ADP晶体的生长丘、台阶微观形貌及台阶棱边能

ADP晶体{100}面族生长的实时与非实时AFM(atomic force microscopy,AFM)研究表明,过饱和度σ处于0.005～0.04,生长温度介于293～313K之间时,晶面上观察到位错生长丘和其它晶体缺陷所形成的生长丘,晶面主要为台阶推进方式生长;位错生长丘上空洞的出现与位错弹性理论相符;随过饱和度σ降低,台阶形貌会发生相应变化;生长温度为298K时,台阶棱边能不小于6.2×10-7J/cm2.     

ADP晶体{100}面族二维成核生长微观形貌的AFM研究

ADP晶体{100}面族微观形貌的非实时AFM(atomic force microscopy,AFM)成像表明,过饱和度σ=0.053时,晶面上出现二维成核生长;随σ增加至0.11,二维岛数量急剧增加,尺寸减小,分布渐趋均匀,二维成核生长逐渐增强,界面呈现出由光滑向粗糙转变的特征;各二维岛形状趋近于长条形,表现出各向异性,长轴平行于[001]晶向;二维岛上有单分子高度的台阶和台阶聚并后高度为2～3nm的大台阶;二维岛间融合时取向相同;σ=0.053时,融合后所形成的较大二维岛的生长呈现出周边快中心慢的情况,将可能导致产生晶体缺陷.     

pH值对水热合成HA晶须形貌的影响

研究了不同pH值条件下水热法制备羟基磷灰石晶须的形貌特征。采用X射线衍射仪(XRD),场发射扫描电子显微镜(FESEM)等分析了pH值对HA晶须组成、形貌和结构的影响。结果表明,在水热条件下,可以成功地合成结晶度高、组成均一的羟基磷灰石晶须。随着pH值的提高,a轴方向尺寸上升,c轴方向基本不变,长径比减小。在微观形貌上羟基磷灰石逐渐由针状向球状形态转变。在pH值=7～8之间,合成的羟基磷灰石晶粒尺寸变化不大,稳定性较高,适合工业化生产。还初步讨论了HA的生长机制。     

pH值对氢氧化镁晶体生长的影响

以氯化镁(分析纯)为原料,反向滴加到氨水中制备普通氢氧化镁,然后在200℃反应釜中对普通氢氧化镁进行水热改性.通过扫描电镜(SEM),X射线多晶衍射仪(XRD),全自动氮物理吸附仪(BET)和激光粒度仪等对样品进行表征分析,得到不同pH条件下晶体生长情况和产品收率.结果表明,常温沉淀过程中pH值为10.0时,产品收率高,粒径分布均匀,分散性好.并且分析了pH值对氢氧化镁晶体生长作用机理.     

pH值对镀铁层性能及结构的影响

研究了在不同ＰＨ值条件下所获得的无刻蚀镀铁层的硬度，金相组织及耐蚀性，结果表明，在ＰＨ值为０．７时，镀铁层致密，结合割固，具有最佳的结构及性能，镀铁层的织构最强，且随ｐＨ值的升高而增强。     

pH值对溶胶凝胶法制备莫来石纳米粉体微观形貌的影响

以氧化钨为催化剂,利用溶胶-凝胶方法制备了具有高长径比的一维莫来石纳米粉体.研究表明,溶胶前驱体的pH值对氧化钨的催化作用有重要的影响.只有当溶胶前驱体的pH值小于7时,才能形成AlWO₄生长模板引导一维莫来石颗粒的形成.随着溶胶前驱体pH值的逐渐升高,前驱体的化学均匀度降低,导致γ-Al₂O₃形成温度升高,WO₃在生成AlWO₄之前已经大量挥发.生长模板的缺失使莫来石粉体的微观形貌从各向异性向各向同性发展.     

溶液pH值对直接沉淀法制备CaF2纳米粉体的影响

以Ca（NO3）2和KF为原料,采用直接沉淀法制备CaF2粉体,借助XRD、SEM、粒径分析方法研究了溶液pH值对产物CaF2粉体晶粒尺寸、颗粒大小及分布的影响,结果表明,在碱性条件下所得CaF2沉淀的晶粒尺寸比在酸性条件下所得CaF2沉淀的小,溶液pH值为13.7时,制备出晶粒大小仅20nm的CaF2纳米粉体。     

亚硫酸铵镀金pH值的探讨

亚硫酸铵镀金具有镀层密实、分散能力和深镀能力好、沉积逯度快和外观悦目等优点，所以已成为工业镀金中一种较重要的工艺方法。但pH值较难控制和调整，槽液稳定性差及污染环境等问题至今尚未引起人们的重视。     

硫酸羟胺和pH值对低温磷化过程的影响

利用多种方法研究了硫酸羟胺(HAS)和pH值对低温锌系磷化过程的影响,结果表明,HAS是一种非常好的低温磷化促进剂,可以使钢铁材料在低温下生成黑灰色均匀的磷化膜.但是其含量并不是越多越好,而是存在一个峰值.pH值的大小是成膜的一个重要因素,过大或过小均不能成膜;另外pH值对HAS的用量也有影响,pH值大时需要的HAS量多,小时所需量少.     

