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As-prepared nanostructured semiconductor materials are usually found in an amorphous form, which needs to be converted into a crystalline one for improving electronic properties and achieving enhanced application functionalities. The most utilized method is thermal annealing in a furnace, which however is time- and energy-consuming and not applicable for low-temperature melting substrates. An alternative is laser annealing, which can be carried out in a relatively short time and, additionally, offers the possibility of annealing localized areas. However, laser-annealed nanostructures are often distorted by melting, while preserving the as-prepared morphology is essential for practical applications. In this work, we analyze conditions of non-thermal ultrafast laser annealing of two kinds of nanostructures: anodic TiO2 nanotube layers and Ge/Si multilayer stacks. For both cases, regimes of crystallization have been found, which yield in preserving the initial nanomaterial morphologies without any melting signs. On these examples, ultrafast non-thermal mechanisms of structural material transformation are discussed, which can provide new opportunities for conversion of amorphous semiconductor nanomaterials into a desired crystalline form that is of high demand for existing and emerging technologies.

In the past, the application of TiO2 slurry reactors has faced difficulties concerning the recovery and reusability of the catalyst. In response to these challenges, immobilized photocatalyst systems have been investigated, wherein the catalyst is fixed onto a solid support, frequently with reduced photocatalytic performance. In the present study, thin TiO2 films were developed in the anatase phase by the sol-gel process and spin-cast on laser-microstructured silicon substrates, to form photocatalytic surfaces of increased activity. The TiO2 films were thoroughly characterized using SEM-EDX, XRD, UV–Vis spectroscopy, and Raman spectroscopy. The photocatalytic activity of these surfaces was evaluated by the degradation of atrazine in aqueous solution under UV irradiation. Their photocatalytic activity was found to be significantly enhanced (mean kobs 24.1 × 10−3 min−1) when they are deposited on laser-microstructured silicon compared with flat silicon (mean kobs 4.9 × 10−3 min−1), approaching the photocatalytic activity of sol-gel TiO2 fortified with Degussa P25, used as a reference material (mean kobs 32.7 × 10−3 min−1). During the photocatalytic process, several transformation products (TPs) of atrazine, namely 2-chloro-4-(isopropylamino)-6-amino-s-triazine (CIAT), 2-chloro-4-amino-6-(ethylamino)-s-triazine (CAET), and 2-chloro-4.6-diamino-s-triazine (CAAT), were identified with LC–MS/MS. The stability of the photocatalytic surfaces was also investigated and remained unchanged through multiple cycles of usage. The surfaces were further tested with two other pollutants, i.e., 2,4,6-trichlorophenol and bisphenol-a, showing similar photocatalytic activity as with atrazine.

We propose a novel approach for synthesizing silicon surfaces ensuring arbitrary apparent contact angle within the range from 0° to 170° for water. Superhydrophilicity of silicon substrates is achieved by nanosecond laser treatment and subsequent change in the contact angle is obtained by deposition of fluoropolymer films with different thicknesses by a hot wire chemical vapor deposition (HWCVD) method. The deposited film thickness needed to obtain superhydrophobicity was determined. The wettability properties of the produced fluoropolymer–silicon system are analyzed using the Wenzel and Cassie theories. [ABSTRACT FROM AUTHOR]