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In-doped ZnO films grown by ultrasonic spray pyrolysis have been studied by means of the scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDS) and X ray diffraction (XRD) methods. The photoluminescence (PL), transmittance and absorbance have been controlled as well. It was shown that the ZnO optical band gap demonstrates the blue high energy shift to 3.31 eV at 300 K and the PL intensity of near band edge (NBE) emission enlarges at In doping 0.5–2.5 at%. Simultaneously, the positions of XRD peaks and their intensities vary insignificantly owing to the difference in the In3+and Zn2+ ionic radii. Meanwhile, intensity decreasing the green PL band confirms the occupation of the zinc vacancies by In ions with the formation of substitutional InZn defects and ZnO crystal quality improving. At higher In contents the new PL band (3.034eV) appears in PL spectra and its peak shifts to lower energy with In content increasing. This PL band was attributed to the emission via the complex defects, formed by Ini interstitial atoms. Simultaneously, the PL intensity and ZnO film crystallinity falling down, the ZnO crystal lattice parameters increase and the ZnO optical band gap demonstrates the red low energy shift. To reveal a nature of the optical transition responsible for the new PL band, PL spectra have been studied in the temperature range 11–290 K. The dependence of the Ini complex defect formation versus In contents in ZnO NC films is analyzed and discussed. The optimal In concentration range to fabricate the ZnO films with high optical parameters has been estimated.

The emission, morphology, structure and chemical composition have been studied in Ag-doped ZnO nanocrystals (NCs) in as-grown state and after aging in ambient air by means of SEM, X-ray diffraction (XRD), photoluminescence (PL) and X-ray photo electronic spectroscopy (XPS) methods. PL spectra of as-grown Ag-doped ZnO NCs include a set of elementary PL bands: near band edge (NBE) emission, green and orange PL bands, as well as Ag related PL bands with the peaks at 2.68 and 2.89 eV. The PL intensity of Ag- related PL bands falls down at aging. Simultaneously, the PL intensity of orange PL band increases. Joint XRD analysis and PL study permit identifying the optical transition connected with the substitutional AgZn defects. At XPS research the variation of AgZn state and the formation of Ag oxide at aging has been revealed. The radiative defect transformations at aging have been analyzed and discussed.

The morphology, structure and emission of Al-doped ZnO nanocrystals (NCs) with the different Al contents (1–4 at.%) were studied by means of the scanning electronic microscopy, energy dispersive X ray spectroscopy, X-ray diffraction and photoluminescence (PL) methods. Ultrasonic spray pyrolysis was applied to obtain the ZnO:Al films. To stimulate the crystallization, the ZnO:Al films were annealed at 400 °C for 4 h in a constant nitrogen flow (8 L/min). It is shown that the Al incorporation in the ZnO films with the concentrations of 2–4 at.% stimulates: the reduction of ZnO:Al grain sizes, decreasing the film crystallinity owing to disordering the ZnO:Al crystal lattice, the change of the surface morphology and increasing the surface roughness. Meanwhile, Al-doping the ZnO films at the concentrations ≤ 2 at.% enlarge significantly the PL intensity of the near band edge emission. Last fact testifies to quality improving the ZnO:Al films. Simultaneously, the PL intensities of green and orange PL bands, connected with the native defects: VZn and Oi, fall down. The ZnO NC films with Al-doping ≤ 2 at.% still keep the planar surface morphology that is important for their applications in electronic device structures.

ZnO nanocrystal (NC) films prepared by ultrasonic spray pyrolysis and doped with Ag have been studied in as-grown and aged states. Photoluminescence (PL) and x-ray photo electronic spectroscopy (XPS) have been used in this study. PL spectra of as-grown ZnO:Ag NCs include a number of PL bands peaking at: 3.18 eV, 2.85 eV, 2.70 eV, 2.50 eV and 2.10 eV. It is revealed that the 2.70 eV and 2.85 eV PL bands are connected with Ag-doping ZnO NCs. PL intensities of the first three PL bands decline at aging, but the PL intensity of the orange PL band increases. This last fact indicates that aging at 300 K is connected with increasing the concentration of oxygen interstitials in ZnO NC films. In XPS research, the variation of substitutional AgZn defects and the formation of Ag-O bounds at aging have been detected. The nature of optical transitions and radiative defects varying at aging have been analyzed and discussed.

