Observation of positive and small electron affinity of Si-doped AlN films grown by metalorganic chemical vapor deposition on n-type 6H–SiC

We have investigated the electron affinity of Si-doped AlN films（N_（Si）= 1.0 × 10^（18）–1.0 × 10_（19）cm^（-3）） with thicknesses of 50, 200, and 400 nm, synthesized by metalorganic chemical vapor deposition（MOCVD） under low pressure on the ntype（001）6H–SiC substrates. The positive and small electron affinity of AlN films was observed through the ultraviolet photoelectron spectroscopy（UPS） analysis, where an increase in electron affinity appears with the thickness of AlN films increasing, i.e., 0.36 eV for the 50-nm-thick one, 0.58 eV for the 200-nm-thick one, and 0.97 e V for the 400-nm-thick one.Accompanying the x-ray photoelectron spectroscopy（XPS） analysis on the surface contaminations, it suggests that the difference of electron affinity between our three samples may result from the discrepancy of surface impurity contaminations.

Characterization of Crystalline Nanoparticles/Nanorods Synthesized by Atmospheric Plasma Enhanced Chemical Vapor Deposition of Perfluorohexane

A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or templates. Scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS） were used to characterize the morphology and the chem- ical compositions of nanoparticles. The average size of particles is about 100 nm and the length of synthesized nanorods is between 1 μm and 2.5/tm. The analyses of transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, selected area electron diffraction（SAED） and X-ray diffraction （XRD） reveals that the nanoparticles and nanorods are crystalline.

The Effect of Pressure on the Dissociation of H_2/CH_4Gas Mixture during Diamond Films Growth via Chemical Vapor Deposition

Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.

Structural and optical properties of Al_(1-x)In_xN epilayers on GaN template grown by metalorganic chemical vapor deposition

This paper reports that Al1-xInxN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%--20%. X-ray diffraction results indicate that all these Al1-xInxN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al1-xInxN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al1-xInxN epilayers. A bowing parameter of 6.5~eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al1-xInxN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al1-xInxN sample.

Room Temperature and Reduced Pressure Chemical Vapor Deposition of Silicon Carbide on Various Materials Surface

At room temperature, 300 K, silicon carbide film was formed using monomethylsilane gas on the reactive surface prepared using argon plasma. Entire process was performed at reduced pressure of 10 Pa in the argon plasma etcher, without a substrate transfer operation. By this process, the several-nanometer-thick amorphous thin film containing silicon-carbon bonds was obtained on various substrates, such as semiconductor silicon, aluminum and stainless steel. It is concluded that the room temperature silicon carbide thin film formation is possible even at significantly low pressure, when the substrate surface is reactive.

Cleaning of nitrogen-containing carbon contamination by atmospheric pressure plasma jet

Atmospheric pressure plasma jet(APPJ)was used to clean nitrogen-containing carbon films(C–N)fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sichuan University(SCU-PSI).The properties of the contaminated films on the surface of pristine and He-plasma pre-irradiated tungsten matrix,such as morphology,crystalline structure,element composition and chemical structure were characterized by scanning electron microscopy,grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy.The experimental results revealed that the removal of C–N film with a thickness of tens of microns can be realized through APPJ cleaning regardless of the morphology of the substrates.Similar removal rates of 16.82 and 13.78μm min^(-1)were obtained for C–N films deposited on a smooth pristine W surface and rough fuzz-covered W surface,respectively.This is a remarkable improvement in comparison to the traditional cleaning method.However,slight surface oxidation was found after APPJ cleaning,but the degree of oxidation was acceptable with an oxidation depth increase of only 3.15 nm.Optical emission spectroscopy analysis and mass spectrometry analysis showed that C–N contamination was mainly removed through chemical reaction with reactive oxygen species during APPJ treatment using air as the working gas.These results make APPJ cleaning a potentially effective method for the rapid removal of C–N films from the wall surfaces of fusion devices.

Arc Discharge Device Working at Atmospheric Pressure

Arc in vacuum is one of the important methods used to prepare carbon materials. However, the use of vacuum increases the cost of the arc method. This paper introduces an arc discharge device working at atmospheric pressure. The current-limiting resistor, capacitor and inductor make the discharge gentle. The electrode temperature can be adjusted from 2040 K to 3673 K. Carbon nanofibres were prepared at the electrode temperature of 3645 K by using this device.

