Ternary metal chalcogenide quantum dots (QDs), such as CuInS2, have attracted significant attention due to their lower toxicity compared to binary counterparts containing cadmium or lead, making them promising candidates for biomedical imaging and solar energy applications. The surfactant choice is critical for controlling nanocrystal nucleation, growth kinetics, and functionalization. This directly affects the toxicity and applications of QDs. In this work, we report a synthesis protocol for PVP-capped CuInS2 QDs in an aqueous solution. Using density functional theory (DFT) calculations, we predicted the coordination patterns of PVP on the CuInS2 QDs surface, providing insights into the stabilization mechanism. The synthesized QDs were characterized using TEM, XRD, XPS, and FTIR to assess their morphology, chemical composition, and surface chemistry. The QDs exhibited dual photoluminescence (PL) maxima at 550 nm and 680 nm, attributed to defect-related emissions, making them suitable for cell imaging applications. Cytotoxicity studies and cell imaging experiments demonstrate the excellent biocompatibility and effective staining capabilities of the PVP-capped CuInS2 QDs, highlighting their potential as fluorescent probes for long-term, multicolor cell imaging including two-photon microscopy.

The photoluminescent properties of autoepitaxial layers of indium arsenide are studied using low-temperature Fourier-transform infrared spectroscopy. The structures are grown by the method of chlorine hydride vapour-phase epitaxy on heavily doped n+-InAs substrates. Sulfide passivation of the substrates is carried out in a unimolar aqueous solution of sodium sulfide at room temperature, which leads to the removal of the natural oxide layer and the formation of a sulfur layer protecting the substrate surface. Three separate peaks are detected in the photoluminescence spectra of the structures, measured with a Fourier-transform infrared spectrometer at a temperature of 8 K. The peak with an energy of 415 meV is attributed to a direct interband transition in indium arsenide. The power dependence of the second peak, with an energy of 400 meV, is sublinear, which makes it possible to attribute it to the emission of bound excitons. In the PL line of the third peak with a maximum at an energy of 388 meV, a fine structure with a series of closely spaced peaks is observed, which allows us to attribute this signal to the emission of donor-acceptor pairs. The influence of substrate sulfidization on the quality of InAs epitaxial layers is assessed by comparing the relative area of the PL peak of bound excitons for sulfidized and nonsulfidized structures. It is shown that the decrease in the relative peak area of bound excitons after sulfidization of the substrate is due to a decrease in the number of defects in the autoepitaxial InAs layers.

Multistacked GeSiSn/Si quantum dot (MQD) structures of different compositions were obtained by molecular-beam epitaxy. The elastically strained state of GeSiSn/Si MQD structures was confirmed by the presence of diffraction maxima on X-ray rocking curves. The optical properties of GeSiSn/Si MQD structures were studied by Fourier transform infrared (FTIR) photoluminescence spectroscopy. The structures exhibited photoluminescence peaks in the 0.6-0.8 eV range originating from the QD region. The calculations showed that the observed peaks correspond to the radiative transition between the Delta(4) conduction band in Si and the energy level of heavy holes in the QDs. The peak positions in the PL spectra are in good correlation with the calculation results. It was demonstrated that the transition energy depends strongly on the composition and size of GeSiSn/Si QDs. The p-i-n photodiodes were developed based on the GeSiSn/Si MQD structures. The cutoff wavelength maximum reached the value of 2.65 mu m for Ge0.80Si0.11Sn0.09/Si MQD p-i-n photodiodes.