Radiative defects, emission and structure of ZnO nanocrystals (NCs) have been studied by means of the scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) and photoluminescence (PL) techniques. ZnO NCs were prepared by etching Zn sheets and annealing at 200–400 °C in ambient air. The NC size and volume of ZnO crystalline phase increase with annealing temperature rising from 200 °C up to 400 °C. Simultaneously, XRD parameters and inter-planar distances in ZnO NCs vary no monotonically: decreasing upon annealing at 200–360 °C and increasing at 400 °C annealing. The PL intensity variation of orange, yellow, green and blue PL bands correlates with the change of XRD parameters. The study of PL band thermal decays, within the range 10–300 K, permits to estimate decay activation energies and to analyze the nature of donors and acceptors responsible for the orange, yellow and green PL bands in ZnO NCs. The electrochemical method allows varying the PL intensity of different PL bands by a controllable way that is interesting for ZnO NC film application in “white” light emitting device structures.

Photoluminescence (PL), its temperature dependence, and SEM images have been applied for the comparative study of the ZnO and ZnO Cu nanocrystals (NCs). NCs were created by the electrochemical (anodization) method with different NC sizes and annealed at 400 °C for 2 hours in ambient air. PL spectra show a near band edge (NBE) emission and three defect-related PL bands in ZnO NCs, and four defect-related PL bands in ZnO Cu NCs. The defect related PL band with the peak at 2.60-2.70 eV is connected with the Cu complexes in ZnO Cu NCs. PL spectra of all PL bands in both NC types were studied in the temperature range 10-300 K. Their integrated PL intensities and the activation energies of PL thermal decays have been estimated. It is shown that the PL intensities of defect related PL bands have been stimulated essentially at doping by the small Cu concentration (2.2 %) in ZnO Cu NCs. It is revealed additionally that the Cu doping leads to decreasing the activation energies of thermal decay for the defect related PL bands in ZnO Cu NCs in comparison with those in ZnO NCs. The physical reason of this effect and the mechanisms of optical transitions for defect related PL bands in ZnO NCs have been discussed. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent conducting Ga-doped ZnO films were grown by ultrasonic spray pyrolysis with the different Ga contents of 1.0–6.5 at. %. The Ga impact on the morphology, crystal structure, photoluminescence (PL), Ga cluster formation, and electrical resistivity of ZnO nanocrystal films has been investigated. ZnO-Ga films are characterized by the hexagonal wurtzite structure with the (002) preferential orientation. It was shown that the PL intensity of near band edge (NBE) emission band A (3.18 eV) enlarges at a Ga doping of 1.0–3.0 at. % together with the decrease in electrical resistivity. Simultaneously, the XRD peaks shift to high values due to the decrease in interplanar distances, and ZnO crystallinity improves. New NBE emission band B (3.08 eV) was detected in the PL spectra of films with the Ga content ≥3.0 at. %. The PL band B was assigned to the optical transitions via Ga-related clusters formed by Ga atoms at higher Ga concentrations. Simultaneously, the 2Θ positions of XRD peaks decrease, owing to the increase in the ZnO crystal lattice parameter, as well as the fall down in the NBE emission intensity and ZnO film crystallinity. To study the Ga ion charge states and Ga cluster formation in the ZnO:Ga films, x-ray photoelectron spectra have been investigated. The optimal Ga concentration in the ZnO films has been estimated.

