Schottky barrier inhomogeneity at Au/Si(111) interfaces investigated using ultrahigh-vacuum ballistic electron emission microscopy

Ultrahigh-vacuum ballistic electron emission microscopy (UHV-BEEM) has been used to study the electron transport across Au/n-type Si(111) interfaces. A BEEM image revealed that an Au film deposited at about 130°C included regions in which the BEEM current was significantly reduced. The ballistic transmissivity across the Au/Si(111) interface was found to be markedly reduced in these regions. Post-annealing of the sample at 300°C in UHV resulted in the absence of ballistic transmissivity throughout the sample. This indicated that the Au-Si alloy formed at the interface scattered the ballistic electrons strongly. We attribute the appearance of the regions to the formation of the Au-Si alloy at the Au/Si interface. We further demonstrate that the growth of Au on a clean Si(111) surface took place in a layer-by-layer fashion at room temperature. The BEEM measurements indicated the formation of a homogeneous interface without regions with reduced ballistic transmissivity.