I propose kinetically determined topological models of lightly doped ($x\lesssim 0.05$) amorphous ${(\mathrm{G}\mathrm{e},\mathrm{S}\mathrm{i})}_{1-x}{Y}_x$ alloys ($Y=\mathrm{H},\mathrm{F},\mathrm{B},\mathrm{P},\dots$). Without adjustable parameters the model relates the lowest concentration ${x_{\mathrm{H}}}^0$ of hydrogen atoms required to quench paramagnetic dangling bonds to the concentration $c_0$ of unpaired spins at $x=0\mathrm{}$. Also discussed are the structural differences between freshly evaporated $\alpha$-(Ge, Si) and various stages of ion-bombarded ("amorphized") crystalline material.

• Received 25 January 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.1151