InAs quantum dots (QDs) embedded in Al0.30Ga0.70As/InGaAs/InGaAlAs/Al0.30Ga0.70As quantum wells (QWs) have been investigated in the as grown state and after thermal annealing at 640 °C or 710 °C for two hours. Two types of QD structures with different InGaAlAs capping layers (In0.15Ga0.85As (#1) and In0.15Al0.4Ga0.45As (#2)) are compared and studied by means of photoluminescence (PL), X-ray diffraction (XRD) and high resolution HR-XRD methods. XRD and HR-XRD techniques are used with the aim to control the quality of crystal structures, as well as the variation of material compositions and elastic strains in QW layers at thermal annealing. The higher PL intensity and lower energy of ground state (GS) emission are detected in the structure with the In0.15Al0.4Ga0.45As capping layer. Thermal annealing leads to the shift of PL spectra into the higher energy range and the value of this shift is more relevant in the structure with the In0.15Ga0.85As capping layer. The variation of GS emission peak versus temperature has been monitored within the range of 10–500 K for as grown and annealed states and is compared with the temperature shrinkage of energy band gap in the InAs and GaAs bulk crystals. It is revealed that the QD composition in #2 is InAs and the efficiency of Ga/Al/In intermixing at thermal annealing in #2 is less than in #1. Thermal decay of the integrated PL intensities has been investigated in studied structures as well. The PL thermal decay 10-fold is revealed for the range of 10–300 K in #1 with the In0.15Ga0.85As capping layer compared with the 5-fold thermal decay in #2 for the In0.15Al0.4Ga0.45As capping layer. Finally the reasons for PL spectrum transformation at annealing, the mechanism of PL thermal decay, and the advantages of QD structures with the In0.15Al0.4Ga0.45As capping layer have been analyzed and discussed.

Photoluminescence (PL), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman scattering have been used for the optical and structural characterization of ZnO nanocrystals (NCs) of various sizes. The samples prepared by an electrochemical method have a size of NCs from the range 60 to 600 nm after a heat treatment for 2 hours at 400 oC in ambient air. The Raman scattering technique presents the several active modes including the surface phonon mode. The Raman intensity increases with decreasing NC size and the Raman spectrum shifts to low energy. Simultaneously the X-ray diffraction diagrams present a small shift of XRD peaks that testifies on a change in the lattice parameters in ZnO NCs with decreasing NC size. Photoluminescence spectra show a free exciton and defect-related emission. The intensity stimulation of exciton-related PL bands with NC size decreasing up to 60 nm is attributed to the realization of the week confinement and the exciton-light coupling with the formation of polariton in small size of ZnO NCs. The numerical calculation of recombination times in the frame of this model has confirmed the presented explanation.

Photoluminescence (PL) of InAs quantum dots (QDs) embedded in the Al0.30Ga0.70As/In0.15Ga0.85As/InGaAlAs/GaAs quantum wells (QWs) have been investigated in the temperature range of 10–500 K for as grown samples and after thermal annealing at 640 °C or 710 °C for two hours. QD samples with the different InAlGaAs capping layers (GaAs or Al0.1Ga0.75 In0.15As) have been studied. The higher PL intensity and lower energy of ground state (GS) emission are detected in the structure with Al0.1Ga0.75 In0.15As layer. This QD structure in as grown state has smaller PL thermal decay in comparison with this parameter in the structure with GaAs layer. The variation of PL intensities and peak positions at annealing are more essential in the QD structure with Al0.1Ga0.75 In0.15As capping layer, apparently, due to more efficient Ga(Al)/In intermixing.

This paper presents briefly the history of emission study in Si quantum dots (QDs) in the last two decades. Stable light emission of Si QDs and NCs was observed in the spectral ranges: blue, green, orange, red and infrared. These PL bands were attributed to the exciton recombination in Si QDs, to the carrier recombination through defects inside of Si NCs or via oxide related defects at the Si/SiO x interface. The analysis of recombination transitions and the different ways of the emission stimulation in Si QD structures, related to the element variation for the passivation of surface dangling bonds, as well as the plasmon induced emission and rare earth impurity activation, have been presented. The different applications of Si QD structures in quantum electronics, such as: Si QD light emitting diodes, Si QD single union and tandem solar cells, Si QD memory structures, Si QD based one electron devices and double QD structures for spintronics, have been discussed as well. Note the significant worldwide interest directed toward the silicon-based light emission for integrated optoelectronics is related to the complementary metal-oxide semiconductor compatibility and the possibility to be monolithically integrated with very large scale integrated (VLSI) circuits. The different features of poly-, micro- and nanocrystalline silicon for solar cells, that is a mixture of both amorphous and crystalline phases, such as the silicon NCs or QDs embedded in a α-Si:H matrix, as well as the thin film 2-cell or 3-cell tandem solar cells based on Si QD structures have been discussed as well. Silicon NC based structures for non-volatile memory purposes, the recent studies of Si QD base single electron devices and the single electron occupation of QDs as an important component to the measurement and manipulation of spins in quantum information processing have been analyzed as well.

