Effect of Zn:S molar ratio in solution on the properties of ZnS thin films and the formation of ZnS nanorods by spray pyrolysis

Abstract

The ZnS layers morphology, structure, composition, and optical properties were investigated with respect to the precursors (zinc chloride and thiocarbamide, Zn:S) molar ratio in spray solution (1:1, 1:2, and 1:3) and growth temperatures in the range of 400–600 °C. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray analysis (EDX), UV–VIS, and PL spectroscopy were applied to characterize the ZnS layers. Layers obtained at temperatures up to 450 °C are not well crystallized and contain residues originated from undecomposed precursors. ZnS films become crystalline at Ts = 500 °C. Layers grown from 1:1 solution at 550 °C are mixture of ZnS and ZnO phases, whereas at 600 °C layers of ZnO were obtained. Films produced from 1:2 solution at 500–600 °C are of ZnS with a wurtzite structure and Eg of 3.66 eV, but contain traces of ZnO phase when grown at 550 or 600 °C. Appearance of ZnO phase in the films grown from 1:1 and 1:2 solutions is explained by the results of the studies on the formation and decomposition of dichlorobis(thiocarbamide)zinc(II) complex as an intermediate compound formed in the solution of zinc chloride and thiocarbamide. Spraying the solutions with Zn:S = 1:3, which contain more thiocarbamide than required for the complex formation, results in single‐phase ZnS layers with wurtzite structure at growth temperatures up to 600 °C. Moreover, ZnS layers obtained from 1:3 solution at 550 °C and higher are composed of highly c‐axis oriented ZnS nanorod‐like crystals with diameter of ca. 80 nm and length of ca. 300 nm.

Sb2S3 grown by ultrasonic spray pyrolysis and its application in a hybrid solar cell

“…So far, we have shown that for growing Sb 2 S 3 by pneumatic CSP the use of SbCl 3 and thiourea (tu) precursors with an SbCl 3 /tu molar ratio of 1:3 dissolved in methanol and sprayed on substrate at a temperature of 255 °C leads to films that consist of orthorhombic stibnite and a secondary phase that was identified as Sb 2 O 3 [23]. To suppress the formation of oxides, an excess of sulfur source in the precursor solution may be required as indicated by similar studies for indium sulfide [25–26], zinc sulfide [27] and tin sulfide [28–29] grown by pneumatic CSP. At the time of the present study, no publications were available on ultrasonically spray-grown Sb 2 S 3 , and on the application of any CSP-grown Sb 2 S 3 in a solar cell, apart from a photoelectrochemical cell that showed an efficiency of 0.3% [30].…”

Spray pyrolysis deposition and characterization of highly c‐axis oriented hexagonal ZnS nanorod crystals

“…Spraying the solution with molar ratio of precursors of 1:3 and deposition temperature of 550 °C resulted in ZnS nanorod‐like crystals formation with d = ca. 80 nm and length of 300 nm, whereas molar ratio of precursors of 1:2 at this temperature resulted in ZnS thin film formation . The nanorods formation in case of 1:3 solution could be explained by creation of proper technological conditions for pure ZnS phase formation, as 1:2 films contained some amount of ZnO phase that could act as disturbing factor for nanorods formation.…”

“…In our previous study on properties of ZnS thin films and the formation of ZnS nanorods by spray pyrolysis we demonstrated that an increase of sulphur source content in the spray solution leads to the formation of ZnS nanostructured layer comprising nanorods instead of ZnS thin film . Spraying the solution with molar ratio of precursors of 1:3 and deposition temperature of 550 °C resulted in ZnS nanorod‐like crystals formation with d = ca.…”

“…Thus, cost‐effective, phase‐ and morphology controlled synthesis is of great importance for both scientific research and technological application of ZnS nanostructures . Spray pyrolysis technique has been widely used method to deposit ZnS thin films with precise composition and good stoichiometry , however, till recently there were no reports on synthesis of ZnS nanostructures by this technique so far. Only in our very recent study on ZnS thin films by spray pyrolysis, we demonstrated that use of ZnCl 2 :thiourea (Zn:S) molar ratio of 1:3 can lead to ZnS nanorod‐like crystals formation instead of thin film, which is usually obtained from 1:1 or 1:2 solutions .…”

Thermal decomposition of tris(O-ethyldithiocarbonato)-antimony(III)—a single-source precursor for antimony sulfide thin films

“…Similarly to thiourea-metal chloride complexes that we used to deposit SnS, ZnS, CuInS 2 , In 2 S 3 , and Sb 2 S 3 thin films by spray pyrolysis for photovoltaic applications [11,[20][21][22][61][62][63][64]], SbEX appears to be an excellent singlesource precursor for producing phase pure Sb 2 S 3 thin films by spray pyrolysis.…”