蓝宝石超精密抛光表面的热修复机理研究

Study on the Thermal Repair Mechanism for the Ultra-precision Polished Surface of Sapphire

通过化学机械抛光获得的超精密蓝宝石表面存在一定厚度的表面损伤层,直接制约蓝宝石元件性能的提升。为降低蓝宝石表层损伤层,研究了蓝宝石超精密抛光表面的热修复工艺。对超精密加工后蓝宝石进行热修复处理,分析了热修复对不同晶面蓝宝石表面微观形貌的影响规律。结合蓝宝石各个晶面原子排布规律,蓝宝石C面的晶层间距最大,相比其他晶面,C面蓝宝石的超精密抛光表面更易形成台阶结构;热修复后,A面、R面蓝宝石微观表面都呈现出有序分布的台阶状结构,M面蓝宝石表面形成薄片状微观结构;在热场作用下,蓝宝石表面原子发生移动,形成台阶状形貌;纳米压痕结果表明热修复后各个晶面蓝宝石的硬度和弹性模量都有一定程度增加;通过聚焦离子束定向提取热修复前后的R面蓝宝石表层纳米厚度的薄片,并在透射显微镜下观测其高分辨原子衍射图像,证实了热修复工艺使表层原子排布由非晶态向晶体有序化转变,同时表面微观形貌也出现了规律性特征,从而使加工表面晶格完整性提升。研究结果表明热修复能有效用于蓝宝石表层质量的提升。

The ultra-precision surface of sapphire machined by chemico-mechanical polishing has a certain thickness of damage layer,which has adverse effects on the performance of sapphire parts.For reducing the damage of sapphire surface,the thermal repair process is studied on the ultra-precision surface of sapphire.The high-temperature annealing treatment are conducted on the sapphire materials after ultra-precision processing.The micro-topography of sapphire surfaces is analyzed before and after thermal treatment.Based on the atomic arrangement rule of various crystalline orientations of sapphire,it reveals that the ultra-precision polished surface of C-plane sapphire is easiest to form the step structure as the interplanar spacing of C-plane of sapphire is largest among the four crystalline orientations.After annealing at high temperature,the surfaces of A-and R-planes sapphire also exhibit ordered step-like structures,and the surface of M-plane sapphire shows a lamellar structure.Under the action of thermal field,the atoms in sapphire surface move leading to the formation of step-structures.The nanoindentation results show that all the nano-hardness and elasticity modulus of sapphire with various crystalline-faces are increased to a certain extent after thermal repair.The nanoscale-thickness materials of R-plane sapphire before and after thermal repair are extracted by the cutting technology of focusing ion beam.The high-resolution atomic diffraction images are observed under transmission microscope.It is verified that the surface atomic arrangement changes from the amorphous to the ordered structures due to high-temperature repair process.At the same time,the surface morphology also tends to be ordered and regular.The ordered lattice arrangements improve the lattice integrity of the processed surface of sapphire.The research highlights that thermal repair is an effective method to the improve the surface-layer quality of sapphire.