分子束外延生长的极性与非极性BeZnO薄膜的比较研究

采用分子束外延设备在不同晶面蓝宝石衬底上(c面,a面,r面)生长BeZnO薄膜。使用复合缓冲层生长得到了高质量的BeZnO薄膜,X射线衍射半高宽达到600 arcsec。在c面与a面蓝宝石衬底上生长得到了极性BeZnO薄膜,在r面蓝宝石上生长得到了非极性BeZnO薄膜。共振拉曼光谱测试结果表明薄膜中的Be含量在同一水平。相对于c面与a面蓝宝石上的极性BeZnO薄膜,生长在r面蓝宝石衬底上的非极性BeZnO薄膜具有较大的表面粗糙度以及较大的半高宽,但是其光致发光谱中的紫外发光峰远远强于极性BeZnO薄膜,并且黄绿光发光峰弱于极性BeZnO薄膜。     

国产SiC衬底上利用AIN缓冲层生长高质量GaN外延薄膜

采用高温AlN作为缓冲层在国产SiC衬底上利用金属有机物化学气相外延技术生长GaN外延薄膜.通过优化AlN缓冲层的生长参数得到了高质量的GaN外延薄膜,其对称(0002)面和非对称(1012)面X射线衍射摇摆曲线的半峰宽分别达到130 arcsec和252 arcsec,这是目前报道的在国产SiC衬底上生长GaN最好的...     

γ-LiAlO2上非极性ZnO薄膜制备及其光谱性质研究

利用激光脉冲沉积(PLD)技术在(302)γ-LiAlO2衬底上成功生长了非极性的a面(11■0)ZnO薄膜.衬底温度为350℃时,薄膜是混合取向(a向和c向),以c面ZnO为主,且晶粒尺寸分布很宽;提高温度达500℃,薄膜变为单一的(11■0)取向,摇摆曲线半高宽0.65°,晶粒尺寸分布趋窄,利用偏振透射谱可以明显看出其面内的各向异性.衬底温度650℃下制备的样品晶粒继续长大,虽然摇摆曲线半高宽变大,但光致发光谱(PL)带边发射峰半高宽仅为105meV,比在350℃,500℃下制备的样品小1/5.     

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。     

基于MOCVD三步生长的GaAs/Si外延技术EI北大核心CSCD

在硅(Si)上外延生长高质量的砷化镓(GaAs)薄膜是实现硅基光源单片集成的关键因素。但是,Si材料与GaAs材料之间较大的晶格失配、热失配等问题对获得高质量的GaAs薄膜造成了严重影响。本文利用金属有机化学气相沉积(MOCVD)技术开展Si基GaAs生长研究。通过采用三步生长法,运用低温成核层、高温GaAs层与循环热退火等结合的方式,进一步降低Si基GaAs材料的表面粗糙度和穿透位错密度。并利用X射线衍射(XRD)ω-2θ扫描追踪采用不同方法生长的样品中残余应力的变化。最终,在GaAs低温成核层生长时间62 min(生长厚度约25 nm)时,采用三步生长、循环热退火等结合的方式获得GaAs(004)XRD摇摆曲线峰值半高宽(FWHM)为401″、缺陷密度为6.8×10^(7) cm^(-2)、5μm×5μm区域表面粗糙度为6.71 nm的GaAs外延材料,在材料中表现出张应力。     

高质量ZnO及BeZnO薄膜的发光性质

用分子束外延设备插入缓冲层在c面蓝宝石上生长得到高质量ZnO和BeZnO薄膜。XRD测试显示薄膜具有六方结构和c轴取向,并具有良好的晶体质量,其中ZnO薄膜的半高宽仅为108 arcsec,Be_xZn_1-xO薄膜的半高宽小于600 arcsec。对ZnO和BeZnO薄膜的拉曼光谱进行对比研究发现,随着Be元素的掺入,A₁(LO)、A₁(2LO)声子模频率往大波数方向移动,并且首次发现了与Be元素掺杂有关的局域振动模。利用变温光致发光光谱研究了薄膜的发光性质,结果显示ZnO薄膜室温光致发光只出现一个紫外发发光峰(378 nm),而低温光谱(80 K)则出现了很强的自由激子发光峰。随着温度的升高,束缚激子发光逐渐湮灭向自由激子发光转变,并且峰值位置红移。相对于ZnO薄膜,BeZnO薄膜的紫外发光主峰位置蓝移,并且由于Be元素的掺入导致薄膜晶体质量下降,在低温(80 K)光致发光光谱中没有出现强的自由激子发光峰。另外,在低温光致发光及拉曼光谱中,主峰位置在100~200 K之间有局部最大值,推测为由于合金晶格热膨胀系数失配而引起的应力效应。     