The study presents an investigation of the optical properties of rectangular -shaped aluminum nanoantenna arrays formed on the surface of an emitting GeSiSn/Si heterostructure with multiple quantum wells. The positions of the localized surface plasmon resonance modes excited along the long ( L ) and short ( S ) sides of the examined nanoantennas are determined utilizing the technique of Fourier -transform infrared reflectance anisotropy spectroscopy. Experimental results demonstrate that both L - and S -modes are located in the near -infrared range, and as the lateral dimensions of the nanoantennas increase, the modes' positions shift towards lower energies with an increase in the intensity of the resonance. The S -mode appears in the spectra as an overlay on the more pronounced L -mode with an intensity an order of magnitude lower. The geometry of the nanoantennas arrays with the resonance position near the photoluminescence peak of Ge 0.84 Si 0.076 Sn 0.084 /Si heterostructures ( E approximate to 0.65 eV) is characterized.

The results of photoluminescence (PL) study of As-doped Cd0.3Hg0.7Te solid solutions layers grown by molecular beam epitaxy on a Si substrate are presented. Analysis of the PL spectra obtained at different temperatures and excitation laser powers allows one to judge the nature of the observed peaks. The activation of arsenic in annealed samples was established, as a result of which small acceptor levels are formed. The effectiveness of arsenic as an acceptor impurity for cadmium-mercury tellurides has been confirmed.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063782624060010

Subject of study. Epitaxial films of Hg0.7Cd0.3Te solid solutions grown by molecular beam epitaxy and doped with arsenic to obtain hole-type conductivity in order to form p-n junctions for the production of infrared photodetector structures are studied. Aim of study. The types and characteristics of defects formed during arsenic doping of epitaxial films of Hg0.7Cd0.3Te solid solutions grown by molecular beam epitaxy and the effect of doping on the level of disorder in the solid solution are determined. Method. Ellipsometry, optical transmittance, photoluminescence, and photoreflectance are used. Main results. The initial material is shown to have high quality in terms of film bulk and surface quality, and the quality was found to improve after two-stage activation thermal annealing. Annealing has been shown to activate the arsenic with the formation of shallow (7-8 meV) acceptor levels. No side defects were found to occur as a result of the introduction of arsenic into the films during growth and annealing. Practicalsignificance. This research demonstrated the effectiveness of doping epitaxial films of Hg0.7Cd0.3Te solid solutions with arsenic as an acceptor impurity in order to produce layers with hole conductivity during the production of photodiode structures. (c) 2024 Optica Publishing Group

A technique has been developed for frequency analysis of the IR reflection spectrum to determine the thickness and order of the layers in the epitaxial structure of silicon carbide. Calculations for the 4H-SiC epitaxial structure have been performed. The method has been shown to be highly sensitive to optical boundaries resulting from a sequential increase in the doping level during the layer growth. Keywords: Silicon carbide, epitaxial layer, IR reflection, spectrum

Photoluminescence (PL) and photoreflectance (PR) spectroscopy were used for the optical study of arsenic doping of HgCdTe grown by molecular beam epitaxy (MBE). Un-doped and arsenic-doped material with cadmium telluride molar fraction x=0.29 grown under similar conditions and subjected to similar types of annealing was studied. The PL spectra of the un-doped material featured signatures of intrinsic defects associated with mercury vacancy, excessive tellurium, and related complexes. In the arsenic-doped material, optical signatures of these defects appeared to be suppressed. After arsenic activation, shallow (7-8meV) acceptor levels were found in the material. These were attributed to the dopant activation, which was confirmed with electrical studies showing p-type conductivity with hole concentration similar to 10(16) cm(-3). The studies showed that the actual pattern of arsenic doping in HgCdTe can be indeed screened by intrinsic defects, which are inherent to MBEgrown HgCdTe and tend to interact with the dopant.

The work demonstrates the use of photomodulation FTIR spectroscopy to study structures containing epitaxial layers of GeSn and GeSiSn in the temperature range of 79-180 K. The photoreflectance method has enabled observation of direct interband transitions, and evaluation of the impact of temperature variation and mechanical strain on their energy values.

