Metallic glass electronic structure peculiarities revealed by UHV STM/STS

We present the results of Ultra high vacuum scanning tunneling microscopy/spectroscopy investigation of metallic glass surface. The topography and electronic structure of Ni$_{63.5}$Nb$_{36.5}$ have been studied. A great number of clusters with size about $5$–$10$ nm have been found on constant current STM images. The tunneling spectra of normalized tunneling conductivity revealed the energy pseudogap in the vicinity of Fermi energy. For energy values above $0.1$ eV the normalized tunneling conductivity changes linearly with increasing of tunneling bias. The obtained results can be understood within suggested theoretical model based on the interplay of elastic electron scattering on random defects and weak intra-cluster Coulomb interaction. The effects of the finite edges of electron spectrum of each cluster have to be taken into account to explain the experimental data. The tunneling conductivity behavior and peculiarities in current images of individual clusters can be also qualitatively analysed in the framework of suggested model.