Materials Science Forum Vols. 663-665

Abstract: The intrinsic carrier concentration is the important parameter for researching strained Si1-xGex materials properties and evaluating Si-based strained devices parameters. In this paper, at the beginning of analyzing the band structure of strained Si1-xGex/(101)Si, the dependence of its effective densities of states for the conduction and valence bands (Nc, Nv) and its intrinsic carrier concentration (ni) on Ge fraction (x) and temperature were obtained. The results show that ni increases significantly due to the effect of strain in strained Si1-xGex/(101)Si. Furthermore, Nc and Nv decrease with increasing Ge fraction (x). In addition, it is also found that as the temperature becomes higher, the increase in Nc and Nv occurs. The results can provide valuable references to the understanding on the Si-based strained device physics and its design.

Abstract: In the environment with H2S/CO2 or Na2S, the corrosion behavior of Lanthanum hexaboride (LaB6) was investigated by electrochemistry methods. The results indicated that the corrosion potential (Ecorr) and Rf of LaB6 increased as the partial pressure of H2S increased, while the corrosion current density (Icorr) decreased. In the environment containing Na2S, as the content of Na2S increased, the corrosion potential (Ecorr) and Rf of LaB6 decreased, while the corrosion current density (Icorr) increased. Thus, the addition of H2S into the environment with H2S/CO2 would inhibit the corrosion of LaB6; while in the environment containing Na2S, the increasing of the content of Na2S would accelerate the corrosion of LaB6.

Abstract: There has been much interest in the Si-based strained technology lately. The improvement of strained-Si device performance is due to the enhancement of the mobility, so the further study on mobility is essential in both theory and practice aspects. In this paper, an analytical model of the electron mobility of strained-Si material, such as biaxial tensile strained-Si material grown on relaxed Si1-xGex (0≤x≤0.6) substrates, as a function of strain and different orientations is obtained. The results show that the electron mobilities for [100] and [010] orientations increase rapidly with increasing Ge fraction x, and there is no electron mobility enhancement for [001] orientation in comparison to relaxed Si material.

Abstract: A chemical oxidative polymerization of aniline sulfosalicylic acid (ANISSA) and aniline sulfate acid (ANIH2SO4) was performed in an aqueous solution. A co-doped polyaniline (PANI) was thus obtained, a higher conductivity than the insoluble H2SO4-doped PANI compressed pellet, and much higher conductivity than that prepared from pure ANISSA. The PANI doped with SSA and H2SO4 was characterized using Fourier-transform infrared spectra (FTIR), Fourier-transform Raman spectra (FT-Raman), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The investigation reveals that SSA and H2SO4 as dopant not only enhances crystallinity of polyaniline but also stability of polyaniline.

Abstract: CuInS2 hollow nanospheres composed of nanoparticles have been fabricated through a solvothermal reaction in ethylene glycol solution (EG) at 200 °C in the absence of any templates or surfactants. The as-obtained CuInS2 products were characterized by XRD, FESEM andTEM. Results show that the synthesized hollow nanospheres are made up of small nanoparticles with a size of 10 nm and the outer diameters of these spheres change from 200 to 400nm. The possible formation mechanism of CuInS2 hollow nanospheres is simply discussed.

Abstract: As an energy conversion material, piezoelectric ceramic lead zirconate titanate (PZT) has been used in a wide range of areas. And a PZT wafer bonding with a silicon wafer technology is a promising method to fabricate micro-sensors and micro-actuators using well-established silicon machining techniques. In order to obtain the excellent piezoelectricity and suitable thickness from the bulk PZT, a method is presented. It is to bond a bulk PZT onto a silicon wafer via an intermediate layer. In this paper, two bonding methods are presented. One is to bond a bulk PZT with a silicon wafer by anodic bonding technique using a thin glass film as the intermediate layer. The other is to bond a bulk PZT with a silicon wafer by eutectic bonding using a thin gold film as the intermediate layer. The glass film is 2µm in thickness, deposited by sputtered method. Anodic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, 250V in voltage and different bonding time. The bonding strength test shows that the maximum bond strength is 13.93 MPa when the bonding time was 60 min. It is void-free structure in the interface of the PZT-Glass-Si structure. The gold film is 1.6µm in thickness, deposited by evaporation method. The eutectic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, and different bonding time. The bond strength of the PZT-Au-Si structure was tested and the maximum value was 13.19 MPa when the bonding time was 60 min.

Abstract: An n-SiC/p-SiCGe/n-SiCGe heterojunction phototransistor with charge compensation layer has been simulated with commercial simulator MEDICI. With wide bandgap SiC emitter and p-type SiCGe charge-compensation layer, device responsivity and breakdown voltage has been improved. It is found that with p-type SiCGe layer, the responsivity is nearly two times of without one. Furthermore, flat electrical field distribution during off-state enable it supports higher reverse bias, thus breakdown voltage increased from 450V to 580V for the given structure, and both breakdown voltage and responsivity increase with light absorption region length.

Abstract: The switching character of SiCGe/SiC heterojunction phototransistors with charge-compensation technique has been simulated with commercial simulator MEDICI. The influences of light power density, wavelength and carrier lifetime on switching characters were studied. Simulation result shown that the devices are latch-free device and fall time is much longer than rise time. The increasing of light power density and wavelength cause shorter rise time and longer fall time unless reaches SiCGe absorption edge 520nm, trade-off must made between responsivity and switching speed when carrier lifetime is considered, the ratio of them gets it maximum values at minority carrier lifetime equal 90ns.

Abstract: The GaAs photoconductive switch is an important device in the measurement of the signal of ultra high-speed. In this paper, the transmission model of transient signals on GaAs photoconductive material is given, and the experimental system of near-field detection is set up. It is gotten that the full width half magnitude of signal is about 2ps. Based on the testing result of delay-time-modulation method, the relationship between signal amplitude and the form of connection mode is analyzed and discussed. It is shown that the coupling of capacity is important to acquire the transient signal.

Abstract: Based on the oxygen ion conductor La1.95K0.05Mo2O8.95, a series of Fe-doped samples La1.95K0.05Mo2-xFexO9- (x=0, 0.025, 0.05, 0.1) were prepared with conventional solid reaction method. The effects of Fe doping on the structure, oxygen ion diffusion and electrical conductivity were studied. Based on the results of conductivity measurements, it can be concluded that Fe doping can improve the conductivity obviously, and doping of both Fe and K samples have better conductivity, which successfully suppresses the phase transition.