The photoluminescence (PL), its temperature dependence and X-ray diffraction (XRD) have been studied in MBE grown GaAs/AlGaAs/InGaAs/AlGaAs /GaAs quantum wells (QWs) with InAs quantum dots embedded in the center of InGaAs layer in the freshly prepared states and after the thermal treatments during 2 hours at 640 or 710 °C. The structures contained two buffer (Al0.3Ga0.7As/In0.15Ga0.85As) and two capping (In0.15Ga0.85As / Al0.3Ga0.7As) layers. The temperature dependences of PL peak positions have been analyzed in the temperature range 10-500K with the aim to investigate the QD composition and its variation at thermal annealing. The experimental parameters of the temperature variation of PL peak position in the InAs QDs have been compared with the known one for the bulk InAs crystals and the QD composition variation due to Ga/Al/In inter diffusion at thermal treatments has been detected. XRD have been studied with the aim to estimate the capping/buffer layer compositions in the different QW layers in freshly prepared state and after the thermal annealing. The obtained emission and XRD data and their dependences on the thermal treatment have been analyzed and discussed.

This paper presents briefly the history of emission study in Si quantum dots (QDs) in the last two decades. Stable light emission of Si QDs and NCs was observed in the spectral ranges: blue, green, orange, red and infrared. The analysis of recombination transitions and the different ways of the emission stimulation in Si QD structures, related to the element variation for the passivation of surface dangling bonds, as well as the plasmon induced emission and rare earth impurity activation, have been discussed. The different applications of Si QD structures in quantum electronics, such as: Si QD light emitting diodes, Si QD single union and tandem solar cells, Si QD memory structures, Si QD based one electron devices and double QD structures for spintronics, have been presented. The different features of poly-, micro- and nanocrystalline silicon for solar cells, that is a mixture of both amorphous and crystalline phases, such as the silicon nanocrystals (NCs) or QDs embedded in a α-Si:H matrix, as well as the thin film 2-cell or 3-cell tandem solar cells based on Si QD structures have been discussed as well. Silicon NC based structures for non-volatile memory purposes, the recent studies of Si QD base single electron devices and the single-electron occupation of QDs as an important component to the measurement and manipulation of spins in quantum information processing have been analyzed as well.

The photoluminescence (PL), its temperature dependence and X ray diffraction (XRD) have been studied in the symmetric In 0.15 Ga 0.85 As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), obtained with the variation of QD growth temperatures (470–535 °C). The increase of QD growth temperatures is accompanied by the enlargement of QD lateral sizes (from 12 up to 28 nm) and by the shift non monotonously of PL peak positions. The fitting procedure has been applied for the analysis of the temperature dependence of PL peaks. The obtained fitting parameters testify that in studied QD structures the process of In/Ga interdiffusion between QDs and capping/buffer layers takes place partially. However this process cannot explain the difference in PL peak positions. The XRD study has revealed the high intensity peaks which correspond to the diffraction of X ray line from the (2 0 0) crystal planes of cubic GaAs. It was shown that the XRD peak is the superposition of the diffraction from the GaAs substrate and GaAs layers of quantum wells. The position of diffraction peaks related to the cubic GaAs substrate coincides with the very well-known XRD data for the bulk GaAs. At the same time the (2 0 0) diffraction peaks in GaAs epitaxial layers shift to the high angles in comparison with the bulk GaAs, testifying the compression strain in GaAs epitaxial layers. The value of elastic strain has been estimated. The minimum of elastic strain is detected in the structure with QD grown at 510 °C that manifests itself by the higher QD PL intensity and lower PL peak energy.

