Plasmon–exciton interaction strongly increases the efficiency of a quantum dot-based near-infrared photodetector operating in the two-photon absorption mode under normal conditions

Semiconductor quantum dots (QDs) are known for their high two-photon absorption (TPA) capacity. This allows them to efficiently absorb infrared photons with energies lower than the bandgap energy. Moreover, TPA in QDs can be further enhanced by the interaction of excitons of the QDs with plasmons of a metal nanoparticle. We fabricated nonlinear plasmon–exciton photodetectors based on QDs and silver nanoplates (SNPs) to demonstrate the optoelectronic application of these effects. A thin layer of CdSe QDs was used as a source of charge carriers for a photoresistor-type photodetector. SNPs with near-infrared plasmon modes were introduced into the layer of QDs to increase the light absorption efficiency. Under near-infrared irradiation, the power of the dependence of the photocurrent on the excitation intensity was twice the power of the corresponding dependence under one-photon excitation with visible light. This proved that the new photodetector efficiently operated under two-photon excitation. Although the SNP light absorption was linear, energy was transferred from plasmons to excitons in the two-quantum mode, which led to a nonlinear dependence. Moreover, we found that the photocurrent from the designed photodetector containing the QD–SNP composite was an order of magnitude higher than that from a photodetector containing QDs alone. This can be explained by the plasmon-induced increase in the TPA efficiency.This study was supported by the Russian Science Foundation, grant no. 18-72-10143. The part of this study dealing with the synthesis and characterization of nanomaterials was supported by the Russian Science Foundation, grant no. 18-19-00588. V. K. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie, grant agreement no. 101025664 (QESPEM). I. N. acknowledges support of the French National Research Agency (ANR-20-CE19-009-02) and co-funding by the European Union via the European Regional Development Fund (FreeBioWave project).Peer reviewe

Research of morphology and structure of 3C–SiC thin films on silicon by electron microscopy and X-ray diffractometry

Thin films of silicon carbide possessing unique properties attract increasing attention of researchers both in the field of semiconductor physics and in the technology of new semiconductor devices for high power, RF and optoelectronics. The growth of the production of silicon carbide based devices promotes the search for more resource saving and safe SiC layer synthesis technologies. Potential method is pulse laser deposition (PLD) in vacuum. This technology does not require the use of chemically aggressive and explosive gases and allows forming thin and continuous coatings with thicknesses of from several nanometers at relatively low substrate temperatures. Submicron thickness silicon carbide films have been grown on single crystal silicon by vacuum laser ablation of a ceramic target. The physical and technological parameters of silicon carbide thin film low temperature synthesis by PLD have been studied and, in particular, the effect of temperature and substrate crystalline orientation on the composition, structural properties and morphology of the surface of the experimental specimens has been analyzed. At above 500 °C the crystalline β-SiC phase forms on Si (100) and (111). At a substrate temperature of 950 °C the formation of textured heteroepitaxial 3C–SiC films was observed

Hyperfine Interactions in the NV-13C Quantum Registers in Diamond Grown from the Azaadamantane Seed

Nanostructured diamonds hosting optically active paramagnetic color centers (NV, SiV, GeV, etc.) and hyperfine-coupled with them quantum memory 13C nuclear spins situated in diamond lattice are currently of great interest to implement emerging quantum technologies (quantum information processing, quantum sensing and metrology). Current methods of creation such as electronic-nuclear spin systems are inherently probabilistic with respect to mutual location of color center electronic spin and 13C nuclear spins. A new bottom-up approach to fabricate such systems is to synthesize first chemically appropriate diamond-like organic molecules containing desired isotopic constituents in definite positions and then use them as a seed for diamond growth to produce macroscopic diamonds, subsequently creating vacancy-related color centers in them. In particular, diamonds incorporating coupled NV-13C spin systems (quantum registers) with specific mutual arrangements of NV and 13C can be obtained from anisotopic azaadamantane molecule. Here we predict the characteristics of hyperfine interactions (hfi) for the NV-13C systems in diamonds grown from various isotopically substituted azaadamantane molecules differing in 13C position in the seed, as well as the orientation of the NV center in the post-obtained diamond. We used the spatial and hfi data simulated earlier for the H-terminated cluster C510[NV]-H252. The data obtained can be used to identify (and correlate with the seed used) the specific NV-13C spin system by measuring, e.g., the hfi-induced splitting of the mS = ±1 sublevels of the NV center in optically detected magnetic resonance (ODMR) spectra being characteristic for various NV-13C systems

Structure and Content Analysis of Raw Materials for Production of Trimanganese Tetraoxide Pigment

The research aims to reveal the structure, phase, and elemental content of manganese ores from deposits—Bogach (Karaganda region, Kazakhstan) and Zhaksy (Akmola region, Kazakhstan). The samples were studied with scanning electron microscopy with energy dispersive analysis (SEM-EDA), X-ray diffractometry (XRD), Infra-red spectroscopy (IRS). During the research, structural peculiarities, elemental and phase content of the samples have been revealed. The mineral matter of the Bogach deposit ore mainly consists of hollandite, cryptomelane, braunite, calcite, bixbyite, quartz. The Zhaksy deposit ore includes quartz, hollandite, bixbyite, pyrolusite. Bogach ore includes (wt.%) C(10.68), O(32.00), Mn(43.26), Ca(6.36), Si(3.51), Na(0.52), Al(1.13), Mg(0.69), K(1.85). The elemental content of Mn in Zhaksy ore is two times lower. Zhaksy ore includes (wt.%) C(23.77), O(32.1), Mn(21.81), Si(10.52), Al(5.13), K(1.21), Fe(5.47). The obtained data of the conducted spectral analysis indicate that both samples represent a polymineral heterogeneous structure. Conducted research allows to conclude, that by phase-elemental content the Bogach ore can be used for obtaining trimanganese tetraoxide pigment similar to manganese ores from West Sumatera deposit (Indonesia) by top-down method using grinding with a milling tool and high-temperature sintering