PLD工艺制备高质量ZnO/Si异质外延薄膜

采用脉冲激光沉积工艺在不同条件下以Si(111)为衬底制备了Zno薄膜.通过对不同氧压下(0～50Pa)沉积的样品的室温PL谱测试表明,氧气氛显著地提高了薄膜的发光质量,在50Pa氧气中沉积的ZnO薄膜具有最强的近带边UV发射.XRD测试说明在氧气氛中得到的薄膜结晶质量较差,没有单一的(002)取向.利用-低温(500℃)沉积的ZnO薄膜作缓冲层,得到了高质量的ZnO外延膜.与直接沉积的ZnO膜相比,生长在缓冲层上的ZnO膜展现出规则的斑点状衍射花样,而且拥有更强的UV发射和更窄的UV峰半高宽(98meV).对不同温度下沉积的缓冲层进行了RHEED表征,结果表明,在600～650℃之间生长缓冲层,有望进一步改善ZnO外延膜的质量.

氧离子束辅助激光淀积生长ZnO/Si薄膜深度剖析

对于在Si(111)上用氧离子束辅助(O~+-assisted)脉冲激光淀积(PLD)生长的ZnO薄膜,用X射线光电子能谱(XPS)深度剖析方法对长成的样品进行了异位测试,分析了导致各峰峰位能移的因素;通过异位与原位XPS谱图的比较,指出O+-assisted PLD法生成的ZnO薄膜中存在孔隙;指出生长出的ZnO薄膜中含si成分的厚度不超过18 nm;同时探讨了在长成的ZnO/Si上继续生长GaN薄膜的可行性.

Si基外延GaN的结构和力学性能

采用MOCVD技术在Si衬底(111)面上生长了GaN外延膜,分析了薄膜表面形貌和Si基GaN的临界载荷,研究了表面发光性能和GaN晶体质量随深度的变化.结果表明,外延层的表面比较平整,多组超晶格插入层可以进一步降低位错密度,提高晶体质量.膜的表面有许多颗粒状的发光中心,除了强的带边峰外,还有弱的黄光带和红光带,这可能是ON与VGa所产生的深能级跃迁产生的.GaN的晶体质量具有梯度变化,GaN外延层的上层晶体质量比较好,界面附近比较差,但是外延层与衬底的结合强度较高,临界载荷达到2.05 N.

Si上外延的n型3C-SiC欧姆接触研究

用LPCVD在si（111）上异质外延了n型3C-SiC，并在所外延的3C-SiC上蒸发Au／Ti，通过不同温度下的RTA（快速热退火）形成欧姆接触。用两种不同的传输线模型对Ti／3C-SiC欧姆接触的ρc（比接触电阻率）进行测量，在750℃退火后Ti／3C-SiC的ρc达到了最低值为3．68×10^-5Ω·cm^2这满足了应用的要求。AES分析结果还表明由于Ti的氧化，更高温度下的退火会使ρc增大。

氧离子束辅助激光淀积生长ZnO/Si的研究

利用X射线衍射(XRD),X射线摇摆曲线(XRC)和X射线光电子能谱(XPS)分析方法对氧离子束辅助激光淀积生长的ZnO/Si异质结薄膜进行了分析.结果表明:用该法可生长出高度c轴单一取向ZnO薄膜,XRC的半高宽度(FWHM)仅为2.918°.表明此生长方法经优化,可生长出单晶质量很好的ZnO/Si薄膜.

低能离子束方法制备重掺杂Fe的Si:Fe固溶体

利用质量分离的低能离子束方法,以离子能量为1000eV,剂量为3×1017cm-2,室温下往p型Si(111)单晶衬底注入Fe离子,注入的样品在400 C真空下进行热处理.俄歇电子能谱法(AES)对原位注入样品深度分析表明Fe离子浅注入到p型Si单晶衬底,注入深度约为42nm.X射线衍射法(XRD)对热处理样品结构分析发现只有Si衬底的衍射峰,没有其他新相.X射线光电子能谱法(XPS)对热处理样品表面分析发现Fe2p束缚能对应于单质Fe的峰,没有形成Fe的硅化物.这些结果表明重掺杂Fe的Si:Fe固溶体被制备.电化学C-V法测量了热处理后样品载流子浓度随深度的分布,发现Fe重掺杂Si致使Si的导电类型从p型转为n型,Si:Fe固溶体和Si衬底形成pn结,具有整流特性.

Si衬底上无坑洞3C-SiC的外延生长研究

在冷壁式不锈钢超高真空系统上，利用低压化学气相淀积（LPCVD）方法在直径为50 mm的单晶Si(100)和Si(111)晶向衬底上生长出了高取向无坑洞的晶态立方相碳化硅（3C-SiC）外延材料，利用反射高能电子衍射（RHEED）和扫描电镜（SEM）技术详细研究了Si衬底的碳化过程、碳化层的表面形貌及缺陷结构，获得了界面平整光滑、没有空洞形成的3C-SiC外延材料，并采用X- 射线衍射（XRD)、双晶X- 射线衍射（DXRD）和霍尔(Hall）测试等技术研究了外延材料的结构和电学特性。

