Effects of Deposition Inclination Angle on Microstructure and Electrical Properties of Al-Doped ZnO Coating Films

A flat plate in the deposition stage is designed to be tilted flexibly to form an inclination angle () between an ion beam and the direction normal to a polyethylene terephthalate (PET) substrate. Five kinds of PET/aluminum-doped zinc oxide specimens were prepared to examine the effects of inclination angle on the microstructures, crystals, chemical compositions, and electrical properties. An increase in the inclination angle results in X-ray diffraction peak intensity variations in ZnO and a reduction in the composite d-spacing. As the measure of the oxygen vacancies, the O-2-peak intensity ratio (IRO2) obtained using the X-ray photoelectron spectrometry (XPS) is evaluated. The IRO2 value increased with increasing the inclination angle, and it is proportional to the porosity integration over the visible light wavelengths. An increase in IRO2 is favorable for the reduction in composite grain size (g(Composite)). A smaller composite grain size (g(Composite)) of ZnO particles and a larger energy gap (E-g) can be obtained from applications of nonzero inclination angle. An appropriate nonzero inclination angle increases hardness and reduced elastic modulus and decreases the carrier concentration and carrier mobility of the specimen significantly.