Thermodynamic pathway for the formation of SnSe and SnSe2 polycrystalline thin films by selenization of metal precursors

Abstract

In this work, tin selenide thin films (SnSe x ) were grown on soda lime glass substrates by selenization of dc magnetron sputtered Sn metallic precursors. Selenization was performed at maximum temperatures in the range of 300 • C to 570 • C. The thickness and the composition of the films were analysed using step profilometry and energy dispersive spectroscopy, respectively. The films were structurally and optically investigated by X-Ray diffraction, Raman spectroscopy and optical transmittance and reflectance measurements. X-Ray diffraction patterns suggest that for temperatures between 300 • C and 470 • C the films are composed of hexagonal-SnSe 2 phase. By increasing the temperature, the films selenized at maximum temperatures of 530 • C and 570 • C show orthorhombic-SnSe as the dominant phase with a preferential crystal orientation along the (400) crystallographic plane. Raman scattering analysis allowed the assignment of peaks at 119 cm −1 and 185 cm −1 to the hexagonal-SnSe 2 and 108 cm −1 , 130 cm −1 and 150 cm −1 to the orthorhombic-SnSe phase. All samples present traces of condensed amorphous Se with a characteristic Raman peak located at 255 cm −1 . From optical measurements, the estimated band gap energies for hexagonal-SnSe 2 were close to 0.9 eV and 1.7 eV for indirect forbidden and direct transitions, respectively. The samples with the dominant orthorhombicSnSe phase presented estimated band gap energies of 0.95 eV and 1.15 eV for indirect allowed and direct allowed transitions, respectively.

Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors

“…As a control, the spectrum for site D was directly taken from the mica substrate, this revealed the peaks at 196.9, 274.4, 317.5, and 370.9 cm −1 . For the thickest fl ake A, the two notable peaks at 118.3 and 185.2 cm −1 are the fi ngerprints of SnSe 2 , as was previously reported, [ 21 ] and no peaks of SnSe have been detected. The former peak is assigned to the E g mode, corresponding to the out-of-plane vibrational mode of the Se-Sn-Se lattice and the latter one is the A 1g mode, corresponding to the in-plane vibrational mode.…”

“…[ 17,18 ] The layered structure, proper electronic properties, and inherent semiconducting characteristics make SnSe 2 attractive in nanoelectronic and optoelectronic fi elds. However, there is no report on ultrathin SnSe 2 yet partially due to the improper precursors, [ 19,20 ] or mixed products (such as SnSe or Se) existing after the reaction, [ 21 ] and thus the detailed electronic and photophysical characterizations of SnSe 2 2D materials toward their optoelectronic applications have never been explored.…”

High‐Performance Thermoelectric SnSe: Aqueous Synthesis, Innovations, and Challenges

“…To explore the thermodynamic conditions of SnSe, Figure 4c shows 1000/ T ‐dependent log p for the Sn–Se system,196 where the unit of pressure p is bars. As can be clearly seen, appropriate temperature and pressure are both needed to achieve pure SnSe and avoid to produce Se and/or SnSe 2 second phases because these two secondary phases show typical n‐type feature,201–204 which harm the performance of p‐type SnSe. Besides, to avoid the evaporation of fabricated SnSe, the temperature and pressure should be controlled within a reasonable range, and the measured vapor pressure of SnSe can be referred as shown in Figure 4d,198–200 which shows a linear relationship between 1000/ T and log p .…”

CZTSe solar cells developed on polymer substrates: Effects of low‐temperature processing

“…The main peaks of the CZTSe phase are clearly identified at 169 and 195 cm −1 , and from the fitting of spectra, a good absorber crystal quality independent from the annealing temperature is observed. However, the main feature brought about by these spectra is the detection of SnSe 2 as confirmed by the intense peaks at 184 cm −1 and, more subtly, at 119 cm −1 . The absence of peaks at 108, 130, 133, and 151 cm −1 indicates that no SnSe coexists with SnSe 2 on the surface of the absorbers .…”

“…However, the main feature brought about by these spectra is the detection of SnSe 2 as confirmed by the intense peaks at 184 cm −1 and, more subtly, at 119 cm −1 . 53 The absence of peaks at 108, 130, 133, and 151 cm −1 indicates that no SnSe coexists with SnSe 2 on the surface of the absorbers. 54 Figure 5 shows the maximum, minimum, and average SnSe 2 concentration found in each of the samples as estimated by the peak area ratio A(SnSe 2 )/A(CZTSe).…”