用Cat-CVD方法制备多晶硅薄膜及结构分析

以金属钨为催化热丝,采用热丝催化化学气相沉积,在300℃的玻璃衬底上沉积多晶硅薄膜。研究了H2稀释率、钨丝与衬底间的距离和反应室气体压力等沉积参数对制备多晶硅薄膜的影响,并通过XRD谱分析,确定了本实验系统的最佳多晶硅成膜条件:FR(SiH4)=5mL/min,FR(H2)=70mL/min,P=50Pa,L衬底与钨丝=7.5cm,T=30min,t衬底=300℃,特征峰在(111)面上。在接触式膜厚仪测量的基础上,计算出薄膜生长速率为0.6nm/s。对最佳成膜条件下制备的多晶硅薄膜进行刻蚀,形成不同的厚度,以便进行逐层分析。采用XRD和SEM方法对不同厚度的薄膜测试发现,随着薄膜厚度的减小,(111)面的XRD特征峰强度逐渐下降,(111)面上的晶粒尺寸基本没有变化,都是50nm左右。根据测试结果分析了薄膜的生长机制,提出了薄膜生长是分步成核,成核后沿(111)面纵向生长的观点。认为反应基元首先随机吸附在衬底上,在H原子的作用下在一些位置上成核,而在其他位置形成非晶相。已形成的晶核逐渐长大并沿(111)面纵向生长;已形成的非晶相也在生长,但上面不断有晶核形成。当薄膜达到一定厚度,非晶相表面完全被晶核占据,整个薄膜表面成为多晶相,此后整个薄膜处于沿(111)面的纵向生长阶段,直至反应结束,完整的晶粒结构呈柱状。     

两步生长和直接生长GaAs/Si单晶薄膜的比较

报道了采用热壁外延(HWE)技术,在(100),(111)和(211)三种典型Si表面通过两步生长和直接生长法制备GaAs单晶薄膜,经过拉曼光谱、霍尔测试和荧光光谱分析比较,得出结论:(1)相同取向Si衬底,两步生长法制备的GaAs薄膜结晶质量比直接生长法制备的GaAs薄膜的要好;(2)采用HWE技术在Si上异质外延GaAs薄膜,其表面缓冲层的生长是降低位错、提高外延质量的基础;(3)不同取向Si衬底对GaAs外延层结晶质量有影响, (211)面外延的GaAs薄膜质量最好,(100)面次之,(111)面最差.     

HWE 生长大面积CdTe/ CdZnTe/ Si 薄膜的结构和形貌分析

用热壁外延法(HWE) 生长直径30mm 的CdTe/ CdZnTe/ Si 薄膜,经XRD 测试说明它是 晶面为(111) 取向的立方闪锌矿结构。SEM对Si 衬底、CdZnTe 缓冲层和CdTe 薄膜三层分别测试,结果发现: Si 衬底表面结构粗糙,CdZnTe 缓冲层较Si 衬底表面结构细致,CdTe 薄膜较CdZnTe 缓冲层表面结构光滑细密,即缺陷较CdZnTe 缓冲层少很多。通过对该片子照像看出其表面如镜面。由此说明大面积CdTe/ CdZnTe/ Si 薄膜可用HWE 技术制备。     

用MOCVD方法在GaAs衬底上低温生长ZnO薄膜

采用二乙基锌(DEZn)和水(H2O)作为生长源,利用金属有机化学气相沉积(MOCVD)的方法,在100～400℃低温范围内,在GaAs(001)衬底上制备了ZnO薄膜.利用X射线衍射(XRD),室温PL,AFM,SEM研究了薄膜的晶体结构特性、发光特性及表面形貌特性.XRD分析表明ZnO薄膜具有很强的c轴取向,(002)峰的FWHM平均值为0.3°.当生长温度达到400℃时从SEM测量结果可以观察到薄膜表面呈六角状结晶.随着生长温度的升高,薄膜的晶粒尺寸变大,结晶质量得到提高但同时表面变粗糙.室温PL测量显示薄膜在370nm附近有强的近带边发射,没有观测到深能级发射峰.     

