Institute of Semiconductor Physics

Rb2KWO3F3 elpasolite was synthesized via the solid-state reaction route. The phase purity of the obtained sample was verified by the XRD analysis with Rietveld refinement in space group Fm-3m, yielding the unit cell parameter a = 8.92413 (17) Å. The electronic structure and chemical states of the constituent elements were investigated using X-ray photoelectron spectroscopy. The binding energy of the W 4f7/2 core level (34.95 eV) was found to be characteristic of the W6+ oxidation state, while the values for Rb 3d, K 2p, O 1s and F 1s levels were consistent with those reported for related oxide and oxyfluoride compounds. First-principles density functional theory calculations were performed to model the electronic structure. The fac-configuration of the WO3F3 octahedra was identified as the most energetically favorable. The calculations revealed a direct band gap of 4.38 eV, with the valence band maximum composed primarily of O 2p orbitals and the conduction band minimum formed by W 5d orbitals. This combined experimental/theoretical study shows that the electronic structure and wide bandgap of Rb2KWO3F3 are governed by the WO3F3 units and are largely insensitive to the Rb/K substitution. The wide bandgap identifies this class of oxyfluorides as a promising platform for developing new UV-transparent materials.

A 20-nm-wide (100)-oriented HgTe quantum well (QW) hosts a two-dimensional (2D) semimetal comprising both electrons and holes. In this study, we report that in addition to the previously observed quadratic temperature dependence of resistance, the system also displays an unexpected linear temperature dependence within specific top-gate voltage ranges. To account for this behavior, we extend the existing theoretical framework for temperature-dependent resistance in HgTe QW-based 2D semimetals with a focus on electron-hole scattering at low temperatures. Using the Boltzmann transport equation, we investigate the role of electron-hole interactions in this 2D semimetal. Our calculations reproduce a resistivity temperature dependence that aligns closely with experimental data. These findings establish this system as a robust platform for exploring interaction-limited transport regimes in a two-component plasma, particularly in the presence of disorder.

This conceptual article proposes a method for improving non-destructive testing systems applied in the fabrication of integrated circuits and semiconductor devices. It proposes the use of z-stacking technology when obtaining digital images of the devices at the stage just after wire bonding but before the packaging stage. The layer-by-layer scanning technology and subsequent analysis of the images using appropriate algorithms both allow determining the quality of the die to substrate assembly, the quality of wire bonding, correct welding in places, the presence or absence of wire breaks and other deficiencies like missing bonding, lift-up, the presence of contamination. In addition, it becomes possible to determine such a defect as exceeding the maximum wire loop height value. The article provides a description of what the corresponding installation should look like, what main parts it consists of, and how the image scanning is performed. The use of technology allows to reduce the number of manufacturing defects and shorten the time of setting up the integrated circuits production line.

The authors successfully prepare here a high-quality side surface of the layered topological insulator Bi_{2}Te_{3}. Using DFT calculations, they clearly demonstrate the reason behind the significant anisotropy of the Dirac state and its relationship with the projection of the bulk states onto the chosen crystallographic plane. Surface spectrum calculations enable them to determine the orientation of the facets on the prepared side surface, which is found to be $(10\overline{1})$, the spectrum of which aligns perfectly with the ARPES measurements.