快速热退火和氢等离子体处理对富硅氧化硅薄膜微结构与发光的影响

采用micro-Raman散射、傅里叶变换红外吸收谱和光致发光谱研究了快速热退火及氢等离子体处理对等离子体增强化学气相沉积法200 ℃衬底温度下生长的富硅氧化硅（SRSO）薄膜微结构和发光的影响。研究发现在300-600 ℃范围内退火，SRSO薄膜中非晶硅和SiO_x:H两相之间的相分离程度随退火温度升高趋于减小；而在600-900 ℃范围内退火，其相分离程度退火温度升高又趋于增大；同时发现SRSO薄膜发光先是随退火温度的升高显著加强，然后在退火温度达到和超过600 ℃后迅速减弱；发光峰位在300 ℃退火后蓝移，此后随退火温度升高逐渐红移。对不同温度退火后的薄膜进行氢等离子体处理，发光强度不同程度有所增强，发光峰位有所移动，但不同温度退火样品发光增强的幅度和峰位移动的趋势不同。分析认为退火能够引起薄膜中非晶硅颗粒尺度、颗粒表面结构状态以及氢的存在和分布等方面的变化。结果表明不仅颗粒的尺度大小，而且颗粒表面的结构状态都对非晶硅颗粒能带结构和光生载流子复合机理发挥重要影响。

Extracting nanobelt mechanical properties from nanoindentation

A three-spring-in-series model is proposed for the nanobelt (NB) indentation test. Compared with the previous two-spring-in-series model, which considers the bending stiffness of atomic force microscope cantilever and the indenter/NB contact stiffness, this model adds a third spring of the NB/substrate contact stiffness. NB is highly flexural due to its large aspect ratio of length to thickness. The bending and lift-off of NB form a localized contact with substrate, which makes the Oliver-Pharr method [W. C. Oliver and G. M. Pharr, J. Mater. Res. 7, 1564 (1992)] and Sneddon method [I. N. Sneddon, Int. J. Eng. Sci. 3, 47 (1965)] inappropriate for NB indentation test. Because the NB/substrate deformation may have significant impact on the force-indentation depth data obtained in experiment, the two-spring-in-series model can lead to erroneous predictions on the NB mechanical properties. NB in indentation test can be susceptible to the adhesion influence because of its large surface area to volume ratio. NB/substrate contact and adhesion can have direct and significant impact on the interpretation of experimental data. Through the three-spring-in-series model, the influence of NB/substrate contact and adhesion is analyzed and methods of reducing such influence are also suggested. (C) 2010 American Institute of Physics. [doi:10.1063/1.3432748]

Non-relativistic conformal symmetries in fluid mechanics

The symmetries of a free incompressible fluid span the Galilei group, augmented with independent dilations of space and time. When the fluid is compressible, the symmetry is enlarged to the expanded Schrodinger group, which also involves, in addition, Schrodinger expansions. While incompressible fluid dynamics can be derived as an appropriate non-relativistic limit of a conformally invariant relativistic theory, the recently discussed conformal Galilei group, obtained by contraction from the relativistic conformal group, is not a symmetry. This is explained by the subtleties of the non-relativistic limit.

Molybdenum L-shell X-ray production by 350-600 keV Xeq+ (q=25-30) ions

Molybdenum L-shell X-rays were produced by Xeq+ (q = 25-30) bombardment at low energies from 2.65 to 4.55 keV/amu (350-600 keV). We observed a kinetic energy threshold of Mo L-shell ionization down to 2.65-3.03 keV/amu (350-400 keV). The charge state effect of the incident ions was not observed which shows that the ions were neutralized, reaching an equilibrium charge state and losing their initial charge state memory before production of L-shell vacancies resulted in X-ray production. The experimental ionization cross sections were compared with those from Binary Encounter Approximation theory. Taking into account projectile deflection in the target nuclear Coulomb field, the ionization cross section of Mo L-shell near the kinetic energy threshold was well described. (C) 2010 Published by Elsevier B.V.

Design optimization of the APF DTL in the SSC-linac

A linear accelerator as a new injector for the SSC (Separated Sector Cyclotron) of the HIRFL (Heavy ton Research Facility Lanzhou) is being designed. The DTL (Drift-Tube-Linac) has been designed to accelerate U-238(34+) from 0.140 MeV/u to 0.97 MeV/u. To the first accelerating tank which accelerates U-238(34+) to 0.54 MeV/u, the approach of Alternating-Phase-Focusing (APF) is applied. The phase array is obtained by coupling optimization software Dakota and beam optics code LINREV. With the hybrid of Multi-objective Genetic Algorithm (MOGA) and a pattern search method, an optimum array of asynchronous phases is determined. The final growth, both transversely and longitudinally, can meet the design requirements. In this paper, the deign optimization of the APF DTL is presented.

《景观生态学原理与方法》简介

由国际著名景观生态学家、国际生态学会秘书长、意大利Ｌｕｎｉｇｉａｎａ自然博物馆主任法瑞纳（ＡｌｍｏＦａｒｉｎａ）博士撰写的又一部景观生态学力作《景观生态学原理与方法》（Ｐｒｉｎｃｉｐｌｅａｎｄｍｅｔｈｏｄｓｉｎｌａｎｄｓｃａｐｅｅｃｏｌｏｇｙ）已于１...

长白山地区蒙古栎光合特性

基于单叶尺度上的光强-光合响应以及CO2-光合响应测定,对长白山地区蒙古栎成树和幼树的光合特性分别进行了研究.结果表明,蒙古栎成树的光补偿点Lcp为21μmol/(m2·s),光饱和点Lsp为1564μmol/(m2·s),表观量子效率α为0·045;幼树的Lcp、Lsp、α以及CO2补偿点、饱和点分别为29μmol/(m2·s)、1581μmol/(m2·s)、0·049、73μmol/mol、625μmol/mol.幼树和成树具有相似的光响应特征,但前者的光合同化能力要高于后者.蒙古栎具有典型的喜光性,但对高光的利用效率要低于弱光.