HWE 生长大面积CdTe/ CdZnTe/ Si 薄膜的结构和形貌分析

用热壁外延法(HWE)生长直径30mm的CdTe／CdZnTe／Si薄膜，经XRD测试说明它是晶面为(111)取向的立方闪锌矿结构。SEM对Si衬底、CdZnTe缓冲层和CdTe薄膜三层分别测试，结果发现：Si衬底表面结构粗糙，CdZnTe缓冲层较Si衬底表面结构细致，CdTe薄膜较CdZnTe缓冲层表面结构光滑细密，即缺陷较CdZnTe缓冲层少很多。通过对该片子照像看出其表面如镜面。由此说明大面积CdTe／CdZnTe／Si薄膜可用HWE技术制备。     

AIN/Si(111)复合衬底上4H-SiC薄膜的异质外延

利用化学气相淀积(CVD)的方法在AlN/Si(111)复合衬底上成功实现了4H-SiC薄膜的异质外延生长,用X射线衍射(XRD)、扫描电子显微镜(SEM)、阴极荧光(CL)等方法对所得样品的结构特征、表面形貌和光学性质进行了表征测量.XRD测量结果显示得到的SiC薄膜的晶体取向单一;室温CL结果表明所得SiC薄膜为4H-SiC,且随着生长温度的升高,SiC薄膜的CL发光效率提高.生长温度、反应气源中C/si比等工艺参数对SiC薄膜的外延生长及其性质影响的研究表明在AIN/Si(111)复合衬底上外延4H-SiC的最佳衬底温度为1230～1270℃,比通常4H-SiC同质外延所需的温度低200～300℃;较为合适的C/Si比值为1.3.     

真空环境中脉冲激光烧蚀制备纳米银晶薄膜的生长特性

采用XeCl准分子脉冲激光,在室温、真空环境下烧蚀银靶,通过改变激光能量密度和靶衬间距,在与靶面平行放置的Si(111)衬底上沉积了一系列纳米银晶薄膜。利用扫描电镜以及X射线衍射仪、选区电子衍射技术对薄膜进行表征,结果表明:薄膜由不同尺寸的银纳米晶粒组成;在固定激光能量密度的条件下,随着靶衬间距增加,薄膜的厚度和晶粒尺寸逐渐减小,晶粒间的聚合程度减弱,薄膜(111)晶面的XRD特征谱线强度减弱,(200)晶面的特征谱线强度增强;在固定靶衬间距的条件下,随着激光能量密度的增大,薄膜的厚度和晶粒尺寸逐渐增大,晶粒间的聚合程度增强,薄膜(111)晶面的特征谱线强度增强,(200)晶面的特征谱线强度略有减弱。结合晶粒成核和传输特性、烧蚀粒子迁移率,以及薄膜沿不同晶面生长所需表面能存在差异的情况,对实验结果进行了分析。     

用MOCVD方法在GaAs衬底上低温生长ZnO薄膜

采用二乙基锌(DEZn)和水(H2O)作为生长源,利用金属有机化学气相沉积(MOCVD)的方法,在100～400℃低温范围内,在GaAs(001)衬底上制备了ZnO薄膜.利用X射线衍射(XRD),室温PL,AFM,SEM研究了薄膜的晶体结构特性、发光特性及表面形貌特性.XRD分析表明ZnO薄膜具有很强的c轴取向,(002)峰的FWHM平均值为0.3°.当生长温度达到400℃时从SEM测量结果可以观察到薄膜表面呈六角状结晶.随着生长温度的升高,薄膜的晶粒尺寸变大,结晶质量得到提高但同时表面变粗糙.室温PL测量显示薄膜在370nm附近有强的近带边发射,没有观测到深能级发射峰.     

CdZnTe衬底对碲镉汞气相外延表面形貌的影响

利用气相外延技术在CdZnTe衬底上生长Hg1-xCdxTe薄膜材料,通过在不同晶向、不同极性、不同晶向偏离角度CdZnTe衬底上的外延结果发现,CdZnTe衬底对外延形貌的影响非常大。(111)面衬底上外延形貌明显优于(211)面衬底的外延形貌。对于同是<111>CdZnTe晶向的衬底,(111)Cd面CdZnTe衬底上的外延形貌明显优于(111)Te面。对于(111)Cd面CdZnTe衬底,当晶向偏离角度不同时,其外延形貌也有差异,晶向偏离角越小表面形貌越好。     

立方相AlxGa1-xN/GaAs(100)的MOCVD外延生长

利用MOCVD生长技术在GaAs(100)衬底上生长了高质量的立方相AlGaN薄膜.通过光致发光 (PL)、扫描电镜(SEM)分析了不同NH3流量、不同生长温度对AlGaN外延层的结晶质量和表面形貌的影响.发现相对高的NH3流量和相对高的生长温度可以提高AlGaN外延层的结晶质量.     

