高温退火处理下SiNx薄膜组成及键合结构变化

采用等离子增强化学气相沉积法, 以氨气和硅烷为反应气体, p型单晶硅为衬底, 低温下(200 ℃)制备了非化学计量比氮化硅(SiN_x)薄膜. 在N₂氛围中, 于500–1100 ℃范围内对薄膜进行热退火处理. 室温下分别使用Fourier变换红外吸收(FTIR)光谱技术和X射线光电子能谱(XPS)技术测量未退火以及退火处理后SiN_x薄膜的Si–N, Si–H, N–H键键合结构和Si 2p, N 1s电子结合能以及薄膜内N和Si原子含量比值R的变化. 详细讨论了不同温度退火处理下SiN_x薄膜的FTIR和XPS光谱演化同薄膜内Si, N, H原子间键合方式变化之间的关系. 通过分析FTIR和XPS光谱发现退火温度低于800 ℃时, SiN_x薄膜内Si–H和N–H键断裂后主要形成Si–N键; 当退火温度高于800 ℃时薄膜内Si–H和N–H键断裂利于N元素逸出和Si纳米粒子的形成; 当退火温度达到1100 ℃时N₂与SiN_x薄膜产生化学反应导致薄膜内N和Si原子含量比值R增加. 这些结果有助于控制高温下SiN_x薄膜可能产生的化学反应和优化SiN_x薄膜内的Si纳米粒子制备参数. 关键词： x薄膜')" href="#">SiN_x薄膜 Fourier变换红外吸收光谱 X射线光电子能谱 键合结构     

药物化学中构效关系的教学方法研究

构效关系是先导化合物修饰、新型药物设计的基础,在药物化学教学中具有至关重要的作用.由于其多样性和复杂性,学生的掌握情况不理想.本文针对这一问题对药物的构效关系进行归纳分类,总结为"三部分一核心多构型"三类,每一类都进行举例讲解,为学生更好地理解与掌握药物化学的构效关系提供一种可行的方式.     

Structural evolution of a-Si:H/SiO2 multilayers upon step by step thermal annealing

a-Si:H/SiO_2 multilayers were prepared by alternatively changing plasma enhanced chemical vapour deposition of a-Si:H layers and in situ plasma oxidation process. Subsequently, as-grown samples were annealed at temperatures from 350℃ to 1100℃ in N_2 ambient with an increment of 100℃. The evolution of bonding configurations and structures with annealing treatments was systematically investigated by Fourier-transform infrared spectroscopy. The peak position of Si－O stretching vibration of SiO_2 layers shift to 1087cm^{-1} after annealing at 1100℃, which demonstrates that the SiO_2 films fabricated by plasma oxidation after high temperature annealing can have similar properties to the thermal grown ones. A Si－O vibration from interfacial SiO_x was identified: the value x was found to increase as increasing the annealing temperature, which is ascribed to the cooperation of hydrogen effusion and reordering of the oxygen bond in SiO_x networks. The H-related bonds were observed in the form of H－Si－O_3 and H－Si－Si_{3-n}O_n (n=1－2) configurations, which are supposed to be present in SiO_2 and interfacial SiO_x layers, respectively. The H atoms bonded in different bonding configurations effuse at different temperatures due to their different desorption energies.     

Ribbon tableaux, ribbon rigged configurations and Hall-Littlewood functions at roots of unity

Hall-Littlewood functions indexed by rectangular partitions, specialized at primitive roots of unity, can be expressed as plethysms. We propose a combinatorial proof of this formula using Schilling's bijection between ribbon tableaux and ribbon rigged configurations.     

On a new interpretation of the classical Maxwell model

Recently, [Rao, I.J., Rajagopal, K.R., 2007. Status of the K-BKZ model within the framework of materials with multiple natural configurations. Journal of Non-Newtonian Fluid Mechanics, 141, 79–84] showed that the K-BKZ Model is a special sub-class of models based on a thermodynamic framework that takes into account the fact that bodies are capable of existing stress free in multiple configurations with special choices being made for the way in which the body stores energy and the way it dissipates energy. They also showed that several generalizations of the K-BKZ model are possible. In this short note we show that two distinct methods of storing energy and dissipating energy lead to the classical Maxwell model. That is, in addition to the classical choice for the storage of energy and rate of dissipation (the usual spring dashpot analogy) a more complicated choice also leads to the same model. This result is rather important as it shows that a variety of means for storing and dissipating energy can lead to the same mechanical response, when one restricts oneself to purely mechanical considerations.     

Optical Mobius Cubes: Integrated Packaging Configurations

Two integrated packaging configurations of optical Mobius cubes are demonstrated. One is based on space division multiplex technique, the other is based on wavelength djvision multiplex technique. The physical constraints from the effect of diffraction on the optical Mdbius cubes are also discussed which defines the upper bound of the space-bandwidth product.     

快速推求等效组态的原子谱项

本文根据置换群方法，运用Ｃ语言编制了计算程序，可快速、准确地推求等效组态ｓ＾Ｎ、ｐ＾Ｎ、ｄ＾Ｎ、ｆ＾Ｎ、…ｘ＾Ｎ、ｙ＾Ｎ、ｚ＾Ｎ的原子谱项。     

A note on maximally repeated sub-patterns of a point set

We answer a question raised by Brass on the number of maximally repeated sub-patterns in a set of n points in R^d. We show that this number, which was conjectured to be polynomial, is in fact Θ(2^n/2) in the worst case, regardless of the dimension d.     

Evidence for multiple band terminations in Pd

The level structure of ¹⁰²Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at I^π = 28⁻ and 32⁺, and tentatively at I^π = 38⁺ and 42⁺. The nucleus ¹⁰²Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations.