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Recently, nanodiamonds with negatively charged luminescent color centers based on atoms of the fourth group (SiV−, GeV−) have been proposed for use as biocompatible luminescent markers. Further improvement of the functionality of such systems by expanding the frequencies of the emission can be achieved by the additional formation of luminescent tungsten complexes in the diamond matrix. This paper reports the creation of diamond matrices by a hot filament chemical vapor deposition method, containing combinations of luminescing Si-V and Ge-V color centers and tungsten complexes. The possibility is demonstrated of creating a multicolor light source combining the luminescence of all embedded emitters. The emission properties of tungsten complexes and Si-V and Ge-V color centers in the diamond matrices were investigated, as well as differences in their luminescent properties and electron-phonon interaction at different temperatures.

Optically addressable high-spin states (S ≥ 1) of defects in semiconductors are the basis for the development of solid-state quantum technologies. Recently, one such defect has been found in hexagonal boron nitride (hBN) and identified as a negatively charged boron vacancy (VB−). To explore and utilize the properties of this defect, one needs to design a robust way for its creation in an hBN crystal. We investigate the possibility of creating VB− centers in an hBN single crystal by means of irradiation with a high-energy (E = 2 MeV) electron flux. Optical excitation of the irradiated sample induces fluorescence in the near-infrared range together with the electron spin resonance (ESR) spectrum of the triplet centers with a zero-field splitting value of D = 3.6 GHz, manifesting an optically induced population inversion of the ground state spin sublevels. These observations are the signatures of the VB− centers and demonstrate that electron irradiation can be reliably used to create these centers in hBN. Exploration of the VB− spin resonance line shape allowed us to establish the source of the line broadening, which occurs due to the slight deviation in orientation of the two-dimensional B-N atomic plains being exactly parallel relative to each other. The results of the analysis of the broadening mechanism can be used for the crystalline quality control of the 2D materials, using the VB− spin embedded in the hBN as a probe.

Transcription factors LXRs, PPARs, and SREBPs have been implicated in a multitude of physiological and pathological processes including atherogenesis. However, little is known about the regulation of these transcription factors at different stages of atherosclerosis progression. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to compare the contents of mRNAs in pairs intact-injured aorta fragments taken from the same donors. Only minor changes in LXRα, LXRβ, PPARα, PPARγ, SREBP1, and SREBP2 mRNA levels were found in initial lesions as compared with intact non-diseased tissue. The contents of all mRNAs but SREBP2 mRNA were found to be progressively up-regulated in fatty streaks and fibrous lipoid plaques. These changes were only partially reproduced in cultured macrophages upon lipid loading. Wave-shaped changes in abundance of correlations between given group of mRNAs and 28 atherosclerosis-related mRNA species in the course of atherogenesis were observed. The impact of specific mRNA correlations on the total correlations also significantly varied between different lesion types. The study suggests that the extent and forms of LXR/PPAR/SREBP participation in intima functions vary nonlinear in individual fashion in atherogenesis. We speculate that the observed changes in mRNAs expression and coupling reflect shifts in lipid ligands availability and cellular composition in the course of atherosclerosis progression.

Fermi level pinning at the oxidized (110) surfaces of III-As nanowires (GaAs, InAs, InGaAs, AlGaAs) is studied. Using scanning gradient Kelvin probe microscopy, we show that the Fermi level at oxidized cleavage surfaces of ternary AlxGa1−xAs (0 ≤ x ≤ 0.45) and GaxIn1−xAs (0 ≤ x ≤ 1) alloys is pinned at the same position of 4.8 ± 0.1 eV with regard to the vacuum level. The finding implies a unified mechanism of the Fermi level pinning for such surfaces. Further investigation, performed by Raman scattering and photoluminescence spectroscopy, shows that photooxidation of the AlxGa1−xAs and GaxIn1−xAs nanowires leads to the accumulation of an excess of arsenic on their crystal surfaces which is accompanied by a strong decrease of the band-edge photoluminescence intensity. We conclude that the surface excess arsenic in crystalline or amorphous forms is responsible for the Fermi level pinning at oxidized (110) surfaces of III-As nanowires. [ABSTRACT FROM AUTHOR]

High-quality crystalline nano-thin SiC films on Si substrates were prepared by carbonization of polyimide (PI) Langmuir–Blodgett (LB) films. The obtained films were characterized by Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, Raman spectroscopy, transmission electon microscopy (TEM), transmission electron diffraction (TED), and scanning electron microscopy (SEM). We demonstrated that the carbonization of a PI film on a Si substrate at 1000 °C leads to the formation of a carbon film and SiC nanocrystals on the Si substrate. It was found that five planes in the 3C-SiC(111) film are aligned with four Si(111) planes. As a result of repeated annealing of PI films containing 121 layers at 1200 °C crystalline SiC films were formed on the Si substrate. It was shown that the SiC films (35 nm) grown on Si(111) at 1200 °C have a mainly cubic 3C-SiC structure with small amount of hexagonal polytypes. Only 3C-SiC films (30 nm) were formed on the Si(100) substrate at the same temperature. It was shown that the SiC films (30–35 nm) can cover the voids with size up to 10 µm in the Si substrate. The current–voltage (I–V) characteristics of the n-Si/n-SiC heterostructure were obtained by conductive atomic force microscopy. [ABSTRACT FROM AUTHOR]

Nanodiamonds with the ‘diamond’ 1332.5 cm−1 Raman line as narrow as 1.8 cm−1 have been produced by reactive ion etching in oxygen plasma of heteroepitaxial diamond particles grown by microwave plasma enhanced chemical vapour deposition (MWPECVD) on silicon. After the etching, a doublet is recorded in the zero-phonon line photoluminescence spectra of an ensemble of silicon-vacancy (SiV) centres at 10 K. Each line of the doublet is split into two lines corresponding to the optical transitions between the split excited and ground energy levels of the SiV centres. These Raman and photoluminescent features have been observed previously only in low-strain homoepitaxial diamond films and single-crystal diamond. [ABSTRACT FROM AUTHOR]