Influence of annealing temperature and Sn doping on the optical properties of hematite thin films determined by spectroscopic ellipsometry

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dc.creatorLígia Parreira de Souza
dc.creatorRodrigo Otávio Gonçalves Chaves
dc.creatorÂngelo Malachias de Souza
dc.creatorRoberto Magalhães Paniago
dc.creatorSukarno Olavo Ferreira
dc.creatorAndre Santarosa Ferlauto
dc.date.accessioned2023-03-22T18:17:58Z
dc.date.accessioned2025-09-09T00:55:55Z
dc.date.available2023-03-22T18:17:58Z
dc.date.issued2016
dc.description.sponsorshipCNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
dc.description.sponsorshipFAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais
dc.description.sponsorshipCAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
dc.identifier.doihttp://dx.doi.org/10.1063/1.4954315
dc.identifier.issn1089-7550
dc.identifier.urihttps://hdl.handle.net/1843/51132
dc.languageeng
dc.publisherUniversidade Federal de Minas Gerais
dc.relation.ispartofJournal of Applied Physics
dc.rightsAcesso Restrito
dc.subjectHematita
dc.subjectFilmes finos
dc.subjectAnálise espectral
dc.subject.otherHematite thin films
dc.subject.otherSpectroscopy
dc.titleInfluence of annealing temperature and Sn doping on the optical properties of hematite thin films determined by spectroscopic ellipsometry
dc.typeArtigo de periódico
local.citation.epage245104-13
local.citation.issue24
local.citation.spage245104-1
local.citation.volume119
local.description.resumoHematite (α-Fe2O3) thin films were prepared by sol-gel route and investigated for application in H2 generation by photo-assisted water splitting. The photoelectrochemical (PEC) performance was shown to increase significantly for films deposited on SnO2:F/glass subjected to high temperature (T) annealing (>750 °C). Strong correlation was found between photogenerated current, donor concentration, and Sn concentration as determined by Mott-Schottky analysis and X-ray photoelectron spectroscopy. The effects of thermal annealing and Sn addition in the resulting microstructure and optical properties of hematite films deposited on fused silica substrates were determined by a combination of structural characterization techniques and spectroscopic ellipsometry. Thermal annealing (>600 °C) induces a higher optical absorption that is associated directly to film densification and grain growth; however, it promotes no changes in the energy positions of the main Fe2O3 electronic transitions. The band gap energy was found to be 2.21 eV and independent of microstructure and of Sn concentration for all studied films. On the other hand, Sn can be incorporated in the Fe2O3 lattice for concentration up to Sn/Fe ∼2%, leading to an increase in energy split of the main absorption peak, attributed to a distortion of the Fe2O3 lattice. For higher concentrations, Sn incorporation leads to a reduction in absorption, associated with higher porosity and the formation of a secondary Sn-rich phase. In summary, the variation in the optical properties induced by thermal annealing and Sn addition cannot account for the order of magnitude increase of the current density generated by photoanodes annealed at high T (>750 °C); thus, it is concluded that the major contribution for the enhanced PEC performance comes from improved electronic properties induced by the n-type doping caused by Sn diffusion from the SnO2:F substrate.
local.identifier.orcidhttps://orcid.org/0000-0002-8703-4283
local.identifier.orcidhttps://orcid.org/0000-0002-0540-7163
local.identifier.orcidhttps://orcid.org/0000-0001-8174-0200
local.identifier.orcidhttps://orcid.org/0000-0003-3056-7289
local.publisher.countryBrasil
local.publisher.departmentICX - DEPARTAMENTO DE FÍSICA
local.publisher.initialsUFMG
local.url.externahttps://aip.scitation.org/doi/10.1063/1.4954315

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