REACTIVE NB/SI(1 1 1) INTERFACES STUDIED BY ELECTRON-SPECTROSCOPY

In order to improve the basic understanding of Schottky junctions, the microscopic electronic properties of the metal-silicon interfaces have been extensively investigated during the past years. Most works have dealt with near-noble transition metals; refractory metals are less explored, perhaps because of the greater difficulties encountered to prepare calibrated submonolayer deposits and to avoid contamination by residual gas during experiments. Room-temperature reactions between refractory metals and silicon surfaces are found to depend strongly on the metal. For example, V forms abrupt junction with Si; the Cr-Si interfaces, on the contrary, are strongly intermixed with Si segregation on the top of the Cr films. Out XPS, UPS and AES study, the main results of which are reported, shows that the formation of the interface between evaporated Nb and clean Si(111) surface begins with an intermixed reactive region and then continues with the metal layer.