Ce-doped glass is a well-established solution for ultraviolet and ionizing radiation shielding of solar cells in space. Traditionally, Ce-glass protected Si or III-V based devices as an overlaying cap. However, for emerging photovoltaics such as halide perovskites, thin Ce-glass coated with transparent conductive layers could serve as a lightweight carrier with an electrode. While indium-tin oxide (ITO) is widely used in solar cells for charge collection, its optical, structural, and electrical properties depend on the substrate quality. In this work, we demonstrated significant differences in properties of ITO deposited on Ce-glass (100 micron thick) compared to standard soda lime glass. ITO on Ce-glass exhibited pronounced compressive strain because of higher oxygen vacancy concentrations, reduced transparency and charge carrier concentration (10^19 cm-3) resulting from altered stoichiometry. Electrical analysis showed increased Hall mobility (66 cm2V-1s-1) but decreased conductivity due to excess tin incorporation. These specific ITO features originated from inelastic collisions with the substrate during deposition. Variations in wettability and surface potential underscore substrate-induced differences critical for developing optimized ITO coatings for space-grade photovoltaics.

The use of mixed cation absorber composition was considered as an efficient strategy to mitigate the degradation effects in halide perovskite solar cells. Despite the reports about partial stabilization at elevated temperatures, unfavorable phase transition after thermocycling and electric field-driven corrosion remains critical bottlenecks of perovskite thin-films semiconductors. In this work, we developed stabilized heterostructures based on CsFAPbI3, modified with mechanically synthesized quasi-2D perovskite incorporating the 5-ammonium valeric acid cation (AVA2FAPb2I7). We found that integration of AVA2FAPb2I7 into grain boundaries boosts phase resilience under harsh thermocycling from -10 up to 100 C and suppresses transitions, as well as decomposition to PbI2. The rapid oxidation of metal contacts in the multi-layer stacks with non-passivated CsFAPbI3 was effectively suppressed in the fabricated heterostructure. A comprehensive interface study of the copper electrode contact revealed that the incorporation of AVA2FAPb2I7 stabilized the lead and iodine states and suppressed contamination of FA cation in ambient conditions. Meanwhile, the metal-perovskite interface remained predominantly in the Cu(0)-Cu(I) state. The observed stabilization in perovskite heterostructure was attributed to an increased activation energy for delta-phase accumulation at the grain boundaries combined with reduced ionic diffusion. The obtained results opened important highlights for the mechanisms of the improved phase stability after thermal cycling and mitigation of the interface corrosion and under an applied electric field.

Indium (iii) selenide is currently one of the most actively studied materials in the two-dimensional family due to its remarkable ferroelectric and optical properties. This study focuses on the luminescent properties of few-layer In2Se3 flakes with thicknesses ranging from 7 to 100 monolayers. To explore the photoluminescence features and correlate them with changes in crystal symmetry and surface potential, we employed a combination of techniques, including temperature-dependent micro-photoluminescence, time-resolved photoluminescence, Raman spectroscopy, atomic force microscopy, and Kelvin probe force microscopy. X-ray diffraction and Raman spectroscopy confirmed that the samples studied possess the alpha-phase structure. The micro-photoluminescence spectrum consists of two bands, A and B, with band B almost completely disappearing at room temperature. Temperature-dependent photoluminescence and time-resolved measurements helped us to elucidate the nature of the observed bands. We find that peak A is associated with emission from interband transitions in In2Se3, while peak B is attributed to defect-related emission. Additionally, the photoluminescence decay times of In2Se3 flakes with varying thicknesses were determined. No significant changes were observed in the decay components as the thickness increased from 7 to 100 monolayers, suggesting that there are no qualitative changes in the band structure.

