Nature of fundamental absorption edge of WO3

Janis Kleperis; Juris Zubkans; Andrejs R. Lusis

doi:10.1117/12.266832

6 February 1997 Nature of fundamental absorption edge of WO₃

Janis Kleperis, Juris Zubkans, Andrejs R. Lusis

Proceedings Volume 2968, Optical Organic and Semiconductor Inorganic Materials; (1997) https://doi.org/10.1117/12.266832
Event: International Conference on Advanced Optical Materials and Devices, 1996, Riga, Latvia

Abstract

The fundamental absorption edge of amorphous, polycrystalline and crystalline tungsten trioxide (WO₃) thin films obtained by different techniques (thermal evaporation, rf plasma sputtering, chemical gas transport) was investigated. Special attention was paid to correct measurements of absorption values of all WO₃ thin films taking into account the scattered light, interference effects and reflection losses. The indirect edge at 2.70 eV was determined for crystalline WO₃, but for crystal WO₃:Ti the direct edge in the same place (2.72 eV) was found. For polycrystalline WO₃ thin film first edge transition located at 2.76 eV had a quadratic dependence similar to the amorphous film at a higher photon energy (3.26 eV). Localized states are involved in these transitions with quadratic dependence. The gap energy shift from crystalline to amorphous WO₃ is explained by changes in the first coordination sphere of octahedral WO₃ cluster. Higher direct allowed transition at 4.1 eV is estimated both for amorphous and polycrystalline thin WO₃ films.

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Janis Kleperis, Juris Zubkans, and Andrejs R. Lusis "Nature of fundamental absorption edge of WO₃", Proc. SPIE 2968, Optical Organic and Semiconductor Inorganic Materials, (6 February 1997); https://doi.org/10.1117/12.266832

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