Structural, optical, and electrical properties of indium-doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition
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Indium-doped cadmium oxide (CdO:In) films were prepared on glass and sapphire substrates by pulsed filtered cathodic arc deposition (PFCAD). The effects of substrate temperature, oxygen pressure, and an MgO template layer on film properties were systematically studied. The MgO template layers significantly influence the microstructure and the electrical properties of CdO:In films, but show different effects on glass and sapphire substrates. Under optimized conditions on glass substrates, CdO:In films with thickness of about 125 nm showed low resistivity of 5.9 × 10−5 Ωcm, mobility of 112 cm2/Vs, and transmittance over 80 % (including the glass substrate) from 500 to 1500 nm. The optical bandgap of the films was found to be in the range of 2.7 to 3.2 eV using both the Tauc relation and the derivative of transmittance. The observed widening of the optical bandgap with increasing carrier concentration can be described well only by considering bandgap renormalization effects along with the Burstein–Moss shift for a nonparabolic conduction band.
KeywordsCarrier Concentration Optical Bandgap Sapphire Substrate Aluminum Dope Zinc Oxide PbI2
The authors would like to thank K.M. Yu and S.H.N. Lim for their contributions to this work. Research was supported by the LDRD Program of Lawrence Berkeley National Laboratory, by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Building Technology, of the U.S. Department of Energy under U.S. Department of Energy Contract No. DE-AC02-05CH11231. Additional support was provided by the National Natural Science Foundation of China (Grant No.51072039 and 51222205), and the Ph.D. Programs Foundation of the Ministry of Education of China (20112302110036).
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