Preparation, characterization and electrochemical properties of boron-doped diamond films on Nb substrates

A series of boron-doped polycrystalline diamond films were prepared by hot filament （HF） chemical vapor deposition on Nb substrates. The effects of B/C ratio of reaction gas on film morphology, growth rate, chemical bonding states, phase composition and electrochemical properties of each deposited sample were studied by scanning electron microscopy, Raman spectra, X-ray diffraction, microhardness indentation, and electrochemical analysis. Results show that the average grain size of diamond and the growth rate decrease with increasing the B/C ratio. The diamond films exhibit excellent adhesion under Vickers microhardness testing （9.8 N load）. The sample with 2% B/C ratio has a wider potential window and a lower background current as well as a faster redox reaction rate in H2SO4 solution and KFe（CN）6 redox system compared with other doping level electrodes.

Effect of deposition temperature on properties of boron-doped diamond films on tungsten carbide substrate

Boron-doped diamond(BDD)films were deposited on the tungsten carbide substrates at different substrate temperatures ranging from 450 to 850°C by hot filament chemical vapor deposition(HFCVD)method.The effect of deposition temperature on the properties of the boron-doped diamond films on tungsten carbide substrate was investigated.It is found that boron doping obviously enhances the growth rate of diamond films.A relatively high growth rate of 544 nm/h was obtained for the BDD film deposited on the tungsten carbide at 650°C.The added boron-containing precursor gas apparently reduced activation energy of film growth to be 53.1 kJ/mol,thus accelerated the rate of deposition chemical reaction.Moreover,Raman and XRD analysis showed that heavy boron doping(750 and 850°C)deteriorated the diamond crystallinity and produced a high defect density in the BDD films.Overall,600-700°C is found to be an optimum substrate temperature range for depositing BDD films on tungsten carbide substrate.

The modulation effect of substrate doping on multi-node charge collection and single-event transient propagation in 90-nm bulk complementary metal-oxide semiconductor technology

Variation of substrate background doping will affect the charge collection of active and passive MOSFETs in complementary metal-oxide semiconductor （CMOS） technologies, which are significant for charge sharing, thus affecting the propagated single event transient pulsewidths in circuits. The trends of charge collected by the drain of a positive channel metal-oxide semiconductor （PMOS） and an N metal-oxide semiconductor （NMOS） are opposite as the substrate doping increases. The PMOS source will inject carriers after strike and the amount of charge injected will irlcrease as the substrate doping increases, whereas the source of the NMOS will mainly collect carriers and the source of the NMOS can also inject electrons when the substrate doping is light enough. Additionally, it indicates that substrate doping mainly affects the bipolar amplification component of a single-event transient current, and has little effect on the drift and diffusion. The change in substrate doping has a much greater effect on PMOS than on NMOS.

Optical Absorption Measurements on Nitrogen-doped 6H-SiC Single Crystals

6H-SiC bulk crystals have been prepared by sublimation method in an inductively heated growth reactor. The effect of nitrogen doping on absorption for 6H-SiC was investigated. The absorption measurement based on optical method is a non-destructive and non-contact method. The band-gap narrowing with higher doping concentration was observed. For n-type doping below band-gap absorption band at 623 nm for 6H-SiC was observed. The peak intensity of the absorption band increased with increasing charge carrier concentration obtained from Hall measurements. It is also found that the nitrogen doping level decreased in the radial direction and it was the highest at the beginning of growth.

Preparation and Characterization of Transparent Conductive Zinc Doped Tin Oxide Thin Films Prepared by Radio-frequency Magnetron Sputtering

High transparent and conductive thin films of zinc doped tin oxide （ZTO） were deposited on quartz substrates by the radio-frequency （RF） magnetron sputtering using a 12 wt% ZnO doped with 88 wt% SnO2 ceramic target.The effect of substrate temperature on the structural,electrical and optical performances of ZTO films has been studied.X-ray diffraction （XRD） results show that ZTO films possess tetragonal rutile structure with the preferred orientation of （101）.The surface morphology and roughness of the films was investigated by the atomic force microscope （AFM）.The electrical characteristic （including carrier concentration,Hall mobility and resistivity） and optical transmittance were studied by the Hall tester and UV- VIS,respectively.The highest carrier concentration of -1.144×1020 cm-3 and the Hall mobility of 7.018 cm2（V ·sec）-1 for the film with an average transmittance of about 80.0% in the visible region and the lowest resistivity of 1.116×10-2 Ω·cm were obtained when the ZTO films deposited at 250 oC.

