Jiang Shusheng

Microstructure and Electron Conduction Mechanism of Hydrogenated Nano-crystalline Silicon Films

The hydrogenated nano-crystalline silicon (nc-Si:H) films have been deposited with plasma enhanced chemical vapor deposition method. The microstructure of these films has been studied by transmission electron microscopy and high resolution transmission electron microscopy. The nc-Si:H films show fiber texture structure. The fractal dimension of this structure has been calculated with a Fourier filtered image. The relationship between conductivity and temperature has also been studied and the mechanism of electron conduction is discussed.

Crystal Tilts in Epitaxially Laterally Overgrown GaN Films Determined by Four-Circle X-Ray Diffraction

Crystal tilts in epitaxially laterally overgrown (ELO) GaN films via hydride vapour phase epitaxy (HVPE) on sapphire substrates have been investigated by using the four-circle x-ray diffraction method. Three diffraction peaks corresponding to the (0002) reflection of vertically epitaxial and tilted GaN domains are observable in the x-ray rocking curve. The angle separations Δω between the main peak and two lobes change with the azimuth angle . The dependence of Δω on and the crystal tilt angle θ has been calculated based on the standard kinetic x-ray diffraction model. The crystal tilt angle of a typical HVPE ELO GaN sample has been determined to be 2.379°.

WHITE-BEAM X-RAY TOPOGRAPHY STUDY OF KTa 1-x Nb x O 3 CRYSTAL WITH SYNCHROTRON RADIATION

The photorefractive Fe-dopoed KTa 1-x Nb x O 3 (KTN) with a Curie point near room temperature has been topographically studied by Beijing synchrotron radiation white-beam X-ray source. Besides inclusions and the [010] oriented growth bands present in KTN, a set of domains perpendicular to the growth bands is shown, the latter is found to disobey the vanishing rule of planar defects, and to be revealed only by X-ray anomalous scattering. A striking wavelength dependence of the domain contrast is shown by tuning the synchrotron radiation, and the contrast reversal of the domains is demonstrated in antiparallel reflections. The domains are ascertained to be 1800 ones. The origins of formation of the domains and the growth features in KTN are outlined.

BRILLOUIN LIGHT-SCATTERING INVESTIGATION OF ELASTIC ANOMALY FROM SUPERLATTICES

In this paper we report some new experimental results concerning the elastic properties of periodic and quasiperiodic superlattices studied by means of Brillouin spectroscopy. The observation of both bulk and surface acoustic phonons as well as the fitting using effective medium approximation on the phonon spectrum enables us to extract accurately some relevant effective elastic constants in both structures. We have verified that the elastic anomaly which occurs in the periodic structures is also present in quasiperiodic ones. These results imply that the interaction mechanism of Fermi electrons with reduced Brillouin zone boundary is not responsible for the observed elastic anomalies. The comparative study of these superlattices proves that the elastic anomaly is relevant directly to interfacial effects.

Brillouin Scattering from Metallic Ta/Al Fibonacci Multilayers

Surface phonon spectra from Ta/Al Fibonacci multilayers are studied via Brillouin scattering. Determination of the frequency positions of the Rayleigh wave and the intensity dip corresponding to the longitudinal threshold has enabled us to extract two effective elastic constants C44 and C11 of the whole structure. The 22.6% enhancement of the shear modulus is found in our experiment.

Double-Crystal x-Ray Diffraction Study on Ta/Al Multilayers

Double-crystal x-ray diffraction has been used to measure the rocking curve of Ta/Al multilayers. The diffraction profiles of the multilayers are different. Besides the normal profile, two kinds of distorted profiles have been found. The simulations show that the deformed profiles of the peaks are caused by the imperfect periodicity (e.g. systematic period deviation and coexistence of two slightly different periods) in the multilayers.

X-ray diffraction of Cu/Ti fibonacci superlattices

1-D quasiperiodic (Fibonacci) Cu/Ti metallic superlattices have been prepared in a dual magnetron sputter deposition system. X-ray scattering measurements of these samples are presented. The x-ray diffraction peaks at low angles can be indexed by the projection method from the high-dimensional periodic structure. In the high angle region, there is one broad peak, which indicates that the samples are amorphous.

Ko-image of the brazil twin boundary in natural quartz crystal by x-ray section topography

Ko-image of the Brazil twin boundary in quartz crystal by x-ray section topography and the same contrasts of the first fringes for entrance and exit surface are shown in this paper.

Grown-in defects in natural beryls by x-ray topography and birefringence

The growth sectors and their boundaries, impurity zonings and dislocations in natural beryls have been observed by means of x-ray diffraction topography and birefringence. The displacements of fault surfaces of the sector boundaries are perpendicular to the fault surfaces. The Burgers vectors of some typical dislocations in (0001) sector are , and . It is found that the techniques of x-ray diffraction topography and optical birefringence are complementary.