Elemental depth profiling of a-Si1 xGex:H films by elastic recoil detection analysis and secondary ion mass spectrometry

The hydrogen content in a-Si1 xGex:H thin films is an important factor deciding the density and the optical band gap. We measured the elemental depth profiles of hydrogen together with Si and Ge by elastic recoil detection analysis (ERDA) combined with Rutherford backscattering (RBS) using MeV He2+ ions. In order to determine the hydrogen depth profiles precisely, the energy- and angle-dependent recoil cross-sections were measured in advance for the standard sample of a CH3 +- implanted Si substrate. The cross-sections obtained here are reproduced well by a simple expression based on the partial wave analysis assuming a square well potential (width: r0 = 2.67 10 13 cm, depth: V0 = 36.9 MeV) within 1%. For the a- Si1 xGex:H films whose elemental compositions were determined by ERDA/RBS, we measured the secondary ions yields of HCs2 +, SiCs2 +, H , Si and Ge as a function of Ge concentration x. As a result, it is found that the useful yield ratios of HCs2 +/ SiCs2 +, H /Si and Ge /Si are almost constant and thus the elemental depth profiles of the a-Si1 xGex:H films can be also determined by secondary ion mass spectrometry (SIMS) within 10% free from a matrix effect.