电子束蒸发制备PbI_2薄膜及其性能表征

采用电子束蒸发工艺在普通玻璃衬底上制备了PbI_2多晶薄膜,研究了不同衬底温度对薄膜结构、表面形貌及紫外-可见光谱的影响.XRD结构表征显示,不同衬底温度下沉积的PbI_2薄膜均属六方结构,低温下呈现(002)方向的c轴择优生长,但随着衬底温度的升高,择优生长弱化;SEM形貌分析结果表明,PbI_2薄膜的晶粒尺寸随着衬底温度的升高而增大,同时晶粒间应力造成的突起减少,薄膜表面致密度和平整度提高;UV光谱测试结果表明,不同衬底温度下制备PbI_2薄膜透过光谱的吸收限均在515nm附近,且呈现陡直的吸收边.计算发现,薄膜禁带宽度约为2.42 eV,随着衬底温度升高而略微增大,显示结晶质量提高.

Abstract：

Polycrystalline lead iodide (PbI_2) thin films were deposited on glass substrates by electron beam evaporation method.The influence of different substrate temperatures on the structure,surface morphology and optical transmittance of the films was studied.XRD analysis shows the PbI_2 films deposited at different temperatures possess hexagonal structure,with a preferred growth orientation of (002) at low temperature,but this preferred growth characteristic vanishes when the substrate temperature increases.SEM micrograph reveals the grain size of PbI_2 thin films increases with the rising substrate temperature,meanwhile,the surface bulges resulted from the strain between grains decrease,making the surface of the films more compact and uniform.UV transmittance shows the steep absorption edge is at 515 nm for all samples grown under different substrate temperatures and the corresponding band gap is about 2.42 eV.     

Single‐Crystal Germanium Growth on Amorphous Silicon

Growing single‐crystal semiconductors directly on an amorphous substrate without epitaxy or wafer bonding has long been a significant fundamental challenge in materials science. Such technology is especially important for semiconductor devices that require cost‐effective, high‐throughput fabrication, including thin‐film solar cells and transistors on glass substrates as well as large‐scale active photonic circuits on Si using back‐end‐of‐line CMOS technology. This work demonstrates a CMOS‐compatible method of fabricating high‐quality germanium single crystals on amorphous silicon at low temperatures of <450 °C. Grain orientation selection by geometric confinement of polycrystalline germanium films selectively grown on amorphous silicon by chemical vapor deposition is presented, where the confinement selects the fast‐growing grains for extended growth and eventually leads to single crystalline material. Germanium crystals grown using this method exhibit (110) texture and twin‐mediated growth. A model of confined growth is developed to predict the optimal confining channel dimensions for consistent, single‐crystal growth. Germanium films grown from one‐dimensional confinement exhibit a 200% grain size increase at 1 μm film thickness compared to unconfined films, while 2D confinement growth achieved single crystal Ge. The area of single crystalline Ge on amorphous layers is only limited by the growth time. Significant enhancement in room temperature photoluminescence and reduction in residual carrier density have been achieved using confined growth, demonstrating excellent optoelectronic properties. This growth method is readily extensible to any materials system capable of selective non‐epitaxial deposition, thus allowing for the fabrication of devices from high‐quality single crystal material when only an amorphous substrate is available.     

Effects of substrate temperature on electrical and structural properties of copper thin films

This paper addresses the effects of substrate temperature on electrical and structural properties of dc magnetron sputter-deposited copper (Cu) thin films on p-type silicon. Copper films of 80 and 500 nm were deposited from Cu target in argon ambient gas pressure of 3.6 mTorr at different substrate temperatures ranging from room temperature to 250 °C. The electrical and structural properties of the Cu films were investigated by four-point probe and atomic force microscopy. Results from our experiment show that the increase in substrate temperature generally promotes the grain growth of the Cu films of both thicknesses. The RMS roughness as well as the lateral feature size increase with the substrate temperature, which is associated with the increase in the grain size. On the other hand, the resistivity for 80 nm Cu film decreases to less than 5 μΩ-cm at the substrate temperature of 100 °C, and further increase in the substrate temperature has not significantly decreased the film resistivity. For the 500 nm Cu films, the increase in the grain size with the substrate temperature does not conform to the film resistivity for these Cu films, which show no significant change over the substrate temperature range. Possible mechanisms of substrate-temperature-dependent microstructure formation of these Cu films are discussed in this paper, which explain the interrelationship of grain growth and film resistivity with elevated substrate temperature.     

基于热光伏电池GaSb多晶薄膜的可控生长

采用物理气相沉积(PVD)法在ITO透明导电衬底上制备GaSb多晶薄膜.研究了衬底温度及薄膜厚度对GaSb薄膜结构特性、电学特性以及光学特性的影响.在一定条件下生长的GaSb薄膜择优取向由GaSb(111)晶向转变为GaSb(220)晶向, 这是在玻璃衬底上生长GaSb薄膜没有发现的现象.择优取向改变为(220)晶向的GaSb薄膜具有更高的霍尔迁移率.因为这种薄膜材料具有更少的晶粒间界和更少的缺陷.经优化后的GaSb薄膜的光学吸收系数在104 cm-1以上, 适用于热光伏薄膜太阳电池中.     

