆曲线衡量真空退火对薄膜晶体质量的优化效果。结果 在(100)MgO衬底上外延生长的Ir膜具有均匀的微结构,该结构由规则且紧密的矩形颗粒排列而成。薄膜表面微结构特征尺寸随溅射功率升高而逐渐减小;当功率为45 W时,Ir(200)X射线衍射峰强度最大、半高宽最宽;而随着厚度的增大,Ir(200)X射线衍射峰的半高宽及强度均增大。经优化的Ir膜表面光滑(Ra<0.5nm)、薄膜晶体质量高(θ_FWHM<0.5°)。结论 功率、厚度和退火处理都会影响薄膜晶体质量和表面微结构尺寸,合适的功率和厚度结合退火处理能获得具有特定表面微结构的高质量Ir膜。     

MOCVD外延Al2O3基AlGaN/GaN超晶格的结构和光学特性

通过X射线衍射分析、透射电镜观察、红外透射光谱分析、紫外-可见吸收光谱分析和光致发光试验,研究了用金属有机物化学汽相沉积（MOCVD）的方法,在带有GaN缓冲层的蓝宝石（Al2O3）衬底上生长的AlGaN/GaN超晶格材料的微观结构、光吸收性质和发光特性.X射线衍射结果表明,GaN基材料均为纤锌矿六方结构,薄膜具有良好的结晶质量,薄膜生长沿c轴择优取向.透射电镜观察表明,超晶格试样的周期结构分布均匀,实际周期为13.3nm，且观察到高密度的位错存在于外延膜中。通过光学试验数据，确定了试样的光学吸收边都是在370nm附近，理论计算显示试样为直接跃迁型半导体，禁带宽度约为3．4eV。试样的折射率随光子能量的增加而增加、随波长的增加而减小，计算表明消光系数的极小值位于370nm处。光致发光测试分析表明，超晶格有很好的发光性能，并发现存在黄带发光。     

VC/TiC超晶格薄膜的微结构及超硬效应

采用磁控溅射工艺制备VC/TiC超晶格薄膜,并采用EDXA、XRD、HRTEM和纳米力学探针研究调制周期对超晶格薄膜的微结构和力学性能的影响。研究结果表明,当超晶格薄膜的调制周期低于临界厚度时,制备的VC/TiC超晶格薄膜能够形成共格生长结构,并获得硬度显著提高的超硬效应。然而,随着调制周期的进一步增大,超晶格薄膜的共格结构遭到破坏,导致薄膜的硬度逐渐降低,并最终趋于其组元的混合平均值。XRD结果表明,当形成共格生长结构时,超晶格薄膜内部将产生共格协调应变,从而改变不同调制层的弹性模量,这也是VC/TiC超晶格薄膜能够获得超硬效应的重要原因。     

GaN基底上集成介电薄膜材料的生长方法研究

将以极化为特征、具有丰富功能特性的介电氧化物材料通过外延薄膜的方式,在半导体GaN上制备介电氧化物／GaN集成薄膜,其多功能一体化与界面耦合效应可推动电子系统单片集成化的进一步发展。然而,由于2类材料物理、化学性质的巨大差异,在GaN上生长介电薄膜会出现严重的相容性生长问题。采用激光分子束外延技术（LMBE）,通过弹性应变的TiO2的缓冲层来减小晶格失配度,降低介电薄膜生长温度,控制界面应变释放而产生的失配位错,提高了介电薄膜外延质量;通过低温外延生长MgO阻挡层,形成稳定的氧化物／GaN界面,阻挡后续高温生长产生的扩散反应;最终采用TiO2／MgO组合缓冲层控制介电／GaN集成薄膜生长取向、界面扩散,降低集成薄膜的界面态密度,保护GaN半导体材料的性能。所建立的界面可控的相容性生长方法,为相关集成器件的研发提供了一条可行的新途径。     

Epitaxial integration of perovskite-based multifunctional oxides on silicon

We review recent developments in the epitaxial integration of multifunctional oxide thin film heterostructures on silicon (Si). Perovskite oxides have been extensively studied for use in multifunctional devices due to a wide range of functional properties. To realize multifunctional oxide devices, these multifunctional films should be integrated directly on Si, maintaining high crystalline quality. Molecular beam epitaxy growth of epitaxial SrTiO₃ (STO) on Si provides a template for incorporating the epitaxial oxide films on Si. However, the dissimilar physical nature of Si from most oxide materials influences the properties of oxide films on Si, especially with regard to structural defects and thermal strains. Therefore, in this review, we present a comprehensive overview of epitaxial integration of various model oxide systems on Si, addressing how STO/Si can be used to explore the novel phenomenon of oxide heterostructures as well as to realize multifunctional devices.     

