Reflectometry-Ellipsometry Reveals Thickness, Growth Rate, and Phase Composition in Oxidation of Copper

Laser-Induced Crystallization of Copper Oxide Thin Films: A Comparison between Gaussian and Chevron Beam Profiles

The use of a laser with a Gaussian-beam profile is frequently adopted in attempts of crystallizing nonsingle-crystal thin films; however, it merely results in the formation of polycrystal thin films. In this paper, selective area crystallization of nonsingle-crystal copper(II) oxide (CuO) is described. The crystallization is induced by laser, laser-induced crystallization, with a beam profile in the shape of a chevron. The crystallization is verified by the exhibition of a transition from a nonsingle-crystal phase consisting of small (∼100 nm × 100 nm) grains of CuO to a single-crystal phase of copper(I) oxide (Cu2O). The transition is identified by electron back scattering diffraction and Raman spectroscopy, which clearly suggests that a single-crystal domain of Cu2O with a size as large as 5 μm × 1 mm develops. The transition may embrace several distinctive scenarios such as a large number of crystallites that densely form grow independently and merge, and simultaneously, solid-state growth that takes place as the merging proceeds reduce the number of grain boundaries and/or a small number of selected crystallites that sparsely form grow laterally, naturally limiting the number of grain boundaries. The volume fraction of the single-crystal domain prepared under the optimized conditions─the ratio of the volume of the single-crystal domain to that of the total volume within which energy carried by the laser is deposited─is estimated to be 32%. Provided these experimental findings, a theoretical assessment based on a cellular automaton model, with the behaviors of localized recrystallization and stochastic nucleation, is developed. The theoretical assessment can qualitatively describe the laser beam geometry-dependence of vital observable features (e.g., size and gross geometry of grains) in the laser-induced crystallization. The theoretical assessment predicts that differences in resulting crystallinity, either single-crystal or polycrystal, primarily depend on a geometrical profile with which melting of nonsingle-crystal regions takes place along the laser scan direction; concave-trailing profiles yield larger grains, which lead to a single crystal, while convex-trailing profiles result in smaller grains, which lead to a polycrystal, casting light on the fundamental question Why does a chevron-beam profile succeed in producing a single crystal while a Gaussian-beam profile fails?

Exploration of Copper Oxide Nanoneedle Electrosynthesis Applied in the Degradation of Methylene Blue

In this study, we report a low cost, fast and unexplored electrochemical synthesis strategy of copper oxide nanoneedles films as well as their morphological and chemical characterization. The nanostructured films were prepared using electrochemical anodization in alkaline electrolyte solutions of ethylene glycol, water and fluoride ions. The film morphology shows nanoneedle-shaped structures, with lengths up to 1–2 μm; meanwhile, high-resolution X-ray photoelectron spectroscopy (HRXPS) and spectroscopy Raman analyses indicate that a mixture of Cu(II) and Cu(I) oxides, or only Cu(I) oxide, is obtained as the percentage of water in the electrolyte solution decreases. A preliminary study was also carried out for the photocatalytic degradation of the methylene blue (MB) dye under irradiation with simulated sunlight in the presence of the nanoneedles obtained, presenting a maximum degradation value of 88% of MB and, thus, demonstrating the potential characteristics of the material investigated in the degradation of organic dyes.

Recent advances in hybrid measurement methods based on atomic force microscopy and surface sensitive measurement techniques

This review summaries the recent progress of the combination of optical and non-optical surface sensitive techniques with the atomic force microscopy.