Investigation on (100) face of KDP crystal poisoned by MoO4 2? impurity

Potassium dihydrogen phosphate (KDP) single crystals doped with molybdate (MoO₄ ²⁻) were grown via the conventional temperature cooling and rapid growth methods, respectively. MoO₄ ²⁻ made KDP crystals tapering for conventional temperature cooling method. When KDP crystals were grown by rapid growth method, MoO₄ ²⁻ could induce liquid inclusions and simultaneous crystals. The measurement on growth rates indicated that MoO₄ ²⁻ broadened the dead zone and decreased the growth rate of (100) face of KDP crystals. The growth kinetic analysis in terms of two-dimensional nucleus and screw dislocation models implied that the energetic parameter γ/kT decreased with an increase of MoO₄ ²⁻ concentration. The influence of MoO₄ ²⁻ growth steps on (100) face of KDP crystal was observed through ex situ AFM technique. It gave evidence that MoO₄ ²⁻ could postpone the step bunching and make the step edge curving and knaggy to reduce the edge free energy, which was in agreement with the growth kinetics calculations. Additionally, the poisoned mechanism of MoO₄ ²⁻ and Fe³⁺ on step morphologies was detailed contrasted. The interaction process was discussed according to electro negativity analysis, which indicated MoO₄ ²⁻ (actually were HMoO₄ ⁻ and H₂MoO₄) could be absorbed onto (100) face through charge-assisted hydrogen bonds and caused more Mo element distributed in prismatic sector.     

简立方晶体(001)晶面生长的蒙特卡罗模拟

通过对简立方晶体(001)晶面生长的蒙特卡罗模拟,获得了不同晶体表面热粗糙度,不同过饱和度,不同平均扩散距离以及不同表面尺寸下晶体生长速率;同时,应用舍维数法,计算了表面分形维数;并对表面形貌及描述表面特性的相关参量作了分析.结果表明,法向生长模式和二维核生长模式,包括单核和多核生长模式,都可能出现,其主要取决于热粗糙度和过饱和度的大小.晶体生长速率与表面的微观特性紧密相关,如扭折、台阶、台面和吸附基元的百分比.     

The adsorption of Ni on the Mo(111) crystal face

STM, LEED, AES, TDS and Δ? measurements were performed to investigate the adsorption of Ni on the molybdenum (111) surface. The adsorption energy of Ni atoms on the Mo(111) surface was determined. At 300 K the layer-by-layer growth mechanism was observed. No faceting of the Mo(111) surface was observed after the annealing. Annealing leads to the adsorbate agglomeration and formation of Ni islands in the shape of pyramids.     

Epitaxial growth of Cu(100) and Pt(100) thin films on perovskite substrates

Pulsed laser deposition has been used to grow epitaxially oriented thin films of Cu and Pt on (100)-oriented SrTiO₃ and LaAlO₃ substrates. X-ray diffraction results illustrated that purely epitaxial Cu(100) films could be obtained at temperatures as low as 100 °C on SrTiO₃ and 300 °C on LaAlO₃. In contrast, epitaxial (100)-oriented Pt films were attained on LaAlO₃(100) only when deposited at 600 °C. Atomic force microscopy images showed that films deposited at higher temperatures consisted of 3D islands and that flat, layered films were obtained at the lowest deposition temperatures. Importantly, Cu films deposited at 100 °C on SrTiO₃(100) were both purely (100)-oriented and morphologically flat. Pt and Cu films displaying both epitaxial growth and smooth surfaces could be obtained on LaAlO₃(100) only by using a three-step deposition process. High-resolution transmission electron microscopy demonstrated an atomically sharp Cu/SrTiO₃ interface. The crystalline and morphological features of Cu and Pt films are interpreted in terms of the thermodynamic and kinetic properties of these metals.     

Epitaxial growth of PbTe on (100) GaAs substrates

The growth of PbTe films on GaAs by molecular beam epitaxy was studied by reflection high energy diffraction. The strains in the films were investigated by X-ray diffraction. Despite a lattice mismatch of 14.2%, oriented films can be grown up to a thickness of 4000 Å. For thicker films the thermal strain causes cracks if the samples are cooled from growth to liquid-nitrogen temperature.     

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In_0.1Ga_0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.     

Molecular-beam epitaxy of (Ga,Mn)As crystal nanowires on surface GaAs(100)

Arrays of (Ga,Mn)As crystal nanowires on a GaAs (100) substrate were first obtained using molecular-beam epitaxy at 485°C. From the diffraction patterns of the reflected fast electrons, it was found that crystal nanowires are formed in this system in a cubic crystallographic phase.     

Temperature dependence of the growth of gallium oxide on CoGa(100)

The oxidation of a CoGa(100) surface at high temperatures has been studied by scanning tunnelling microscopy (STM) and auger electron spectroscopy (AES). When CoGa(100) is oxidised at a sufficiently high temperature (>600 K), an ordered Ga₂O₃ film is formed. The stability of the film depends on the sample temperature and partial oxygen pressure of the ambient gas. At negligible oxygen pressure (<10⁻¹¹ mbar) the oxide is stable up to 850 K. At an oxygen pressure of 10⁻⁶ mbar the oxide is stable up to 930 K and some of the oxide remains present up to 970 K. The oxide film is found to be very uniform. The thickness of the film is constant and independent of the oxidation temperature (600 K<T<930 K), oxygen pressure (<10⁻⁶ mbar), and exposure (10⁻⁴–10⁻² mbar.s≈10²–10⁴ L). We find a clear improvement of the order of the oxide film surface with increasing oxidation temperature. In STM images, a domain structure of the oxide film is observed. The size of the domains increases by a factor of 5–10 when the oxidation temperature is increased from 700 to 900 K.