Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

• Published in: Materials research (São Carlos, São Paulo, Brazil) São Paulo, Brazil), 2010-12, Vol.13 (4), p.437-443
• Main Authors: Floriano, E A, Scalvi, L V A, Sambrano, J R, Geraldo, V
• Format: Article
• Language: eng ; por
• Subjects: Banded structure; Electronic properties; electronic structure; ENGINEERING, CHEMICAL; MATERIALS SCIENCE, MULTIDISCIPLINARY; Mathematical analysis; METALLURGY & METALLURGICAL ENGINEERING; Nanostructure; optical absorption; sol-gel; Surface chemistry; Thin films; Tin dioxide; Tin oxides
• ISSN: 1516-1439; 1980-5373; 1516-1439
• DOI: 10.1590/S1516-14392010000400004

The absorption edge and the bandgap transition of sol-gel-dip-coated SnO2 thin films, deposited on quartz substrates, were evaluated from optical absorption data and temperature-dependent photoconductivity spectra. Structural properties of these films help to interpret the bandgap transition nature, since the obtained nanosized dimensions of crystallites depend on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by density functional theory applied to periodic calculations at B3LYP hybrid functional level. The experimentally obtained absorption edge was compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which gives a direct bandgap transition.