ZnO／AlN／Si（111）薄膜的外延生长和性能研究

用常压金属化学气相沉积法(MOCVD)在Si(111)衬底上制备了马赛克结构ZnO单晶薄膜。引入低温Al N缓冲层以阻止衬底氧化、缓解热失配和晶格失配。薄膜双晶X射线衍射2θ/ω联动扫描只出现了Si(111)、ZnO(000l)及Al N(000l)的衍射峰。ZnO/Al N/Si(111)薄膜C方向晶格常量为0.5195nm,表明在面方向处于张应力状态;其对称(0002)面和斜对称(1012)面的双晶X射线衍ω摇摆曲线半峰全宽分别为460″和1105″;干涉显微镜观察其表面有微裂纹,裂纹密度为20cm-1;3μm×3μm范围的原子力显微镜均方根粗糙度为1.5nm;激光实时监测曲线表明薄膜为准二维生长,生长速率4.3μm/h。低温10K光致发光光谱观察到了薄膜的自由激子、束缚激子发射及它们的声子伴线。所有结果表明,采用金属化学气相沉积法并引入Al N为缓冲层能有效提高Si(111)衬底上ZnO薄膜的质量。     

常压化学气相沉积法在Ag/Si(111)模板上生长ZnO薄膜及其性能研究

在Si衬底上利用磁控溅射的方法沉积1.5 nm厚度的Ag膜用以阻挡Si衬底被氧化。采用常压金属有机化学气相沉积法(MOVCD),在Ag/Si(111)衬底上成功地生长出马赛克结构的ZnO薄膜。用光学显微镜观察表面形貌,结果显示有带晶向特征的微裂纹,裂纹密度为100 cm-1。依据X射线晶体衍射的结果,薄膜结晶质量良好,呈C轴高度择优取向。用双晶X射线衍射得到(002)面的ω扫描半峰宽为1.37°。温度10 K时光致发光谱(PL)观察到自由激子、束缚激子发射及它们的声子伴线。结果表明,金属有机化学气相沉积法方法在Si(111)衬底上制备ZnO薄膜时,Ag是一种有效的缓冲层。     

常压化学气相沉积技术生长ZnO∶H薄膜的光学性质

采用常压金属有机物化学气相沉积技术(APMOCVD),以二乙基锌(DEZn)为Zn源,去离子水(H2O)为氧源,N2作载气,在外延ZnO薄膜的反应气氛中通入少量氢气,在cAl2O3衬底上生长出了ZnO∶H薄膜。用X射线双晶衍射和光致发光谱对ZnO∶H薄膜的结晶性能和光学性质进行表征。结果表明,ZnO∶H薄膜(002)和(102)面的Ω扫描半峰全宽分别为46.1 mrad和81.4 mrad,表明该薄膜具有良好的结晶性能；室温下,ZnO∶H薄膜具有较强的紫外光发射(380 nm),在低温10 K光致发光谱中观测到位于3.3630 eV处与氢相关的中性施主束缚激子峰(I4)及其位于3.331 eV处的双电子卫星峰(TES)。采用退火的方法,通过观测I4峰的强度变化,研究了氢在ZnO∶H薄膜中的热稳定性。发现随着退火温度的升高,I4峰的强度逐渐减弱,表明在高温下退火,氢会从ZnO薄膜中逸出。     

N2O为氧源金属有机化学气相沉积生长ZnO薄膜的光学性能研究

采用常压金属有机化学气相沉积(AP-MOCVD)技术、三步生长法,分别以H2O和N2O为氧源,DEZn为Zn源,N2作载气,在c-Al2O3衬底上生长出了晶体质量较好的ZnO薄膜。用X射线双晶衍射(DCXRD)和光致发光谱对ZnO薄膜的结晶性能和光学性质进行表征。结果显示,ZnO倾斜对称面(10-12)的ω扫描半峰全宽为350″,表明ZnO薄膜结晶性能良好;低温10 K光致发光谱结果表明,N2O为氧源生长的ZnO膜和H2O为氧源生长的ZnO膜的发光特性明显不同,没有观察到与氢有关的中性施主束缚激子对应的3.331 eV双电子卫星峰(TES)。这一结果表明,用N2O为氧源生长的ZnO薄膜中不易引进氢杂质。     

