Influence of reaction gas flows on the properties of SiGe:H thin film prepared by plasma assisted reactive thermal chemical vapour deposition

A new preparing technology, very high frequency plasma assisted reactive thermal chemical vapour deposition （VHFPA-RTCVD）, is introduced to prepare SiGe：H thin films on substrate kept at a lower temperature. In the previous work, reactive thermal chemical vapour deposition （I^TCVD） technology was successfully used to prepare SiGe：H thin films, but the temperature of the substrate needed to exceed 400℃. In this work, very high frequency plasma method is used to assist RTCVD technology in reducing the temperature of substrate by largely enhancing the temperature of reacting gases on the surface of the substrate. The growth rate, structural properties, surface morphology, photo- conductivity and dark-conductivity of SiGe：H thin films prepared by this new technology are investigated for films with different germanium concentrations, and the experimental results are discussed.

Method of measuring one-dimensional photonic crystal period-structure-film thickness based on Bloch surface wave enhanced Goos–H?nchen shift

This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave(BSW) enhanced Goos–Hanchen(GH) shift in one-dimensional photonic crystal(1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization(PSO) algorithm.The relationship between the structure of a 1DPC film composed of TiO_(2) and SiO_(2) layers and the GH shift, is investigated.Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1 × 10^(3) times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift.

Weak avalanche multiplication in SiGe heterojunction bipolar transistors on thin film silicon-on-insulator

In this paper, we propose an analytical avalanche multiplication model for the next generation of SiGe silicon- on-insulator （SOI） heterojunction bipolar transistors （HBTs） and consider their vertical and lateral impact ionizations for the first time. Supported by experimental data, the analytical model predicts that the avalanche multiplication governed by impact ionization shows kinks and the impact ionization effect is small compared with that of the bulk HBT, resulting in a larger base-collector breakdown voltage. The model presented in the paper is significant and has useful applications in the design and simulation of the next generation of SiCe SOI BiCMOS technology.

Growth Rate of a-Si∶H Film Influenced by Magnetic Field Gradient in MWECR CVD Plasma System

The magnetic field profiles,which are produced by three ways in the deposition chamber and plasma chamber of single coil divergent field MWECR CVD system,are investigated.The magnetic field gradient of these magnetic field profiles is obtained quantitatively by using Lorentz fit.The results indicate that the gradient value of the magnetic field profile near by the substrate,which is produced by a coil current with 137.7A if a SmCo permanent magnet is equipped under the substrate holder,is the largest;when the SmCo permanent magnet is taken away,the larger one is produced by the coil current with 137.7A and the smallest one produced by a coil current with 115.2A.High deposition rate of a-Si∶H film is observed near by the substrate with high magnetic field gradient.But uneven deposition rate along the radius of the sample holder is also found by infrared analysis technology when sample is deposited in magnetic field profile,which is produced by the coil current with 137.7A if the SmCo permanent magnet is equipped under the substrate holder.

Fabrication of Hydrogenated Microcrystalline Silicon Thin Films at Low Temperature by VHF-PECVD

Using H 2 diluted silane,series of μc Si∶H films are fabricated at low temperature with VHF PECVD.The thickness measurements reveal that the deposition rates are obviously enhanced with higher plasma excitation frequency or working pressure,but increase firstly and then decrease with the increase of plasma power density.Raman spectra show that the crystallinity and the average grain sizes of the films strongly depend on the temperature of substrate and the concentration of silane.However,the plasma excitation frequency only has effect on the crystallinity,and a maximum occurs during the further increase of plasma excitation frequency.From XRD and TEM experiments,three preferential crystalline orientations (111),(220) and (311) are observed,and the average grain sizes are different for every crystalline orientation.

Influence of Pressure on SiNx：H Film by LF-PECVD

Hydrogenated silicon nitride films as an effective antireflection and passivation coating of silicon solar cell were prepared on p-type polished silicon substrate （1.0 f^em） by direct LF-PECVD （low frequency plasma enhanced chemical vapor deposition） of Centrotherm. The preferable passivation effect was obtained and the refractive index was in the range of 2.017-2.082. The refractive index of the hydrogenated silicon nitride films became larger with the increase of the pressure. Fourier transform infrared spectroscopy was used to study the pressure influence on the film structural properties. The results highlighted high hydrogen bond and high Si-N bonds density in the film, which were greatly influenced by the pressure. The passivation effect of the films was infuenced by the Si dangling bonds density. Finally the effective minority liftetime degradation with time was shown and discussed by considering the relationship between the structural properties and passivation.

