The use of electron Rutherford backscattering to characterize novel electronic materials as illustrated by a case study of sputter-deposited NbOx films

Electrons scattered over large angles at relatively high energies (40 keV) are used to study NbOx films. These films were deposited by reactive sputter deposition on a Si substrate using a Nb target and an Ar/O2 gas mixture. Energy spectra of electrons scattered from such samples exhibit elastic scattering peaks for each component due to the energy difference associated with scattering from different masses. The spectra provide in this way information about the film thickness as well as its stoichiometry. The stoichiometry and the deposition rate depends on the concentration of O2 in the mixture. For Nb2O5-like films the energy loss measurements also give an estimate of the band gap, but for Nb films with lower O concentration the band gap is not resolved. This work illustrates the possibility of characterizing modern transition metal oxide films in a fairly simple electron scattering experiment.