使用 X射线衍射技术判定 Si C单晶体的结构和极性（英文）

使用四圆衍射仪和双晶衍射技术，分析了SiC体单晶的结构和极性。SiC单晶体由化学气相淀积法获得。六方{10-15}极图证明了该单晶结构为6H型。三轴晶衍射中的ω模式衍射强度的差异判定了该单晶的Si终端面和C终端面，即极性面。两个面的一、二、三级衍射强度的测量比值与经过散射因子修正后计算的结构振幅平方比值｜F(000L)｜~2/｜F(000-L)｜~2非常吻合。因此，利用极性面的衍射强度差异，可以方便、严格地判断具有类似结构如2H{0001}、4H{0001}及3C-SiC{111}的极性。

图形衬底上应变SiGe/Si超晶格的结构及光致发光研究

该文研究了在Si的图形衬底上生长应变SiGe/SI超晶格的结构和其光致发光性质。图形衬底由光刻形成的类金字塔结构组成。发现在组成倒金字塔结构的(111)面的交界处有富Ge的SiGe量子线出现。对相同条件下图形衬底和平面衬底上的应变SiGe层的光致发光光谱进行了比较，图形衬底上总的发光强度相对提高了5.2倍。认为这种提高同富Ge的SiGe量子线的产生相关。

MOCVD growth of high quality crack-free GaN on Si(III) substrates

High quality crack free GaN epilayers were grown on Si(111) substrates. Low temperature AlN interlayer grown under low V/III ratio was used to effectively eliminate the formation of micro-cracks. It is found that tensile stress in the GaN epilayer decreases as the N/Al ratio decreases used for AlN interlayer growth. The high optical and structural qualities of the GaN/Si samples were characterized by RBS, PL and XRD measurements. The RT-PL FWHM of the band edge emission is only 39.5meV The XRD FWHM of the GaN/Si sample is 8.2arcmin, which is among the best values ever reported.

Influence of the rapid thermal annealing on the properties of thin a-Si films

The variation of the structure, morphology and the electrical properties of thin amorphous silicon films caused by Rapid Thermal Annealing is studied. The films annealed at 1200degreesC for 2 minutes change their structure to polycrystalline and as a result their resistivity decreases by 4 orders of magnitude. Due to the small thickness of the as deposited amorphous silicon the obtained poly-Si is strongly irregular and has many discontinuities in its texture.

Dielectric properties of Bi2Ti2O7 films grown on Si(100) substrate by APMOCVD

The growth of Bi2Ti2O7 films with (111) orientation on Si(100) substrate by atmospheric pressure metal-organic chemical vapor deposition(APMOCVD) technique at 480similar to550 degreesC is presented. The films were characterized by X-ray diffraction analysis, atomic force microscopy and electron diffraction. The results show high quality Bi2Ti2O7 films with smooth shinning surface. The dielectric properties and C-V characterization of the films were studied. The dielectric constant (epsilon) and loss tangent (tgdelta) were found to be 180 and 0.01 respectively. The charge storage density was 31.9fC/mum(2). The resistivity is higher than 1x10(12) Omega. .cm under the applied voltage of 5V. The Bi2Ti2O7 films are suitable to be used as a new insulating gate material in dynamic random access memory (DRAM).

Si-based resonant-cavity-enhanced photodetector

Resonant-cavity-enhanced (RCE) photodetectors have been demonstrated to be able to improve the bandwidth-efficiency product. We report one top-illumination and one bottom-illumination SiGe/Si multiple quantum-well (MQW) RCE photodetectors fabricated on a separation-by-implanted-oxygen (SIMOX) wafer operating near 1300nm, The buried oxide layer in SIMOX is used as a mirror to form a vertical cavity with the silicon dioxide/silicon Bragg reflector deposited on the top surface. A peak responsivity with a reverse bias of 5V is measured 10.2mA/W at 1285nm, and a full-width at half maximum of 25nm for the top-illumination RCE photodetector, and 19mA/W at 1305nm, and a full-width at half maximum of 14nm for the bottom-illumination one. The external quantum efficiency of the bottom-illumination RCE photodetector is up to 2.9% at 1305nm with a reverse bias of 25V. The responsivity of the bottom-illumination RCE photodetector is improved by two-fold compared with that of the top-illumination one.

The effects of carbonized buffer layer on the growth of SiC on Si

Carbonized buffer layers were formed with C2H4 on Si(100) and Si(111) substrates using different methods and SIC epilayers were grown on each buffer layer at 1050 degrees C with simultaneous supply of C2H4 and Si2H6. The structure of carbonized and epitaxy layers was analyzed with in situ RHEED. The buffer layers formed at 800 degrees C were polycrystalline on both Si(100) and Si(111) substrates whereas they were single crystals, with twins on Si(100) and without tu ins on Si(111)substrates. when formed with a gradual rise in substrate temperature from 300 degrees C to growth temperature. Raising the substrate temperature slowly results in the formation of more twins. Epilayers grown on carbonized polycrystalline lavers are polycrystalline. Single crystal epilayers without twins grow on single crystalline buffer layers without twins or with a few twins. (C) 1999 Elsevier Science B.V. All rights reserved.

Aluminum induced crystallization of strongly (111) oriented polycrystalline silicon thin film and nucleation analysis

A polycrystalline silicon thin film was fabricated on glass substrate by means of aluminum induced crystallization (AIC). Al and alpha-Si layers were deposited by magnetron sputtering respectively and annealed at 480A degrees C for 1 h to realize layer exchange. The polycrystalline silicon thin film was continuous and strongly (111) oriented. By analyzing the structure variation of the oxidation membrane and lattice mismatch between gamma-Al2O3 and Si, it was concluded that aluminum promoted the formation of (111) oriented silicon nucleus by controlling the orientation of gamma-Al2O3, which was formed at the early stage of annealing.