Invisible electronics: Metastable Cu-vacancies chain defects for highly conductive p-type transparent oxide

Abstract Non-stoichiometric copper chromium delafossite has lately attracted a high interest in the community of oxide materials due to its high p-type electrical conductivity and adequate transparency in the visible range. This study reports record electrical conductivity of Cu 0.66 Cr 1.33 O 2 thin films deposited by chemical vapour deposition and investigates their properties. As-deposited samples show conductivities greater than 100 S cm −1 and carrier concentrations around 10 21  cm −3 , highest reported value for any non-intrinsically doped delafossite system. A new structural defect consisting in Cu-vacancies chains is identified. This defect, never observed or presumed before, heals upon annealing at 900 °C under argon environment, resulting in an electrical conductivity's reduction of six orders of magnitude. Through a wide-range of structural, chemical and transport measurement techniques, a structure-defect-property correlation of this system is established and the metastability of the non-stoichiometry induced defects is investigated. The possibility of manipulating the defects and carrier concentrations through high-temperature annealing and the outstanding electrical properties associated with the large-scale deposition technique and moderate deposition temperature could be of great technological interest. This material could find important applications as hole injection or extraction layer in all-oxide photovoltaic and light emitting devices.