Study Of Transparent Conducting CdO Thin Films With A Tunable Band-gap Deposited On Organic Substrates

Cadmium Oxide (CdO) is a direct wide bandgap semiconductor material. Traditionally, CdO is widely used as transparent condcting electrode, transparent heating elements for aircraft and automobile windows, antistatic coatings for instrument windows, heating-reflecting mirrors for glass windows and incandescent bulbs, antireflecting coating, gas sensor, electrodes for liquid crystal. Compared to other wildly studied wide band semiconductors, CdO is promising: low synthesis temperature, high crystallinity with high carrier mobility at room temperature, it's high carrier concentration due to its interstitial cadmium or oxygen vacancies, which act as doubly charged donors. Besides, the bandgap of CdO film is fit with visible spectrum region of solar radiation. CdO films can be used as solar cell window material with Si, CdTe, CuInSe₂, and photodetector, etc.In this paper, the various TCO materials, growth techniques of CdO films and progresses in the research of CdO were reviewed. CdO films were synthesized on PET and glass substrates at room temperature by reactive magnetron sputtering. The properties of the films and the effects of growth parameters on quality of CdO films were studied by using X-ray diffraction, Hall, optical absorption, SEM techniques etc.To modify the energy gap of CdO, Zn and ZnAl alloy targets were used, to obtain Zn_xCd_1-xO and Zn_xCd_1-xAl_yO films. The electrical and optical properties of CdO films with different dopant concentration at different substrate temperature were also investigated.