Strain engineering is a powerful tool for the development of nanostructured semiconductor devices. In this work, the effect of high external elastic strain is investigated on the photoluminescence of GaN nanowires (NWs). Individual horizontal NWs are strained to bending strains up to 2.2% using an atomic force microscope (AFM) probe. Novel nanomanipulation techniques for mechanical fixation of strained low aspect ratio NWs transferred on the auxiliary substrate are developed, including the "nanoscale welding" based on conductive AFM. The optical properties of the strained GaN NWs are investigated using spatial mapping of the microphotoluminescence. It is shown that bending strain leads to symmetric broadening of photoluminescence peak. The obtained spectra are numerically analyzed taking into account the non-uniform strain distribution, selection rules, and strain-induced bandgap modification, showing that the main contribution to luminescence corresponds to transitions from the conduction band to the heavy hole band. A linear coefficient of shift (broadening) of the luminescence maximum was derived for a bending (uniaxial) deformation of 131.5-136.5 meV/GPa.

Using high-temperature annealing of thin gold nanofilms deposited onto the (001) surface of doped p-GaAs crystal with an ultrathin oxide layer, the nanoclusters of gold (Au2Ga alloy) are fabricated. The gold clusters have the wedge shapes with rectangular bases elongated in [110] direction at GaAs(001) surface. This assertion is confirmed by the data of diagnostics of Au/p-GaAs(001) structures. Anisotropic plasmons localized on equally oriented wedge-shaped Au (Au2Ga) clusters are investigated with the optical reflectance anisotropy spectroscopy and spectroscopy of polarized light reflection. It is shown that the spectral peak at the energy about 0.9 eV in the near infrared range is associated with plasmons polarized along the longest sides of clusters in crystallographic direction [110]. Another peak—at the energy of 1.8 eV—is due to plasmons having polarization in direction [11̅0] .

Wedge-shaped nanoclusters of gold (Au2Ga) are fabricated by high-temperature annealing of a gold nanofilm deposited onto (001) surface of p-doped GaAs crystal with a very thin overlayer of natural oxide. The data of diagnostics confirm the presence in prepared Au/p-GaAs(001) structures of the wedge-shaped Au-intermetallic nanoclusters elongated in [110] direction at GaAs surface. A crystallographic model of the wedge-shaped Au (Au2Ga) nanoclusters conditioned by GaAs(001) surface is discussed in relation with their physicochemical nature. Anisotropic plasmons localized on equally oriented Au-based nanoclusters are detected optically with the reflectance anisotropy spectroscopy and investigated thoroughly with the spectroscopy of polarized light reflection. It is proved experimentally and theoretically that the inhomogeneously broadened infrared spectral peak at the energy about 1.1 eV is associated with plasmons polarized along the wedge-shaped clusters in [110] crystal direction. Another peak - at the energy approximately of 1.8 eV - is due to plasmons having orthogonal polarization in direction [110].

Efficient doping of semiconductor nanowires remains a major challenge towards the commercialization of nanowire-based devices. In this work we investigate the growth regimes and electrical properties of MBE-grown p- and n-type gallium phosphide nanowires doped with Be and Si respectively. Electrical conductivity of individual nanowires is quantitatively studied via atomic force microscopy supported with numerical analysis. Based on conductivity measurements, we provide growth strategies for achieving the doping level up to 5E18 and 2E19 $cm^{-3}$ for GaP:Si and GaP:Be nanowires respectively, which is high enough to be demanded for technological applications.

