Thin films of arsenic sulfide by chemical deposition and formation of InAs

Abstract

We report a method for obtaining thin films of arsenic sulfide by chemical bath deposition and the subsequent formation of InAs by heating the films with a vacuum-deposited coating of In. X-ray diffraction (XRD) studies have shown that the thin film deposited from chemical baths of pH ∼2, prepared by mixing aqueous acidic solutions of As(III) with sodium thiosulfate, is a composite film of crystalline As 2 O 3 and As 2 S 3 , with the incorporation of sulfur. When heated at 150-250 • C, the As 2 O 3 component transforms to As 2 S 3 , but still with very few identifiable peaks in the XRD patterns of the annealed samples. The films have a direct band gap of ≈2.7 eV (as-prepared) and ≈2.52 eV (heated at 250 • C), with forbidden optical transitions. The sheet resistance of the film (300 nm thick) is 10 12 , and the electrical conductivity is 10 −8 −1 cm −1. After being heated in a sulfur-rich atmosphere at >200 • C, the films show photosensitivity. The As 2 O 3 /As 2 S 3 thin film with an evaporated indium film, when heated at 250 • C in nitrogen or air, produces InAs as a major crystalline component. In this case, In 2 S 3 or In 2 O 3 may be present as a minor component in the films, depending on whether heating is done in nitrogen or air, respectively. The optical band gap of this InAs component is direct, 0.5 to 0.8 eV, depending on the film thickness and heating process. These composite films are photosensitive; a dark conductivity of 0.05 −1 cm −1 in the films formed in nitrogen is ascribed to InAs and 5 −1 cm −1 in the films formed by heating in air is ascribed to the In 2 O 3 component. The photoconductivity of the films is of the same order of magnitude as the dark conductivity in each case.

As2S3 thin films deposited by atomic layer deposition

“…SEM images (not shown) revealed that the film was badly damaged, but EDS measurements showed that at least some As and S were still left. Our results are in agreement with literature where sublimation upon annealing at 150-250 °C has been reported for films deposited by thermal evaporation 28 and by chemical bath deposition 29 . Furthermore, As 2 S 3 is known to be very reluctant to crystallization 30 .…”

Size-dependent photoluminescence of zinc oxide quantum dots through organosilane functionalization

“…where d is the lm thickness, T is the transmittance and R is the reectance of the investigated samples. [26][27][28][29] The thickness of the deposed thin lms was determined with a MII-4 interference microscope (Linnik) with an error #0.01 mm using the multiple-beam Fizeau fringe method. 30 The thickness of the thin lms was about 258 nm.…”

Antibacterial and Photocatalytic Coatings Based on Cu-Doped ZnO Nanoparticles into Microcellulose Matrix

“…The optical band gap energy, E g , of the Cu-doped ZnO NPs dispersed in ethylic alcohol and deposited as thin films on Soda lima glass substrates by spin-coating technique (at 2000 rpm) was estimated from the fundamental absorption edge in their optical transmittance and reflectance spectra, acquired in air at room temperature with a Perkin Elmer Lambda 35 spectrometer, at normal incidence, in the 200–1100 nm spectral range. For E g evaluation, the absorption coefficient was calculated using the following Equation (1) [ 40 ]: where d is the film thickness, T is the transmittance and R reflectance of the ZnO 1D nanostructured thin films. The E g values were calculated from the dependence of absorption coefficient vs. the photon energy, hν, based on the following Equation (2) [ 19 , 20 , 21 , 41 ]: where A is a parameter that depends on the transition probability.…”