Temperature Dependence of Photoluminescence from Single and Ensemble InAs/GaAs Quantum Dots

We investigate the temperature dependence of photoluminescence from single and ensemble InAs/GaAs quantum dots systematically. As temperature increases, the exciton emission peak for single quantum dot shows broadening and redshift. For ensemble quantum dots, however, the exciton emission peak shows narrowing and fast redshift. We use a simple steady-state rate equation model to simulate the experimental data of photoluminescence spectra. It is confirmed that carrier-phonon scattering gives the broadening of the exciton emission peak in single quantum dots while the effects of carrier thermal escape and retrapping play an important role in the narrowing and fast redshift of the exciton emission peak in ensemble quantum dots.     

Photoluminescence studies in bulk gallium antimonide

A detailed analysis of Photo Luminescence spectroscopy (PL) on undoped and Te- and Zn-doped samples of high-quality GaSb is presented. Temperature variations of PL peak position and intensity have been used to find the origin of various transitions. The PL peaks of undoped samples have been assigned to unintentional impurities, native defects and excitons bound to the defect. The zinc- and tellurium-related peaks have been identified and the effect of doping concentration on their position and PL efficiency have been studied.     

Photoluminescence Characterization of Silicon Nanoparticles Hybridized Europium Complex

A europium complex Eu (DBM)3 TPPO (Eu tris(benzoylmethide)-(triphenylphosphine oxide)) and silicon nanoparticles have been hybridized.The hybridization can evidently change the photoluminescence (PL) characteristics of the Eu complex in the following aspects:under an excitation of 390nm,the intensity of the PL peak at 611nm due to the ^5Du-^7F2 transition of the Eu^3 ions has been increased by 30%,and thc integrated PL intensity in the visible range has been increased by nearly 3 times;the PL excitation efficiency beyond 440nm has been improved cvidently;the peak in the PL excitation spectrum shifts from 408nm to 388nm,and the PL decay time decreases from 2.07 to 0.96μs,The experimental results indicatde that in the PL process,the photoexcited energy may transfer from the silicon nanoparticlcs to the Eu^3 ions.     

Photoluminescence study of manganese in AlSb

We have investigated Czochralski-grown manganese-doped AlSb by low-temperature photoluminescence spectroscopy. Discrete donor-acceptor pair lines are resolved, which involve the Mn acceptor. A Mn acceptor binding energy (E _A =92±5 meV) is deduced from the donor-acceptor pair luminescence.     

Temperature-dependent photoluminescence of Mg-doped CdS nanowires

Sixfold symmetrical Mg-doped CdS nanowires have been fabricated through high temperature vapor-solid deposition process. The experimental study of the temperature-dependent photoluminescence properties of the Mg-doped CdS nanowires from 10 K to 300 K was reported. The Mg-doped CdS nanowires show intensive cyan-color light emission properties from 10 K to 200 K. The results indicate that there are two strong peaks situated at the green emission (at 528 nm) and red emission (at 655-695 nm), and two weak UV emission peaks at 378 nm and 417 nm, respectively. The ratio of green to red emission was decreased with temperature increased. When the temperature is above 200 K, the orange-color light was observed from the Mg-doped CdS nanowires. Therefore, the intensive emission properties of the Mg-doped CdS nanowires have a great potential for use as nanoscaled optoelectronic intensive light emitters under different temperature.     

Inter-Layer Energy Transfer through Wetting-Layer States in Bi-layer InGaAs/GaAs Quantum-Dot Structures with Thick Barriers

The inter-layer energy transfer in a bi-layer InGaAs/GaAs quantum dot structure with a thick GaAs barrier is studied using temperature-dependent photoluminescence. The abnormal enhancement of the photoluminescence of the QDs in the layer with a larger amount of coverage considering the resonant Forster energy transfer between the at 110K is observed, which can be explained by wetting layer states at elevated temperatures.     

Photoluminescence from electron irradiated ZnO

Photoluminescence of ZnO ceramics irradiated with electrons of 0.8 MeV and 2.6 MeV energy has been investigated. The irradiated samples have been annealed in air at temperatures up to 1100° C. Irradiation causes quenching of the PL green band and as a consequence a peak at 470 nm emerges. Results indicate that part of the quenching can be attributed to damage in the oxygen sublattice.     

Photoluminescence of Si nanocrystals under selective excitation

Photoluminescence of Si nanocrystals passivated by different alkanes (hexane, octane, and tridecane) was studied at room temperature. It is shown that the emission band shape is not affected by the length of the carbon chain in the alkanes used for passivation. A pronounced fine structure of the photoluminescence band consisting of peaks separated by 150-160 meV was observed under resonant excitation. The structure is interpreted by predominant contribution from Si nanocrystal groups with particular stable size/shape existing in addition to the previously reported nanocrystals with “magic” numbers of Si atoms. The contribution of these stable nanocrystals is revealed using selective resonant photoexcitation to the higher energy states in the discrete energy spectrum of such nanocrystals.     