This paper describes different growth modes of AlN layers on micro-cone patterned c-sapphire substrates (μ-PSSs) using plasma-assisted molecular beam epitaxy. Ordered arrays of AlN nanoprisms and microrods were selectively grown on the tips of μ-PSS's microcones according to a bottom-up formation mechanism using sequential migration enhanced and metal-modulated epitaxy (MME) under metal-rich growth conditions at 820 °C. Transmission electron microscopy revealed structurally perfect AlN regions above the tips of the μ-PSSs, which initiate as inverted nanopyramids with {1011¯} side faces, evolving into hexagonal nanoprisms with orientations of {11¯00} and (0001) for side and top surfaces, respectively. The diameter and height of these ordered hexagonal nanoprisms, which have a 60% probability of nucleating, were about 1 μm. Long-term MME growth of these nanoprisms in both vertical and lateral directions led to the formation of AlN(0001) microrods with a maximum possible diameter of two micrometers and a height of up to 6 μm. Atomic force microscopy revealed a mixed step-flow and 2D nucleation growth mechanism for the flat tops of these AlN nanoprisms and microrods with an average surface roughness of 1–2 monolayers. Micro-Raman spectroscopy demonstrated narrow E2 (high) linewidths of 3.8 and 4.2 cm−1 for essentially stress-free AlN nanoprisms and microrods, respectively.

Efficient doping of semiconductor nanowires remains a major challenge towards the commercialization of nanowire-based devices. In this work we investigate the growth regimes and electrical properties of MBEgrown p- and n-type gallium phosphide nanowires doped with Be and Si, respectively. Electrical conductivity of individual nanowires is quantitatively studied via atomic force microscopy supported with numerical analysis. Based on conductivity measurements, we provide growth strategies for achieving the doping level up to N D =5 & sdot; 10 18 cm -3 and N A =2 & sdot; 10 19 cm -3 for GaP:Si and GaP:Be nanowires respectively, which is high enough for technological applications.

This work demonstrates how to create the structures Au/GaAs with perfect on-surface gold nanoclusters. In doing so, used is covering the GaAs substrate with chemically stable atomic monolayers of sulphur to prevent subsequently a chemical reaction of Au with GaAs. The structures Au/S/GaAs with monolayers of chemisorbed sulphur atoms are fabricated, characterized and studied by polarized reflection spectroscopy. The anisotropy of on-surface gold nanoclusters is established, and the anisotropic plasmons localized in Au clusters are investigated using the spectra of polarized reflection and interpreted theoretically.

Triboelectric generation during the friction of the boron doped diamond probe on the p-doped silicon surface with a native oxide layer was studied. Triboelectric generation was detected at the probe loading force higher than 1 mu N leading to the modification of the studied surface. Triboelectric current density reached value of 4104 A/m2. Removal of the native oxide layer confirmed the tribo-tunneling mechanism of the electric current generation. Increase in the triboelectric current by the high loading force was explained by the increase in the contact area and the generation of the dangling bonds during the friction.

The elastic deformations in the conical nanowires are considered. An analytical expression was obtained for the distribution of elastic deformations along the length of the conical nanowire. It was found that at certain cone angles in nanowire there is an extended area of sufficiently high deformations comparable or even large than the deformation at the base of the nanowire. So, for example, when bending the conical (conical coefficient a=-0.7) nanowire with length L=1 μm and radius R=50 nm by Delta z=200 nm, the maximum deformation values are εxx,max=8%, while more than 95% of the nanowire is deformed by >3%. Keywords: nanowires, elastic deformations, conical nanowires, Young's modulus.

The generation of triboelectric current during friction of diamond probes on the surface of p-Si substrates with a native oxide layer was studied. The choice of probes with different doping, as well as substrates with different surface orientations, made it possible to establish the determining influence of the probe-surface work functions difference on the direction and value of the triboelectric current. The generation of triboelectric current occurs due to the tunneling of non-equilibrium charge carriers resulting from the chemical bonds breaking during friction. Under illumination conditions, an increase in the triboelectric current was observed, as well as the photocurrent appearance due to the charge carriers separation in the space charge region.