The paper presents the transformation of photoluminescence (PL) spectra of nonconjugated and bioconjugated core/shell CdSe/ZnS QDs covered by PEG polymer at the aging in ambient air. Studied QDs are characterized by the sizes: (i) 3.6–4.0 nm and color emission with the maxima at 560–565 nm (2.19–2.25 eV) and (ii) 5.2–5.3 nm and with emission at 605–610 nm (2.02–2.08 eV). The part of 565 nm CdSe/ZnS QDs has been bioconjugated to the mouse anti PSA (Prostate-Specific Antigen) antibodies and the part of 605 nm QDs has been bioconjugated to the antihuman IL10 (Interleukin 10) antibodies using the commercially available 565 nm and 605 nm QD conjugation kits. It is revealed that the aging process in ambient air has the very strong impact on PL spectra of nonconjugated core/shell CdSe/ZnS QDs covered with PEG polymer. The aging process relates to the polymer modification in ambient air that is accompanied by the three effects: (i) polymer transparency increasing for the emission of CdSe cores (2.03 or 2.20 eV), (ii) the intensity stimulation of high energy PL bands (2.37, 2.73 and 3.06 eV) related to the interface states at the ZnS/PEG polymer interface and (iii) the elastic strain modification in QD systems. The concentration of interface states at the ZnS/polymer interface increases at the aging of PEG polymer in ambient air.

The paper presents the results of SiC nanocrystal (NC) characterization using the photoluminescence (PL), its temperature dependence and X-ray diffraction (XRD) techniques. It is revealed that original n-type 6H-SiC wafers and porous 6H-SiC layers consisted inclusions of 2H-SiC, 4H-SiC, and 8H-SiC polytypes. The photoluminescence study has shown that in porous SiC layers the emission intensity of high energy PL bands enlarges. Temperature dependences of high energy PL bands testify that these PL bands related to excitons bounded at nitrogen donors in different SiC polytypes. The PL intensity enhancement of donor-bound exciton PL bands in the big size (50-250nm) SiC nanocrystals has been attributed to the realization of exciton weak confinement and exciton-polariton coupling in SiC nanocrystals. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The photoluminescence (PL) of nonconjugated and bioconjugated core-shell CdSe/ZnS quantum dots (QDs) has been discussed in this paper. Commercial CdSe/ZnS QDs with the size of 3.6-4.0 nm covered by polymer with emission at 560-565 nm (2.19-2.22 eV) have been used. The QD bioconjugation is performed with the mouse anti PSA (Prostate-Specific Antigen) antibody (mab). PL spectra of nonconjugated QDs are characterized by a superposition of PL bands related to exciton emission in the CdSe core (2.19-2.22 eV) and to hot electron-hole emission via surface states (2.37, 2.73 and 3.06 eV) at the CdSe/ZnS or ZnS/polymer interfaces. The PL spectrum of bioconjugated QDs has changed dramatically, with essential decreasing of the hot electron-hole recombination flow via interface states. This effect is explained on the base of re-charging of QD interface states at the bioconjugation. It is shown that the CdSe/ZnS QDs with interface states are very promising for the study of bioconjugation effects to antibodies (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper presents the results of PL spectrum study for Si nano-clusters in amorphous silicon matrix. The hydrogenated amorphous Si layers were prepared by the hot-wire CVD method on glass substrates. The layers were deposited at different wafer temperatures 280, 360, 420 and 460 °C and at one filament temperature of 1650 °C. The joint analysis of PL and X-ray diffraction spectra in dependence on the technological conditions and on different sizes of Si nano-clusters has been done. The mechanisms of PL are discussed as well.

This paper presents the results of PL spectrum studies for Si nano-crystallites embedded in amorphous silicon matrix. Investigated layers were deposited by the hot-wire CVD method on glass substrates at the wafer temperature 300°C and different filament temperatures from the range 1650-1950°C. It was shown that variation of temperatures of filament (hot-wire) allows to produce the films with desirable parameters. Using of X-ray diffraction and photoluminescence methods the correlation between some photoluminescence bands and the sizes of Si nano-crystallites as well as the amorphous phase volume was shown. The nature of light emission is discussed.

