Papers by Author: Quan Xie

Abstract: A detailed theoretical study on the influence of lattice vacancy on structural and optical properties of the magnesium silicide Mg₂Si has been performed based on the first-principles pseudopotential method. The results show that Mg₂Si has changed from indirect band gap semiconductor to direct band gap semiconductor because of Mg vacancy. Compared with the dielectric function, absorption coefficient, refractive index, reflectivity and photon conductivity of Mg₂Si, those peaks of Mg₁₅Si₈ appear from 0 to 1.8 eV. And the loss function’s biggest peak of Mg₁₅Si₈ moves to the direction of high energy.

Abstract: In this paper, we have prepared the beta-FeSi₂ thin film on Si substrate through the direct current magnetron sputtering technology. We have tested the samples by XRD, optical digital microscope (ODM), spectrophotometer, and SEM. Under the same annealing temperature at 1153 K, the annealing time has important influence on the optical characteristic of beta-FeSi₂ thin film. More the thickness of the beta-FeSi₂ thin film is thinner, and more the absorptivity of photo is higher. We should use the thinner beta-FeSi₂ thin film with appropriate value of the thickness and must adopt the anti-reflection layer to fabricate the solar cell.

Abstract: The two groups of Ca films were directly and respectively deposited on Si(100) substrates by Radio Frequency (R.F.) magnetron sputtering system (MS) and subsequent were annealed at 600°C for 5h, 6h, 8h, 10h and 12h in a vacuum furnace. The structural and morphological features of the resultant films are tested by XRD, EDAX and FT-IR. The cubic phase Ca2Si film is grown selectively from Ca-Si system of the existence of multiple silicide phases by an interdiffusion reaction of solid phase between the deposited particles and clusters and substrate constituents. And, the structure of the deposited films, annealing temperature and annealing time are the principal factor for the selective growth.

Abstract: Structural and dynamical properties of the rapid solidification process of liquid Ge have been investigated by molecular-dynamics calculations based on the Stillinger-Weber potential. The variations of microstructures during the solidification process are analyzed by the self-diffusion coefficient D(T), pair correlation function g(r) curves and the HA bond-type index method. The melting point implicated in D(T) is about 2100 K. The pair correlation function g(r) obtained by the simulated in liquid Ge is good agreement with experiment, the fist-peak of g(r) gradually becomes higher and sharper with the temperature decreasing, when temperature drops to 1400 K, the second-peak of g(r) begins to split. The change of HA bond-type indicated that the most important structural change occurs in the temperature range 1400 K-700 K.

Abstract: Semiconducting orthorhombic BaSi2 films were synthesized on Si(111) substrates using magnetron sputtering (MS) and subsequent annealing by interdiffusion between the deposited Ba film and Si(111) substrate. The structural and morphological features of the result films are analysed. The growth mechanism and the evolution of the silicides are discussed. The effects of annealing temperature and annealing time on the growth of the BaSi2 film are studied.

Abstract: The Kondo insulator FeSi was prepared by DC magnetron sputtering and the effects of sputtering parameters on the formation of FeSi were investigated in detail. The formation of monosilicide FeSi was clarified using X-ray diffraction (XRD) and its microstructure was characterized by scanning electron microscopy (SEM). The results indicate that the sputtering gas pressure, the sputtering power and the Ar flux all have significantly effects on formation of FeSi and the crystalline of the film. The sputtering gas pressure has effects on sputtering yields, depositing rate and the energy of sputtering atoms, the sputtering power has effects on the kinetic energy and the diffusion ability of deposing atoms and the gas flux has the effects on the flowing state of Ar gas. The most optimal sputtering parameters for the preparation of the Kondo insulator FeSi by DC magnetron sputtering are given: 1.5 Pa for sputtering Ar pressure, 100 W for sputtering power and 20 SCCM for sputtering Ar flux.

Abstract: Semiconducting Mg2Si films were fabricated on Si (111) substrates by magnetron sputtering and subsequent annealing, and the effects of sputtering pressure on the Mg2Si film growth were studied. The structural and morphological properties of Mg2Si films were investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the Mg2Si (220) main diffraction peak intensity increased and then decreased with the increasing of sputtering pressure. The (220) diffraction peak got its maximum at 3.0 Pa sputtering pressure. The intensity of Mg2Si (200) and (400) diffraction peaks increased rapidly as the sputtering pressure decreased when the pressure was lower than 1.5 Pa. The films prepared at higher sputtering pressure had very irregular microstructures, and the surface of semiconducting Mg2Si films became smoother with the decreasing of the sputtering pressure.

Abstract: Semiconducting Mg2Si films were fabricated on Si (111) substrates by magnetron sputtering and subsequent annealing, and the effects of annealing atmosphere on the Mg2Si film growth were studied. The structural and morphological properties of Mg2Si films were investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that annealing atmosphere was an important factor that affected the growth of Mg2Si thin films, and vacuum annealing was not suitable for preparing Mg2Si thin films. Only Si (111) substrate diffraction peaks were observed, and no Mg2Si diffraction peak was observed when the first six Mg/Si samples were annealed under vacuum annealing condition. However, many Mg2Si diffraction peaks were observed besides the Si substrate diffraction peaks when the second six Mg/Si samples were annealed under Ar gas atmosphere. In addition, compact and smooth Mg2Si thin films annealed under Ar gas atmosphere were obtained.