Paper OX+EM+MI+NS+TF-MoM2
Structural Characterization of Heterojunction n-ZnO/p-NiO Thin Films Epitaxially Deposited on (0002)Al2O3 Substrates
Monday, October 29, 2012, 8:40 am, Room 007
| Session: |
Structure–Property Relationships in Epitaxial Oxide Interfaces |
| Presenter: |
Y.H. Kwon, Sungkyunkwan University, Republic of Korea |
| Authors: |
Y.H. Kwon, Sungkyunkwan University, Republic of Korea
J.H. Lee, KAIST, Republic of Korea
S.H. Chun, Sungkyunkwan University, Republic of Korea
J.Y. Lee, KAIST, Republic of Korea
H.K. Cho, Sungkyunkwan University, Republic of Korea
|
| Correspondent: |
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Recently, oxide semiconductors with superior electical properties have been considered as candidates to replace Si based electronics. Furthermore, their thermally and chemically stable characteristic is preferable for devices. Especially, among a lot of oxides, ZnO based semiconductors have been extensively investigated to apply in wide application such as thin film transistor and light emitting diode. ZnO is an intrinsic n-type semiconductor which characteristic comes from Zn interstitials and O vacancies. And band-gap and exciton binding energy are 3.37 eV and 60 meV, respectively, which is suitable for optical application operating in ultra-violet region. Therefore, p-n homojunction diode structure combined with n-ZnO and p-ZnO having well matched interface had been studied by a lot of researchers.[1] However, it was not reliable since p-type ZnO synthesized by doping of group V elements is unstable and return to the n-type by self-compensation.[2]
Therefore, p-n heterojunction diode composed of n-ZnO and stable p-type oxide such as Cu2O and NiO was alternatively studied.[3] Among the p-type oxides, NiO with wide direct band-gap (3.7 eV) have been expected to apply in optical applications. And conductivity of NiO could be significantly controlled by Li+ doping. Furthermore, according to T. Dutta et. al., (111) plane of NiO could well matched with (0002) of ZnO by domain match epitaxy.[4]
In this study, heterojunction diode structure was fabricated with n-type ZnO and p-type NiO on [0002] oriented Al2O3 substrates. RF magnetron sputtering method was used for deposition of NiO and ZnO films. After the deposition of NiO films at 400°C in O2 atmosphere, ZnO films were grown at 600°C and in Ar and O2, mixed gas atmosphere. XRD result showed the NiO films were fabricated with high crystallinity and preferred orientation of [111]NiO. And sixfold symmtery of (100)NiO plane obtained by phi-scan indicates that the NiO films were bi-epitaxially grown on Al2O3 substrates. In addition, electrical properties of NiO showed relatively low resisitivity (1.648 Ωcm) and high mobility (14.52 cm2/Vs) due to Li+ doping. Sixfold symmetry of (1-102)ZnO observed at phi-scan result indicates that ZnO films were also epitaxially grown on [111] oriented NiO films.
REFERENCES
[1] F. Zhuge, L. Zhu, Z. Ye, D. Ma, J. Lu, J. Huang, F. Wang, Z. Ji, S. Zhang, Applied Physics Letters, 87 (2005) 092103.
[2] C. Park, S. Zhang, S.H. Wei, Physical Review B, 66 (2002) 073202.
[3] H. Kawazoe, H. Yanagi, K. Ueda, H. Hosono, MRS Bulletin, 25 (2000) 28.
[4] T. Dutta, P. Gupta, A. Gupta, J. Narayan, Journal of Applied Physics, 108 (2010) 083715.