الفهرس 
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Abstract
Transparent conducting oxide (TCO) have been extensively used in scientific and technological applications. Currently, n-type TCOs are present in many electronic devices, while their p-type counterparts are not largely commercially available and have limitations in stability and material synthesis. Nickel oxide (NiO) is a promising candidate as a p-type transparent conducting oxide film due to superior characteristics, such as high chemical stability, good crystallinity, wide direct energy gap in the range of 3.5 – 4.0 eV and low material cost. The preparation of controlled quality NiO films at low deposition temperature is challenging task because their properties depend on the film stoichiometry.
In the present work, NiO films were deposited by chemical bath deposition (CBD) and chemical spray pyrolysis (CSP) methods which allow improving the quality of the deposited films by changing of deposition parameters. XRD analysis proved that the as-deposited films by CBD are nickel hydroxide phase which transformed to poly-crystalline NiO phase by annealing process at 450°C in air for 4 hours. SEM images showed that the NiO films have a nanoflakes structure which makes these films fitting for gas sensing application. In addition, NiO films have been deposited by CSP using different precursor solution as well as different deposition temperature. The XRD prove the sprayed NiO films are polycrystalline and have a cubic crystal structure with (111) preferred orientation. The SEM images showed that the surface morphology of sprayed NiO films was changed by using different precursor solution. XPS results confirmed that the changes of initial nucleation, chemical composition and structure of NiO films depend on the Ni/O ratio of different precursor. The optical band gap energies of the sprayed NiO films using nickel nitrate, nickel chloride and nickel acetate are 3.5, 3.2 and 3.43 eV respectively. Also, the average value of refractive index for sprayed films using nickel nitrate, nickel chloride and nickel acetate are 2.1, 1.6 and 1.85 respectively. We attribute the observed behavior in the optical band gap and optical constants due to the change of the Ni/O ratio. We found that the optimal deposition temperature is 450°C. In addition, the sprayed NiO using nickel nitrate have lower roughness and high optical transmission, which make these films proper as a p-type transparent oxide for optoelectronic applications.
In addition, we have used the deposited NiO films by (CBD) and (CSP) for gas sensing application as well as optoelectronic application. In the gas sensing performance tests, we found that the maximum response is obtained at 300°C. The best dynamic range was observed for the sprayed NiO films using nickel chloride with 31.7 to 142.5 % for 25 and 150 ppm NH3, respectively. The highest average response was found for the NiO film prepared by CBD with 114.3 to 141.3 % for 25 and 150 ppm NH3 due to their nanoflakes structure. This behavior can be useful for the “caution” detection of ammonia, providing warning signals to the customers. For an optoelectronic application, the n-ZnO/p-Si and n-ZnO/p-NiO/p-Si junction devices were successfully fabricated and tested. XRD results showed that the prepared ZnO/Si by chemical vapor deposition (CVD) has a hexagonal structure with (101) preferred orientation, while the ZnO/NiO/Si film has a (002) preferred orientation. SEM study confirmed that the shape and surface morphology of ZnO films were changed by inserting the sprayed NiO layer on the Si substrate. The PL measurements for ZnO/Si and ZnO/NiO/Si showed that the UV emission of free exciton-related to near-band-edge emission (NBE) at 377.3 nm, and the deep-level emission (DLE) in the visible-light region. The I–V characteristic showed an improvement of rectifying behavior for ZnO/NiO/Si junction.
Keywords: Nickel oxide; chemical spray pyrolysis; chemical bath deposition; optical properties; Gas sensor; Nanoflakes; p-n junction