29Si magnetic resonance study of amorphous hydrogenated silicon plasma deposited at 50 °C

Abstract

We deposit compact amorphous hydrogenated silicon (a-Si:H) films at 50 °C, using low silane partial pressures in silane/hydrogen reaction mixtures. The 29Si chemical shift and infrared signature of our films are strongly affected by the silane feed partial pressure, but are insensi- tive to the hydrogen feed partial pressure, indicating that hydrogen ‘‘etching’’ does not play a significant role in the film growth process. Interestingly, the 29Si chemical shift and infrared signature of our compact 50 °C films are similar to those of a-Si:H films deposited at standard ‘‘optimum’’ conditions, but the electronic properties are very different. Upon thermal annealing at 150 °C for 3 h, the spin defect density may be reduced by as much as 2 orders of magnitude, while the hydrogen content, 29Si chemical shift and infrared signature remain unchanged. Therefore, it seems possible to first grow a compact silicon network structure in a-Si:H at 50 °C, and then equilibrate the electronic structure at 150 °C, without significantly altering the silicon network.