Low-cost, high-efficiency and high quality Cl-doped ZnO (ZnO:Cl) thin films that can simultaneously function as transparent conducting oxides (TCOs) and photocatalysts are described. The films have been fabricated by a facile and inexpensive solution-source aerosol-assisted chemical vapour deposition technique using NH4Cl as an effective, cheap and abundant source of Cl. Successful ClO substitutional doping in the ZnO films was evident from powder X-ray diffraction, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry results, while scanning electron microscopy reveals the impact of Cl doping on the ZnO thin film morphology. All ZnO:Cl films deposited were transparent and uncoloured; optical transmittance in the visible region (400-700 nm) exceeded 80% for depositions using 5-20 mol% Cl. Optimal electrical properties were achieved when using 5 mol% Cl with a minimum measured resistivity of 2.72 ± 0.04 × 10-3 Ω.cm, in which the charge carrier concentration and mobility were measured at 8.58 ± 0.16 × 1019 cm-3 and 26.7 ± 0.1 cm2 V-1 s-1 respectively, corresponding to a sheet resistance (Rsh) of 41.9 •-1 at a thickness of 650 nm. In addition to transparent conducting properties, photocatalytic behaviour of stearic acid degradation in the ZnO:Cl films was also observed with an optimal Cl concentration of 7 mol% Cl, with the highest formal quantum efficiency () measured at 1.63 ± 0.03 × 10-4 molecule/photon, while retaining a visible transparency of 80% and resistivity  = 9.23 ± 0.13 × 10-3 Ω.cm. The dual functionality of ZnO:Cl as both a transparent conductor and an efficient photocatalyst is a unique combination of properties making this a particularly unusual material.

A simple, economical and effective solution-based chemical vapour deposition (CVD) technique, aerosol-assisted CVD, has been successfully applied to produce inexpensive Cl-doped ZnO films using Zn acetate dihydrate and FeCl₃. X-ray photoelectron spectroscopy and the increase in cell parameters from powder X-ray diffraction determined that Cl had been doped into the wurtzite ZnO lattice. The Cl-doping had a significant effect on the morphology of the thin films synthesised and resulted in an improvement in the visible light transmission and lower electrical resistance (typical resistivities of doped films ∼10⁻² Ω cm). The highest transmittance (% T) of 85% was obtained when 7 mol% FeCl₃ was used in the precursor solution and the lowest resistivity of 4.28 ± 0.41 × 10⁻² Ω cm was obtained with 5 mol% FeCl₃. The greatest photocatalytic activity of stearic acid degradation under UVA irradiation was obtained on using 10 mol% FeCl₃, resulting in the highest formal quantum efficiency (FQE) of 3.0 ± 0.1 × 10⁻⁴ molecule per photon. These films, therefore, display transparent conducting oxide and photocatalytic properties, giving multifunctional characteristics and promising applications.

Scandium(III) oxide thin film deposition has been historically difficult to achieve without the use of vacuum-based or wet chemical systems due to precursor limitations of low vapour pressure or ambient instability. In this letter, the adoption of aerosol-assisted delivery of scandium(III) acetylacetonate has enabled the chemical vapour deposition of polycrystalline and amorphous Sc₂O₃ thin films at ambient pressure with high growth rates (ca. 500 nm h⁻¹). The scandia films were intrinsically highly photoluminescent, exhibiting broad emission bands centred at $3.6$ and $3.0\hspace{0.17em}\text{eV}$ , which increased significantly in intensity upon aerobic annealing, accompanying a transition from amorphous to crystalline, while bands appearing at $2.1$ and $2.3\hspace{0.17em}\text{eV}$ seemed to occur only in the crystalline films. In addition, both amorphous and crystalline scandia films exhibited blue-green vibronic fine structure between $2.3\hspace{0.17em}\text{and}\hspace{0.17em}3.2\hspace{0.17em}\text{eV}$ attributed to the electronic transition $B{}^2{\Sigma }^{+}\to {\rm X}{}^2{\Sigma }^{+}$ in surface ${\hspace{0.17em}}_{\cdots O-}^{\cdots O-}Sc=O$ groups and split by a vibrational mode observed at $920\pm 60\hspace{0.17em}{\text{cm}}^{-1}$ by infrared spectroscopy. Band gaps of amorphous and crystalline Sc₂O₃ were determined to be $5.3$ and $5.7\hspace{0.17em}\text{eV}$ , respectively via diffuse reflectance. All films had high refractive indices, varying between 1.8 and 2.0 at $400\hspace{0.17em}\text{nm}$ depending on film thickness and carrier gas used in the deposition; film thicknesses less than ca. $300\hspace{0.17em}\text{nm}$ were observed to have a strong influence on the refractive index measured, while there was little variation for films thicker than this. The synthesis process itself is exceedingly low-cost and facile thus promising streamlined industrial scalability.