Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

Stela Canulescu; K. Rechendorff; C. N. Borca; N. C. Jones; Kirill Bordo; Jørgen Schou; Lars Pleth Nielsen; S. V. Hoffmann; Rajan Ambat

doi:10.1063/1.4866901

Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

Stela Canulescu, K. Rechendorff, C. N. Borca, N. C. Jones, Kirill Bordo, Jørgen Schou, Lars Pleth Nielsen, S. V. Hoffmann, Rajan Ambat

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Abstract

The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al2O3). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al2O3, mainly caused by Ti 3d orbitals localized at the Ti site.

Original language	English
Article number	121910
Journal	Applied Physics Letters
Volume	104
Issue number	12
Number of pages	5
ISSN	0003-6951
DOIs	https://doi.org/10.1063/1.4866901
Publication status	Published - 2014

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title = "Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying",

abstract = "The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. \%. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al2O3). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al2O3, mainly caused by Ti 3d orbitals localized at the Ti site.",

author = "Stela Canulescu and K. Rechendorff and Borca, \{C. N.\} and Jones, \{N. C.\} and Kirill Bordo and J{\o}rgen Schou and Nielsen, \{Lars Pleth\} and Hoffmann, \{S. V.\} and Rajan Ambat",

year = "2014",

doi = "10.1063/1.4866901",

language = "English",

volume = "104",

journal = "Applied Physics Letters",

issn = "0003-6951",

publisher = "American Institute of Physics",

number = "12",

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TY - JOUR

T1 - Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

AU - Canulescu, Stela

AU - Rechendorff, K.

AU - Borca, C. N.

AU - Jones, N. C.

AU - Bordo, Kirill

AU - Schou, Jørgen

AU - Nielsen, Lars Pleth

AU - Hoffmann, S. V.

AU - Ambat, Rajan

PY - 2014

Y1 - 2014

N2 - The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al2O3). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al2O3, mainly caused by Ti 3d orbitals localized at the Ti site.

AB - The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al2O3). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al2O3, mainly caused by Ti 3d orbitals localized at the Ti site.

U2 - 10.1063/1.4866901

DO - 10.1063/1.4866901

M3 - Journal article

SN - 0003-6951

VL - 104

JO - Applied Physics Letters

JF - Applied Physics Letters

IS - 12

M1 - 121910

ER -

Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

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