常压化学气相沉积技术生长ZnO:H薄膜的光学性质

采用常压金属有机物化学气相沉积技术(AP-MOCVD),以二乙基锌(DEZn)为Zn源,去离子水(H2O)为氧源,N2作载气,在外延ZnO薄膜的反应气氛中通入少量氢气,在c-Al2O3衬底上生长出了ZnO∶H薄膜。用X射线双晶衍射和光致发光谱对ZnO∶H薄膜的结晶性能和光学性质进行表征。结果表明,ZnO∶H薄膜(002)和(102)面的Ω扫描半峰全宽分别为46.1 mrad和81.4 mrad,表明该薄膜具有良好的结晶性能;室温下,ZnO∶H薄膜具有较强的紫外光发射(380 nm),在低温10 K光致发光谱中观测到位于3.3630 eV处与氢相关的中性施主束缚激子峰(I4)及其位于3.331 eV处的双电子卫星峰(TES)。采用退火的方法,通过观测I4峰的强度变化,研究了氢在ZnO∶H薄膜中的热稳定性。发现随着退火温度的升高,I4峰的强度逐渐减弱,表明在高温下退火,氢会从ZnO薄膜中逸出。     

MOCVD法生长ZnO薄膜的结构及光学特性

采用MOCVD方法在c Al2 O3衬底上生长出了具有单一c轴取向的ZnO薄膜 ,采用X射线衍射 (XRD)、Raman散射、X射线光电子能谱 (XPS)及光致发光 (PL)谱等方法对ZnO薄膜的结构及光学特性进行分析测试。XRD分析只观察到ZnO薄膜 (0 0 0 2 )衍射峰 ,其FWHM数值为 0 1 84°。Raman散射谱中 ,4 35 32cm- 1 处喇曼峰为ZnO的E2 (high)振动模 ,A1 (LO)振动模位于 5 75 32cm- 1 处。XPS分析表明 :ZnO薄膜表面易吸附游离态氧 ,刻蚀后ZnO薄膜O1s光电子能谱峰位于 5 30 2eV ,更接近Zn—O键中O1s电子结合能 (5 30 4eV)。PL谱中 ,在3 2 8eV处观察到了自由激子发射峰 ,而深能级跃迁峰位于 2 5 5eV ,二者峰强比值为 4 0∶1 ,表明生长的ZnO薄膜具有较高的光学质量     

脉冲激光沉积(PLD)法生长高质量ZnO薄膜及其发光性能

采用脉冲激光沉积(PLD)法在单晶Si(100)衬底上生长ZnO薄膜,以X射线衍射(XRD)、原子力显微镜(AFM)和透射电镜(TEM)等手段分析了所得ZnO薄膜的晶体结构和微观形貌。优化工艺(700℃,20Pa)下生长的ZnO薄膜呈c轴高度择优取向,柱状晶垂直衬底表面生长,结构致密均匀。室温光致发光(PL)谱分析结果表明,随着薄膜生长时O₂分压的增大,近带边紫外发光峰与深能级发光峰之比显著增强,表明薄膜的结晶性能和化学计量比都有了很大的改善。O₂分压为20Pa时所生长的ZnO薄膜具有较理想的化学计量比和较高的光学质量。     

