Each dopant was at its appropriate content and all films were fabricated under optimum-processing-parameter conditions to achieve lower resistivity and higher transmittance.
ions, which minimizes the Zn O lattice deformations even at higher doping concentrations [18, 21].
Several elements are doped in Zn O films, such as B [16, 17], Al, Ga, In (from group III elements) , F (from group VII element) , and so forth.
Among them the most studied are Al-doped Zn O and Ga-doped Zn O.
The crystallinity of thin films improved and the surface smoothness decreased with increasing growth temperature.
In x-ray reflection analysis with respect to Zn O (0002) peak, the full width at half maximum (FWHM) of 0.4°was achieved at 400°.Besides, it has a more proper work function for the transparent contact cathode electrodes of transparent OLEDs .Nevertheless, many problems associated with substituting Zn O-based TCO films for ITO still exist. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Zn O-based transparent conductive thin films have attracted much attention as a promising substitute material to the currently used indium-tin-oxide thin films in transparent electrode applications.However, with the market of ITO expanding, a stable supply may be difficult to ensure because of the high cost and scarcity of indium [9, 10].Fortunately, Zn O thin films are a promising alternative to the commonly used ITO, which are low cost, nontoxic, highly durable against hydrogen plasma compared to ITO .Even if the films are prepared by the same method, thickness, substrate, growth temperature, dopant, and their content will play a crucial role in structural, electrical, and optical properties of films.Therefore, whether we can optimize the fabrication of high-quality doped zinc oxide thin films at low cost determines the future of Zn O-based TCO films.For the design and realization of Zn O-based devices, one of the most significant issues is doping, which necessarily involves the heavy doping with trivalent elements from the group III (Al, Ga, In).Minami summed up the resistivity of impurity-doped binary compound TCO films reported among thirty years and found that the obtained minimum resistivity of impurity-doped Zn O films is still decreasing, while Sn O films have essentially remained unchanged .