The present study employs the FTIR spectroscopy methods, such as polarized transmittance measurements and the reflectance anisotropy spectroscopy technique, to characterize the optical properties of black phosphorus -a layered semiconductor with a narrow band gap. Our results reveal a notable crystal absorption anisotropy within the 0.26-0.42 eV range with strong linear dichroism, wherein a polarization-dependent feature is observed in the reflectance anisotropy spectra with a maximum near 0.33 eV. This feature is believed to be related to a direct interband transition E0, which is permitted for linearly polarized incident radiation along the AC crystal direction and forbidden for the ZZ direction.

We present the results of a temperature-dependent photoluminescence (PL) spectroscopy study on CuInS2 quantum dots (QDs). In order to elucidate the influence of QD size on PL temperature dependence, size-selective precipitation was used to obtain several nanoparticle fractions. Additionally, the nanoparticles’ morphology and chemical composition were studied using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The obtained QDs showed luminescence in the visible–near infrared range. The PL energy, linewidth, and intensity were studied within an 11–300 K interval. For all fractions, a temperature decrease led to a shift in the emission maximum to higher energies and pronounced growth of the PL intensity down to 75–100 K. It was found that for large particle fractions, the PL intensity started to decrease, with temperature decreasing below 75 K, while the PL intensity of small nanoparticles remained stable.

Fourier-transform infrared photoreflectance (PR) spectroscopy was used to study the energy spectrum of InSb/InAs/In(Ga,Al)As/GaAs metamorphic heterostructures with a superlattice waveguide at room temperature (RT). Theoretical calculations in the framework of the eight-band Kane model were performed to obtain a reliable knowledge of the actual energies of the most probable optical transitions. The experimental results were analyzed to determine the influence of the design features and stress balance on the energy spectra of the structures. Photoluminescence studies performed at 11 K and RT, as well as the determination of the internal quantum efficiency of luminescence, enabled us to characterize the emission characteristics of the structures, regardless of their waveguide efficiency. The structure with a 5-nm-thick GaAs insertion within the metamorphic buffer layer exhibited the highest probability of the main optical transition observed in the PR spectra as well as the highest luminescence intensity and quantum efficiency.

Interband photoluminescence was obtained for structures with multiple quantum wells (MQWs) with different content of germanium and tin. Peak position in photoluminescence spectra obtained from the MQW of Ge _0.93-x Si _x Sn _0.07 /Si shifts to the long wavelength region with an increase in the Ge content in the solid solution and is observed in the energy range 0.85-0.68 eV for the germanium content from 30 to 78 % . Thus, the shift of the peak along the wavelength was observed from 1.46 to 1.82 μ m, and the total spectral range of MQW luminescence covered by these structures was 1.3–2.1 μ m. An even more significant shift of the MQW photoluminescence peak to the long-wavelength region was achieved by increasing the tin content. Increasing the fraction of Sn from 7 to 14 % while keeping the 30 % Ge fraction constant led to a shift of the peak from 0.85 to 0.75 eV. A simultaneous increase in the content of both tin and germanium in the solid solution (up to 14 and 79 μ m. A sharp ‘‘red’’ shift in the position of the photoluminescence peak with increasing temperature was discovered and its value reached 50 meV when the sample heating temperature was changed from 11 to 60–80 K. Such a significant shift in the position of the MQW photoluminescence peak is explained within the framework of a model that assumes that at low temperatures, charge carriers are randomly localized on spatial inhomogeneities of the MQW, and as the temperature increases, they are redistributed and transition to a thermodynamically equilibrium state with the lowest energy.

The paper presents the results of studies of InSb/In(Ga,Al)As/GaAs heterostructures using the photoreflectance method. Based on the results of the work, the temperature dependences of the observed transition energies were obtained, the values of the miniband width and spin-orbit splitting were determined.

