We demonstrate the formation of laser-induced periodic surface structures (LIPSS) in bismuth (Bi) thin films by irradiation with nanosecond laser pulses. We report on the formation and the destruction of the LIPSS as a result of the delivered number of pulses; both the formation and destruction threshold were very well determined. Results show that the obtained LIPSS are perpendicular to the laser polarization, and their ripple periodicity is on the order of the irradiation wavelength. Although all the irradiation experiments were done in ambient air, Raman micro-spectroscopy indicates that the LIPSS are constituted by metallic bismuth, i. e. the LIPSS formation is oxidation free.

Molybdenum oxide is an attractive material for application in several technology fields such as sensors, displays, and batteries, among many others. In this work, we present a reliable laser direct writing (LDW) method for synthesizing multi-phase molybdenum oxide (MoO_x) on a single processing step. We use femtosecond laser pulses to produce up to five distinct crystalline phases of molybdenum oxide at once. We demonstrate how the laser irradiation conditions determine the MoO_x stoichiometry, phase, and morphology. We show that by conveniently adjusting either the per-pulse laser fluence or the exposure time, MoO_x can be obtained in nano or micro-structured form. We found that this ultrashort pulse laser processing method allows for the formation of unusual MoO_x phases such as o-Mo₁₈O₅₂, which is rarely reported in the literature. In addition, it is possible to synthesize other sub-stoichiometric molybdenum oxide phases such as o-Mo₄O₁₁ and m-Mo₈O₂₃ all at atmospheric air conditions, with no need for demanding oxygen pressure precautions.

Zinc oxide (ZnO) films with different structural, morphological, and optical properties were obtained by (fixed) thermal oxidation of deposited metallic zinc (Zn) films. The main characteristics of the oxidized films are discussed in terms of the Zn film thickness. On-axis preferential crystallographic oriented growth of ZnO can be tuned based on the control of the thickness of the deposited Zn: c-axis (a-axis) for the thinnest (thicker) Zn film. The thicker ZnO film is rather a-textured, whereas the grains hosted by the ZnO films corresponding to the Zn films of intermediate thicknesses are more randomly oriented. For Zn films of ever-increasing thickness, a tendency towards the crystallization of larger ZnO nanocrystals holds, combined with a continuous increment on the surface roughness. In contrast, the fundamental bandgap of the resultant oxide-based films decreases with thickness. The roughness of the ZnO films is not directly measured. It is qualitatively described by the analysis of Zn-film micrographs obtained by Scanning Electron Microscopy and by the demonstration of strong optical scattering interactions present in the thicker ZnO films by their random lasing activity.

Bismuth nanoparticles (NPs) colloids synthesized in deionized water by laser ablation of solids in liquids technique (LASL) were oxidized using NaClO solutions at different concentrations. Oxidized nanomaterials were characterized using several techniques. The crystalline phases of the bismuth compound were determined using Raman microspectroscopy, and the crystallographic structure was identified by x-ray diffraction (XRD). The size and morphology of the obtained nanomaterials were studied by transmission electron microscopy (TEM). The chemical states were determined using x-ray photoelectron spectroscopy (XPS), and the optical properties of the colloids were characterized by UV–vis spectroscopy. The absorption spectra were analyzed using the Tauc method to determine the band gaps of the obtained nanomaterials. Our results showed morphological changes, starting from small nanoparticles to nanosheets and a mixture of nanosheets with hollow nanoparticles. Two kinds of nanomaterials were found depending on the NaClO solution concentration: Bi₂O₂CO₃ single phase and a mixture of δ-Bi₂O₃ and Bi₂O₂CO₃. Some samples were tested as photocatalysts and showed good performance in the degradation of methylene blue in solution. To the best of our knowledge, this is the first study on the oxidation process of bismuth colloidal nanoparticles at room temperature.