Thin films of nanocomposite of zinc oxide–reduced graphene oxide (ZnO-rGO) deposited on soda-lime glass substrates were prepared using ultrasonic spray pyrolysis (USP) at 460 °C. The preparation process does not use harsh acids and is environmentally friendly. The deposition period of 2, 3.5 and 5 min resulted in compact, uniform samples with thicknesses of 148, 250 and 365 nm, respectively. After performing structural, morphological, optical and electrical characterization of the prepared nanocomposite, an influence of the deposition time on the physical properties of the obtained films was determined. TEM analyses indicate that the ZnO-rGO nanocomposite presents ZnO nanoparticles anchored on graphene sheets, while XRD, X-ray Photoelectron Spectroscopy (XPS) and Raman results show the presence of a ZnO phase in the ZnO-rGO films. HR-SEM studies showed changes of the ZnO-rGO thin films morphology due to the incorporation of graphene into the ZnO films. Here, the particles of ZnO are similar to small grains of rice and graphene films have the appearance of a little “rose”. As the thickness of the film increases with deposition time, it reduces the structure of resistance of the nanocomposite thin films to 135 Ω. In addition, the optical transmission of the thin films in the visible region resulted affected. Here, we report a simple methodology for the preparation of ZnO-rGO nanocomposite thin films.

In the present work, non-stoichiometric silicon oxide films (SiO_x) deposited using a hot filament chemical vapor deposition technique at short time and simple parameters of depositions are reported. This is motivated by the numerous potential applications of SiO_x films in areas such as optoelectronics. SiO_x films were characterized with different spectroscopic techniques. The deposited films have interesting characteristics such as the presence of silicon nanoclusters without applying thermal annealing, in addition to a strong photoluminescence after applying thermal annealing in the vicinity of 1.5 eV, which may be attributed to the presence of small, oxidized silicon grains (less than 2 nm) or silicon nanocrystals (Si-nc). An interesting correlation was found between oxygen content, the presence of hydrogen, and the formation of defects in the material, with parameters such as the band gap and the Urbach energies. This correlation is interesting in the development of band gap engineering for this material for applications in photonic devices.

This work is focused on making a correlation between results obtained by using spectroscopy and microscopy techniques from single and twofold-layer Silicon-Rich Oxide (SRO) films. SRO films single-layer and twofold-layer characterizations were compared considering the conditions as-grown and with thermal treatment at 1100 °C for 60 min in a nitrogen atmosphere. The thickness of the single-layer film is 324.7 nm while for the twofold-layer film it is 613.2 nm; after heat-treated, both thicknesses decreased until 28.8 nm. X-ray Photoelectron Spectroscopy shows changes in the excess-silicon in single-layer SRO films, with 10% in as-grown films and decreases to 5% for the heat-treated films. Fourier Transform Infrared Spectroscopy (FTIR) exhibits three characteristic vibrational modes of SiO₂, as well as, the vibrating modes associated with the Si-H bonds, which disappear after the heat treatment. With UV–Vis spectroscopy results we obtained the absorbance and the absorption coefficient for the SRO films in order to calculate the optical bandgap energy (Eg_opt), which increased with heat-treatment. The energy peaks of the photoluminescence spectra were used to calculate the silicon nanocrystal size, obtaining thus an average size of 1.89 ± 0.32 nm for the as-grown layer, decreasing the size to 1.64 ± 0.01 nm with the thermal treatment. On the other hand, scanning electron microscopy and high-resolution transmission electron microscopy images confirm the thickness of the twofold-layer SRO films as 628 nm for the as-grown layer and 540 nm for the layer with heat-treatment, and the silicon nanocrystal size of 2.3 ± 0.6 nm for the films with thermal treatment.