Optical spectra and interfacial band offsets of pulse-laser-deposited metal-oxides: SnO2, TiO2, and ZnO
Nhan V. Nguyen, Nam Nguyen, Jason Hattrick-Simpers, Oleg A. Kirillov, Martin L. Green
Transparent conducting oxides are electrically conductive materials with high optical transmittance in the visible region of the spectrum and are useful in a wide range of applications. In this study, the optical spectra of a set of transparent conducting oxides SnO2, ZnO, and TiO2 grown by pulse laser deposition are measured by vacuum ultra-violet spectroscopic ellipsometry and the optical band gaps are determined to be 3.30 ± 0.05 eV, 3.13 ± 0.05 eV, and 3.95 ± 0.05 eV, respectively. SnO2 and ZnO optical responses at the band gap reveal that they are a direct band gap while TiO2 appears to show an indirect type. For the interfacial electronic characteristics, internal photoemission measurement shows that the electronic barriers of these naturally n-type doped metal oxides adjacent to an Al2O3 layer originate from Fermi level in their conduction bands. The band offset determination shows the barrier heights are similar and have small internal field dependence. The work functions are then estimated from the measured barrier heights
, Nguyen, N.
, Hattrick-Simpers, J.
, Kirillov, O.
and Green, M.
Optical spectra and interfacial band offsets of pulse-laser-deposited metal-oxides: SnO2, TiO2, and ZnO, Applied Physics Letters, [online], https://dx.doi.org/10.1063/5.0039368, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=931161
(Accessed May 23, 2022)