SiGe∶H薄膜太阳能电池研究进展

针对氢化非晶硅(a-Si∶H)薄膜太阳能电池在发展过程中所面临的问题,阐述了氢化硅锗(SiGe∶H)薄膜在太阳能电池制备方面的优越性及其最新研究进展,总结了提高SiGe∶H薄膜太阳能电池效率的几种方法,着重介绍了叠层太阳能电池内部运行机理,分析了影响叠层太阳能电池转换效率的因素,最后对SiGe∶H薄膜材料在太阳能电池领域的应用前景以及一些亟待解决的问题进行了展望。

基于电容结构的α-SiGe∶H膜电学退化特性

针对航天一次可编程(OTP)存储器高可靠应用需求,基于电容结构和肖特基接触模型,分析得出α-SiGe∶H膜退化前电流传输机制较好地符合热电子发射-扩散模型,并计算得到零偏α-SiGe∶H/TiW界面肖特基势垒高度为0.41 eV。通过实验发现,在电压应力作用下,α-SiGe∶H膜漏电随时间增大并逐渐饱和,且不同应力电压下对应饱和漏电大小及饱和点时间不同。分析应力下漏电增大与非晶网络弱键断裂造成的缺陷相关,漏电机制由初始的扩展态主导转变为由缺陷密度决定的局域态主导,漏电饱和归因于α-SiGe∶H膜中缺陷密度的饱和,采用近邻跳跃电导模型可以很好地拟合实测J-V曲线,并计算得到饱和缺陷密度为5×10^19 eV^-1·cm^-3。

Analytical base collector depletion capacitance in vertical SiGe heterojunction bipolar transistors fabricated on CMOS-compatible silicon on insulator

The base-collector depletion capacitance for vertical SiGe npn heterojunction bipolar transistors （HBTs） on silicon on insulator （SOI） is split into vertical and lateral parts. This paper proposes a novel analytical depletion capacitance model of this structure for the first time. A large discrepancy is predicted when the present model is compared with the conventional depletion model, and it is shown that the capacitance decreases with the increase of the reverse collector- base bias-and shows a kink as the reverse collector-base bias reaches the effective vertical punch-through voltage while the voltage differs with the collector doping concentrations, which is consistent with measurement results. The model can be employed for a fast evaluation of the depletion capacitance of an SOI SiGe HBT and has useful applications on the design and simulation of high performance SiGe circuits and devices.

Nanocomposite TiC/a-C：H film prepared on titanium aluminium alloy substrates by PSII assistant MW-ECRCVD

Thin films of titanium carbide and amorphous hydrogenated carbon have been synthesized on titanium aluminium alloy substrates by PSII assisted MW-ECRCVD with a mirror field. The microstructure, chemical composition and mechanical property were investigated. Using XPS and TEM, the films were identified to be a-C：H film containing TiC nanometre grains （namely, the so-called nanocomposite structure）. The size of TiC grains of nanocomposite TiC/DLC film is about 5 nm. The nanocomposite structure has obvious improvement in the mechanical properties of DLC film. The hardness of a-C：H film with Ti is enhanced to 34 G Pa~ while that of a-C：H film without Ti is about 12 G Pa, and the coherent strength is also obviously enhanced at the critical load of about 35N.