Preparation and characterization of microcrack-free thick YBa2Cu3O7-δ films

High quality epitaxial YBa2Cu3O7-δ （YBCO） superconducting films were fabricated on （00l） LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness （up to 2.0 μm） without mi-crocracking was attributed in part to the presence of pores correlated with yttrium-rich composition in the films. The influ-ence of the film thickness on the microstructure was investigated by X-ray diffraction conventional scan （θ-2θ,ω-scan,pole figure） and high-resolution reciprocal space mapping. The films were c-axis oriented with no a-axis-oriented grains up to the thickness of 2 μm. The surface morphology and the critical current density （Jc） strongly depended on the film thickness. Furthermore,the reasons for these thickness dependences were elucidated in detail.     

Cluster-assembled cobalt doped ZnO nanostructured film prepared by low energy cluster beam deposition

Cobalt doped ZnO film assembled by the nanoparticles was prepared by low energy cluster beam deposition. The microstructure, phase structure and optical properties were investigated for the nanostructured films. The results show that the nanostructured film was assembled by monodisperse spherical nanoparticles with average diameter of about 29.3 nm which are distributed uniformly and compactly. The results of X-ray diffraction (XRD) show that cobalt doped ZnO nanostructured film is indexed to a wurtzite structure of ZnO, and no Co-phase structure and other phases are observed. The UV-visible absorption spectra show that the optical band-gap of the film is broadened after doping.     

Structural and optical properties of tellurium films obtained by chemical vapor deposition（CVD）

1 Introduction Te thin films have been extensively used in various technological areas, especially in microelectronic devices such as gas sensor [1?3], optical information storage [4] and other applications [5?7]. All these applications are due to remark…     

Recent progress in thin film epitaxy across the misfit scale (2011 Acta Gold Medal Paper)

This paper discusses recent progress in thin film epitaxy across the misfit scale through the paradigm of domain matching epitaxy (DME). This epitaxy across the misfit scale is critical for integrating multifunctionality on a chip and creating smart structures for next-generation solid-state devices. There are three sources of strains that are cumulative at the growth temperature, and the relaxation process starts during the growth process. Upon cooling, unrelaxed lattice, thermal and defect strains give rise to net residual strains. In large misfit (ε ? 10%) systems, where lattice misfit strain is predominant, it can be relaxed completely, and then only thermal and defect strains remain upon cooling. In low misfit systems, all three sources contribute to the residual strain upon cooling, as result of incomplete lattice relaxation. The predominant strain relaxation mechanism in thin films is by nucleation of dislocations at the free surface, as the nucleation energy in the bulk is considerably higher. At the free surface, the activation barrier for dislocation nucleation is considerably lower at the steps. Since the step formation energy is lower under a compressive stress compared with tensile stress, it reduces nucleation energy under compressive stress and lowers the critical thickness compared with tensile stresses in thin films. Once the dislocation nucleates, it propagates or glides to the interface to relieve the strain. However, if lattice frictional stress in the film is high, most dislocations may not reach the interface, depending upon the growth temperature and rate. Thus, these two key steps, dislocation nucleation and propagation, play a critical role in the thin film relaxation process. Once the dislocations reach the interface, the atomic structure of the dislocation at the heterointerfaces determines its electronic properties, specifically trapping and recombination characteristics. It is found that the atomic structure of the dislocation is determined by the interplay between strain and chemical free energies. Thus, the dislocations (representing missing or extra planes) play a critical role in the relaxation of thin film heterostructures. This paper focuses on epitaxy across the misfit scale, based upon matching of integral multiples of lattice planes. If the misfit falls between the integral multiples, it is accommodated by the principle of domain variation, where domains alternate to accommodate the misfit. Details of epitaxy from low misfit (～4%) in Ge/Si) to large misfit (～22%) in TiN/Si are shown. In III-nitride/sapphire and II-oxide/sapphire systems, this paper deals with polar orientations, where misfit is uniform in the basal plane, and non-polar orientations, where misfit varies over an order of magnitude in the film plane. It is shown that the DME paradigm is key to the integration of thin film heterostructures across the misfit scale and other complex systems such as vanadium oxide and PZT systems on Si(1 0 0) substrates for the integration of functionalities on a computer chip. Finally, it is shown that the formation of epitaxial and self-assembled nanodots on Si(1 0 0) provides a critical advance, with tremendous implications for information and data storage and related nanomagnetics applications.     

