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【期刊论文】Structural characteristics of SrTiO3 thin films processed by rapid thermal annealing
李言荣, S.W. Jiang, Q.Y. Zhang, Y.R. Li*, Y. Zhang, X.F. Sun, B. Jiang
Journal of Crystal Growth 274(2005)500-505,-0001,():
-1年11月30日
The amorphous SrTiO3 (STO) thin films prepared on Si (111) substrates by pulsed laser deposition (PLD) deposition were crystallized at different temperatures for various annealing time using rapid thermal annealing (RTA) process. Grazing incidence X-ray diffraction and atomic force microscopy were applied to investigate the crystallinity and surface morphology of annealed STO thin films. The results showed that the formation of STO crystalline phase was strongly dependent on the annealing temperature, and the increase of annealing temperature led to an improvement in the crystalline quality. However, at a certain annealing temperature, though the crystalline quality and surface morphology could be improved with increasing annealing time, the grain growth showed a saturation of grain size which was independent on the annealing time. Moreover, with increasing temperature, the saturated grain size decreased at lower temperatures while increased slightly at higher temperatures. A phenomenological assumption had been introduced to explain the experimental observations.
A1., Crystallization, A1., Rapid thermal annealing, A1., Structural characteristics, A3., SrTiO3 thin films
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李言荣, Shiming He*, Yanrong Li, Xingzhao Liu, Bowan Tao, Dehong Li, Qingfang Lu
Thin Solid Films 478(2005)261-264,-0001,():
-1年11月30日
The effects of grain size on nonlinear dielectric properties of as-deposited SrTiO3 (STO) thin films were studied by using interdigital capacitor. C-axis-oriented STO thin films with different grain size were deposited onto interdigital electrodes made from YBa2Cu3O7 x thin films by pulsed laser deposition (PLD) technique. The grain size of as-eposited STO thin films increased with substrate temperature, and reached a maximum value at 700 8C. With further increase of substrate temperature, the grain size decrease rapidly because of the negative oxygen supersaturation and the high nucleation density. The nonlinear dielectric properties measurements showed to be highly correlated with the grain size of STO thin films; the zero-bias dielectric constant, the dielectric dissipation, and the tunability decreased with the decrease of the grain size.
Atomic force microscopy (, AFM), , Dielectric properties, Grain boundary, Growth mechanism, Ferroelectric materials, Pulse laser deposition, X-ray diffraction
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【期刊论文】Surface diffusion duringlayer growth of SrTiO3 films with pulsed laser molecular beam epitaxy
李言荣, Y.R. Li*, S.W. Jiang, Y. Zhang, X.W. Deng, X.H. Wei
Journal of Crystal Growth 278(2005)629-632,-0001,():
-1年11月30日
In the layer-by-layer growth regime of SrTiO3 films with pulsed laser molecular beam epitaxy, the relaxation behaviors of RHEED intensity after termination of growth were studied. From the characteristic relaxation times as a function of substrate temperatures, it was revealed that the surface relaxation occurred with low activity energy for diffusion of 0.3 eV and slow relaxation process, which was argued to be attributed to the diffusion of charge-neutral SrTiO3 units.
A1., RHEED, A1., Terminated deposition, A3., Pulsed laser molecular beam epitaxy, B1., Perovskite films
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【期刊论文】Ab initio total energy study of ZnO adsorption on a sapphire (0001) surface
李言荣, Yang Chun, Li Yan-rong, Li Jin-shan
PHYSICAL REVIEW B 70, 045413 (2004),-0001,():
-1年11月30日
The sapphire (0001) surface and the adsorption of ZnO are theoretically calculated by using a plane wave ultrasoft pseudo-potential method based on density functional theory. By comparing the PDOS of the Al and the O before and after the surface relaxation, we demonstrate different apphire (0001) surface states, and changes in surface chemical bonding resulting from Al and O are analyzed. The bonding processing of a ZnO molecule on the surface of Al2O3, adsorption energy and bonding orientation, and change in surface structure as well as the characters of surface chemical bonding are further investigated. We conclude that the surface inward relaxation in the first layer Al-O is weakened, even eliminated after the surface adsorption of the ZnO; chemical bonding energy achieved 4.4±0.4 eV. There is a deflected angle of 30° between the chemical bonding of the ZnO s0.185±0.01 nmd and the adjacent surface Al-O bonding; the stable chemical adsorption site of Zn is just about 30 deflected from the O-hexagonal symmetry of the a-Al2O3s0001d surface. Through analysis of the atomic populations, density of state, and bonding electronic density before and after the adsorption, it is revealed that the chemical bonding formed by the O2− of the ZnO and the surface Al3+ is characterized by strong ionic bonding, while the bond of the Zn2+ and the surface O2− has a covalent character, which mainly comes from the hybridization of the Zn 4s and the O 2p and partially from the hybridization of the Zn 3d and the O 2p, so as to facilitate the forming of tetrahedral coordination in the initial stage of the ZnO films growth. Hence it is favorable for the formation of the wurtzite structure.
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【期刊论文】Theoretical study of ZnO adsorption and bonding on Al2O3 (0001) surface
李言荣, LI Yanrong, YANG Chun, , XUE Weidong, LI Jinshan & LIU Yonghua
Science in China Ser. G Physics, Mechanics & Astronomy 2004 Vol. 47 No.6 664-675,-0001,():
-1年11月30日
ZnO adsorption on sapphire (0001) surface is theoretically calculated by using a plane wave ultrasoft pseudo-potential method based on ab initio molecular dynamics. The results reveal that the surface relaxation in the first layer Al-O is reduced, even eliminated after the surface adsorption of ZnO, and the chemical bonding energy is 434.3 (±38.6) kJ·mol−1. The chemical bond of ZnO (0.185±0.01nm) has a 30° angle away from the adjacent Al-O bond, and the stable chemical adsorption position of the Zn is deflected from the surface O-hexagonal symmetry with an angle of about 30°. The analysis of the atomic populations, density of state and bonding electronic density before and after the adsorption indicates that the chemical bond formed by the O2− of the ZnO and the surface Al3+ has a strong ionic bonding characteristic, while the chemical bond formed by the Zn2+ and the surface O2− has an obvious covalent characteristic, which comes mainly from the hybridization of the Zn 4s and the O 2p and partially from that of the Zn 3d and the O 2p.
α-Al2O3 (, 0001), , ZnO, ab initio molecular dynamics, chemical adsorption, density of states.,
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