GaNの添加によるCrNの硬度改善とその固溶限評価

In order to improve in hardness of CrN thin film, solubility limit of B1(NaCl type)-GaN in the B1-(Cr,Ga)N phase was evaluated. Cr-Ga-N thin films with various GaN contents were prepared on MgO(100) substrates by pulsed laser deposition. Rutherford backscattering spectroscopy revealed that the ratio of the amount of GaN to the amount of CrN plus GaN (CGaN) in all Cr-Ga-N thin films was in the range of 0 to 59 mol%. X-ray diffraction and micro structure observation showed that Cr-Ga-N thin films with CGaN ≤ 32 mol% were composed of a single B1 phase:B1-(Cr,Ga)N, indicating B1-GaN dissolved in B1-CrN. On the other hand, Cr-Ga-N thin films with CGaN ≥ 47 mol% contained three phases. Although its main phase was B1 type, other phases seemed to be B3(zincblende type)-GaN and α-Ga slightly existed. It was found solubility limit of B1-GaN in the B1-(Cr,Ga)N phase was in the range of 32 to 47 mol%. B1-(Cr,Ga)N thin film with CGaN=27 mol% showed indentation hardness of 37 GPa. It was confirmed the addition of GaN to CrN was effective for increasing the hardness of CrN.