Single-Photon Emission from a Single InAs Quantum Dot

Excitation power-dependent micro-photoluminescence spectra and photon-correlation measurement are used to study the optical properties and photon statistics of single InAs quantum dots. Exciton and biexciton emissions, whose photoluminescence intensities have linear and quadratic excitation power dependences, respectively, are identified. Under pulsed laser excitation, the zero time delay peak of second order correlation function corresponding to exciton emission is well suppressed, which is a clear evidence of single photon emission.     

Temperature-dependent photoluminescence from bicrystalline ZnS (core/shell) nanocables

The experimental study of the temperature-dependent photoluminescence properties of bicrystalline ZnS core/shell nanocables under 10 K to 300 K was reported. The results show that there are two distinct peaks situated at the UV (about 372.6 nm) and green (about 500 nm) regions, respectively, and one blue-shoulder band (about 465 nm) superimposed between them for all spectra. The UV peak shows an obvious redshift with increasing temperature. The analyses of Gaussian-fitted the blue-shoulder band and the green bands from 10 K to 300 K reveal that all spectra can be well fitted by three Gaussian peaks: blue peak (B, about 2.67 eV), two green peaks (G1, about 2.47 eV and G2, about 2.42 eV). With increasing temperature, the blue band shows blueshift. The green bands show anomalous transition: green band G1 shows blueshift-redshift transition and green band G2 shows redshift-blueshift. The origins of these bands and their temperature-dependent shifts are explained based on defect levels and strong carrier localization effect at the defect levels in addition to band-gap shrinkage.     

Photoluminescence study of acceptor-carbon complexes in irradiated silicon: Aluminum-related defects

The paper reports photoluminescence studies on two defects, All at 0.836 eV and Al2 at 0.886 eV, created by aluminum complexing in irradiated silicon after thermal annealing at around 300 °C. The optical data include perturbation spectroscopy (uniaxial stress and magnetic field) revealing rhombic I (Al1) or monoclinic I (Al2) site symmetry of the defects. For Al a carbon isotope shift in the no-phonon line is detected. These and other data are discussed in conjunction with Ga- or B-related defects exhibiting similar optical features.     

Photoluminescence of Electrospun Poly-Methyl-Methacrylate:Alq3 Composite Fibres

Tris（8-hydroxyquinoline） aluminium doped poly-methyl-methacrylate （PMMA：Alq3） composite nanofibres are fabricated by electrospinning. The morphology of fibres is characterized by scanning electron microscopy. The photoluminescence of a series of the nanofibres with various contents of Alq3 to PMMA is investigated. UVvisible absorption and the PL spectra analysis are employed to analyse the interaction between the polymer and the luminescent molecule.     

Strain Effect on Photoluminescences from InGaN MQWs with Different Barriers Grown by MOCVD

InGaN/GaN MQWs, InGaN/AlGaN MQWs and InGaN/AlInGaN MQWs are grown on （0001） sapphire substrates by MOCVD. Membrane samples are fabricated by laser lift-off technology. The photoluminescence spec-ra of membranes show a blue shift of peak positions in InGaN/GaN MQWs, a red shift of peak positions in InGaN/AlGaN MQWs and no shift of peak positions in InGaN/AIlnGaN MQWs from those of samples with substrates. Different changes in Raman scattering spectra and HR-XRD （0002） profile of InGaN/AlInGaN MQWs, from those of InGaN/GaN MQWs and InGaN/AlGaN MQWs, are observed. The fact that the strain changes differently among InGaN MQWs with different barriers is confirmed. The AIlnGaN barrier could adjust the residual stress for the least strain-induced electric field in InGaN/AIlnGaN quantum wells.     

Photoluminescence Property of Co3O4 Nanowires

Co3O4 nanowire arrays are fabricated by electrodeposition with following heat-treatment in atmosphere ambient. Photoluminescence is investigated at 295K. In the experiment, when increasing the excitation light wavelength from 260 nm to 360 nm, two kinds of emissions corresponding to the increasing excitation light wavelength are observed. One of them alters the excited emission position, another keeps its emission position. The distinct behaviour of excited emissions related to the increasing excitation wavelength indicates that the mechanism of them must be different. According to the experimental comparison and first-principle calculation, the two kinds of emissions are discussed.     

