Magnetic properties of epitaxially grown semiconducting Zn 1-xCo xO thin films by pulsed laser deposition

Jae Hyun Kim; Hyojin Kim; Dojin Kim; Young Eon Ihm; Woong Kil Choo

doi:10.1063/1.1513890

Magnetic properties of epitaxially grown semiconducting Zn _1-xCo _xO thin films by pulsed laser deposition

Jae Hyun Kim, Hyojin Kim, Dojin Kim, Young Eon Ihm, Woong Kil Choo

Division of Energy Techonology

Research output: Contribution to journal › Article › peer-review

350 Scopus citations

Abstract

We have characterized Zn _1-xCo _xO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (T _S) was varied from 300 to 700°C and the O ₂ pressure (P _O2) from 10 ^-6 to 10 ^-1Torr. When T _S is relatively low (≲600°C), homogeneous alloy films with a wurtzite ZnO structure are grown and predominantly paramagnetic, whereas inhomogeneous films of wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases form when T _S is relatively high and P _O2 is fairly low (≲10 ^-5Torr). The presence of Co clusters leads to room temperature ferromagnetism in inhomogeneous films. The temperature dependence of the magnetization for the homogeneous Zn _1-xCo _xO (x=0.25) films shows spin-glass behavior at low temperature and high temperature Curie-Weiss behavior with a large negative value of the Curie-Weiss temperature, indicating strong antiferromagnetic exchange coupling between Co ions in Zn _1-xCo _xO. We have found that Co can be dissolved in ZnO over 40% under an optimum growth condition of T _S=600°C and P _O2=10 ^-5Torr, where epitaxial homogeneous Zn _1-xCo _xO (x=0.25) films of the best crystalline quality are obtained.

Original language	English
Pages (from-to)	6066-6071
Number of pages	6
Journal	Journal of Applied Physics
Volume	92
Issue number	10
DOIs	https://doi.org/10.1063/1.1513890
State	Published - 15 Nov 2002

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title = "Magnetic properties of epitaxially grown semiconducting Zn 1-xCo xO thin films by pulsed laser deposition",

abstract = "We have characterized Zn 1-xCo xO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (T S) was varied from 300 to 700°C and the O 2 pressure (P O2) from 10 -6 to 10 -1Torr. When T S is relatively low (≲600°C), homogeneous alloy films with a wurtzite ZnO structure are grown and predominantly paramagnetic, whereas inhomogeneous films of wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases form when T S is relatively high and P O2 is fairly low (≲10 -5Torr). The presence of Co clusters leads to room temperature ferromagnetism in inhomogeneous films. The temperature dependence of the magnetization for the homogeneous Zn 1-xCo xO (x=0.25) films shows spin-glass behavior at low temperature and high temperature Curie-Weiss behavior with a large negative value of the Curie-Weiss temperature, indicating strong antiferromagnetic exchange coupling between Co ions in Zn 1-xCo xO. We have found that Co can be dissolved in ZnO over 40% under an optimum growth condition of T S=600°C and P O2=10 -5Torr, where epitaxial homogeneous Zn 1-xCo xO (x=0.25) films of the best crystalline quality are obtained.",

author = "Kim, {Jae Hyun} and Hyojin Kim and Dojin Kim and Ihm, {Young Eon} and Choo, {Woong Kil}",

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T1 - Magnetic properties of epitaxially grown semiconducting Zn 1-xCo xO thin films by pulsed laser deposition

AU - Kim, Jae Hyun

AU - Kim, Hyojin

AU - Kim, Dojin

AU - Ihm, Young Eon

AU - Choo, Woong Kil

PY - 2002/11/15

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N2 - We have characterized Zn 1-xCo xO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (T S) was varied from 300 to 700°C and the O 2 pressure (P O2) from 10 -6 to 10 -1Torr. When T S is relatively low (≲600°C), homogeneous alloy films with a wurtzite ZnO structure are grown and predominantly paramagnetic, whereas inhomogeneous films of wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases form when T S is relatively high and P O2 is fairly low (≲10 -5Torr). The presence of Co clusters leads to room temperature ferromagnetism in inhomogeneous films. The temperature dependence of the magnetization for the homogeneous Zn 1-xCo xO (x=0.25) films shows spin-glass behavior at low temperature and high temperature Curie-Weiss behavior with a large negative value of the Curie-Weiss temperature, indicating strong antiferromagnetic exchange coupling between Co ions in Zn 1-xCo xO. We have found that Co can be dissolved in ZnO over 40% under an optimum growth condition of T S=600°C and P O2=10 -5Torr, where epitaxial homogeneous Zn 1-xCo xO (x=0.25) films of the best crystalline quality are obtained.

AB - We have characterized Zn 1-xCo xO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (T S) was varied from 300 to 700°C and the O 2 pressure (P O2) from 10 -6 to 10 -1Torr. When T S is relatively low (≲600°C), homogeneous alloy films with a wurtzite ZnO structure are grown and predominantly paramagnetic, whereas inhomogeneous films of wurtzite ZnO phase mixed with rock-salt CoO and hexagonal Co phases form when T S is relatively high and P O2 is fairly low (≲10 -5Torr). The presence of Co clusters leads to room temperature ferromagnetism in inhomogeneous films. The temperature dependence of the magnetization for the homogeneous Zn 1-xCo xO (x=0.25) films shows spin-glass behavior at low temperature and high temperature Curie-Weiss behavior with a large negative value of the Curie-Weiss temperature, indicating strong antiferromagnetic exchange coupling between Co ions in Zn 1-xCo xO. We have found that Co can be dissolved in ZnO over 40% under an optimum growth condition of T S=600°C and P O2=10 -5Torr, where epitaxial homogeneous Zn 1-xCo xO (x=0.25) films of the best crystalline quality are obtained.

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Magnetic properties of epitaxially grown semiconducting Zn _1-xCo _xO thin films by pulsed laser deposition

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