梯度铝镓氮缓冲层对氮化镓外延层性质的影响

采用金属有机物化学气相沉积系统在硅面碳化硅衬底的(0001)面上生长氮化铝缓冲层,并通过改变3层梯度铝镓氮(Al_xGa_(1-x)N:x=0.8,0.5,0.2)缓冲层的生长温度和氨气流量,制备出了高质量的氮化镓外延层。分别采用X射线衍射、原子力显微镜、光致发光谱和拉曼光谱对氮化镓外延层进行表征。实验结果表明,随着氮化镓外延层中张应力的降低,样品的晶体质量、表面形貌和光学质量都有显著提高。在最优的梯度铝镓氮缓冲层的生长条件下,氮化镓外延层中的应力值最小,氮化镓(0002)和(1012)面的摇摆曲线半峰宽分别为191 arcsec和243 arcsec,薄膜螺位错密度和刃位错密度分别为7×10~7cm~(-2)和3.1×108cm~(-2),样品表面粗糙度为0.381 nm。这说明梯度铝镓氮缓冲层可以改变氮化镓外延层的应力状态,显著提高氮化镓外延层的晶体质量。     

TFA-MOD方法制备YBCO超导薄膜研究

采用TFA-MOD方法在LaAlO3(001)单晶基片上制备了性能良好的YBCO超导薄膜:临界电流密度(Jc)可达3MA/cm2(77K,0T),超导转变温度Tc≈90K,转变宽度ΔTc=0.5K,其一次涂层厚度达338nm.通过X射线衍射(XRD)分析表明YBCO具有纯c-轴取向、无a-轴取向的晶粒存在.ω扫描分析表明该YBCO薄膜具有很好的面外外延性,其摇摆曲线的半高宽(FWHM)为0.653°. 用SEM分析也表明膜的表面无裂纹存在,表面平整,没有a轴晶粒生长.     

用等离子体辅助分子束外延生长氧化锌单晶薄膜

利用等离子体辅助分子束外延(P-MBE)方法,通过优化生长条件,在c平面蓝宝石(Al_2O_3)上生长出氧化锌(ZnO)单晶薄膜。使用反射式高能衍射仪(RHEED)原位监测到样品表面十分平整,X射线摇摆曲线(XRC)测得ZnO薄膜的<002>取向半峰全宽为0.20°,证实为ZnO单晶薄膜。室温下吸收谱(ABS)和光致发光(PL)谱显示了较强的激子吸收和发射,且无深能级(DL)发光。电学性能测量表明,生长的ZnO为n型半导体,室温下载流于浓度为7×10~(16) cm~(-3),与体单晶ZnO中的载流子浓度相当。     

分子束外延PbTe单晶薄膜的反常拉曼光谱研究

采用分子束外延(MBE)方法在BaF₂(111)衬底上生长了高质量的PbTe单晶薄膜， 拉曼光谱测量观察到了表面氧化物的振动模、布里渊区中心(q≈0)纵光学(LO)声子振动模以 及声子-等离子激元耦合模振动.随着显微拉曼光谱仪激光光斑聚焦深度的改变，各拉曼散射 峰的峰位、积分强度、半高宽等都表现出不同的变化趋势. 随着激光光斑聚焦位置从样品表 面上方3μm处变化到表面下方3μm处，PbTe外延薄膜的LO声子频率从119cm^-1移 动到124cm^{-1关键词： PbTe外延薄膜 拉曼散射 纵光学声子}     

ZnO薄膜肖特基二极管的研制

采用直流反应磁控溅射的方法,在Al/Si(100)衬底上沉积了ZnO晶体薄膜.利用Al和Pt作为与ZnO接触的欧姆电极与肖特基电极,制作了ZnO薄膜肖特基二极管.X射线衍射测试结果表明ZnO薄膜具有高度的c轴择优取向.原子力显微分析表明:样品表面光洁平整,晶粒尺寸约100nm,扩展电阻分析表明ZnO薄膜的厚度为0.4μm,载流子浓度为1.8×1015 cm-3,此后的霍尔测试证实了这一结果并说明ZnO的导电类型为n型.室温下的I-V测试显示ZnO肖特基二极管具有明显的整流特性.Pt与n型ZnO接触的势垒高度为0.54eV.文中的ZnO肖特基二极管为首次研制的原型器件,其性能可以通过器件结构与制作工艺的进一步优化而得到改善.     