Influence of Argon Gas Pressure on the ZnO:Al Films Deposited on Flexible TPT Substrates at Room Temperature by Magnetron Sputtering

Aluminium doped ZnO thin films（ZnO︰Al） were deposited on transparent polymer substrates at room temperature by rf magnetron sputtering method from a ZnO target with Al2O3 of 2.0 wt%. Argon gas pressure varied from 0.5 Pa to 2.5 Pa with radio frequency power of 120 W. XRD results showed that all the ZnO︰Al films had a polycrystalline hexagonal structure and a （002） preferred orientation with the c-axis perpendicular to the substrate. The grain sizes of the films were 6.3-14.8 nm.SEM images indicated the ZnO︰Al film with low Argon gas pressure was denser and the deposition rate of the films depended strongly on the Argon gas pressure, increasing firstly and then decreasing with increasing the pressure. The highest deposition rate was 5.2 nm/min at 1 Pa. The optical transmittance of the ZnO︰Al films increased and the blue shift of the absorption edge appeared when the Argon gas pressure increased. The highest transmittance of obtained ZnO︰Al films at 2.5 Pa was about 85% in the visible region. The electrical properties of the films were worsened with the increase of the Argon gas power from 1 Pa to 2.5 Pa. The resistivity of obtained film at 1.0 Pa was 2.79×10-2 Ω·cm.

Effect of substrate doping on threshold voltages of buried channel pMOSFET based on strained-SiGe technology

The effect of substrate doping on the threshold voltages of buried channel pMOSFET based on strained-SiGe technology was studied.By physically deriving the models of the threshold voltages,it is found that the layer which inversely occurs first is substrate doping dependent,giving explanation for the variation of plateau observed in the C-V characteristics of this device,as the doping concentration increases.The threshold voltages obtained from the proposed model are-1.2805 V for buried channel and-2.9358 V for surface channel at a lightly doping case,and-3.41 V for surface channel at a heavily doping case,which agrees well with the experimental results.Also,the variations of the threshold voltages with several device parameters are discussed,which provides valuable reference to the designers of strained-SiGe devices.

Characteristics of In_(0.52)Al_(0.48)As Grown on InP(100) Substrates by Molecular Beam Epitaxy: Growth Optimisation and Effects of Si Doping

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

膨胀土边坡水泥基生境基材外掺纤维改性研究

分析外掺纤维对膨胀土边坡水泥基生境基材护坡性能的影响,为膨胀土边坡防护及生态修复提供理论依据。分别外掺聚丙烯纤维、玄武岩纤维和棕纤维制备3种不同的水泥基生境基材,通过边坡模型试验定期测定各边坡生境基材的物理、力学及生态指标。结果表明:①与对照组(CK组)相比,聚丙烯纤维、玄武岩纤维及棕纤维的掺入可显著改善基材的内部孔隙结构,其渗透系数降低范围分别为28.43%~39.39%、5.58%~10.13%、31.36%~43.14%;纤维掺入提高了基材的抗剪强度,其黏聚力提高范围分别为28.37%~32.75%、12.23%~14.82%、32.52%~37.21%,内摩擦角提高范围分别为0.07%~1.62%、0.41%~1.21%、1.31%~2.07%。②纤维的加入通过改善基材的孔隙结构,促进了植物生长,从全期平均含量来看,3组外掺纤维组相较CK组的地下生物量分别提高了26.38%、8.93%、51.06%。③边坡土体在经历自然降雨后,土体含水率随深度的增加而减小,随降雨量的增大而增大,外掺纤维组降雨前后含水率差值明显低于CK组,其作用效果依次为棕纤维>聚丙烯纤维>玄武岩纤维。综合分析得出:外掺纤维对膨胀土边坡水泥基生境基材的护坡性能有明显的提升效果;综合环保及成本因素,棕纤维运用于实际工程更符合可持续发展理念。该研究成果可对膨胀土边坡生态防护提供理论支撑及技术指导,并对其他特殊土边坡生态防护具有借鉴意义。