以Au为缓冲层在Si衬底上生长ZnO薄膜

采用化学气相沉积(CVD)方法在Si(001)衬底上分别制备了有金属Au缓冲层以及无Au缓冲层的ZnO薄膜。其中Au缓冲层在物理气相沉积(PVD)设备中蒸发,厚度大约为300nm。有Au缓冲层的ZnO薄膜晶体质量比直接在Si衬底上生长有了显著提高。利用X射线衍射(XRD)研究了所生长ZnO薄膜的结晶质量,有Au缓冲层的ZnO薄膜虽然仍为多晶,但显示出明显的择优取向。用光学显微镜研究了ZnO薄膜的表面特征,金属Au缓冲层显著地提高了在Si衬底上生长的ZnO薄膜的晶粒尺寸及平整度。同时利用室温光致发光(PL)谱研究了ZnO薄膜的光学性质,并分析了有Au缓冲层的ZnO薄膜NEB发光峰强度反而弱的可能原因。     

用锌有机源和CO2/H2混合气源PECVD沉积ZnO薄膜

在等离子体作用下,以CO2/H2混合气为氧源,Zn(C2H5)2锌为锌源,在单晶硅上生长出高度择优取向的氧化锌薄膜。X射线衍射分析表明,薄膜为六方结构,c轴高度择优;原子力显微镜观察到晶粒是有规律地按六方排布,薄膜的表面粗糙度较小;从光致发光谱还发现在380 nm处有非常强的紫外峰。     

Si衬底对ZnO薄膜性能影响的研究

使用脉冲激光沉积(pulsed laser deposition,PLD)技术,采用两种不同纯度(99.5%和99.99%)的ZnO靶材,在p型Si衬底上制备了两种ZnO/Si薄膜.原子力显微镜与X射线衍射分析表明,两种样品具有相似的显微形貌与相同的晶体结构.霍尔效应测试发现,两种ZnO/Si薄膜都展现出了低电阻率、高迁移率的电学性能,但是其导电类型完全相反.研究结果表明,衬底的性能对霍尔效应测试有巨大影响.利用二次离子质谱仪,发现了在低纯度的样品中存在着S杂质向Si衬底中扩散的现象,并直接导致了衬底的导电性能的反型.     

AlN缓冲层对Si基GaN外延薄膜性质的影响

采用金属有机化合物化学气相沉积（MOCVD）方法制备了不同AlN缓冲层厚度的GaN样品,研究了AlN缓冲层厚度对GaN外延层的应力、表面形貌和晶体质量的影响。研究结果表明：厚度为15 nm的AlN缓冲层不仅可以有效抑制Si扩散,而且还给GaN外延层提供了一个较大的压应力,避免GaN薄膜出现裂纹。在该厚度AlN缓冲层上制备的GaN薄膜表面光亮、无裂纹,受到的张应力为0.3 GPa,（0002）和（1012）面的高分辨X射线衍射摇摆曲线峰值半高宽分别为536 arcsec和594 arcsec,原子力显微镜测试得到表面粗糙度为0.2 nm。     

Nanocrystalline ZnO Film Grown on Porous SnO2/Si(111) Substrate

Porous tin oxide was prepared on silicon(111) substrate by the sol–gel route. Then, the samples were dried in air at 600°C for 30 min in an electric furnace. Scanning electron microscope (SEM) images indicated the high density of the pores. Circular microvoids formed by the rigid shaped microarray network of 200–300 nm sizes are clearly seen in the plan view SEM image. The high homogeneity and uniformity of the porous region could also be visualized by this easy method. Nanocrystalline zinc oxide (ZnO) thin films have been deposited onto porous SnO₂substrates at high growth rates by radio frequency (RF) sputtering using a ZnO target. The surface morphology of the nanocrystalline ZnO films was characterized by scanning electron microscope (SEM). Photoluminescence (PL) spectroscopy is a powerful, contactless and excellent nondestructive optical tool to study the acceptor binding energy of ZnO nanostructures. The PL measurements were also operated at room temperature. The peak luminescence energy in nanocrystalline ZnO on porous SnO₂ is blue-shifted with regard to that in bulk ZnO (381 nm). PL spectra peaks are distinctly apparent at 375 nm for ZnO film grown on porous SnO₂/Si(111) substrates.     

