Site Preference of Manganese on the Copper Site in Mn-Substituted CuInSe₂ Chalcopyrites Revealed by a Combined Neutron and X-ray Powder Diffraction Study

Abstract

Ternary chalcopyrite systems are of interest for a number of applications, including host materials for dilute magnetic semiconductors and thin film photovoltaic cells. There are two cation sites, 4a and 4b, in the chalcopyrites, and the location of transition-metal ions in the chalcopyrites plays an important role in determining their magnetic and electrical properties. In this work, neutron and X-ray powder diffraction of the Mn-substituted CuInSe 2 compounds, namely, CuIn 1-x Mn x Se 2 (x = 0.05 and 0.10) and Cu 1-y In 1-y Mn 2y Se 2 (2y = 0.05, 0.15, and 0.20), has been carried out. Rietveld refinements using the neutron and X-ray diffraction data reveal a site preference of manganese ions on the copper site (4a) rather than the indium site (4b), in both series, namely, under In-poor conditions and under Cu-poor and In-poor conditions. The major fraction of Mn ions occupies the copper site, which thus pushes the expelled copper ions to the indium site, resulting in antisite Cu In defects. These results can help to explain why Mn-substituted CuInSe 2 compounds display antiferromagnetic interactions instead of ferromagnetic coupling as predicted by first-principles calculations. High frequency electron paramagnetic resonance measurements suggest that the oxidation state of the manganese ions is divalent.

Thermoelectric properties ofp-type CuInSe2chalcopyrites enhanced by introduction of manganese

“…5). Our structural analysis reveals that Mn occupies both cation sites with the preference of Mn occupation on the Cu site, Mn Cu , and the presence of anti-site Cu In defects, 19 increasing the degree of lattice disorder and thus diminishing the thermal conductivity. The degree of lattice disorder is also supported by the Raman measurements on our Mn-substituted samples.…”

“…To understand the relationship between the thermoelectronic properties and the incorporation of Mn in chalcopyrites, the calculations were performed for CuInSe 2 19 and then the symmetry was reduced to P-4 to allow Mn to occupy a quarter of the Cu and In sites. The structural parameters of CuInSe 2 were taken from the data determined by neutron and X-ray powder diffraction refinements.…”

“…The structural parameters of CuInSe 2 were taken from the data determined by neutron and X-ray powder diffraction refinements. 19 The exchange and correlation functional was treated by the generalized gradient approximation proposed by Perdew-Burke-Ernzerhof. 23 The energy cutoff for the plane-wave basis set is 350 eV and Monkhorst-Pack scheme 24 for integration in the Brillouin zone was adopted, and a k-point grid of 5 × 5 …”

“…The nature of the divalent Mn ion in CuInSe 2 has also been verified by our high frequency electron paramagnetic resonance measurements. 19 The Cu 2p, In 3d, and Se 3d XPS spectra for four members of the CuIn (Fig. 3).…”

“…According to our crystal structure analysis based on X-ray diffraction and neutron data, the unsubstituted CuInSe 2 compound is Cu-poor and Se-poor, indicating the existence of copper (V Cu ) and selenium (V Se ) vacancies. 19 The V Cu and V Se defects act as acceptors and donors, respectively.…”