ZnO is a relevant semiconductor that continues to expand its applications. The development of new devices requires overcoming the limitations of rigid substrates. Various techniques have been used to deposit materials on flexible substrates; however, their costs are high. Therefore, the spray pyrolysis technique is promising due to its homogeneity over large surfaces, low cost, and simplicity.
For the first time, fluorine-doped ZnO films at an atomic ratio [F/Zn] of 15 at.% were deposited on polyimide substrates in a temperature range of 320-400 °C under air or N2 carrier gas using the spray pyrolysis technique. Structural, morphological, and electrical properties were investigated using X-ray diffraction, scanning electron microscopy, four-point technique, and profilometry. All films were polycrystalline with a hexagonal wurtzite structure. Films deposited at 320 and 350 °C with air gas exhibited a preferential (100) orientation, while those deposited at 350 and 400 °C with N2 gas showed a preferential (002) orientation. The size of the crystallites increased with the temperature and N2 gas. The morphology changed between columnar and wedge-shaped, depending on the temperature and the type of carrier gas. The resistivity decreased from 1.117x102 to 9.45x10-2 Ω-cm with increasing temperature. At a temperature of 350 °C, the resistivity decreased by two orders of magnitude when using N2 gas compared to the deposition with air.
The improved incorporation of fluorine and hydrogen into ZnO, using N2 gas, probably contributed to the decrease in resistivity. Spray pyrolysis was presented as an alternative method for depositing ZnO:F films on polyimide for applications in flexible electronics.
