Effects of inclination angle during Al-doped ZnO film deposition and number of bending cycles on electrical, piezoelectric, optical, and mechanical properties and fatigue life

A flat plate with an adjustable inclination angle between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate is designed for a deposition stage. Five inclination angles are used to prepare PET/aluminum-doped zinc oxide specimens in order to examine the effects of inclination angle and number of bending cycles on several parameters. The O₂ peak intensity ratio (IRO2), obtained from x-ray photoelectron spectroscopy, is identified as one of the controlling factors of the electrical, optical, piezoelectric, and mechanical properties. The effect of inclination angle on IRO2 and the effects of IRO2 on the peak intensity ratios, IR_ZnO (002) and IR_ZnO (103), obtained from x-ray diffraction analyses, the composite grain size, and the residual stress in the thin film are investigated systematically. An increase in the inclination angle increases the peak intensity ratios of IRO2 and IRAl2O3, and reduces that of IR_ZnO. An increase in IRO2 decreases the volume fraction of IR_ZnO (002) but increases the residual stress of the thin film, and is favorable for the reduction of the composite grain size. The carrier mobility and electrical resistance decrease and carrier concentration increases when IRO2 and IRAl2O3 increase or IR_ZnO decreases. An increase in the residual stress reduces the fatigue life and piezoelectric coefficient of specimens. The application of a nonzero inclination angle increases the transmittance integration (TI) over the wavelengths of visible light and the intensities of the three peaks in the photoluminescence spectrum. A reduction in film thickness leads to increases in the energy gap and electrical resistance and a decrease in TI.