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Composition and properties of ZnS thin films prepared by chemical bath deposition from acidic and basic solutions

Liudmila V. Makhova 1Igor Konovalov 1Rüdiger Szargan 1Nurdin Ashkenov 2Thomas Chasse 3

1. Universität Leipzig, Willhelm-Ostwald-Institut für Physikalische und Theoretische Chemie (WOI), Linnestr.2, Leipzig 04103, Germany
2. Universität Leipzig, Institut für Experimentelle Physik II, Linnestr. 5, Leipzig 04103, Germany
3. Eberhard Karls Universität Tübingen, Institut für Physikalische und Theoretische Chemie, auf der Morgenstelle 8, Tübingen 72076, Germany

Abstract

The method of chemical bath deposition (CBD) has been successfully employed to deposit films of ZnS. ZnS is a semiconductor material with a wide direct bandgap, which is interesting for application in photovoltaic and optoelectronic devices. The CBD process typically involves decomposition of a suitable precursor in a solution, giving the chalcogenide ions for the reaction with the metal salt. The result of the CBD process preparing ZnS thin films on different substrates depends on the composition of the chemical bath influencing on the aghesion, homogeneity of the films and also the ratio of concurrent deposition rates of ZnS and ZnO. We have performed a comparative study of ZnS growth by CBD on soda lime glass, Si and GaP substrates using an acidic bath (thioacetamide and acetic acid) and a basic bath ( ammonia-thiourea) at various temperatures (in the range from 60 to 85C) and deposition times (in the range from 5 to 180 min). The thickness of the films was varied from a few nm to 100 nm. Our observations suggest a homogeneous growth mechanism in the acidic bath. The chemical and crystalline nature of thick (70-100nm) films was investigated and proved by X-ray photoelectron spectroscopy and X-ray diffraction methods. The in-depth composition of the ZnS layers was studied by means of X-ray fluorescence method. The optical band-gap energy was determined to be 3.64 eV from the best fit of the spectroscopic ellipsometry measurements.

 

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Related papers

Presentation: poster at E-MRS Fall Meeting 2004, Symposium F, by Liudmila V. Makhova
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 15:18
Revised:   2009-06-08 12:55