Rotationally anisotropic second-harmonic generation studies of the structure and thermal stability of Cu(110)

Abstract

Rotationally anisotropic surface second‐harmonic generation (SHG) has been used to investigate the surface structure and thermal stability of a clean, well‐characterized Cu(110) single crystal surface in ultrahigh vacuum. The results show clear evidence of the sensitivity of optical SHG to changes in surface structure. At a fixed Cu(110) sample azimuthal angle, the temperature dependence of the second‐harmonic radiation field from the surface was measured at two different wavelengths and found to be in agreement with other experiments performed using very different surface probes that show a sharp change in slope above ∼600 K associated with a possible order–disorder transition. The rotationally anisotropic SH intensity from Cu(110) was found to dramatically decrease as the surface temperature was increased above ∼600 K indicating a loss of surface order and symmetry. A simple model is proposed where thermally induced one‐dimensional disordering accounts for all of the experimental observations between ∼600 and ∼800 K, and where the Cu(110) surface has thermally disordered in two‐dimensions above ∼800 K.