硅掺杂对不同衬底的氮化铝薄膜的影响研究

选择硅作为N型杂质源,采用高温热扩散的方式进行实验研究.采用磁控溅射法在硅/蓝宝石衬底上外延的AlN薄膜上沉积纯硅.硅的溅射时间决定了硅层的厚度,从而决定了硅的掺杂剂量.在氮气气氛下高温(1150℃)热扩散4小时后,AlN薄膜表面的硅原子扩散进入AlN晶格,取代铝原子的位置,形成掺杂硅的AlN薄膜.有效的硅掺杂导致AlN(002)衍射峰向一个较大的角度偏移,且偏移的角度随掺杂的浓度升高而增大.且硅衬底上的样品,使用能量色散光谱仪测试结果表明,衬底硅将作为固定的扩散源扩散到薄膜中,增加非故意掺杂浓度,因此可以在整个薄膜截面内测量到硅元素.蓝宝石的衬底的样品在热扩散后出现裂纹.

Mn_(3)O_(4)-Ni/C@FeOOH复合材料的界面构筑及其在电解水制氢中的应用

为制备一种高效、低能耗的电解水制氢催化剂,采用溶剂热法制备了Ni掺杂的前驱体Mn-Ni MIL,再通过高温热处理法将其碳化成Mn_(3)O_(4)-Ni/C基底,随后以水浴沉积法将无定型结构FeOOH超细颗粒负载在Mn_(3)O_(4)-Ni/C基底表面,得到同时含Mn、Ni、Fe 3种金属元素的复合材料Mn_(3)O_(4)-Ni/C@FeOOH。基于Mn_(3)O_(4)-Ni/C@FeOOH复合材料的形貌和结构表征可知,其保留了前驱体的八面体形貌,其中Ni以金属单质形式均匀分布在碳质基底中,且FeOOH的负载保证了材料的高比表面积,为后续的催化反应提供充足的活性位点。电化学性能测试结果显示所得复合材料Mn_(3)O_(4)-Ni/C@FeOOH的碱性电解水阳极析氧催化活性优良,在驱动电流密度10 mA/cm2时所需的过电势为288 mV,与其复合前的单独组分Mn_(3)O_(4)-Ni/C(334 mV)和FeOOH(342 mV)相比,分别提升了14%和16%。通过界面构筑合成的Mn_(3)O_(4)-Ni/C@FeOOH复合材料具有低成本、长周期稳定的竞争优势,在商业应用方面前景广阔。

Effects of La^(3+) Non-Uniformly Doping in TiO_2 Films on Photocatalytic Activities

TiO2 thin films non-uniformly doped by La^3＋ were prepared by sol-gel method. The comparison of thin film activities, which was characterized by photocatalytic degradation of methyl orange, shows that doping modes have great activities. The non-uniformly effects on photocatalytic doped TiO2 films resuh in good photocatalytic activities with an optimal concentration; about 0. 5% （ atom fraction ）. UV-Vis transmittance spectra indicate that the absorption edges of these TiO2 thin films shift to ward longer wave- lengths remarkably, and electrochemical behavior also reveales that e^- -h^＋ pairs are prone to formation and separation under UV irradiation. The mechanism of photocatalytic activities are enhanced by La^3＋ non-uniformly doping was discussed on the analogy of the theory of “window effect” of solar cell heterojunction.

Photocatalytic properties of P25-doped TiO_2 composite film synthesized via sol–gel method on cement substrate

TiO2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO2 composite film on a cement substrate via a sol–gel method. In this case, Rhodamine B（Rh B）was employed as the target organic pollutant. The self-generated TiO2 film and the P25-TiO2 composite film were characterized by X-ray diffraction（XRD）, N2 adsorption/desorption measurements, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and diffuse reflectance spectroscopy（DRS）. The photodegradation efficiencies of the two films were studied by Rh B removal in water under UV（ultraviolet） irradiation. Over 4 day exposure, the P25-TiO2 composite film exhibited higher photocatalytic performance than the self-generated TiO2 film. The photodegradation rate indicated that the efficiency of the P25-TiO2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants.

Improved breakdown voltage of AlGaN/GaN HEMTs grown on Si substrates using partially Mg-doped GaN buffer layer by MOCVD

AlGaN/GaN high electron mobility transistors(HEMTs) were grown on Si substrates by MOCVD.In the HEMT structure,a 1 μm GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer leakage.The AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg doping.For the device with the partially Mg-doped GaN buffer layer,a lower drain leakage current density of 55.8 nA/mm,a lower gate leakage current density of 2.73 μA/mm,and a higher off-state breakdown voltage of 104 V were achieved with device dimensions Lg/Wg/Lgs/Lgd=1/10/1/1 μm,better than the device with the undoped GaN buffer layer,which has a higher drain leakage current density of 9.2 μA/mm,a higher gate leakage current density of 91.8 μA/mm,and a lower off-state breakdown voltage of 87 V with the same device dimensions.