This paper presents the analysis of photoluminescence (PL) and Raman scattering spectra of CdSe/ZnS quantum dots (QDs) covered by the amine (NH2)-derivatized PEG polymer nonconjugated and bioconjugated to ovarian cancer (OC 125) antibodies and localized on the Si substrate. Commercial CdSe/ZnS QDs used are characterized by the color emission with the maxima at 525 nm (2.36 eV) and 605 nm (2.05 eV) at 300 K. PL spectra of nonconjugated 525 nm QDs can be presented as a superposition of PL bands related to exciton emission in CdSe cores (2.36 eV) and to hot electron-hole emission via interface states (2.04, 2.20, 2.71 and 3.06 eV) localized at the CdSe/ZnS or ZnS/polymer interfaces. It is revealed that PL spectra of bioconjugated 525 nm QDs have changed dramatically with essential decreasing the hot electron-hole recombination flow via interface states. This effect is explained on the base of the model deals with re-charging QD interface states at the bioconjugation to OC125 antibodies. Raman scattering spectra of bioconjugated QDs can be presented as a superposition of Raman lines related to the silicon substrate. Raman lines deal with the vibration of COH, CH and OH groups of PEG polymer, which covered QDs, were detected additionally in nonconjugated QDs. It is revealed that the QD bioconjugation to OC 125 antibodies is accompanied by the changes in the intensity of all types of Raman lines. The explanation of details of bioconjugation effects has been proposed and discussed (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The photoluminescence (PL), its power and temperature dependences have been studded for the ensembles of InAs quantum dots (QD) embedded in symmetric In0.15Ga0.85As/GaAs quantum wells prepared at different QD growth temperatures from the range 470–535 °C. The solution of the set of rate equations for exciton dynamics was used to analyze the nature of thermal activation energies of the QD PL quenching. It is revealed three different stages of thermally activated quenching of the QD PL intensity caused by thermal escape of excitons from the In0.15Ga0.85As/GaAs buffer and capping quantum wells (QWs) into the GaAs barrier and from the QDs into the GaAs barrier or into barrier/QW interfaces with their subsequent nonradiative recombination. The variety of activation energies of PL thermal quenching is discussed as well.

This paper presents the analysis of Raman scattering spectra of CdSe/ZnS QDs covered by the amine-derivatized polyethylene glycol (PEG) polymer with and without bioconjugation to bio-molecules: mouse ovarian cancer (OC 125) antibodies (mab). Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 525 nm (2.36 eV) at 300K. Samples of CdSe/ZnS QDs (bio-conjugated and non -conjugated) in the form of an 5 mm-size spot were dried on a polished surface of crystalline Si substrate to ensure a low level of light scattering background.Raman scattering spectra of non-conjugated QDs can be presented as a superposition of Raman lines: 212.2, 222.5, 308.3, 440.3, 521.0, 618.0, 667.8 943.5, 986.7, cm-1 related to the CdSe core and silicon substrate. The Raman lines 1003.9, 1317.8, 1452.9, 1656.8, 2870.4, 2931.8 and 3059.9 cm-1 deal with the vibration of COH, CH and OH groups of polymer, which covered QDs, were detected additionally. It is revealed that the QD bio-conjugation to the OC 125 antibodies is accompanied with the changes in the intensity of all types of Raman lines: related to the CdSe core, silicon substrate and polymer groups. The explanation of bioconjugation effects has been proposed and discussed.

This paper presents the results of photoluminescence study of core-shell CdSe/ZnS quantum dots (QDs) with radiative interface states in nonconjugated and bioconjugated conditions. PL spectra of nonconjugated QDs are characterized by a superposition of PL bands related to exciton emission in CdSe cores (2.36 eV) and to electron-hole emission via interface states (2.00, 2.75 and 3.04 eV) at the CdSe/ZnS or ZnS/polymer interfaces. The CdSe/ZnS QDs with emission at 525 nm have been conjugated with bio-molecules – mouse ovarian cancer (OC 125) antibodies. It is revealed that PL spectrum of bioconjugated QDs has changed dramatically with essential decreasing of the hot electron-hole recombination flow via interface states. This effect is explained on the base of the model deals with re-charging of QD interface states at the bioconjugation with OC125 antibodies. The nature of interface states and their changes at the QD aging process have been discussed as well.