Temperature-Controlled Vapor Deposition of Highly Conductive p-Type Reduced Molybdenum Oxides by Hydrogen Reduction.

Reduced molybdenum oxide, generally MoO, becomes increasingly metallic as the oxygen level decreases during the reduction of MoO to MoO. Its interesting properties have recently intrigued research on MoO in electrical and electrochemical areas. Lacking effective tools to control the oxygen level is one of the research difficulties for MoO. Herein, we report facile temperature-controlled synthesis of triangular MoO and square MoO. The triangular and square flakes showed metallic behavior with conductivity as high as ∼940 and ∼28 S/cm in DC measurement, respectively. The decrease in oxygen level from MoO to MoO affected the density of states mapped in Mo 4d orbitals, leading to higher conductivity for triangular MoO. Further Mott-Schottky analysis on MoO regrown on carbon fiber paper (CFP) revealed hole mobility of 10-10 cm V s. The hole carriers at high frequencies are attributed to potential oxygen acceptors, and molybdenum vacancies resulted from limited reduction power of hydrogen.