Growth of CuGaS₂ Single Crystals by Chemical Vapor Transport and Characterization

Abstract

Single crystals of CuGaS2 (CGS) compounds were grown by a chemical vapor transport technique in a closed system using iodine as a transporting agent at different growth conditions. The grown crystals exhibit different colors such as yellow, green, and orange depending on the temperature of the growth zone. Single-crystal X-ray diffraction studies confirmed the chalcopyrite structure of the grown crystals. The powder X-ray diffraction showed the presence of the secondary phase in the yellow (Cu2S) and orange (Ga2S3) crystals. Scanning electron microscope analysis disclosed step growth, lateral expansion, and layer growth patterns on the yellow-, orange-, and green-colored single crystals, respectively. Energy dispersive X-ray analysis revealed the stoichiometric composition of the green crystals, whereas rich Cu and Ga were found in yellow and orange crystals, respectively. Raman spectra of green-colored CGS single crystals exhibited a high-intensity peak of the A1 mode at 315 cm-1. For yellow and orange crystals, this mode was shifted toward higher and lower frequencies, respectively. This is due to the presence of a higher amount of copper in yellow crystals and a higher amount of gallium in orange crystals. The absorption coefficient's fall is sharper of green-colored than yellow- and orange-colored CGS single crystals due to the presence of secondary phases in them. Nevertheless, the reason for the lower band gap of yellow and orange crystals might be due to the presence of defect states. Photoluminescence spectra of green and orange crystals show only one emission line each. Surprisingly, the yellow crystals now discharged two emission lines. The hole mobility and hole concentration of the green-colored CGS single crystal were found to be high when compared with those of the orange and yellow single crystals at room temperature. Because of lattice disordering, the disorder of cation vacancies was also found to be low for the green-colored single crystal. All three different-colored CGS single crystals have shown p-type conductivity.

One-pot hydrothermal preparation of wurtzite CuGaS2 and its application as a photoluminescent probe for trace detection of l-noradrenaline

“…It can be seen that the Raman spectrum of CuGaS 2 is dominated by a narrow band around 307 cm −1 , corresponding to A 1 mode which is associated with the breathing mode appearing in I-III-IV 2 ternary chalcogenides [49,50]. In the case of A 1 mode, the S atom is in perpendicular motion to the c-axis while Cu and Ga atoms remain at rest [22,26]. Moreover, it can also found that there exist two Raman peaks at 112 cm −1 and 386 cm −1 , respectively.…”

“…However, it is difficult how to control the stoichiometric composition and phase purity of product. For this reason, a variety of new methods, such as electrodeposition [16,17], X-ray irradiation [18], vacuum thermal evaporation method under thermal gradient [19], metal organic chemical vapor deposition [20], electron beam evaporation [21], chemical vapor transport [22], hot-injection [23,24], thermolysis of dithiocarbamate precursors [14], were developed. And CuGaS 2 with stoichiometric composition and high phase purity was obtained.…”

Single crystal growth and characterization of copper aluminum indium disulfide chalcopyrites

“…Single crystals of Cu(Al x In 1 À x )S 2 solid solutions with x ¼0, 0.2, 0.4, 0.5, 0.6, 0.7, and 1.0 were grown by CVT method [15,16] using ICl 3 as a transport agent. Cu(Al x In 1À x )S 2 compounds were prepared from the powdered mixture of elements (Cu: purity 99.995%, Al: purity 99.9995%, In: purity 99.9999%, and S: purity 99.999%) in the stoichiometric proportion by reaction at 850 1C for 3 days in evacuated quartz ampoules.…”

Electrodeposition of CuGaSe2 and CuGaS2 thin films for photovoltaic applications

“…For a direct allowed transition or direct bandgap such as CuGaSe2 and CuGaS2, n assumes the value of ½ and then the plot of ( h ) 2 versus photon energy (h ) forms a straight line whose intercept with the ( h ) 2 =0 axis yields the value of the energy bandgap (Eg) [19,20]. films with respect to CuGaSe2 films is evident.…”