重掺硅片表面APCVD法生长SiO_(2)薄膜的致密性

在硅片加工过程中,金属杂质的存在会增大pn结器件的漏电流,甚至直接导致pn结禁带宽度变窄,为防止出现硅外延过程中造成的自掺杂现象,通常在硅片表面生长一层高致密性的SiO_(2)薄膜。基于常压化学气相沉积(APCVD)法在6英寸(1英寸≈2.54 cm)n型硅片表面生长SiO_(2)薄膜,首先研究不同沉积温度、SiH_(4)和O_(2)的体积流量比对沉积速率和SiO_(2)薄膜致密性的影响,进一步探究了不同退火温度对SiO_(2)薄膜致密性的影响,以期获得致密性较高的SiO_(2)薄膜。采用HF腐蚀速率法表征其致密性,采用扫描电子显微镜(SEM)观察SiO_(2)薄膜的表面形貌,采用F50膜厚测试仪测试SiO_(2)薄膜的厚度。结果表明,沉积温度为400℃,SiH_(4)和O_(2)的体积流量比为1∶10,退火温度为1100℃时,制备的SiO_(2)薄膜的致密性为0.096 nm/s(采用体积分数为1%的HF腐蚀)。

基于大厚度六方氮化硼中子探测器的制备

六方氮化硼是一种中子敏感材料。介绍了使用低压气相化学沉积在1673K下以大约20μm/h的生长速率制备了高质量203μm厚的六方氮化硼。在氮化硼的两侧沉积厚度为100nm的金电极,制备了垂直结构的六方氮化硼中子探测器。该器件的电学性质表明制备的六方氮化硼材料的迁移率寿命的乘积(μτ)为2.8×10^(-6)cm^(2)/V,电阻率为1.5×10^(14)Ω·cm。在850V电压下,该探测器对热中子的探测效率为34.5%,电荷收集效率为60%。

8英寸晶圆低损耗厚氮化硅波导的工艺开发

在8英寸晶圆上制备氮化硅膜厚度超过400 nm时,产生的拉伸应力会使薄膜产生裂纹,为此,采用大马士革工艺,通过低压化学气相沉积分两步沉积、抛光氮化硅薄膜,同时结合棋盘格结构,减小应力,降低薄膜出现裂纹的风险。使用此方法成功在8英寸晶片上制造了截面尺寸为800 nm×0.8µm的氮化硅波导。两步沉积过后进行两次退火处理,可以进一步降低波导损耗,通过采用cut-back的方式测试波导传输损耗在1550 nm处为0.087 dB/cm,在1580 nm处为0.062 dB/cm。波导的弯曲损耗在半径为50µm时为0.0065 dB,在半径为80µm时仅为0.006 dB。

腔体材料对氧化铜箔衬底上制备石墨烯的影响

传统的化学气相沉积法制备的石墨烯普遍存在晶畴面积小、晶界缺陷多的问题,严重制约了大面积石墨烯的性能及应用。本文采用低压化学气相沉积技术在受限生长腔中的氧化铜箔衬底上制备石墨烯,对比研究了石英和刚玉两种材质的受限生长腔中,不同甲烷流量和生长时间条件下氧化铜箔衬底上石墨烯的形核生长状况。结果表明,相同生长条件下,相较于石英受限生长腔,虽然刚玉受限生长腔中石墨烯的晶畴尺寸较小,但是氧化铜箔衬底表面沉积的杂质颗粒较少,因而石墨烯的形核密度较低,晶体质量较高,更有利于大尺寸、高质量石墨烯的制备。

TOPCon太阳电池单面沉积Poly-Si的工艺研究

目前隧穿氧化层钝化接触(TOPCon)电池制造技术越来越成熟,所耗成本不断降低。行业内普遍采用低压化学气相沉积(LPCVD)方式进行双面沉积或单面沉积。单面沉积存在Poly-Si绕镀问题,严重影响电池片转化效率和外观质量,同时正面绕镀层去除难度较大,在用碱溶液去除绕镀层的同时,存在绕镀层去除不彻底或者非绕镀区域P^(+)层被腐蚀的风险,导致P^(+)发射极受损,严重影响电池片外观质量与性能。双面沉积可避免上述问题,但产能减少一半,制造成本增加。本文对单面沉积Poly-Si工艺及绕镀层去除工艺进行研究,在TOPCon电池正面及背面制作了一层合适厚度的氧化层掩膜,搭配合适的清洗工艺、去绕镀清洗工艺,既可有效地去除P^(+)层绕镀的Poly-Si,也可很好地保护正面P^(+)层及背面掺杂Poly-Si层不受破坏,同时可大幅提升产能。

