Single step preparation of quaternary Cu₂ ZnSnSe₄ thin films by RF magnetron sputtering from binary chalcogenide targets

Cu₂ ZnSnSe₄ (CZTSe) thin films were grown in a single step procedure by RF magnetron sputtering from a compacted powder consisting of blended chalcogenides. Targets with various chalcogenide mole ratios were designed for the purpose of preparing stoichiometric as-grown films. The material concentrations of the films grown at room temperature were found to depend on the mole ratio of the chalcogenides in the targets. It was found that a significant deviation of material concentration of the films from ideal stoichiometry led to the formation of CuSe, ZnSe and SnSe secondary phases. CZTSe films with a stannite phase could be grown even at room temperature from the sputtering target containing Cu₂ Se with corresponding growth orientations of (101), (112), (220/204), (312/116) and (332/316). The p-type CZTSe film grown at a substrate temperature of 150 ^{{ring operator}} C showed a high absorption coefficient of 10⁴ cm^{- 1} with an optical band gap of 1.56 eV, resistivity as low as 1.482 Ω cm and carrier concentration of 1 × 10¹⁹ cm^{- 3}. These results suggested that the control of the target compositions was crucial to grow single phase and stoichiometric quaternary CZTSe films.