STRUCTURAL MODEL FOR THE METAL-INDUCED SI(111)3X1 RECONSTRUCTION

We present a structural model for the metal-induced Si(111)3 x 1 recon struction. Fivefold Si rings form one-dimensional pi-bonded chains alo ng [110BAR]. These chains are separated by empty channels that can acc ommodate 1/3 monolayer of metal atoms. We propose that pi-bonded chain s undergo a strong disturbance resulting in the formation of alternati ng dimers consistent with published scanning tunneling microscope imag es [K.J. Wan et al., Phys. Rev. B 46, 13635 (1992)]. Unlike previous m odels, this model accounts for most experimental observations, includi ng a large band gap and chemical passivation.