Si(111)衬底上GaN的MOCVD生长

利用LP-MOCVD在Si（111）衬底上,以高温AIN为缓冲层,分别用低温GaN（LT-GaN）和偏离化学计量比富Ga高温GaN（HT-GaN）为过渡层外延生长六方相GaN薄膜。采用高分辨率双晶X射线衍射（DCXRD）,扫描电子显微镜（SEM）,原子力显微镜（AFM）和室温光致荧光光谱（RT-PL）进行分析。结果表明,有偏离化学计量比富Ga HT-GaN为过渡层生长的GaN薄膜质量和光致荧光特性均明显优于以LT-GaN为过渡层生长的GaN薄膜,得到GaN（0002）和（1012）的DCXRD峰,其半峰全宽（FWHM）分别为698s和842s,室温下的光致荧光光谱在361nm处有一个很强的发光峰,其半峰全宽为44．3meV。     

Influence of AlN Buffer Thickness on GaN Grown on Si(111) by Gas Source Molecular Beam Epitaxy with Ammonia

Hexagonal GaN is grown on a Si(111) substrate with AlN as a buffer layer by gas source molecular beam epitaxy (GSMBE) with ammonia. The thickness of AlN buffer is changed from 9 to 72nm. When the thickness of AlN buffer is 36nm, the surface morphology and crystal quality of GaN is optimal. The in-situ reflection high energy electron diffraction (RHEED) reveals that the transition to a two-dimensional growth mode of AlN is the key to the quality of GaN. However, the thickness of AlN buffer is not so critical to the residual in-plane tensile stress in GaN grown on Si(111) by GSMBE for AlN thickness between 9 to 72nm.     

ZnO Nanostructures Grown on A1N/Sapphire Substrates by MOCVD

ZnO nanorods and nanotubes are successful synthesized on A1N/sapphire substrates by metal-organic chemical vapour deposition （MOGVD）. The different morphology and structure properties of ZnO nanorods and nanotubes are found to be affected by the A1N under-layer. The photoluminescence spectra show the optical properties of the ZnO nanorods and nanotubes, in which a blueshift of UV emission is observed and is attributed to the surface effect.[第一段]     

SiC缓冲层对Si表面生长的ZnO薄膜结构和光电性能的改善

用脉冲激光沉积(PLD)技术制备了ZnO/SiC/Si和 ZnO/Si薄膜并制成了紫外探测器。利用X射线衍射(XRD),光致发光(PL)谱,I-V曲线和光电响应谱对薄膜的结构和光电性能进行了研究。实验结果表明:SiC缓冲层改善了ZnO薄膜的结晶质量和光电性能,其原因可能是SiC作为柔性衬底能够减少ZnO与Si 之间大的晶格失配和热失配导致的界面缺陷和界面态。     

Influence of Al Preflow Time on Surface Morphology and Quality of AlN and GaN on Si(111) Grown by MOCVD

We investigate the influence of Al preflow time on surface morphology and quality of AIN and GaN. The AIN and GaN layers are grown on a Si(111) substrate by metal organic chemical vapor deposition. Scanning electron microscopy, atomic force microscopy, x-ray diffraction and optical microscopy are used for analysis. Consequently,we find significant differences in the epitaxial properties of AIN buffer and the GaN layer, which are dependent on the Al preflow time. Al preflow layers act as nucleation sites in the case of AIN growth. Compact and uniform AIN nucleation sites are observed with optimizing Al preflow at an early nucleation stage, which will lead to a smooth AIN surface. Trenches and AIN grain clusters appear on the AIN surface while melt-back etching occurs on the GaN surface with excessive Al preflow. The GaN quality variation keeps a similar trend with the AIN quality, which is influenced by Al preflow. With an optimized duration of Al preflow, crystal quality and surface morphology of AIN and GaN could be improved.