2003 Fiscal Year Final Research Report Summary
Development of amorphous transparent conductive oxide films and their applications to transparent electrodes
| Project/Area Number |
14550301
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | The University of Tokushima |
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Principal Investigator |
TOMINAGA Kikuo The University of Tokushima, Faculty of Engineering, Associate Professor, 工学部, 助教授 (10035660)
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| Co-Investigator(Kenkyū-buntansha) |
NAKABAYASHI Ichiro The University of Tokushima, Faculty of Engieeering, Professor, 工学部, 教授 (70035624)
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| Project Period (FY) |
2002 – 2003
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| Keywords | TCO films / Transparent conductive oxide films / amorphous films / In_2O_3-ZnO / SnO_2-ZnO / ZnO-SnO_2 / Infrared absorption film / Highly transparent oxide films |
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| Research Abstract |
We deposited In_2O_3-ZnO transparent conductive films by simultaneous sputtering of ZnO and In_2O_3 ceramic targets. Amorphous and homologous phases appeared with increasing δ=Zn/(Zn+In) ratios. Carrier generation mechanism was discussed for these films. Native oxygen defects are the primary donors for the In_2O_3-ZnO films. Then the low resistivities of 2〜4×10^<-4> Ω cm were attained within a narrow range of δ=Zn/(Zn+In) in the amorphous phase film. 2 wt% Al_2O_3-doping decreased the resistivity to 1.5〜2.1×10^<-4>Ωcm. At doping of 3 wt% and 4 wt% Al_2O_3, film resistivities of 2-4×10^<-4> were attained for a relatively wide range of δ in the amorphous phase due to an increase in carrier concentration at δ=0.3-0.6. On the other hand, Al_2O_3 doped in the homologous Zn_kIn_2O_<k+3> crystalline films did not act as donor impurities. The optical bandgap energy for the films deposited above 2 wt% Al_2O_3 for amorphous film was proportional to Al_2O_3 content, ascribed to lattice distortion
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by Al_2O_3. Post annealing under the reductive gas flow was effective on improving unevenness of the amorphous films.
Thin films of ZnO-SnO_2 system were also deposited by the same method, where ZnO and SnO_2:Sb (Sb_2O_5 3wt% doped) targets were faced each other. Compositions in as-deposited films were changed with the current ratio δ. Amorphous transparent films appeared in a range of 0.47【less than or equal】δ【less than or equal】0.80 (Zn/(Sn+Zn)=0.28-0.76) at Ts=150℃, in a range of 0.33【less than or equal】δ【less than or equal】0.73 (Zn/(Sn+Zn)=0.32-0.66) at Ts=250℃. At δ=0.62 (Zn/(Sn+Zn)=1/2) or 6=0.73 (Zn/(Sn+Zn)=2/3) and any other ratio in as-deposited films we could obtain neither crystalline ZnSnO_3 nor Zn_2SnO_4 Amorphous films would exist as forms of (ZnSnO_3)_x(SnO_2)_<1-x> in a range of 0.5【less than or equal】δ【less than or equal】0.62 (0【less than or equal】δ【less than or equal】) and (ZnSnO_3)_<1-y>(ZnO)_y, in a range of 0.62【less than or equal】δ【less than or equal】0.73 (0【less than or equal】y【less than or equal】0.5). Minimum resistivity of amorphous films deposited was 3.6×10^<-2> Ωcm at δ=0.50 (Zn/(Sn+Zn)=0.33), Ts=250℃. Less
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