Temperature dependent photoreflectance study of Cu2SnS3 thin films produced by pulsed laser deposition

Abstract

The energy band structure of Cu2SnS3 (CTS) thin films fabricated by pulsed laser deposition was studied by photoreflectance spectroscopy (PR). The temperature-dependent PR spectra were measured in the range of T = 10–150 K. According to the Raman scattering analysis, the monoclinic crystal structure (C1c1) prevails in the studied CTS thin film; however, a weak contribution from cubic CTS (F-43m) was also detected. The PR spectra revealed the valence band splitting of CTS. Optical transitions at EA = 0.92 eV, EB = 1.04 eV, and EC = 1.08 eV were found for monoclinic CTS at low-temperature (T = 10 K). Additional optical transition was detected at EAC = 0.94 eV, and it was attributed to the low-temperature band gap of cubic CTS. All the identified optical transition energies showed a blueshift with increasing temperature, and the temperature coefficient dE/dT was about 0.1 meV/K.

Effect of KF Addition to (Cu,Ag)2SnS3 Thin Films Prepared by Sulfurization Process

“…Furthermore, similar results were reported by other CTS research groups . Aihara et al and Raadik et al investigated this phenomenon by photoluminescence measurement and photoreflectance measurement, respectively, and reported the cause to be valence band splitting . Therefore, it is inferred that the existence of two steps of the sharp optical absorptions in this study is due to valence band splitting.…”

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu2SnS3 Thin Films

“…[24] An anomalous blue-shift of the band gap energy has been observed for some copper-and silver-based chalcogenide compounds at low temperature. [25][26][27] More recently, although the transition energy values were slightly different, Raadik et al [28] have observed the blue-shift of A-band with increasing temperature from 10 to 130 K. However, considering the strong absorption tailing, the temperature-dependent band gap energy could not be evaluated precisely for the Cu-poor CTS thin film in the present study. For the Cu-rich sample, the band gap energy for three bands showed a large approximately monotonic blue-shift from 6 to 300 K with increasing temperature.…”

Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3

“…These confusions concern mainly the modes at 351 cm −1 that was attributed either to CTS c 27 or to CTS t 55 – 57 , and at 352 cm −1 assigned to CTS m 19 , 26 , 29 , 49 , 57 , 58 or to CTS t structure 59 . Also, the peak located at 354 cm −1 was identified belonging to monoclinic structure of the CTS phase 50 , 54 , 60 , 61 , while Raadik et al described this mode as a signature of CTS c 30 . Moreover, Oliva et al assigned the peak at 356 cm −1 to CTS t phase 26 , while Fernandes et al stated that it belongs to the CTS c structure 59 .…”

“…Usually, CTS crystallizes in the tetragonal structure at temperatures around 350 °C 29 . On the other hand, a sulfurization process above 400 °C, needed to enlarge the crystallites, leads to the formation of cubic and/or monoclinic CTS 30 . Finally, the used precursors, the synthesis technique and process can also influence the final structure of the CTS films 26 .…”

“…Finally, the used precursors, the synthesis technique and process can also influence the final structure of the CTS films 26 . Various physical and chemical techniques have been employed to synthesize CTS films, such as pulsed laser deposition (PLD) 30 , spray pyrolysis 31 , thermal evaporation 32 , chemical bath deposition (CBD) 19 , solvothermal synthesis 33 , wet chemical method 29 and magnetron sputtering 34 . Magnetron sputtering is a physical technique for the synthesis of large-area and highly uniform films with controllable thickness and composition.…”