The volume production of GaAs and related compounds by MOVPE

An increasing market for advanced telecommunications has dramatically increased the demand for high-performance heterostructure compound semiconductor devices. Among a variety of epitaxial technologies for compound semiconductor materials growth, metalorganic vapor-phase epitaxy has succeeded in producing a wide variety of epitaxial wafers for optical devices such as laser diodes, optical detectors, and high-brightness light-emitting diodes. Although molecular-beam epitaxy has been applied to high-speed electronic devices, the continuous R&D efforts on metalorganic vaporphase epitaxy have made the technology a valuable alternative. The performance of the most advanced heterostructure devices, such as pseudomorphic high-electron mobility transistors or heterostructure bipolar transistors, greatly depends upon the qualities of the epitaxial wafer, as does the manufacturing cost. In the future, epitaxial materials supply must become a robust, real-production technology in order to keep the cost-performance ratio of the heterostructure devices competitive with other technologies (such as ion-implanted GaAs metal-semiconductor field-effect transistors) and silicon-based devices. Masahiko Hata earned his M.S. in solid-state photochemistry at the University of Kyoto in 1981. He is currently a senior research associate at Sumitomo Chemical Company, Ltd.     

{001}LaAlO_3衬底上沉积YBa_2Cu_3O_（7-x）薄膜的HRXRD研究

采用脉冲激光沉积技术（PLD）在{001}LaAlO3（LAO）衬底上生长YBa2Cu3O7-x（YBCO）薄膜,并通过极图、摇摆曲线以及倒易空间图谱等高分辨X射线衍射技术（HRXRD）对其微结构进行表征。结果表明,YBCO薄膜的晶粒取向主要为{001}YBCO//{001}LAO,〈100〉YBCO//〈100〉LAO,但还有2%的{001}YBCO//{001}LAO,〈110〉YBCO//〈100〉LAO取向。摇摆曲线结果表明,YBCO的面外取向有一定的漫散（宽度为0.75°）;薄膜面内存在90°±0.65°〈110〉孪晶畴结构,主要是由四方到正交的相变过程中较大的局部应力以及〈100〉和〈010〉方向应力差异引起的。     

衬底与缓冲层的晶格失配对CeO_2缓冲层外延生长的影响

采用金属有机沉积(MOD)技术在La Al O3(LAO)、Y稳定的氧化锆(YSZ)和Ni-W衬底上沉积了Ce O2缓冲层薄膜,并研究了衬底与缓冲层的晶格失配对其外延生长的影响。结果表明,随着衬底和缓冲层薄膜之间晶格失配的增大,缓冲层薄膜内部的压应变增加,晶界浓度增加,晶粒生长速率减小。衬底和缓冲层薄膜之间的晶格失配越小,越有利于薄膜织构度的增大。Ce O2薄膜的表面形貌及粗糙度的演化对衬底和缓冲层薄膜之间的晶格失配并没有明确的依赖关系。     

Preparation and characterization of microcrack-free thick YBa2Cu3O7-δ films

High quality epitaxial YBa2Cu3O7-δ (YBCO) superconducting films were fabricated on (00l) LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness (up to 2.0 μm) without microcracking was attributed in part to the presence of pores correlated with yttrium-rich composition in the films. The influence of the film thickness on the microstructure was investigated by X-ray diffraction conventional scan (θ-2θ, ω-scan, pole figure) and high-resolution reciprocal space mapping. The films were c-axis oriented with no a-axis-oriented grains up to the thickness of 2 μm. The surface morphology and the critical current density (Jc) strongly depended on the film thickness.Furthermore, the reasons for these thickness dependences were elucidated in derail.