Behavior of N atoms after thermal nitridation of Si1 − xGex surface

Behavior of N atoms after thermal nitridation of Si_1 − xGe_x (100) surface in NH₃ atmosphere at 400 °C was investigated. X-ray photoelectron spectroscopy (XPS) results show that N atomic amount after nitridation tends to increase with increasing Ge fraction, and amount of N atoms bonded with Ge atoms decreases by heat treatment in H₂ at 400 °C. For nitrided Si_0.3Ge_0.7(100), the bonding between N and Si atoms forms Si₃N₄ structure whose amount is larger than that for nitrided Si(100). Angle-resolved XPS measurements show that there are N atoms not only at the outermost surface but also beneath surface especially in a deeper region around a few atomic layers for the nitrided Si(100), Si_0.3Ge_0.7(100) and Ge(100). From these results, it is suggested that penetration of N atoms through around a few atomic layers for Si, Si_0.3Ge_0.7 and Ge occurs during nitridation, and the N atoms for the nitrided Si_0.3Ge_0.7(100) dominantly form a Si₃N₄ structure which stably remains even during heat treatment in H₂ at 400 °C.