No abstract

Annealing in air and argon each produces an increase of a factor of 5 or more in the photoconductivity/dark conductivity ratio (G ph /G dark ) of vacuum-evaporated tin sulfide (SnS) thin films on glass substrates with copper contacts. No significant increase in G ph /G dark is observed after annealing SnS thin films with silver contacts. Annealing in air at or above 250 • C for 5 min dramatically increases the dark conductivity of the films. Annealing in Ar produces no significant increase in dark conductivity. It is probable that the rise in dark conductivity that accompanies annealing in air is caused by thermal activation of oxygen acceptors followed at higher temperatures by the conversion of SnS to SnO 2 . The films display photoconductivity from the near-infrared to the ultraviolet. The thinnest films we have produced (18 nm) display the highest G ph /G dark and are three times more photoconductive at 400 nm than they are at 700 nm.

Films of gray‐black Sn1−xS false(Enormalg∼1.0–1.3 normaleVfalse) , brown Sn2±xS3 false(Enormalg∼1.6–1.9 normaleVfalse) , and/or SnS2−x false(Enormalg∼2.1–2.3 normaleVfalse) were deposited onto nonconductive substrates by (i) an “electroless,” chemical precipitation mechanism in organic normalacid/H2O baths of SnCl2 , S, and Sn(II)‐complexing agents and/or (ii) a novel, above‐solution CVD mechanism involving condensation and reaction of Sn and S species such as SnCl4 and H2S . H2O and complexing agent (potassium gluconate or tartaric acid) concentrations critically affect film stoichiometry due to their “freeing” (with acid ionization) or chelating of the Sn(II). A surface area‐minimizing Sn(II,IV)‐S(‐ II) exchange reaction is postulated to explain slow transfer of SnxS deposit/precipitate to smooth surfaces. Mixed phases are often present, as evidenced by x‐ray diffraction, microprobe analysis, and optical absorbance data. Other data, including conductance vs. T−1 , photoconductance vs. t, and open‐circuit film voltage in a Sn(II) bath, are presented and proposed film growth mechanisms discussed.

Indium (III) sulfide has recently attracted much attention due to its potential in optical sensors as a photoconducting material and in photovoltaic applications as a wide direct bandgap material. On the other hand, optical absorption properties are key parameters in developing high photosensitivity photodetectors and high efficiency solar cells. We show that indium sulfide nanorod arrays produced by glancing angle deposition technique have superior absorption and low reflectance properties compared to conventional flat thin film counterparts. We observed an optical absorption value of approximately 96% for nanorods in contrast to 80% for conventional amorphous-to-polycrystalline thin films of indium sulfide. A photoconductivity response was also observed in the nanorod samples, whereas no measurable photoresponse was detected in conventional thin films. We give a preliminary description of the enhanced light absorption properties of the nanorods by using Shirley-George model which predicts diffusion of light by the roughness on the surface.