Crystallographic study on self-annealing of electroplated copper at room temperature

Self-annealing in electroplated Cu films is the dramatic evolution of the microstructure in electroplated Cu near room temperature, and it occurs during a transient period of hours following the electroplating process. This study discusses the change of grain size and orientation in self-annealing of Cu films electroplated by an additive-free sulfate bath using X-ray diffraction and electron backscatter diffraction techniques. We found that the self-annealing started at the interface between the substrate and the electroplated Cu film. Immediately after the electroplating process, orientation of the Cu grains in the region near the interface was similar to that of the substrate. This indicates that the grain growth was affected by the substrate. Then, grain growth and change in orientation of the electroplated Cu film at room temperature became independent from the orientation of the substrate. The electroplated Cu film had many high-angle-grain boundaries (HAGBs) before incubation, and the fraction of HAGBs reduced as incubation time increased. Self-annealed Cu grains in the electroplated Cu film had many multiple twins, which came from low stacking-fault energy of Cu.     

Influence of growth temperature and thickness on the orientation of Cu(In,Ga)Se2 film

Cu(In,Ga)Se2(CIGS) films are deposited on the Na-free glass substrate using three-stage co-evaporation process,and the effects of thickness and growth temperature on the orientation of CIGS film are investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM).When the growth of CIGS film does not experience the Cu-rich process,the increase of the growth temperature at the second stage(Ts2) promotes the(112) orientation of CIGS film,and weakens the(220) orientation.Nevertheless,when the growth of CIGS film experiences Cu-rich process,the increase of Ts2 significantly promotes the(220) orientation.In addition,with the thickness of CIGS film decreasing,the extent of(In,Ga)2Se3(IGS) precursor orientation does not change except for the intensity of Bragg peak,yet the(220) orientation of following CIGS film is hindered,which suggests that(112) plane preferentially grows at the initial growth of CIGS film.     

The stability of α-Sn grown on CdTe by molecular beam epitaxy

We have examined the effect of the substrate orientation, thickness, growth rate, substrate temperature and inclusion of small amounts of Ge on the transition temperature of α-Sn films grown on CdTe. The transition temperature from α-Sn to β-Sn was determined by optical microscopy to be as high as 132° C. CdTe(ll0) is a somewhat better orientation than CdTe(100), and CdTe(lll)B appears to be totally unacceptable. The transition temperature from α-Sn to β-Sn depends on the film thickness; thinner films have a somewhat higher transition temperature than thicker films. The film quality can be increased by lowering the growth rate and raising the growth temperature to about 75° C. Since the transition from α-Sn to β-Sn starts at defects in the film, improving the film quality by lowering the growth rate and raising the growth temperature raises the transition temperature. Also by adding small amounts of Ge (∼2%) the transition temperature of films grown on CdTe can be significantly increased.     

ZnO纳米晶须的形态控制及其结构表征

采用激光分子束外延法先在Si(111)衬底上制备Zn薄膜,在不同的氧气体积流量和生长温度下,用热蒸发法在镀有Zn薄膜的Si(111)衬底上制备了不同形貌的ZnO纳米晶须。分别用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)对样品的成分、微结构和形貌进行了表征。Zn薄膜在高温下被氧化,并为晶体生长提供均匀的成核点,有利于形成一定大小和数量的ZnO晶核。研究结果表明,氧气体积流量和生长温度对ZnO纳米晶须的形貌有一定的影响。     

沉积温度对PbTe薄膜结构和光学性能的影响

采用电阻热蒸镀法,分别以不同的沉积温度在锗基底上制备了PbTe薄膜。用X射线衍射仪(XRD)、原子力显微镜(AFM)和红外光谱测试仪(System2000)表征了不同沉积温度下薄膜的微结构和光学特性.结果表明,沉积温度对PbTe薄膜的结构、择优取向、生长方向、晶粒大小、禁带宽度以及短波吸收限均有明显影响.     

ITO衬底上LiTaO3薄膜的制备与介电特性

用溶胶凝胶法在ITO衬底上制备了钽酸锂(LiTaO3)薄膜,利用XRD、SEM和AFM对薄膜的晶向、表面形态等作了表征;研究了不同溶剂对LiTaO3溶胶稳定性的影响和不同退火条件对LiTaO3薄膜结晶的影响;利用Al/LiTaO3/ITO结构,测试了薄膜的介电系数和介电损耗.结果表明:每层薄膜都晶化退火比交替使用焦化、结晶退火能生长出质量更好的LiTaO3薄膜;频率1KHz时,介电损耗约0.4,相对介电系数约53.并讨论了介电损耗增大的原因.