Photoluminescence of ZnO and Mn-Doped ZnO Polycrystalline Films Prepared by Plasma Enhanced Chemical Vapour Deposition

ZnO and Mn-doped ZnO polycrystalline films are prepared by plasma enhanced chemical vapour deposition at low temperature （220℃）, and room-temperature photoluminescence of the films is systematically investigated. Analysis from x-ray diffraction reveals that a11 the prepared films exhibit the wurtzite structure of ZnO, and Mndoping does not induce the second phase in the films. X-ray photoelectron spectroscopy confirms the existence of Mn^2＋ ions in the films rather than metalic Mn or Mn^4＋ ions. The emission efficiency of the ZnO film is found to be dependent strongly on the post-treatment and to degrade with increasing temperature either in air or in nitrogen ambient. However, the enhancement of near band edge （NBE） emission is observed after hydrogenation in ammonia plasma, companied with more defect-related emission. Furthermore, the position of NBE shifts towards to high-energy legion with increasing Mn-doped concentration due to Mn incorporation into ZnO lattice.     

Reversible Carriers Tunnelling in Asymmetric Coupled InGaN/GaN Quantum Wells

Temperature-dependent photoluminescence （PL） and time resolved photoluminescence （TRPL） are performed to study the PL characteristics and carrier transfer mechanism in asymmetric coupled InGaN/GaN multiple quantum wells （AS-QWs）. Our results reveal that abnormal carrier tunnelling from the wide quantum well （WQW） to the narrow quantum well （NQW） is observed at temperature higher than about lOOK, while a normal carrier tunnelling from the NQW to the WQW is observed at temperature lower than 100 K. The reversible carrier tunnelling between the two Q Ws makes it possible to explore new types of temperature sensitive emission devices. It is shown that PL internal quantum efficiency （IQE） of the NQW is enhanced to about 46% due to the assistant of the abnormal carrier tunnelling.     

Impurity Activation in MBE-Grown As-Doped HgCdTe by Modulated Photoluminescence Spectra

Modulated photoluminescence spectra have been performed to investigate the impurity activation in MBE-grown As-doped Hg1-xCdxTe （x ≈ 0.3）. The results show that the doped As mainly acting as donors in the as-grown samples can be fully activated as AsTe by two-stage anneals of 285℃/16 h ＋ 240℃/48h, of which the ionization energy has been determined to be about lO.5 meV, slightly smaller than that of intrinsic VHg （about 14.5 meV）. However, the higher activation temperature （e.g. 400℃） at the first-stage can produce large numbers of excessive VHg and seriously deteriorate the quality of epilayers. This couM give a brief guideline for preparing extrinsic p-type HgCdTe materials or devices.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Novel Na3Y9O3（BO3）8：Tb^3＋ Phosphor

The novel vacuum ultraviolet （VUV） excited Na3 Y9O3 （BO3）8：Tb^3＋ （NYOB：Tb^3＋） green phosphor is prepared. Strong VUV photoluminescence and high quenching concentration of Tb^3＋ （20 wt%） are observed in NYOB： Tb^3＋ and the strong emission are correlated with the unique layer-type structure of NYOB. All the characteristic 4 f - 5d transitions of Tb^3＋ and the host absorption band in VUV region are identified in the excitation spectrum. Based on the results, the energy levels scheme of Tb^3＋ in NYOB：Tb^3＋ is first established. This newly developed NYOB：Tb^3＋ phosphor shows excellent optical properties when compared with the commercial Zn2SiO4：Mn^2＋ and would be a potential VUV-excited green phosphor.     

Single-Photon Emission at Liquid Nitrogen Temperature from a Single InAs/GaAs Quantum Dot

We report on the single photon emission from single InAs/GaAs self-assembled Stranski-Krastanow quantum dots up to 80 K under pulsed and continuous wave excitations. At temperature 8OK, the second-order correlation function at zero time delay, g^（2）（0）, is measured to be 0.422 for pulsed excitation. At the same temperature under continuous wave excitation, the photon antibunching effect is observed. Thus, our experimental results demonstrate a promising potential application of self-assembled InAs/GaAs quantum dots in single photon emission at liquid nitrogen temperature.     

Indium-incorporation-induced transformation of optical, photoluminescence and lasing properties of InGaN epilayers

A comparative combined study of photoluminescence (PL), PL kinetics, stimulated emission (SE) and photoreflectance (PR) properties in In_xGa_1−xN epilayers is carried out in the composition range 0≤x≤0.19. In-incorporation up to 4% leads to the sufficient longer radiative recombination decay time due to the decrease in non-radiative recombination channels, which are peculiar to GaN, and band-to-band optical transitions predominate the spontaneous PL spectrum. Further In-incorporation (x>4%) leads to the localization of carriers and/or excitons at band-tails in the In-rich areas. Correlation between the position of dominant low-energy PR oscillation due to the main band gap and SE peak position shows that band-to-band transitions are responsible for lasing and dominate the PL spectrum in all highly pumped In_xGa_1−xN samples.