Determination of the DOS in Nb(110) from scanning tunneling spectroscopy

We investigate the electronic structure of Nb(110)/Al2O3(0001) by means of scanning tunneling spectroscopy (STS) at 6.2 K. To enable a comprehensive analysis of the local electronic structure of niobium, we employ standard I-V as well as I-z and dI/dz-z spectroscopy. The experimental results will be discussed in the framework of a recently developed method for recovering the electronic density of states (DOS) from STS data. Based on the one-dimensional WKB approximation this method should enable recovering the DOS of the sample semi-quantitatively, and it should allow principally a deconvolution of tip and sample DOS. In this contribution we first elucidate the effect of data evaluation on the recovered DOS separating contributions from the bulk and the surface. We then try to deconvolute the DOS of tip and sample at least partially by comparing I-V data and differential barrier measurements taken at different locations of the sample with the same tunneling tip