The paper reports on heterostructures for mid-ultraviolet (UVC) emitters with multiple (up to 400 periods) and single two-dimensional (2D)-GaN/AlN quantum disks/quantum wells with a nominal thickness below the critical thickness of ~2 monolayers (MLs) characterizing the transition of the 2D growth mode to 3D.The structures were grown by plasma-assisted molecular beam epitaxy (PA MBE) using low growth temperatures (~690C) in a wide range of gallium and activated nitrogen flux ratios Ga/N2* = 0.6  2.2 on various AlN/csapphire templates fabricated either by PA MBE or MOCVD.This made it possible to vary the surface topography from a 3D type under nitrogen-rich conditions to various types of 2D topographies in the structures grown under metal(Ga)-rich conditions.The absence of a Stranski-Krastanov transition in the latter structures was confirmed by a streaky RHEED pattern throughout the growth of QWs and barrier layers.The growth runs were monitored also by multi-beam optical stress sensor, which revealed an unusual stress relaxation in the ML-thick GaN/AlN heterostructures.Structural properties of GaN/AlN heterostructures were studied using X-ray diffraction analysis, including measurement of X-ray reflectance curves, atomic force microscopy, and high-resolution transmission microscopy.The results of these studies, together with the measurements of photoluminescence spectra, both cw and time-resolved, made it possible to suggest the formation of twodimensional GaN quantum disks with a thickness of either 1 or 2 ML and different lateral sizes on the stepped surface of the AlN barrier layers, which can lead to effective carrier localization.Moreover, we demonstrate a unique functional property of these atomically thin QW to maintain stable excitons, resulting in a particularly high radiation yield at room temperature.As a result, the emission energy (wavelength) from GaN/AlN 400QW structures could be varied from 5.21 eV (238 nm) to 4.68 eV (265 nm) and was connected with a simultaneous increased of charge carrier localization.Using electron-beam pumping with a plasma cathode ferroelectric electron gun ensuring a maximum pulse current of 2 A at an electron energy of 12.5 keV, a maximum output optical power of 50 W was achieved for the 265 nm structure, while the structure emitting at 238 nm demonstrated a power of 10 W, as shown in Fig. 1.In addition, we discussed the optical properties of cylindrical nanorods with diameters from 50 to 5000 nm, fabricated by the topdown technology from ML-thick GaN/AlN single QWs using a combination of wet and reactive ion etching.Photoluminescence measurements in an ultra-small QW region enclosed in a nanorod revealed narrow lines of individual excitons localized on potential fluctuations attributed to GaN quantum nano-disks 2-3 MLs high, which appear in a QW with an nominal thickness of 1.5 ML.A model that takes into account dark and bright exciton states was used to explain the features in the PL spectra, including their behavior with increasing temperature.This research was funded by

The principal role of chemical passivation of GaAs surface in the formation on it of oriented anisotropic nanoclusters of gold is discussed. The nanoclusters are fabricated by thermal annealing of a gold film deposited onto GaAs(001) surface passivated as a preliminary by a monolayer of nitrogen or sulfur atoms. These atoms, bonded chemically to gallium atoms of the crystal surface, form a crystal lattice and prevent the chemical interaction of Au with GaAs. As a result of annealing, the arrays of anisotropic (elongated) nanoclusters of chemically pure Au oriented preferably in crystal [11̅0] direction are formed on passivated GaAs(001) surface. The presence of strong anisotropy and orientation of Au clusters on passivated GaAs surfaces is established by the methods of probe diagnostics and of optical reflectance anisotropy spectroscopy and polarized reflection spectroscopy. Using an optical model of plasmonic polarizability of elongated Au spheroids, it is shown that the spectral features observed in polarized reflection originate from anisotropic plasmons of Au nanoclusters polarized mainly in direction [11̅0] of crystal.

