Analyzing UV/Vis/NIR spectra with the single-layer model—Sputtered SnS thin films I: Space–time dependencies

• Published in: Thin solid films Vol. 519; no. 22; pp. 7951 - 7958
• Main Authors: Stadler, A., Schimper, H.-J., Brendel, U., Topa, D., Basch, A., Dittrich, H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-09-2011; Elsevier
• Subjects: Approximation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Direct current; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Glass; Materials science; Mathematical models; Methods of deposition of films and coatings; film growth and epitaxy; Nondestructive testing; Optical conductivity; Optical spectroscopy; Physics; Solar cells; Spectra; Sputtering; Thin films; Tin-sulphide; UV/Vis/NIR; Thin films; Tin-sulphide; Optical spectroscopy; UV/Vis/NIR; Sputtering; Optical conductivity; Electrical conductivity; Semiconductor materials; UVNis/NIR; Data acquisition; Infrared spectra; Tin sulfide; Reflection spectrum; Thin film devices; Electrical conductivity measurement; Near infrared spectrum; Ultraviolet visible spectrum; Absorption spectra; Sputter deposition; Radiofrequency sputtering
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.04.234

Exact, contact-free and non-destructive, optical analysis of semiconducting layers, are advantageous for thin film solar cell applications. A non-numerical theoretical model has been developed to extract approximation-free optical and electrical data from UV/Vis/NIR spectra. Special focus has been set on single layers; an adequate single-layer model is provided. Complex parameter evaluation is possible.
This exact data acquisition model provides deeper insights in the process–parameter dependencies of pulsed direct current and radio frequency sputtered, opaque tin-sulphide thin films upon glass substrates. They have been analysed with respect to space–time dependencies of the sputter process. Therefore, sputter-depositions have been examined, referring to positions upon the substrate,
r, target-substrate distances,
d
TarSub
, and sputter durations,
t
Sp
. Theoretical sputter-concepts were proved and enhanced. Results were compared with those of the well-known Keradec/Swanepoel model. The necessity of taking both spectra—transmission and reflection spectra—into account has been shown.
A non-contact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been provided. Optically evaluated conductivities,
σ
L
, were compared with electrically taken values, by use of a four-tip measurement system.