This paper presents the structural, optical and electrical characterization of ZnO thin films obtained by ultrasonic spray pyrolysis (USP). Based on these characterizations, the deposition conditions that provide films with higher crystallinity and greater absorption were determined. The resistivity of the films was reduced by annealing in nitrogen environment and was measured with a 4-point probe. The annealed films were characterized by AFM, SEM and XPS. Two photoconductive detectors were fabricated, with high and low resistivity films, and the responsivity was obtained for both. The two detectors showed a high UV response, but the photodetector developed from the annealed film demonstrated a maximum responsivity of 3000 A/W at 369 nm with a 2 V bias voltage. This result is higher than results obtained with low-cost techniques such as sol-gel, pneumatic spray pyrolysis, and even some results reported by sputtering.

Copper from a solid source was diffused into undoped n-type bulk ZnO (001) single crystals at 1000 °C under a nitrogen atmosphere at different diffusion times. The Cu diffusion profiles were obtained by Secondary ion mass spectroscopy (SIMS), and the fitting reveals a diffusion case from a constant concentration source. A value for the diffusion coefficient of 2.42(±0.2) × 10⁻¹² cm²∙s⁻¹ was obtained. Electrical measurements present an increment of carrier concentration with diffusion time, but remains n-type which indicates an increase in the donor levels produced by structural defects in ZnO. Photoluminescence (PL) spectra showed an increment of green emission intensity associated with Cu incorporation.

A reliable process for the formation of nanoporous ZnO films supported on amorphous quartz and (100) silicon substrates via the processing of ZnO/Zn precursor films is reported. The process is based on the sublimation mechanism of Zn implemented in a novel ZnO/Zn precursor film to produce a nanoporous film. A scanning electron microscopy analysis of the nanoporous ZnO films’ surfaces revealed the presence of ZnO nano-features with round tips; in contrast, the nanoporous ZnO films supported on (100) Si substrates showed hexagonal nut-like nanostructures. The crystallite size of the nanoporous ZnO films decreased as the sublimation temperature was increased. X-ray photoelectron spectroscopy studies demonstrated that formations of oxygen vacancies were produced during the processing stages (as the main structural lattice defects in the ZnO nanoporous films). The analysis of the photoluminescence response confirmed that the active deep-level centers were also related to the oxygen vacancies generated during the thermal processing of the ZnO/Zn precursor films. Finally, a qualitative mechanism is proposed to explain the formation of nanoporous ZnO films on quartz and crystalline Si substrates. The results suggest that the substrates used have a strong influence on the nanoporous ZnO structures obtained with the Zn-sublimation-controlled process.

The optical, electrical, and thermal properties of indium selenides are strongly influenced by their crystal structure. At room temperature (RT), the indium selenide with the stoichiometry In₂Se₂ exhibits two coexisting crystalline phases namely α and β, both can crystallize in two different crystal structures, hexagonal (2H) and rhombohedral (3 R). In polycrystalline In₂Se₃ powders, the presence of both phases has been observed. In this study, the rhombohedral β (3 R) phase of In₂Se₃ was synthesized by prior mechanical pulverization of powders of selenium and beads of indium, followed by mechanical alloying, achieved after 30 h of milling, and identified by x-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed a morphological evolution with a predominance of agglomerates smaller than 500 nm. Photoluminescence (PL) spectra show an emission of around 1.26 eV, lower than that reported in the literature, and the optic band gap energy E_g, determined by transmission spectra and the Tauc method, was 1.23 eV, a value not previously reported for this phase.