Abstract

Molybdenum oxynitride (MoNxOy) thin films were 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 electrical properties of the films depend on the chemical composition. Thin films grown using mixtures up to 2% O-2 have gamma-Mo2N phase and display superconductivity. The superconducting critical temperature T-c reduces from similar to 6.8 K to below 3.0 K as the oxygen increases. On the other hand, the films are mostly amorphous for gas mixtures above 2% O-2. The electrical conductivity shows a semiconductor-like behavior well described by variable-range hopping conduction. The analysis of the optical properties reveals that the samples do not have a defined semiconductor bandgap, indicating that the high structural disorder produces electron excitation for a wide range of energies.