Crystal orientation-dependent scribing of A-, C-, and M-plane sapphires by an ultraviolet laser

Abstract

The ultraviolet nanosecond laser processing of microgrooves was conducted on A-, C-, and M-plane sapphire sheets along different crystal orientations. The influences of crystal orientation on the mechanical cleaving of sapphire sheets containing laser-processed microgrooves were investigated. Experimental results revealed that laser-induced cracks within the microgrooves, ablation threshold, and material removal rate of sapphire were closely related to crystal orientation. The removal energies of aluminum and oxygen ions per unit length along different crystal orientations were theoretically calculated; the difference in material removal rates along different crystal orientations was explained. Mechanical cleaving indicated that sapphire sheets could be separated along the A-M, C-A, C-M, and M-A orientations, whereas cleaving sapphire along A-C and M-C orientations was difficult. Moreover, the changes in the structure of laser-processed sapphire were also analyzed.