To analyze and describe the behavior and mechanisms occurring in the thermal oxidation process of AlN, bulkAlN single crystals were thermally treated with different temperatures. As a result, it was confirmed that full-scaleoxidation of bulk AlN and growth of Al-oxide occurred from the temperature of 800oC, which confirmed that the weight%of O elements tended to increase while the N elements decreased with increasing the temperature. In the case of thermaltreatment at 900oC, the grown Al-oxides were merged with neighboring Al-oxides and began to form -Al2O3 poly-crystals.
During thermal treatment at the temperature of 1000oC, hexagonal pyramidal shaped poly-crystalline -Al2O3 was clearlyobserved. Through the X-ray diffraction pattern analysis, the changes of surface crystal structure according to thetemperature of bulk AlN were investigated in detail.