Defect levels in SnS thin films prepared using chemical spray pyrolysis

Abstract

The origin of various defect levels in the SnS thin films deposited using chemical spray pyrolysis (CSP) technique has been explored in this manuscript, by employing low‐temperature photoluminescence (PL) technique. Concentration of Sn in the samples was varied purposefully by ex situ diffusion in order to alter the defect levels. The acceptor level obtained at 0.22 eV from the Arrhenius plot, has been assigned as the defect level caused by the Sn vacancies present in the lattice. Two shallow donor levels are conclusively identified and their activation energies have been estimated. The present study could also unearth a trap level in the forbidden energy gap which was due to the oxygen contaminant occupied by the vacancy of Sn. This trap level could be removed by annealing the sample in vacuum or through the ex situ diffusion of Sn. Employing Kelvin probe force microscopy (KPFM), the work‐function of SnS was obtained as 4.925 eV, from which the position of the Fermi level could be assigned. Based on the present work, an energy level scheme for SnS thin films is proposed outlying origin of various defect levels.

Growth of Large Single Crystals of n-Type SnS from Halogen-Added Sn Flux

“…Figure shows the UPS spectra for the (100) surfaces of the Cl-doped and Br-doped SnS. The ionization potential (IP) derived from the energy difference between the secondary electron cutoff and valence band edge was 5.06 and 5.11 eV for the Cl-doped and Br-doped crystals, respectively; these values are almost identical to those of previously reported p-type SnS thin films determined via in situ UPS (5.1 eV) and Kelvin probe force microscopy (5.03 eV) . On the basis of the UPS and XPS results, band diagrams for the undoped, Cl-doped, and Br-doped SnS single crystals are revealed, as schematically shown in Figure .…”

“…On the basis of the UPS and XPS results, band diagrams for the undoped, Cl-doped, and Br-doped SnS single crystals are revealed, as schematically shown in Figure . The obtained work function (WF) of the Cl-doped and Br-doped SnS crystals (WF = 4.11 and 4.26 eV, respectively) was smaller than those of the p-type SnS thin films (WF = 4.6 and 4.92 eV, respectively). , Hence, the results show that the obtained Cl-doped and Br-doped SnS crystals are n-type with respect to their electronic structures as well as their electrical properties. We believe that the large n-type SnS crystals obtained in this work would lead to the fabrication of p-n homojunction SnS solar cells with a high conversion efficiency.…”

Single Phase Formation of SnS Competing with SnS2 and Sn2S3 for Photovoltaic Applications: Optoelectronic Characteristics of Thin-Film Surfaces and Interfaces

“…range from 5.2 to 5.3 eV, 46,47 while that of SnS is about 4.9 eV; these values were all measured using KPFM. 48 Therefore, the other phase on the surface, which was mentioned in Figure 6d and Figure 6h, could be SnS 2 . The results of the micro-Raman scattering and HRTEM measurements can thus be used to determine the presence of SnS 2 on the surface.…”

“…SnS 2 has a larger band gap than SnS, and the work function of SnS 2 (Φ SnS2 = 5.36 ± 0.45 eV) is higher than that of SnS (Φ SnS = 4.4–4.9 eV). Reported values of the work function of SnS 2 range from 5.2 to 5.3 eV, , while that of SnS is about 4.9 eV; these values were all measured using KPFM . Therefore, the other phase on the surface, which was mentioned in Figure d and Figure h, could be SnS 2 .…”

Fabrication of SnS quantum dots for solar-cell applications: Issues of capping and doping

“…Figure again confirms the presence of 0.62 and 0.84 eV peaks, moreover, another strong 0.4 eV peak is also observed. We tentatively assign the 0.62 and 0.84 eV peaks to transitions involving deep levels in the bandgap of SnS . We hypothesize the absorption peak at 0.4 eV to be due to transfer of dopant electrons from sodium impurities to the lowest unoccupied quantum‐confined orbital (LUQCO) of SnS QD.…”