Tuning the size and color of the p-type wide band gap delafossite semiconductor CuGaO2 with ethylene glycol assisted hydrothermal synthesis

Abstract

Delafossite CuGaO₂ is a prototype p-type transparent semiconducting oxide. We report here a new ethylene glycol (EG) mediated hydrothermal synthesis route to this material from soluble hydrated metal nitrates. We found that EG acts as a reducing agent which eases the formation of CuGaO₂ by stabilizing Cu(I) at low temperature in hydrothermal conditions. Moreover, we observed that the initial pH of the precursors solution is a key parameter to tune the particle sizes (from 2 µm to 300 nm) and subsequently the color (from dark brown to light gray) of the CuGaO₂ powder. The optimal synthesis conditions to obtain the brightest product are described. In these conditions, the CuGaO₂ powder exhibits a pale grayish color and contains 300 nm large nano-layered particles approximately 20 nm thick.