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

Reduced molybdenum oxide, generally MoO3-x, becomes increasingly metallic as the oxygen level decreases during the reduction of MoO3 to MoO2. Its interesting properties have recently intrigued research on MoO3-x in electrical and electrochemical areas. Lacking effective tools to control the oxygen level is one of the research difficulties for MoO3-x. Herein, we report facile temperature controlled synthesis of triangular MoO2 and square Mo4O11. The triangular and square flakes showed metallic behavior with conductivity as high as, similar to 940 and similar to 28 S/cm in DC measurement, respectively. The decrease in oxygen level from Mo4O11, to MoO2 affected the density of states mapped in Mo 4d orbitals, leading to higher conductivity for triangular MoO2. Further Mott-Schottky analysis on MoO3-x regrown on carbon fiber paper (CFP) revealed hole mobility of 10(5)-10(8) cm(2) V-1 s(-1). The hole carriers at high frequencies are attributed to potential oxygen acceptors, and molybdenum vacancies resulted from limited reduction power of hydrogen.