Structural and optical characterisation of CuGaS 2 thin films grown by MOVPE

Abstract

Epitaxial growth of CuGaS 2 using atmospheric pressure metalorganic (MO) vapour phase epitaxy (MOVPE) was carried out using two different copper metalorganic precursors, namely, cyclopentadienyl copper triethylphosphine (CpCuTEP) and hexafluoroacetylacetate copper triethylamine (Cu(hfac) 2·NEt 3). A change in the Cu content (most significant for epilayers grown using the former precursor) was found to occur along the flow direction. A study using X-ray diffractometry could not conclusively determine which of the possible structure types were present in the epilayer. Analysis of the transmission electron diffraction (TED) patterns using the <211> zone axes indicates that a mixture of disordered zinc blende and CuPt-type ordering occurs in both types of epilayers, whereas a tetragonal crystal structure (chalcopyrite or CuAu-type ordering) likely occurs within surface crystallites found in epilayers grown using Cu(hfac) 2·NEt 3. The photoluminescence (PL) for both epilayers consisted of a broad band at 580–620 nm, typical of Ga-rich material.