In/Si(111): Self-Assembled One and Two-Dimensional Electron Gases

Abstract

We present angle-resolved photoemission measurements for ultrathin In films on Si(111). Depending on the coverage, this system self-organizes into a metallic monolayer with either 4x1 or !7x!3 symmetry relative to the substrate. Electronically, they behave like ideal one-and twodimensional electron gases (1DEG and 2DEG), respectively. The 4x1 system has atomic chains of In whose energy bands disperse only parallel to the chains, while for the !7x!3 system, the dominant reciprocal space features (in both diffraction and bandstructure) resemble a pseudosquare lattice with only weaker secondary features relating to the !7x!3 periodicity. In both materials the electrons show coupling to the structure. The 1DEG couples strongly to phonons of momentum 2k F , leading to an 8x"2" Peierls-like insulating ground state. The 2DEG appears to be partially stabilized by electron gap formation at the !7x!3 zone boundary.