【作者】 喻江涛；

【导师】 李明伟；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2008， 博士

【摘要】 当今时代,对微观领域的认识变得越来越迫切和重要,而科技的发展与进步,则使这种需求的实现成为可能,原子力显微镜（atomic force microscope, AFM）正是这样一种使人们得以在微观领域纵横驰骋的有力工具。对于晶体生长领域而言,原子力显微镜的出现,虽极大地促进了其微观生长机理的研究,但晶体生长过程的复杂性,使得这方面的工作还任重而道远,尤其是在无机小分子晶体的微观生长机理研究方面。作为应用广泛,生长容易的ADP晶体,历来被选作晶体生长理论研究的重要材料。近年来随着对其特性的深入了解,新用途的开发,ADP晶体在人类生活中也扮演着越来越重要的作用。但在ADP晶体微观生长机理的研究方面,相关的微观实验数据还较为缺乏,这正逐渐制约着该晶体的制备与应用。本文工作即是运用原子力显微镜,从热动力学的角度对ADP晶体的微观生长过程进行实时和非实时的研究。其主要内容为:①运用原子力显微术观测相变驱动力为0.005 kT /ω_s⁰.11 kT /ω_s下ADP晶体相变界面的微观形貌。实验数据表明,在相变驱动力为0.01 kT /ω_s 0.04 kT /ωs时,ADP晶体（100）面的平均面粗糙度和均方面粗糙度均不到0.3nm,远小于该晶面间距0.75nm,微观结构表现为光滑界面,与杰克逊模型、特姆金模型及卡恩模型相符,观测到螺位错生长;在相变驱动力为0.053 kT /ω_s 0.11 kT /ω_s时,ADP晶体的（100）面的平均面粗糙度和均方面粗糙度,介于1.8nm⁴.2nm之间,大于该晶面间距0.75nm,微观结构粗糙度增加,趋向于粗糙界面,可用特姆金的弥散界面模型解释,界面上观测到多二维核生长。②运用原子力显微术AFM（atomic force microscopy,AFM）观察了ADP晶体生长时相界面上动态微观形貌的变化并测算了台阶传播速率。实验结果表明,在相变驱动力介于0.005 kT /ω_s⁰.05 kT /ω_s,生长温度介于20⁴0℃之间时,相变界面表现出台阶面的基本特征;相变界面上台阶推移的动力学系数体现出溶质输运趋向于体扩散控制;微晶融合的过程说明ADP晶体生长中,微晶融入与大分子晶体的同类过程有显著不同,不会形成晶体缺陷。③详细研究了在较小的相变驱动力下（0.005 kT /ω_s⁰.04 kT /ω_s）ADP晶体生长的纳米级微观形貌。过饱和度σ处于0.005⁰.04,生长温度介于20⁴0℃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;台阶露台上的空洞可能造成台阶聚并;随过饱和度σ降低,台阶形貌会发生相应的变化;生长温度为25℃时,台阶棱边能不小于6.2×10^-3J/m²。④开展了点状籽晶的晶体生长实验。相变驱动力f介于0.005 kT /ω_s 0.03 kT /ω_s之间时,ADP晶体点状籽晶生长中,（100）晶面的生长速率随过饱和度的增加而线性增加;在相变驱动力一定时,晶面生长速率随温度的升高而呈指数增加;晶面的生长动力学规律与体扩散输运机制下的螺位错生长机制相符;晶体生长存在着热力学因素造成的死区。相变驱动力f介于0.05 kT /ω_s 0.11 kT /ω_s之间时（100）晶面的生长速率随过饱和度的增加而呈非线性增加,晶面生长趋近于多二维核生长机制,但同时也存在着其它生长机制。更多还原

【Abstract】 Today the understanding of the micro-domain is increasingly urgent and important. The development and advancement of the science and technology make the needs realizable. The atomic force microscope （AFM） is just a powerful instrument which helps people move about freely and quickly in the micro-domain. Though the invention of AFM push greatly the research on crystal growth micro-mechanism forward, there are shoulder heavy responsibilities in this area because of the complexity of crystal growth process, especially in the micro-mechanism research fields on inorganic small molecule.For the wide application and easy to grow, the ADP crystal is one of the important materials in the crystal growth theory research fields. With the deep understanding of its property and the new purposes to be found recently, ADP crystals have played the more and more important role in the human beings’life, but the lack of the micro-experiment data on the ADP crystal growth micro-mechanism research fields is gradually restricting its preparation and application. In situ and ex situ AFM investigation of the ADP crystal growth have been carried out from the point of thermodynamics and kinetics in the present dissertation. The main works can be summarized as follows:①By atomic force microscopy the micro morphology of the phase interface of ADP crystals were observed under the condition that the phase transition drive force is within 0.005kT/ω_s⁰.11kT/ω_s. The results show that both crystal surface average roughness Ra and mean square root roughness RMS are less than 0.3nm and the （100） inter-planar spacing of 0.75nm, the micro-structure of interfaces is characteristic of smoothness when drive force is within 0.01kT/ω_s⁰.04kT/ω_s, which are agreement with the theory model from Jackson, Temkin and Cahn, meanwhile the screw dislocation growth is observed. The crystal surface average roughness Ra and mean square root roughness RMS are within 1.8⁴.2nm, they are bigger than the inter-planar distances of （100） 0.75nm, surface micro-structure becomes rough when drive force is within 0.053kT/ω_s 0.11kT/ω_s, which is agreement with the model theory from Temkin, in this case, multi-2D nucleation growth is observed.②By in situ atomic force microscopy （AFM） measurement the dynamic topographic changes were observed on the phase interface of ADP crystals and the step propagation rates of ADP crystals were measured when phase transition force was between 0.005kT/ω_s 0.05kT/ω_s and the temperature was between 20⁴0℃. The results of AFM experiments indicated that the phase interface is basely characterized by step surface. the step kinetic coefficient shows that the mass transfer is controlled by bulk diffusion. The process of ADP micro-crystals incorporation is different from similar process of macromolecular crystals, which doesn’t result in crystal defect.③The {100} surface topography of ADP crystal has been investigated by in-situ and ex-situ atomic force microscopy （AFM）. The results show that the step propagation is the main growth mechanism of the crystal face {100} when super-saturation is within 0.005 0.04 and the growth temperature is between 20⁴0℃. Hillocks caused by dislocation and other crystal defects are observed. The appearance of hollow cores in the dislocation growth hillock is in accordance with dislocation elastic theory. Hollow cores on step terraces may result in step bunching. Step morphology changes with the decreasing of the super-saturation. The step edge free energy is greater than 6.2×10^-3J/m² when growth temperature is 25℃.④The point seed crystal growth experiments have been performed. The growth rate of （100） surface increases linearly with the increase of super-saturation when drive force f is within 0.005kT/ω_s 0.03kT/ω_s. The growth rate of （100） surface increases exponentially with the rise of temperature when drive force is constant. The crystal surface growth kinetics mechanism is agreement with the screw dislocation growth under the condition of bulk diffusion transfer mechanism. There are death zone resulted from thermodynamics in crystal growth. The growth rate of （100） surface increases nonlinearly with increasing super-saturation when drive force f is within 0.05kT/ω_s 0.11kT/ω_s. The crystal growth is dominated mainly by the 2D-nucleation mechanism, but meanwhile some other growth mechanism still exists together with it.更多还原