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide(ZnO:In) thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate.1 and 2 at.% indium doped single-layer ZnO:In thin films with different amounts of acetic acid added in the initial solution were fabricated.The 1 at.% indium doped single-layers have triangle grains.The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82×10-3Ω·cm and particle grains.The doublelayers structure is designed to fabricate the ZnO:In thin film with low resistivity(2.58×10-3Ω·cm) and good surface morphology.It is found that the surface morphology of the double-layer ZnO:In film strongly depends on the substratelayer,and the second-layer plays a large part in the resistivity of the double-layer ZnO:In thin film.Both total and direct transmittances of the double-layer ZnO:In film are above 80% in the visible light region.Single junction a-Si:H solar cell based on the double-layer ZnO:In as front electrode is also investigated.     

Effect of aging time of ZnO sol on the structural and optical properties of ZnO thin films prepared by sol-gel method

In this work, ZnO thin films were prepared by sol-gel method and the effect of aging time of ZnO sol on the structural and optical properties of the films was studied. The structural characteristics of the samples were analyzed by an atomic force microscope and an X-ray diffractometer. The optical properties were studied by a UV-vis spectrophotometer and a fluorophotometer. The results show that the ZnO thin film prepared by the as-synthesized ZnO sol had relatively poor crystalline quality, low optical transmittance in the visible range and relatively weak ultraviolet emission performance. After the as-synthesized ZnO sol was aged for 24 h, the degree of the preferred crystal orientation along the c-axis of the ZnO thin film prepared by this aged sol was improved. At the same time, this film had a very smooth surface with uniform grains and both its visible range transmittance and ultraviolet emission intensity were obviously increased. These results suggest that appropriate aging of ZnO sol is very important for the improvement of structural and optical quality of ZnO thin films derived from sol-gel method.     

Induced growth of high quality ZnO thin filmsby crystallized amorphous ZnO

This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds (buffer layer), ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.     

基底对光学薄膜弱吸收测量的影响

 对表面热透镜技术测量光学薄膜弱吸收低频调制时不同基底对测量的影响进行了理论分析。用Lambda—900分光光度计测量了K9和石英基底的Ti₃O₅单层膜的吸收值,将该组样品作为定标片;用表面热透镜装置分别测量了BK7和石英空白基底及HfO₂,ZnO两组不同基底不同厚度单层膜样品的吸收。通过分析比较同一工艺条件下镀制的不同基底薄膜样品用与其同种和不同种基底定标片定标测量的结果,表明在低频测量时需要用与测量样品同种基底的定标片定标;不同厚度样品的测量结果表明,在不能严格满足热薄条件时,测量结果需引入修正值。     

低温外延生长平整ZnO薄膜

在较低温度下实现平整ZnO薄膜的生长有利于ZnO的可控p型掺杂以及获得陡峭异质界面。本文使用分子束外延方法,采用a面蓝宝石为衬底,在450 ℃下生长了一系列ZnO薄膜样品。在富氧生长的条件下,固定氧流量不变,通过调节锌源温度来改变锌束流,以此调控生长速率。样品的生长速率为40~100 nm/h。通过扫描电镜（SEM）表征发现：在高锌束流的生长条件下,样品表面有很多不规则的颗粒;降低锌的供应量后,样品表面逐渐平整。原子力显微镜（AFM）测试结果表明：样品的均方根表面粗糙度（RMS）只有0.238 nm,接近于原子级平整度。这种平整表面的获得得益于较低的生长速率,以及ZnO外延薄膜与a面蓝宝石衬底之间小的晶格失配。     

Low-temperature-processed ZnO thin films as electron transporting layer to achieve stable perovskite solar cells

Morphology and surface property of ZnO thin films as electron transporting layer in perovskite solar cells are crucial for obtaining high-efficient and stable perovskite solar cells. In this work, two different preparation methods of ZnO thin films were carried out and the photovoltaic performances of the subsequent perovskite solar cells were investigated. ZnO thin film prepared by sol–gel method was homogenous but provided high series resistance in solar cells, leading to low short circuit current density. Lower series resistance of solar cell was obtained from homogeneous ZnO thin film from spin-coating of colloidal ZnO nanoparticles (synthesized by hydrolysis–condensation) in a mixture of 1-butanol, chloroform and methanol. The perovskite solar cells using this film achieved the highest power conversion efficiency (PCE) of 4.79% when poly(3-hexylthiophene) was used as a hole transporting layer. In addition, the stability of perovskite solar cells was also examined by measuring the photovoltaic characteristic for six consecutive weeks with the interval of 2 weeks. It was found that using double layers of the sol–gel ZnO and ZnO nanoparticles provided better stability with no degradation of PCE in 10 weeks. Therefore, this work provides a simple method for preparing homogeneous ZnO thin films in order to achieve stable perovskite solar cells, also for controlling their surface properties which help better understand the characteristics of perovskite solar cells.     