Van der Waals (vdW) heterostructures are promising fornext-generationtwo-dimensional electronic and optoelectronic devices. The performanceof such devices is completely determined by the properties of theinterface. However, due to a lack of contamination-free fabricationtechniques, obtaining an ideal interface is still a challenge. Meanwhile,the efficiency of photodetectors and solar cells is highly dependenton the charge separation on the interface. Thus, the questions onthe effect of interfacial conditions on a contact type, charge redistribution,and photoluminescence still exist. In this work, the effect of interfacialconditions on the optical and electronic properties of MoSe2/Au heterostructure is studied. The tip of an atomic force microscopeis used to clean the interface and change interfacial conditions.Kelvin probe microscopy revealed that the work function of the MoSe2 monolayer increases by 40 meV, the bilayer by 28 meV, andthe trilayer by 12 meV due to charge redistribution after the cleaning.Micro-photoluminescence (& mu;-PL) investigation shows that thecleaning leads to the fall of photoluminescence intensity of about75% for a monolayer and 60% for a bilayer. Raman spectroscopy indicatesthat the cleaning procedure did not damage the MoSe2 flake.It is shown that the presence of interfacial contamination in vdWheterostructures severely affects its electronic and optical properties.The results of the work are of great importance to vdW device fabrication.

Experimental characterization, analytical growth models, and numerical simulations are combined to define strategies for tailoring doping inside planar GaAs nanowires.

A study is performed of the pinning of the Fermi level on oxidized (110) surfaces of AIII–Sb (GaSb, Ga0.78In0.22As0.18Sb0.82, and Ga0.66Al0.34As0.025Sb0.975) semiconductors. It is shown that the Fermi level is pinned at a distance of 4.65 ± 0.1 eV from the vacuum level. The presence of Sb on the surfaces of photo-oxidized Ga0.78In0.22As0.18Sb0.82 and Ga0.66Al0.34As0.025Sb0.975 is demonstrated. The formation of Sb on the surfaces due to the faster oxidation of Group III elements results in Fermi level pinning at the same distance from the vacuum level in the III–Sb compounds.

Transition metal dichalcogenides (TMDs) are promising for new generation nanophotonics due to their unique optical properties. However, in contrast to direct bandgap TMD monolayers, bulk samples have an indirect bandgap that restricts their application as light emitters. On the other hand, the high refractive index of these materials allows for effective light trapping and the creation of high-Q resonators. In this work, a method for the nanofabrication of microcavities from indirect TMD multilayer flakes, which makes it possible to achieve pronounced resonant photoluminescence enhancement due to the cavity modes, is proposed. Whispering gallery mode (WGM) resonators are fabricated from bulk indirect MoSe2 using resistless scanning probe lithography. A micro-photoluminescence (μ-PL) investigation revealed the WGM spectra of the resonators with an enhancement factor up to 100. The characteristic features of WGMs are clearly seen from the scattering experiments which are in agreement with the results of numerical simulations. It is shown that the PL spectra in the fabricated microcavities are contributed by two mechanisms demonstrating different temperature dependences. The indirect PL, which is quenched with the temperature decrease, and the direct PL which almost does not depend on the temperature. The results of the work show that the suggested approach has great prospects in nanophotonics.

Exciton-polaritons are unique quasiparticles with hybrid properties of an exciton and a photon, opening ways to realize ultrafast strongly nonlinear systems and inversion-free lasers based on Bose-Einstein polariton condensation. However, the real-world applications of the polariton systems are still limited due to the temperature operation and costly fabrication techniques for both exciton materials and photon cavities. 2D perovskites represent one of the most prospective platforms for the realization of strong light-matter coupling since they possess room-temperature exciton states with large oscillator strength and can simultaneously provide planar photon cavities with high field localization due to the huge refractive index of the material. In this work, we demonstrate for the first time the mechanical scanning probe lithography method for the realization of low-cost room-temperature exciton-polariton systems based on the 2D perovskite (PEA)$_2$PbI$_4$ with exciton binding energy exceeding 200 meV. Precisely controlling the lithography parameters, we broadly adjust the exciton-polariton dispersion and radiative losses of polaritonic modes in the range of 0.1 to 0.2 of total optical losses. Our findings represent a versatile approach to the fabrication of planar high-quality perovskite-based photonic cavities supporting the strong light-matter coupling regime for the development of on-chip all-optical active and nonlinear polaritonic devices.