Electrodeposition of low-resistivity Y-doped ZnO and its thermal stability

Y-doped ZnO films have been electrochemically deposited on ITO-coated glass and Ag-coated stainless steel substrates. Without Y doping, the sheet resistance of the ZnO/ITO stack is 6.8 kΩ/sq. After adding a Y precursor to the deposition solution, the sheet resistance of the ZnO/ITO stack is reduced to as low as 1.5 Ω/sq, measured by four-point probe. This sheet resistance is obtained after annealing the 400-nm Y-doped ZnO film on ITO in 1 ATM N₂ ambient at 300°C for 3 hours. The corresponding resistivity for the ZnO film is 6.3×10^-5 Ω-cm, extracted by considering the ZnO/ITO stack as a parallel circuit. Even with possible measurement errors considered, the corresponding resistivity is only 1×10^-4 Ω-cm. The low-resistivity Y-doped ZnO also shows high transmittance (above 80%) and low absorbance (below 10%) by UV-vis spectroscopy. Y-doped ZnO deposited on Ag-coated stainless steel substrates shows stable resistivity (1×10^-4 Ω-cm) and high reflectance (~60%) after annealing in 1 ATM N₂ ambient at 500°C for 1 hour.