Preparation of (Bi, Sb)2S3 semiconductor films by photochemical deposition method

The photochemical deposition (PCD) technique has the advantages of economy, the capability of large area deposition and of a fast reaction rate. In this report, the PCD method using UV light of an ultra-high pressure mercury lamp was applied to form (Bi-x, Sb1-x)(2)S-3 semiconducting compounds from solutions containing BiCl3 and/or SbCl3 Na2S2O3 at pH in the acidic range 1-3. The pH of the solution was adjusted with the addition of dilute HCl solution. The substrate for the film deposition was pretreated onto the commercial pyrex-glass plate surface with the well-known solution agent of I'd activator plus Sn sensitizer. In the PCD process, the film is only deposited onto the irradiated region of the substrate so as to make a pattern using the mask. This deposition process shows the heterogeneous nucleation and growth mechanism on the substrate surface. The deposition rate of the film using a 500 W mercury lamp was about 1 mum/30 min. The crystallization characteristics of the amorphous (Bi2S3) deposits were studied by means of X-ray diffraction, thermal analysis (DSC) and optical transmitted spectra evaluation in order to clarify the amorphous to crystal phase transformation. The amorphous deposits showed gradual light absorption in a wide range of optical wavelengths. On the contrary, annealed film showed a sharp absorption edge near 800 run. The crystallization temperature of the amorphous deposits was about 250-300degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.