Sn掺杂ZnO薄膜的室温气敏性能及其气敏机理

采用化学气相沉积方法在预制好电极的玻璃基底上制备出Sn掺杂ZnO薄膜和纯ZnO薄膜. 两种样品典型的形貌为四足状ZnO晶须, 其直径约为150-400 nm, 呈疏松状结构. 气敏测试结果显示Sn掺杂ZnO薄膜具有优良的室温气敏性, 并对乙醇具有良好的气敏选择性, 而纯ZnO薄膜在室温条件下对乙醇和丙酮均没有气敏响应. X射线衍射结果表明两种样品均为六方纤锌矿结构. Sn掺杂ZnO样品中没有出现Sn及其氧化物的衍射峰, 其衍射结果与纯ZnO样品对比, 衍射峰向小角度偏移. 光致发光结果表明, Sn掺杂ZnO薄膜与纯ZnO薄膜均出现紫外发光峰和缺陷发光峰, 但是Sn的掺杂使得ZnO的缺陷发光峰明显增强. 将Sn掺杂ZnO样品在空气中退火后, 其室温气敏性消失, 说明Sn掺杂ZnO样品的室温气敏性可能与其缺陷含量高有关. 采用自由电子散射模型解释了Sn掺杂ZnO薄膜的室温气敏机理.     

过渡金属与F共掺杂ZnO薄膜结构及磁、光特性

采用溶胶-凝胶法在玻璃衬底上制备了过渡金属元素与F共掺杂Zn_0.98-xTM_xF_0.02O (TM_x=Cu_0.02, Ni_0.01, Mn_0.05, Fe_0.02, Co_0.05)薄膜, 进而利用X射线衍射仪、扫描电子显微镜、紫外-可见透过谱、光致发光及振动样品磁强计等研究了薄膜的表面形貌、微结构、禁带宽度及光致发光(PL)和室温磁学特性. 研究表明: 掺杂离子都以替位的方式进入了ZnO晶格, 掺杂不会破坏ZnO的纤锌矿结构. 其中Zn_0.93Co_0.05F_0.02O薄膜样品的颗粒尺寸最大, 薄膜的结晶度最好且c轴择优取向明显; Zn_0.93Mn_0.05F_0.02O薄膜样品的颗粒尺寸最小, 薄膜结晶度最差且无明显的c轴择优取; Cu, Ni, Fe与F共掺杂样品的颗粒尺寸大小几乎相同. TM掺杂样品均表现出很高的透过率, 同时掺杂后的薄膜样品的禁带宽度都有不同程度的红移. PL谱观察到Zn_0.98-xTM_xF_0.02O薄膜的发射峰主要由较强的紫外发射峰和较弱的蓝光发射峰组成. Zn_0.93Mn_0.05F_0.02O薄膜样品的紫外发光峰最弱, 蓝光发射最强, 饱和磁化强度最大; 与之相反的是Zn_0.96Cu_0.02F_0.02O薄膜, 其紫外发光峰最强, 蓝光发射最弱, 饱和磁化强度最小. 结合微结构和光学性质对Zn_0.98-xTM_xF_0.02O薄膜的磁学性质进行了讨论.     

In_2O_3:Sn中间层改善B掺杂ZnO薄膜的性能及其应用研究

金属有机化学气相沉积(MOCVD)法生长的掺硼氧化锌(BZO)薄膜,具有天然的"类金字塔"绒面结构,作为硅基薄膜太阳电池的前电极具有良好的陷光效果.但直接获得的BZO薄膜表面形貌过于尖锐,影响后续硅基薄膜材料生长质量及太阳电池的光电转换效率.本文设计了以一层超薄In2O3:Sn(ITO)薄膜(～4 nm厚度)作为中间层的多层膜,并通过对顶层BZO薄膜的厚度调制,改善BZO薄膜的表面特性,薄膜结构为:glass/底层BZO/ITO/顶层BZO.合适厚度的顶层BZO薄膜有助于获得类似"菜花状"形貌特征,尖锐的表面趋于"柔和",而较厚的顶层BZO薄膜仍然保持"类金字塔状"结构."柔和"的BZO薄膜表面结构有助于提高后续生长薄膜电池的结晶质量.将获得的新型"三明治"结构多层膜应用于p-i-n型氢化微晶硅(μc-Si:H)薄膜太阳电池,相比传统的BZO薄膜,电池的量子效率QE在500—800 nm波长范围提高了～10%,并且电池的Jsc和Voc均有所提高.