Investigation On The Dislocations And Optical Performance Of Sapphire Crystal

Sapphire crystal is alumina monocrystal, with good optical properties, mechanicalproperties, thermal properties, electrical properties and chemical stability. It is a kind ofhighly technological crystal with good comprehensive performance, widely used ininfrared military equipment, satellite space technology, substrate materials ofsemiconductor materials such as silicon, GaN, ZnO, high strength of the laser substratematerials and so on. Sapphire crystal preparation methods include Verneuil, Czochralski,EFG, heat exchange method, Kyropoulos and so on. Sapphire crystal defects especiallydislocation directly affect its usability, and the optical performance not only directlyaffect the optical applications, but also the study of the crystal defect structure and form,therefore carrying out the study of sapphire single crystal of dislocation and opticalperformance is of great significance.The dislocation display and characterization techniques of sapphire single crystalare firstly studied in this paper. The sapphire corrosion process is studied with a wetetching technology and analysis technologies of metallographic microscope, SEM andenergy spectrometer. It is found that the best corrosion process of sapphire crystaldislocation is the sapphire crystal be corroded in290℃in the molten KOH corrosionfor20minutes. With the analysis of different crystal morphology of micro defects, it isfound that the dislocation corrosion pit for the sapphire crystal with11-20surfaces is adiamond, a isosceles triangle for1-102, and a triangle for0001. The sapphire crystaldislocation density is calculated through the nine-point average dislocation etch pitdensity （EPD） testing method, and the results show that: the dislocation density ofsapphire single crystal with Kyropoulos growth is minimum, only2.57×10³cm^-2.Similar microdefect morphology is also found in the experiment. The infrared spectrum and Raman spectrum of sapphire single crystal is alsostudied in this paper. Through the infrared spectrum test, the infrared spectrum ofsapphire single crystal with different dislocation density is studied, and the result showsthat the dislocation density of sapphire single crystal has corresponding relation with itsinfrared transmittance, the mechanism of which is high density defects group in thelattice corresponding with high density dislocation leads to strong infrared absorption.The sapphire single crystal with Kyropoulos growth transmittance for the infrared wavewith the wave number over2000cm^-1 is the highest, which can achieve85%above.Variable temperature infrared spectrum researches show that sapphire single crystalinfrared transmittance increases with temperature rising, which can reach more than95%in400℃. Raman spectrum research shows that the micro defects group has adirect impact on the number and position of Raman spectrum peak. High qualityKyropoulos with sapphire and standard sapphire Raman spectrum goodness of fit highcharacteristic peak number and peak position.The sapphire crystal optical uniformity is studied finally in the paper. Withinterference of convergent polarized light, the optical uniformity of sapphire crystalwith different quality is researched and the results show that the distortion ofKyropoulos sapphire crystal lattice is minimum, which shows that its micro defects andstress are the lowest.