Influence of the distance between target and substrate on the properties of transparent conducting Al-Zr co-doped zinc oxide thin films

Highly transparent and conducting Al-Zr co-doped zinc oxide （ZAZO） thin films were successfully prepared on glass substrate by direct current （DC） magnetron sputtering at room temperature. The distance between target and substrate was varied from 45 to 70 mm. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 70 to 50 mm. However, as the distance decreases further, the crystallinity decreases and the electrical resistivity increases. When the distance between target and substrate is 50 ram, it is found that the lowest resistivity is 6.9 × 10^-4Ω cm. All the deposited films show a high average transmittance of above 92% in the visible range.

Improved Non-uniformity Correction Method for Uncooled Microbolometer

The uncooled microbolometer has a severe temperature requirement for non-uniformity correction. An improved two-point non-uniformity correction method is proposed, which can operate in wider uniform substrate temperatures. This method can control the bias voltage of MOS transistors by memory and DAC to meet two restrictions about responsivity and offset before traditional two-point calibration is implemented. The simulation results seem that this non-uniformity correction can work at uniform substrate temperature with fluctuant range of 4K.

硫硒元素掺杂金刚石表面的生长位点研究

采用基于密度泛函理论的第一性原理计算方法,研究了硫(S)掺杂、硒(Se)掺杂以及硫硒共掺杂金刚石基底对化学气相沉积金刚石涂层时的不同活性基团的吸附生长过程,计算分析了三种不同基底对沉积气氛中不同碳氢基团(C、CH、CH_(2)、CH_(3))的吸附能、Mulliken电荷分布和化学键重叠布居数等性质。计算结果表明:硫掺杂模型与C、CH和CH_(2)之间,硒掺杂模型与C、CH基团之间,硫硒共掺杂模型与C、CH和CH_(2)之间都通过电荷转移形成了共价键,硫掺杂模型与CH基团以及硫硒共掺杂模型与C基团之间的成键很接近理想金刚石的C—C键,添加硫元素和硒元素可以在原有的金刚石颗粒同质外延生长的基础上增加更多生长活性位点。

Al掺杂量和衬底温度对ALD沉积的ZnMgO∶Al薄膜的影响

ZnMgO∶Al具有近紫外透明导电薄膜的应用潜力.使用原子层沉积(ALD)制备了ZnMgO∶Al薄膜,研究了Al掺杂量和衬底温度对ZnMgO∶Al薄膜的物相和光电性能的影响.研究结果表明,在较高Mg含量下,Al重掺杂(>5%)将破坏ZnMgO∶Al的结晶性,迅速恶化其电学性能.ZnMgO∶Al的光学性质对衬底温度不敏感,但较高的衬底温度(210℃)能大幅改善薄膜的导电性.

薄膜厚度对ZnO∶Al透明导电膜性能的影响

铝掺杂的氧化锌 (ZnO∶Al)透明导电膜是采用射频磁控溅射法在有机衬底 (Polypro pyleneadipate,PPA)和Corning 70 5 9玻璃上制备的。详细研究了薄膜的结构性质、光学和电学性质随薄膜厚度的变化关系。制备的ZnO∶Al薄膜具有 (0 0 2 )面的单一择优取向的多晶六角纤锌矿结构 ,性能优良的薄膜电阻率在两种衬底上分别为 2 .5 5× 1 0 - 3 Ω·cm和1 .89× 1 0 - 3 Ω·cm ,平均透射率达到了 80 %和 85 %。

铜铟镓硒(CIGS)薄膜太阳能电池的研究进展

综述了CIGS薄膜太阳能电池近年来的研究进展。概述了CIGS薄膜的组织结构、性能特性及其之间的联系;介绍了CIGS薄膜吸收层的多种制备方法,如多元共蒸发法、溅射后硒化法、电沉积法、喷涂高温分解法等;概述了Na掺杂对CIGS电池性能的促进作用及其机理;总结了柔性衬底CIGS薄膜太阳能电池的研究情况;最后从理论和实验研究方面展望了CIGS薄膜太阳能电池的研究方向。