氧分压与沉积速率对ITO薄膜性能的影响

本文侧重研究利用电子束蒸发技术制备ITO透明导电薄膜过程中氧分压、沉积速率对其性能的影响.研究发现,随着氧分压的增大,样品透光性和导电性均呈现先增大后减小的趋势;通过计算得出禁带宽度随着氧分压的增大也呈现先增大后减小的趋势.对沉积速率对样品性能的影响进行了研究,结果表明沉积速率降低有利于样品性能的改善.     

灯丝温度对热丝CVD法制备p型氢化纳米晶硅薄膜微结构与光电性能的影响

本文采用热丝化学气相沉积法在不同灯丝温度(1650 - 1850℃)下沉积了p型氢化纳米晶硅薄膜,研究了灯丝温度对薄膜微结构、光学性能及电学性能的影响.结果表明,随着灯丝温度的升高,薄膜的晶化率先增大后略微减小,最大值是55.5;.载流子浓度和霍尔迁移率先分别从5×1017 cm-3和0.27 cm2/V·s增加到1.32×1020 cm-3和0.43 cm2/V·s后略微减小,同时电导率从0.02 S/cm显著增加到8.95 S/cm,而电导激活能则从271.5 meV急剧减小至25 meV.     

InP纳米线场效应晶体管的制备及其电学性能的研究

利用化学气相沉积法在Si/SiO2衬底上生长出了InP纳米线,制备了基于InP纳米线的底栅场效应晶体管并研究了其电输运特性.对不同生长温度器件的阈值电压、亚阈值斜率、场效应迁移率以及载流子浓度等参数进行了计算和比较.结果表明,生长温度对InP纳米线的形貌影响较大.800℃生长温度的InP纳米线性能较好,该器件阈值电压约为-8.5V,亚阈值斜率为142.4 mV/decade,跨导为258.6 nS,开关比＞106,场效应迁移率高达177.8cm2/(V·s),载流子浓度达2.1×101s cm-3.     

基于单根InAs纳米线场效应晶体管的制备及其电学性能研究

利用化学气相沉积法在Si衬底上生长合成了InAs纳米线,制备了基于InAs纳米线场效应晶体管并研究了电输运特性.对器件的阈值电压、亚阈值斜率、跨导、场效应迁移率以及载流子浓度等参数进行了计算和讨论.结果表明,InAs纳米线器件阈值电压约为-6.0 V,亚阈值斜率为180.86 mV/decade,跨导值达0.85 μS,最大开关比达108,场效应迁移率高达436.3 cm2/(V·s),载流子浓度达6.6×1017 cm-3.     

磁控溅射工艺参数对碳膜表面形貌及浸润性的影响

为了分析磁控溅射工艺对碳膜表面形貌及浸润性的影响,在室温下采用磁控溅射技术在硅片表面沉积碳膜,并利用原子力显微镜(AFM)、扫描电镜(SEM)、静态接触角测量仪对所得碳膜进行表征.结果表明:随着溅射功率的提高,碳膜表面粗糙度先减小后增大,致密性逐渐改善,静态接触角先增大后减小;随着溅射时间的延长,碳膜的表面粗糙度逐渐增加,均匀性在一定的溅射时间内逐渐改善,静态接触角呈现先减小后增大再减小的趋势;随着溅射压强的增加,碳膜表面粗糙度先增大后减小,致密性在过高的溅射压强下会变差,静态接触角先减小后增大.     

SiNX覆盖层厚度对非晶In-Ga-Zn-O薄膜退火晶化的影响研究

采用射频磁控溅射在二氧化硅衬底上沉积一层厚度200 nm的非晶In-Ga-Zn-O(IGZO)薄膜,并在IGZO膜层上沉积厚度分别为20 nm、50 nm、60 nm、70 nm、90 nm的SiNX薄膜覆盖层,于350℃条件下N2气氛中退火1 h.采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量色散谱仪(EDS)对IGZO薄膜的微观结构及成分进行研究.研究结果表明,退火后无覆盖层的IGZO膜层仍为非晶状态,70 nm以上SiNX覆盖层下的IGZO薄膜不发生晶化.与此不同,20～60 nm的SiNX覆盖层下IGZO膜层与SiNX覆盖层的界面处存在纳米凸起柱,使IGZO薄膜与SiNX覆盖层的接触界面脱离,此厚度的SiNX覆盖层具有诱导非晶IGZO薄膜晶化的作用,IGZO膜层内部的晶粒直径约10 nm.成分分析结果表明,结晶处In原子含量增加,IGZO薄膜中In原子的局域团聚是IGZO薄膜发生晶化的原因.     

