Ge₂Sb₂Te₅ based devices attract the attention of researchers due to wide opportunities in designing phase change memory. Herein, we studied a possibility to fabricate periodic micro- and nanorelief at surfaces of Ge₂Sb₂Te₅ thin films on silicon oxide/silicon substrates under multi-pulse femtosecond laser irradiation with the wavelength of 1250 nm. One-dimensional lattices with periods of 1250 ± 90 and 130 ± 30 nm were obtained depending on the number of acted laser pulses. Emergence of these structures can be explained by plasmon-polariton generation and laser-induced hydrodynamic instabilities, respectively. Additionally, formation of the lattices whose spatial period is close to the impacted laser wavelength can be modelled by considering the free carrier contribution under intensive photoexcitation. Raman spectroscopy revealed both crystallization and re-amorphization of the irradiated films. The obtained results show a possibility to fabricate rewritable all-dielectric data-storage devices based on Ge₂Sb₂Te₅ with the periodic relief.

The processes of femtosecond laser annealing of thin-film multilayer structures based on amorphous silicon and germanium produced by plasma-chemical deposition on a glass substrate have been studied. The formation of periodic structures on the surface of irradiated films has been detected by the scanning electron microscopy method. Analysis of Raman spectra has shown that amorphous germanium crystallizes and a mixing of germanium and silicon layers depending on the pulse energy density occurs in the absence of amorphous silicon layers crystallization as a result of exposure to femtosecond laser pulses.

Ge₂Sb₂Te₅ (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment at the 1250 nm wavelength of 200 nm thin amorphous GST225 films on silicon oxide/silicon substrates. A raster treatment mode and photoexcited surface plasmon polariton generation allowed us to produce mutually orthogonal periodic structures, such as scanline tracks (the period is 120 ± 10 μm) and laser-induced gratings (the period is 1100 ± 50 nm), respectively. Alternating crystalline and amorphous phases at the irradiated surfaces were revealed according to Raman spectroscopy and optical microscopy studies for both types of structures. Such periodic modulation leads to artificial optical and electrophysical anisotropy. Reflectance spectra in the near infrared range differ for various polarizations of probing light, and this mainly results from the presence of laser-induced periodic surface structures. On the other hand, the scanline tracks cause strong conductivity anisotropy for dc measurements in the temperature range of 200–400 K. The obtained results are promising for designing new GST225-based memory devices in which anisotropy may promote increasing the information recording density.

A new binuclear "paddle-wheel" complex, [Co₂(bhbz)₄(EtOH)₂]·4EtOH (1, Hbhbz-3,5-di(tert-butyl)-4-hydroxybenzoic acid); an isostructural zinc complex (2); a and magnetically diluted sample of [Zn_1.93Co_0.07(bhbz)₄(EtOH)₂]·4EtOH (3) were obtained. Molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. DFT calculations for 1 indicate strong Co-Co antiferromagnetic exchange interactions in the binuclear fragment. It was shown that when one paramagnetic ion in the binuclear molecule is replaced by a diamagnetic zinc(II) ion, the remaining cobalt(II) ion can be considered as an isolated center with magnetic anisotropy, the parameters of which are determined by ab initio calculations. Magnetic properties for samples 1 and 3 were investigated and analyzed in detail.

Phase transitions and periodic surface modification in amorphous Ge₂Sb₂Te₅ thin films on multilayer substrate were revealed as a result of the samples irradiation by femtosecond laser pulses with the wavelength of 1250 nm. Raman spectroscopy revealed partial crystallization in the treated samples. Calculations and analysis of scanning electron and atomic-force microscopy data showed that formation of the periodic surface structures is related to photoinduced surface plasmon-polariton excitation and depends on laser radiation fluence. The obtained results are useful for design and fabrication of new promising data-storage and polarization optics devices.

It was shown that the ablation of meso- and microporous silicon layers by picosecond laser pulses in water and ethanol leads to the formation of nanosilicon suspensions with a diameter of less than 100 nm. It has been demonstrated that the use of porous silicon allows to reduce the thresholds of laser ablation and increase the concentration of particles in suspensions in comparison with the case of crystalline silicon ablation.