This paper identifies several important non-statistical bonding environments in alloyed and doped a-Si:H. These include O-Si-H linkages in a-Si,O:H alloys, and P+-Si-H and Si-B--H linkages that play a significant role in the doping processes in a-Si:H. We present the experimental evidence for these bonding arrangements, and a model that accounts for their creation during film deposition.