MEMS微热板结构设计与仿真

微热板作为很多微机电系统(MEMS)传感器和执行器的基础结构,对器件性能影响极大,在气体传感器、燃料电池等领域都有着重要的应用。本文提出了几种悬浮式结构的微热板设计,并利用有限元分析方法(FEA),在气体传感器常用的工作温度400℃下,从热稳定性、机械稳定性、功耗和效率多方面对微热板进行了仿真,结果表明:螺旋形微热板的综合性能更好。进一步对可能影响微热板性能的多个因素,如电极电压、支撑层厚度、微加热器线宽间距比等进行了优化,获得了综合性能最优的微热板图形及参数设计。

培育大单晶金刚石的现状与未来

金刚石以其卓越的硬度和广泛的应用领域而闻名。由于天然金刚石的供应不足和高昂的价格,人工培育的大单晶金刚石成为了一种备受关注的替代品。文章首先阐述了金刚石的独特性质及其在科技领域的重要作用,解析了天然金刚石的稀缺性问题。然后详述了培育大单晶金刚石的发展历程,介绍了高温高压法和化学气相沉积法两种主要的合成方法及当前面临的技术难题。文章预测了培育大单晶金刚石的未来发展前景,分析了其在珠宝首饰、半导体、量子技术等领域的广阔应用空间及实现这些应用的技术挑战。最后,给出了加快培育大单晶金刚石技术成熟和产业化进程的几点建议。文章旨在全面系统地综述培育大单晶金刚石研究的现状与发展趋势,为该领域的科研工作者和产业界提供参考。

低压化学气相沉积氮化硅薄膜工艺研究

低压化学气相沉积法(Low-Pressure Chemical Vapor Deposition,LPCVD)沉积的氮化硅薄膜(LPSi_(3)N_(4))具有质量高、副产物少、厚度均匀性好等特性,常应用于局部氧化的掩蔽膜、电容的介质膜、层间绝缘膜等工艺制程。介绍低压化学气相沉积氮化硅薄膜(LPSi_(3)N_(4))的制备工艺,以及不同工艺参数的调试对氮化硅薄膜均匀性和沉积速率的影响。

Growth of large-area atomically thin MoS2 film via ambient pressure chemical vapor deposition

Atomically thin MoS2 films have attracted significant attention due to excellent electrical and optical properties.The development of device applications demands the production of large-area thin film which is still an obstacle.In this work we developed a facile method to directly grow large-area MoS2 thin film on Si O2 substrate via ambient pressure chemical vapor deposition method. The characterizations by spectroscopy and electron microscopy reveal that the as-grown MoS2 film is mainly bilayer and trilayer with high quality. Back-gate field-effect transistor based on such MoS2 thin film shows carrier mobility up to 3.4 cm2V-1s-1 and on/off ratio of 105. The large-area atomically thin MoS2 prepared in this work has the potential for wide optoelectronic and photonic device applications.

Effect of pressure on the semipolar GaN(10-11) growth mode on patterned Si substrates

In this paper, we investigate the effect of pressure on the growth mode of high quality （10-11） GaN using an epi- taxial lateral over growth （ELO） technique by metal organic chemical vapor deposition （MOCVD）. Two pressure growth conditions, high pressure （HP） 1013 mbar and low pressure growth （LP） 500 mbar, are employed during growth. In the high pressure growth conditions, the crystal quality is improved by decreasing the dislocation and stack fault density in the strip connection locations. The room temperature photoluminescence measurement also shows that the light emission intensity increases three times using the HP growth condition compared with that using the LP growth conditions. In the low temperature （77 K） photoluminescence, the defects-related peaks are very obvious in the low pressure growth samples. This result also indicates that the crystal quality is improved using the high pressure growth conditions.

Characterization of the heteroepitaxial growth of 3C-SiC on Si during low pressure chemical vapor deposition

3C-SiC heteroepitaxial layers were grown on Si substrates using a horizontal,hot-wall low pressure chemical vapor deposition system.The crystal quality,surface morphology and thickness uniformity of the layers were characterized by X-ray diffraction,atomic force microcopy and Fourier transform infrared spectroscopy,respectively.Growth of the epitaxial layer was determined to follow a three-dimensional island mode initially and then switch to a step-flow mode as the growth time increases.

Preparation of rutile TiO_(2) thin films by laser chemical vapor deposition method

TiO_(2) thin films were prepared on Pt/Ti/SiO_(2)/Si substrate by laser chemical vapor deposition(LCVD)method.The effects of laser power(P_(L))and total pressure(p_(tot))on the microstructure of TiO_(2) thin films were investigated.The deposition temperature(T_(dep))was mainly affected by P_(L),increasing with P_(L) increasing.The single-phase rutile TiO_(2) thin films with different morphologies were obtained.The morphologies of TiO_(2) thin films were classified into three typical types,including the powdery,Wulff-shaped and granular microstructures.p_(tot) and T_(dep) were the two critical factors that could be effectively used for controlling the morphology of the films.