Mn incorporation in CuInS2 chalcopyrites: Structure, magnetism and optical properties

The Mn-substituted CuInS2 compounds (CuIn1–xMnxS2 with x = 0–0.20 and Cu1–yMnyInS2 with y = 0.05–0.10) were synthesized using high-temperature solid–state reactions. Single-phase materials with the chalcopyrite structure persist with up to 10% of the Cu/In sites being replaced with Mn. The introduction of manganese results in a linear expansion of the lattice parameters as a function of Mn concentration, following Vegardʹs law. Rietveld refinements on a combination of X-ray and neutron powder diffraction data reveal a site preference of Mn for the In site under In-poor conditions and the existence of cation anti-site occupation, CuIn and InCu. The Mn substitution increases the anion displacement, accentuating the cation-anion bond length mismatch. The greater variance in the bond alternation and the addition of Mn d–S p hybridization near the Fermi level result in a decrease in the bandgap by ∼0.1 eV. The CuInS2:Mn compounds display paramagnetic behavior with short-range antiferromagnetic interactions. X-ray photoelectron spectroscopy suggests the presence of Cu+, Mn2+, and In3+ in the samples.