A typical schematic for both spray pyrolysis set-up and ZrO_x-based TFT device, and the corresponding electrical performance.

Solution-processed metal oxides require a great deal of thermal budget in order to achieve the desired film properties. Here, we show that the deposition temperature of sprayed zirconium oxide (ZrO_x) thin film can be lowered by exposing the film surface to an ultraviolet (UV) ozone treatment at room temperature. Atomic force microscopy reveals a smooth and uniform film with the root mean square roughness reduced from ~ 0.63 nm (UVO-O) to ~ 0.28 nm (UVO-120) in the UV–ozone treated ZrO_x films. X-ray photoelectron spectroscopy analysis indicates the formation of a Zr–O network on the surface film, and oxygen vacancy is reduced in the ZrO_x lattice by increasing the UV–ozone treatment time. The leakage current density in Al/ZrOx/p-Si structure was reduced by three orders of magnitude by increasing the UV-ozone exposure time, while the capacitance was in the range 290–266 nF/cm², corresponding to a relative permittivity (k) in the range 5.8–6.6 at 1 kHz. An indium gallium zinc oxide (IGZO)-based thin film transistor, employing a UV-treated ZrO_x gate dielectric deposited at 200 °C, exhibits negligible hysteresis, an I_on/I_off ratio of 10⁴, a saturation mobility of 8.4 cm² V⁻¹S⁻¹, a subthreshold slope of 0.21 V.dec⁻¹, and a V_on of 0.02 V. These results demonstrate the potentiality of low-temperature sprayed amorphous ZrO_x to be applied as a dielectric in flexible and low-power-consumption oxide electronics.

Doping is an effective material re-engineering technique, which provides a possibility of improving properties of materials for different applications. Herein, a Zr-doped TiO₂ thin film was deposited applying the chemical spray pyrolysis method and the influence of varying zirconium dopant concentrations on the properties of the film was studied. Morphological studies showed that the Zr–TiO₂ films were homogeneous with smaller grain sizes compared to the undoped TiO₂ films. As-deposited Zr–TiO₂ films were amorphous while the undoped TiO₂ films were crystalline with anatase structure as revealed by both X-ray diffraction and Raman spectroscopy studies. The optical band gap of the Zr–TiO₂ film was higher (3.44 eV) than that of the undoped TiO₂ films (3.13 eV) showing a strong dependence on the phase composition. As revealed by energy dispersive spectroscopy analysis, the Zr/Ti ratio in the film increased from 0.014 to 0.13 as the doping concentration in the spray solution was increased from 5 to 40 mol%. The current–voltage (I–V) characteristic revealed a reduction of the leakage current in the Zr-doped TiO₂ film (6.06 × 10^–5 A) compared to the undoped TiO₂ films (1.69 × 10^–3 A) at 1 forward bias voltage. The dielectric relaxation response at the oxide–electrode interface dipole was strongly influenced by the Zr doping concentration in the film.

The deposition of nickel oxide (NiO_x) thin film from an acetylacetonate source using many solution-based techniques has been avoided owing to its poor solubility in alcohol solvents. From this perspective, this work provides a systematic investigation of the development of NiO_x thin film, using a combinative approach of ultrasonic spray pyrolysis (USP) and Li dopant for the synthesis and optimization of structural and optoelectronic properties of the films. An in-depth comparative analysis of nickel acetylacetonate-based precursor, employing acetonitrile and methanol as solvents, is provided. It is demonstrated that USP from acetylacetonate precursor yielded uniform, well-compact, and transparent films, with polycrystalline cubic NiO_x crystal structures. By screening the deposition temperature in the range of 300–450°C, a temperature of 400°C was identified as an optimal processing temperature leading to uniform, compact, highly transparent, and p-type conductive films. At optimized deposition conditions (400°C), lithium-doped NiO_x (Li:NiO_x) thin film was deposited. The shift of the main (200) XRD peak position from 43.48° (0-Li:NiO_x) to 43.56° (60-Li:NiO_x) indicated Li incorporation into the NiO_x lattice. An X-ray photoelectron spectroscopy (XPS) study was employed to unravel the incorporation of Li into the deposited Li:NiO_x thin films. With the deconvolution of the Ni 2p core level for the as-deposited (0, 60)-Li:NiO_x films, the intensity of Ni³⁺ related peak was found to increase slightly with Li doping. Furthermore, all the deposited Li:NiO_x thin films showed p-type conductivity behavior, and the resistivity was reduced from 10⁴ Ωcm (0-Li:NiO_x) to 10² Ωcm (60-Li:NiO_x). Based on these results, the deposited NiO_x and Li:NiO_x thin films suggested that USP-deposited Li:NiO_x is highly suitable for application in inverted structure solar cells as the hole transport layer.