Properties of oxide films grown on 25Cr20Ni alloy in air-H_2O and H_2-H_2O atmospheres

The oxidation kinetics,surface morphology and phase structure of oxide films grown on 25Cr20Ni alloy in air-H2O and H2-H2O atmospheres at 900 ℃ for 20 h were investigated.The anti-coking performance and resistance to carburization of the two oxide films were compared using 25Cr20Ni alloy tubes with an inner diameter of 10 mm and a length of 850 mm in a bench scale naphtha steam pyrolysis unit.The oxidation kinetics followed a parabolic law in an air-H2O atmosphere and a logarithm law in a H2-H2O atmosphere in the steady-state stage.The oxide film grown in the air-H2O atmosphere had cracks where the elements Fe and Ni were enriched and the un-cracked area was covered with octahedral-shaped MnCr2O4 spinels and Cr1.3Fe0.7O3 oxide clusters,while the oxide film grown in the H2-H2O atmosphere was intact and completely covered with dense standing blade MnCr2O4 spinels.In the pyrolysis tests,the anti-coking performance and resistance to carburization of the oxide film grown in the H2-H2O atmosphere were far better than that in the air-H2O atmosphere.The mass of coke formed in the oxide film grown in the H2-H2O atmosphere was less than 10％ of that in the air-H2O atmosphere.The Cr1.3Fe0.7O3 oxide clusters converted into Cr23C6 carbides and the cracks were filled with carbon in the oxide film grown in the air-H2O atmosphere after repeated coking and decoking tests,while the dense standing blade MnCr2O4 spinels remained unchanged in the oxide film grown in the H2-H2O atmosphere.The ethylene,propylene and butadiene yields in the pyrolysis tests were almost the same for the two oxide films.

Research on the optimum hydrogenated silicon thin films for application in solar cells

Hydrogenated silicon （Si：H） thin films for application in solar ceils were deposited by using very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at a substrate temperature of about 170 ℃, The electrical, structural, and optical properties of the films were investigated. The deposited films were then applied as i-layers for p-i-n single junction solar cells. The current-voltage （I - V） characteristics of the cells were measured before and after the light soaking. The results suggest that the films deposited near the transition region have an optimum properties for application in solar cells. The cell with an i-layer prepared near the transition region shows the best stable performance.

High-Pressure Plasma Deposition of a-C:H Films by Dielectric-Barrier Discharge

The fabrication of a-C:H films from methane has been performed using dielectric-barrier discharges at atmospheric pressure. The effect of combined-feed gas, such as carbon dioxide, carbon monoxide or acetylene on the formation of a-C:H films has been investigated. It has been demonstrated that the addition of carbon monoxide or acetylene into methane leads to a remarkable improvement in the fabrication of a-C:H films. The characterization of carbon film obtained has been conducted using FT-IR, Raman and SEM.

Fabrication and characterization of iron and iron carbide thin films by plasma enhanced pulsed chemical vapor deposition

A new pulsed chemical vapor deposition（PCVD） process has been developed to fabricate iron（Fe） and iron carbide(Fe1-xCx) thin films at low temperature range from 150 ℃ to 230 ℃.The process employs bis（1,4-di-tert-butyl-1,3-diazabutadienyl）iron（Ⅱ） as iron source and hydrogen gas or hydrogen plasma as the coreactant.The films deposited with hydrogen gas are demonstrated polycrystalline with body-centered cubic Fe.However,for the films deposited with hydrogen plasma,the amorphous phase of iron carbide is obtained.The influence of the deposition temperature on iron and iron carbide characteristics have been investigated.

反应磁控溅射制备h-BN薄膜及其日盲紫外探测器

随着电子信息技术的飞速发展,具有更高抗干扰能力以及更高灵敏度的日盲紫外探测器引起了广泛关注。六方相氮化硼(h-BN)凭借其超宽带隙、高光吸收系数、高热导率及高击穿场强等优势成为日盲紫外探测器研究的热点材料。此外,h-BN良好的机械强度和光学透明性使其兼具柔性探测器的潜力。然而室温条件下制备的h-BN薄膜常具有较多缺陷,极大程度上限制了其柔性探测器的发展。本文在室温条件下采用反应磁控溅射,以B为生长源,在蓝宝石和Si衬底上实现了较高质量h-BN薄膜的制备,并在此薄膜的基础上制备了高性能日盲紫外探测器。3 V电压下,其探测器拥有极低的暗电流(0.07 pA)、较高的响应度(1.37μA/W)和探测率(2.73×10^(10)Jones)。本文的研究结果证实了室温制备h-BN薄膜及其日盲紫外探测器的可行性,为实现可在室温下工作的h-BN探测器的应用提供了参考。

Study on stability of hydrogenated amorphous silicon films

Hydrogenated amorphous silicon （a-Si：H） films with high and same order of magnitude photosensitivity （-10^5） but different stability were prepared by using microwave electron cyclotron resonance chemical vapour deposition system under the different deposition conditions. It was proposed that there was no direct correlation between the photosensitivity and the hydrogen content （CH） as well as H-Si bonding configurations, but for the stability, they were the critical factors. The experimental results indicated that higher substrate temperature, hydrogen dilution ratio and lower deposition rate played an important role in improving the microstructure of a-Si：H films. We used hydrogen elimination model to explain our experimental results.

Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

Highly conductive boron-doped hydrogenated mieroerystalline silicon （μc-Si：H） films are prepared by very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at the substrate temperatures （Ts） ranging from 90℃ to 270℃. The effects of Ts on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical （dark conductivity, carrier concentration and Hall mobility） and structural （crystallinity and grain size） properties are all strongly dependent on Ts. As Ts increases, it is observed that 1） the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at Ts=210℃, 2） the crystalline volume fraction （Xc） and the grain size increase initially, then reach their maximum values at TS=140℃, and finally decrease, 3） the dark conductivity （σd）, carrier concentration and Hall mobility have a similar dependence on Ts and arrive at their maximum values at Ts-190℃. In addition, it is also observed that at a lower substrate temperature Ts, a higher dopant concentration is required in order to obtain a maximum σd.

Optical Characterization of Amorphous Hydrogenated Carbon(a-C:H)Thin Films Prepared by Single RF Plasma Method

Methane （CH4） plasma was used to produce amorphous hydrogenated carbon （a- C：H） films by a single capacitively coupled radio frequency （RF） powered plasma system. The system consists of two parallel electrodes： the upper electrode is connected to 13.56 MHz RF power and the lower one is connected to the ground. Thin films were deposited on glass slides with different sizes and on silicon wafers. The influence of the plasma species on film characteristics was studied by changing the plasma parameters. The changes of plasma species during the deposition were investigated by optical emission spectroscopy （OES）. The structural and optical properties were analyzed via Fourier transform infrared （FTIR） spectroscopy, X-ray diffraction （XRD） and UV-visible spectroscopy, and the thicknesses of the samples were measured by a profilometer. The sp3/sp2 ratio and the existing H atoms play a significant role in the determination of the chemical properties of thin films in the plasma. The film quality and deposition rate were both increased by raising the power and the flow rate.

Structure and tribological properties of Si/a-C:H(Ag)multilayer film in stimulated body fluid

Si/a-C:H(Ag)multilayer films with different modulation periods are prepared to test their potential applications in human body.The composition,microstructure,mechanical and tribological properties in the simulated body fluid are investigated.The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm.Whereas the C content has an opposite variation trend.Notably,the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film.The a-C:H sublayer of the film with an appropriate Ag concentration(8.97 at.%)(modulation period of 512 nm)maintains the highest sp3/sp2 ratio,surface roughness and hardness,and excellent tribological property in the stimulated body fluid.An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating.This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.

A Comparative Study of Boron and Phosphorus Doping Effects in SiC: H Films Prepared by ECR-CVD

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) technique from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the microwave power on the deposition rate and optical bandgap were investigated, and variations in the photoand dark-conductivities and activation energy were studied in conjunction with film analysis using the Raman scattering technique. In the case of boron-doped samples, the conductivity increased rapidly to a maximum, followed by rapid reduction at high microwave power. The ratio of the photo- to dark-conductivity (σph/σd) peaked at microwave power of ~600 W. Under conditions of high microwave power, Raman scattering analysis showed evidence of the formation and increase in the silicon microcrystalline and diamond-like phases in the films, the former of which could account for the rapid increase and the latter the subsequent decrease in the conductivity.In the case of phosphorusdoped SiC:H samples, it was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the films which occurred in correspondence to a rapid increase in the conductivity and reduction in the activation energy The conductivity increase stabilised in samples deposited at microwave power exceeding 500 W probably as a result of dopant saturation. Results from Raman scattering measurements also showed that phosphorus doping had the effect of enhancing the formation of the silicon microcrystals in the film whereas the presence of boron had the effect of preserving the amorphous structure.