Enhanced p-Type Transparent Semiconducting Characteristics for ALD-Grown Mg-Substituted CuCrO2 Thin Films

The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 339478. Acronym LAYERENG-HYBMAT. | openaire: EC/FP7/339478/EU//LAYERENG-HYBMATMagnesium-substituted CuCrO2 delafossite is a promising candidate for p-type transparent conducting oxide applications owing to its relatively high electrical conductivity and optical transparency in the visible range. Here, the atomic layer deposition fabrication of semiconducting Cu(Cr1- xMgx)O2 (up to x = 0.043) thin films based on Cu(thd)2 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate), Cr(acac)3 (acac = acetyl acetonate), and Mg(thd)2 as metal precursors and ozone as the oxygen source is reported. Smooth and homogeneous thin films with an accurately controlled Mg content are obtained at the deposition temperature of 250 °C. A limited substitution level is revealed from X-diffraction patterns: peaks due to the spinel-structured MgCr2O4 secondary phase appear for x ≥ 0.015 while the increase in lattice parameters of the delafossite Cu(Cr,Mg)O2 phase continues even up to x ≈ 0.03. The direct bandgap as determined from UV-vis spectrophotometric measurements is observed to decrease from 3.09 eV for x = 0 to 2.87 eV for x = 0.015 before increasing to 3.15 eV for x = 0.043. The observed transmittance is close to 80% in the visible range. These characteristics are superior to the thin films of the copper delafossite family prepared by any thin-film technique.Peer reviewe