Abstract
A combined experimental and theoretical/band structure investigation is reported of Ga-doped CdO (CGO) and In-doped CdO (CIO) thin films grown on both amorphous glass and single-crystal MgO(100) substrates at 410°C by metal-organic chemical vapor deposition (MOCVD). Film phase structure, microstructure, and electrical and optical properties are systematically investigated as a function of doping stoichiometry and growth conditions. XRD data reveal that all as-deposited CGO and CIO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CGO and CIO thin films exhibit excellent optical transparency, with an average transmittance of > 80% in the visible range. Ga and In doping widens the optical band gap from 2.85 to 3.08 and 3.18 eV, respectively, via a Burstein-Moss shift. On MgO(100), room temperature thin film conductivities of 11 500 and 20 000 S/cm are obtained at an optimum Ga and In doping levels of 1.6% and 2.6%, respectively. Together, the experimental and theoretical results reveal that dopant ionic radius and electronic configuration have a significant influence on the CdO-based TCO structural, electronic, and optical properties: (1) lattice parameters contract as a function of dopant ionic radius in the order Y (1.09 Å) <In (0.94 Å) <Sc (0.89 Å), Ga (0.76 Å), with the smallest radius ion among the four dopants only shrinking the lattice marginally and exhibiting low doping efficiency; (2) carrier mobilities and doping efficiencies decrease in the order In > Y > Sc > Ga; (3) the Sc and Y dopant d states have substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.
| Original language | English |
|---|---|
| Pages (from-to) | 220-230 |
| Number of pages | 11 |
| Journal | Chemistry of Materials |
| Volume | 20 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Jan 8 2008 |
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ASJC Scopus subject areas
- Materials Chemistry
- Materials Science(all)
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Tuning the properties of transparent oxide conductors. Dopant ion size and electronic structure effects on CdO-based transparent conducting oxides. Ga- and in-doped CdO thin films grown by MOCVD. / Jin, Shu; Yang, Yu; Medvedeva, Julia E.; Wang, Lian; Li, Shuyou; Cortes, Norma; Ireland, John R.; Metz, Andrew W.; Ni, Jun; Hersam, Mark C; Freeman, Arthur J; Marks, Tobin J.
In: Chemistry of Materials, Vol. 20, No. 1, 08.01.2008, p. 220-230.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Tuning the properties of transparent oxide conductors. Dopant ion size and electronic structure effects on CdO-based transparent conducting oxides. Ga- and in-doped CdO thin films grown by MOCVD
AU - Jin, Shu
AU - Yang, Yu
AU - Medvedeva, Julia E.
AU - Wang, Lian
AU - Li, Shuyou
AU - Cortes, Norma
AU - Ireland, John R.
AU - Metz, Andrew W.
AU - Ni, Jun
AU - Hersam, Mark C
AU - Freeman, Arthur J
AU - Marks, Tobin J
PY - 2008/1/8
Y1 - 2008/1/8
N2 - A combined experimental and theoretical/band structure investigation is reported of Ga-doped CdO (CGO) and In-doped CdO (CIO) thin films grown on both amorphous glass and single-crystal MgO(100) substrates at 410°C by metal-organic chemical vapor deposition (MOCVD). Film phase structure, microstructure, and electrical and optical properties are systematically investigated as a function of doping stoichiometry and growth conditions. XRD data reveal that all as-deposited CGO and CIO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CGO and CIO thin films exhibit excellent optical transparency, with an average transmittance of > 80% in the visible range. Ga and In doping widens the optical band gap from 2.85 to 3.08 and 3.18 eV, respectively, via a Burstein-Moss shift. On MgO(100), room temperature thin film conductivities of 11 500 and 20 000 S/cm are obtained at an optimum Ga and In doping levels of 1.6% and 2.6%, respectively. Together, the experimental and theoretical results reveal that dopant ionic radius and electronic configuration have a significant influence on the CdO-based TCO structural, electronic, and optical properties: (1) lattice parameters contract as a function of dopant ionic radius in the order Y (1.09 Å) <In (0.94 Å) <Sc (0.89 Å), Ga (0.76 Å), with the smallest radius ion among the four dopants only shrinking the lattice marginally and exhibiting low doping efficiency; (2) carrier mobilities and doping efficiencies decrease in the order In > Y > Sc > Ga; (3) the Sc and Y dopant d states have substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.
AB - A combined experimental and theoretical/band structure investigation is reported of Ga-doped CdO (CGO) and In-doped CdO (CIO) thin films grown on both amorphous glass and single-crystal MgO(100) substrates at 410°C by metal-organic chemical vapor deposition (MOCVD). Film phase structure, microstructure, and electrical and optical properties are systematically investigated as a function of doping stoichiometry and growth conditions. XRD data reveal that all as-deposited CGO and CIO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CGO and CIO thin films exhibit excellent optical transparency, with an average transmittance of > 80% in the visible range. Ga and In doping widens the optical band gap from 2.85 to 3.08 and 3.18 eV, respectively, via a Burstein-Moss shift. On MgO(100), room temperature thin film conductivities of 11 500 and 20 000 S/cm are obtained at an optimum Ga and In doping levels of 1.6% and 2.6%, respectively. Together, the experimental and theoretical results reveal that dopant ionic radius and electronic configuration have a significant influence on the CdO-based TCO structural, electronic, and optical properties: (1) lattice parameters contract as a function of dopant ionic radius in the order Y (1.09 Å) <In (0.94 Å) <Sc (0.89 Å), Ga (0.76 Å), with the smallest radius ion among the four dopants only shrinking the lattice marginally and exhibiting low doping efficiency; (2) carrier mobilities and doping efficiencies decrease in the order In > Y > Sc > Ga; (3) the Sc and Y dopant d states have substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.
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U2 - 10.1021/cm702588m
DO - 10.1021/cm702588m
M3 - Article
VL - 20
SP - 220
EP - 230
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 1
ER -