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

Shu Jin, Yu Yang, Julia E. Medvedeva, Lian Wang, Shuyou Li, Norma Cortes, John R. Ireland, Andrew W. Metz, Jun Ni, Mark C Hersam, Arthur J Freeman, Tobin J Marks

Research output: Contribution to journalArticle

51 Citations (Scopus)

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 languageEnglish
Pages (from-to)220-230
Number of pages11
JournalChemistry of Materials
Volume20
Issue number1
DOIs
Publication statusPublished - Jan 8 2008

Fingerprint

Organic Chemicals
Organic chemicals
Oxides
Electronic structure
Chemical vapor deposition
Tuning
Metals
Doping (additives)
Ions
Thin films
Optical properties
Single crystals
Microstructure
Epitaxial films
Optical band gaps
Phase structure
Conduction bands
Stoichiometry
Electronic properties
Band structure

ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

Cite this

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 journalArticle

@article{1fca905d70a642bcbac7948042b95f8f,
title = "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",
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 {\AA}) <In (0.94 {\AA}) <Sc (0.89 {\AA}), Ga (0.76 {\AA}), 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.",
author = "Shu Jin and Yu Yang and Medvedeva, {Julia E.} and Lian Wang and Shuyou Li and Norma Cortes and Ireland, {John R.} and Metz, {Andrew W.} and Jun Ni and Hersam, {Mark C} and Freeman, {Arthur J} and Marks, {Tobin J}",
year = "2008",
month = "1",
day = "8",
doi = "10.1021/cm702588m",
language = "English",
volume = "20",
pages = "220--230",
journal = "Chemistry of Materials",
issn = "0897-4756",
publisher = "American Chemical Society",
number = "1",

}

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.

UR - http://www.scopus.com/inward/record.url?scp=39149085018&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=39149085018&partnerID=8YFLogxK

U2 - 10.1021/cm702588m

DO - 10.1021/cm702588m

M3 - Article

AN - SCOPUS:39149085018

VL - 20

SP - 220

EP - 230

JO - Chemistry of Materials

JF - Chemistry of Materials

SN - 0897-4756

IS - 1

ER -