Compositional effects on the electrical properties of extremely disordered molybdenum oxynitrides thin films

Abstract

We report on the influence of the chemical composition on the electronic properties of molybdenum oxynitrides thin films grown by reactive sputtering on Si (100) substrates at room temperature. The partial pressure of Ar was fixed at 90 %, and the remaining 10 % was adjusted with mixtures N 2 :O 2 (varying from pure N 2 to pure O 2 ). The crystalline and electronic structures and the electrical transport of the films depend on the chemical composition. Thin films grown using oxygen mixtures up 2 % have γ-Mo 2 N phase and display superconductivity. The superconducting critical temperature T c reduces from ~ 6.8 K to below 3.0 K as the oxygen increases. On the other hand, films grown using oxygen mixtures richer than 2 % are mostly amorphous. The electrical transport shows a semiconductor-like behavior with variable-range hopping conduction at low temperatures. The analysis of the optical properties reveals that the samples have not a defined semiconductor band gap, which can be related to the high structural disorder and the excitation of electrons in a wide range of energies.

Nanocrystalline superconducting γ-Mo2N ultra-thin films for single photon detectors

“…The presence of oxides with a thickness of around 1 nm should directly impact the superconducting properties of ultra-thin films by reducing the effective thickness. Moreover, as we have shown before, interstitial oxygen suppresses the superconducting critical temperature compared to pure nitride films [21].…”