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

J. A. HOFER; S. BENGIO; G. ROZAS; P. D. PEREZ; M. SIRENA; S. SUAREZ; N. HABERKORN

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2020 vol. 242 p. 122075 - 122080

0254-0584

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 N2:O2 (varying from pure N2 to pure O2). The electrical properties of the films depend on the chemical composition. Thin films grown using mixtures up to 2 % O2 have -Mo2N phase and display superconductivity. The superconducting critical temperature Tc reduces from ~ 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 % O2. 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.