氧分压对HfOxNy薄膜结构和力学性能的影响

采用射频磁控反应溅射法在不同氧分压条件下制备了氮氧化铪薄膜,薄膜沉积过程在氧气、氮气和氩气的混合气氛中进行,所用衬底为多光谱硫化锌材料.用X射线衍射、扫描电子显微镜、纳米硬度计等分别研究了不同氧分压条件下HfOxNy薄膜的晶体结构、显微结构、力学性能等.结果表明:在氧分压为0.05～0.30范围内,HfOxNy薄膜都为多晶结构,但随着氧分压的降低,HfOxNy薄膜的沉积速率逐渐增大,薄膜的晶体结构由单斜氧化铪转变为氮氧化铪相;不同氧分压下沉积的HfOxNy薄膜都符合薄膜区域结构模型中典型的柱状结构且氧分压较低时薄膜表面粗糙度较大;不同氧分压条件下沉积的HfOxNy薄膜硬度和弹性模量都远大于衬底硫化锌的硬度和弹性模量,氧分压为0.15时最大硬度和弹性模量值分别为11.6 GPa和160 GPa.     

磷石膏在醋酸铵溶液中的溶解量及滤渣产物的变化

本文研究了磷石膏在醋酸铵溶液中不同溶剂浓度、溶解温度、固液比、溶解时间对磷石膏溶解量和溶解后残渣物相的变化,采用XRD对滤渣样品的物相进行表征.结果表明:磷石膏溶解量随着醋酸铵溶液浓度的增大,先增大后减小,减小的原因是浓度太大时生成硫酸铵沉淀.随着温度的升高,磷石膏溶解量的增加和减小变化幅度较大,温度为60℃时生成铵石膏,100℃时生成硫酸铵钙;随着固液比的增大,磷石膏溶解量先增大后减小,固液比越大,越易生成铵石膏.当固液比为8.3 g∶100 mL时,在10 min时,磷石膏溶解量即达到最大,随后基本保持不变,2 min时生成硫酸铵.固液比为10.0 g∶100 mL时,随着溶解时间的增大,磷石膏溶解量先增大后减小;溶解时间越长,越易生成铵石膏.在90℃时,8 mol/L醋酸铵溶液,固液比为10.0 g∶100 mL,优化时间区间为10～30 min,20min时磷石膏溶解量可达最大8.86 g/100 mL,溶解率为88.60;.     

真空退火温度对射频磁控溅射制备非晶In-Ga-Zn-O薄膜性能影响的研究

采用射频磁控溅射技术在室温下玻璃衬底上制备了铟镓锌氧(In-Ga-Zn-O)透明导电薄膜,并对该薄膜进行了真空退火.研究了不同退火温度对In-Ga-Zn-O薄膜结构、电学和光学性能的影响.X射线衍射(XRD)表明,在300℃至500℃退火温度范围内,In-Ga-Zn-O薄膜为非晶结构.随着退火温度的增加,薄膜的电阻率先减小后增大.透射光谱显示退火后In-Ga-Zn-O薄膜在500～ 800 nm可见光区平均透过率超过80;,且在350 nm附近表现出较强的紫外吸收特性.经过退火的薄膜光学禁带宽度随着退火温度的增加先增大后减小,350 ℃最大达到3.91 eV.     

硒化镉纳米线在应力作用下的第一性原理研究

基于密度泛函理论的第一性原理计算分析了不同横向尺寸的硒化镉(cdse)纳米线在拉伸和压缩单轴应力作用下的能带结构、载流子(电子和空穴)的有效质量以及迁移率的变化.计算结果表明,CdSe纳米线在施加应变或改变横向尺寸时,均表现为直接带隙半导体.随着压缩应变(0;～-10;)和拉伸应变(2;～10;)的增加,CdSe纳米线的带隙逐渐减小,但横向尺寸小的纳米线的带隙相对宽些.导带底电子迁移率随着应变从-10;至10;变化而逐渐减小,而价带顶空穴迁移率在施加应变从4;至10;变化时也缓慢减小.直径为1.2 nm的CdSe纳米线在施加的压缩应变为-10;时,电子和空穴迁移率最大,分别为2890em2·V-1·s-1和2273 cm2·V-·s-1.因此,横向尺寸较小的CdSe纳米线在合适的压应力调控下有望成为一种制备高性能新型纳米电子器件的候选材料.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.