A new method of reflection anisotropy spectroscopy (RAS) with increased mid-IR efficiency owing to the use of a Fourier transform infrared (FT-IR) spectrometer has been developed. An optical setup was implemented using a photoelastic modulator (PEM) to modulate the direction of linear polarization of the probe beam originating from the Michelson interferometer. An original measurement algorithm was proposed to eliminate the influence of spectral inhomogeneity of the PEM efficiency on the obtained spectra using appropriate calibration. It was shown that to preserve the sign of the RAS signal, it is necessary to use a specialized procedure for phase correction of the interferogram registered by the FT-IR spectrometer. In the visible range, good agreement was confirmed between the obtained reflection anisotropy (RA) spectra of a semiconductor crystal and the results of independent measurements using a conventional diffraction-grating spectrometer–based setup. The RA spectrum of a III–V semiconductor heterostructure in the mid-infrared range (λ up to 8 µm) is demonstrated. Application of the developed FT-IR RAS method to layered black phosphorus has enabled characterization of anisotropic interband transitions in this graphene-like semiconductor crystal.

Thin GaTe films were grown by molecular beam epitaxy (MBE) on GaAs(001) substrates. X-ray powder diffraction confirmed the coexistence of the h- and m-GaTe phases in all grown layers. A quantitative correlation between the MBE growth conditions and the phase composition of the grown films is established, and the upper limit of the MBE growth temperature for thin GaTe/GaAs(001) films is experimentally determined. New data are presented confirming the defect-related origin of the broad emission line with an energy maximum of 1.45–1.46 eV, which dominates the low-temperature photoluminescence spectra of the grown GaTe/GaAs(001) layers.

The use of low-temperature (LT) GaAs layers as dislocation filters in GaAs/Si heterostructures (HSs) was investigated in this study. The effects of intermediate LT-GaAs layers and of the post-growth and cyclic in situ annealing on the structural properties of GaAs/LT-GaAs/GaAs/Si(001) HSs were studied. It was found that the introduction of LT-GaAs layers, in combination with post-growth cyclic annealing, reduced the threading dislocation density down to 5 × 106 cm−2, the root-mean-square roughness of the GaAs surface down to 1.1 nm, and the concentration of non-radiative recombination centers in the near-surface GaAs/Si regions down to the homoepitaxial GaAs level. Possible reasons for the improvement in the quality of near-surface GaAs layers are discussed. On the one hand, the presence of elastic deformations in the GaAs/LT-GaAs system led to dislocation line bending. On the other hand, gallium vacancies, formed in the LT-GaAs layers, diffused into the overlying GaAs layers and led to an increase in the dislocation glide rate. It was demonstrated that the GaAs/Si HSs obtained with these techniques are suitable for growing high-quality light-emitting HSs with self-assembled quantum dots.

The results of studying the photoluminescence of nanoheterostructures with multiple Ge1-x-ySixSny/Si quantum wells grown by molecular beam epitaxy on silicon substrates and annealed at different temperatures are presented. As a result of the annealing of the structures, a multifold increase in the intensity of the luminescence peak close in energy to the optical transitions within the multiple quantum wells is observed. The optimal annealing temperature and duration are determined in terms of the intensity of photoluminescence. The luminescent properties of a series of annealed Ge0.93-xSixSn0.07/Si structures with different Ge compositions are investigated. As a result, a shift of the low-temperature photoluminescence peak towards lower energies with an increase in the fraction of germanium in the alloy composition is shown. Thus, the possibility of controlling the luminescence spectrum of Ge0.93-xSixSn0.07/Si nanoheterostructures in the wavelength range of 1.3 −2.0 µm is demonstrated.

A synthesis protocol of polyvinylpyrrolidone-capped AgInS2 quantum dots in aqueous solution is reported. Nanoparticle morphology and chemical composition were studied by means of TEM, XRD, XPS, and FTIR. The obtained quantum dots were luminescent in the visible range. The photoluminescence intensity dependence on the polyvinylpyrrolidone amount was demonstrated. The wavelength of the emission maximum varied with changing the [Ag]:[In] molar ratio. The temperature dependence of the photoluminescence intensity of the polyvinylpyrrolidone-capped AgInS2 quantum dots was investigated within the temperature range of 11–294 K.