Infrared Luminescence Bands Research Articles

Optical Absorption of Excimer Laser‐Induced Dichlorine Monoxide in Silica Glass and Excitation of Singlet Oxygen Luminescence by Energy Transfer from Chlorine Molecules

An optical absorption (OA) band of interstitial dichlorine monoxide molecules with peak at 4.7 eV and halfwidth 0.94 eV is identified in F2 laser‐irradiated (ħω = 7.9 eV) synthetic silica glass bearing both interstitial O2 and Cl2 molecules. Alongside with intrinsic defects, this OA band can contribute to solarization of silica glasses produced from SiCl4. Although only the formation of ClClO is confirmed by its Raman signature, its structural isomer ClOCl may also contribute to this induced OA band. Thermal destruction of this band between 300 °C and 400 °C almost completely restores the preirradiation concentration of interstitial Cl2. An additional weak OA band at 3.5 eV is tentatively assigned to ClO2 molecules. The strongly forbidden 1272 nm infrared luminescence band of excited singlet O2 molecules is observed at 3–3.5 eV excitation, demonstrating an energy transfer process from photoexcited triplet Cl2 to O2. The energy transfer most likely occurs between Cl2 and O2 interstitial molecules located in neighboring nanosized interstitial voids in the structure of SiO2 glass network.

Light-emitting defects formed in GeO/SiO2 heterostructures with assistance of swift heavy ions

Germanium suboxide films and GeO/SiO2 multilayer heterostructures deposited onto Si(001) substrates using evaporation in high vacuum were modified using irradiation of 167 MeV Xe+26 ions with fluences varying from 1011 to 1013 cm−2. According to Raman spectroscopy data, the swift heavy ion irradiation does not lead to the expected decomposition of germanium suboxide in germanium nanoclusters and GeO2. Infrared absorption spectroscopy measurements show that under irradiation the GeO/SiO2 layers were intermixed with formation of Ge-O-Si bonds. We report strong photoluminescence in the visible range at room temperature, which is most probably due to Ge-related defect-induced radiative transitions. Moreover, a new infrared luminescence band (~0.8 eV) was observed in irradiated structures, which can be related to defects or defects complexes in GexSiyO2 glass.

Infrared luminescence in Bi-doped Ge–S and As–Ge–S chalcogenide glasses and fibers

Experimental and theoretical studies of spectral properties of chalcogenide Ge-S and As-Ge-S glasses and fibers are performed. A broad infrared (IR) luminescence band which covers the 1.2-2.3~$\mu$m range with a lifetime about 6~$\mu$s is discovered. Similar luminescence is also present in optical fibers drawn from these glasses. Arsenic addition to Ge-S glass significantly enhances both its resistance to crystallization and the intensity of the luminescence. Computer modeling of Bi-related centers shows that interstitial Bi$^+$ ions adjacent to negatively charged S vacancies are most likely responsible for the IR luminescence.

Electron paramagnetic resonance, optical absorption and photoluminescence properties of Cu2+ ions in ZnO–Bi2O3–B2O3 glasses

Glass of the composition 23B2O3–5ZnO–72Bi2O3–xCuO (where, x=0.0003, 0.0012 and 0.003at%, in excess) were prepared by a melt-quench technique. The effects of the copper ions on the structural and optical properties of ZnO–Bi2O3–B2O3 glass matrix were analyzed using various spectroscopic techniques. The infrared spectra showed the presence of some bands that are assigned to vibrations of Bi–O bonds from BiO6 octahedral units and B–O bonds from BO3 and BO4 units. The electron paramagnetic resonance spectra revealed the presence of Cu2+ ions in the glass structure in an axially distorted octahedral environment. The number of Cu2+ ions participating in resonance and its paramagnetic susceptibility has been evaluated. The UV–vis spectra show a broad absorption band at 785nm and another band at 438nm which are due to d-d transitions of Cu2+ ions. These glasses are found to exhibit visible and near infrared luminescence bands centered at 548 and 652, and 804nm when excited at 400 and 530nm, respectively. The luminescence centers are supposed to be caused by the lower valence state of bismuth, such as Bi2+ and Bi+ ions, generated during in-situ redox reactions.

DNA-modified silicon nanocrystals studied by X-ray luminescence and X-ray absorption spectroscopies: Observation of a strong infra-red luminescence band

Silicon nanocrystals (SiNCs) modified with 18-mer DNA oligonucleotides have been studied by X-ray excited optical luminescence (XEOL) and X-ray absorption spectroscopy (XAS) in photoluminescence yield (PLY) and total electron yield (TEY) modes. Luminescence spectra from the DNA-modified SiNCs under X-ray excitation display distinct differences from simple alkyl terminated SiNCs. The DNA-modified SiNCs show strong luminescence at 540 ± 10 nm under vacuum ultraviolet excitation which is assigned to nitrogen 1s – σ* transitions within the DNA bases. Under excitation at 130 eV the PLY spectra from the same samples show the native nanocrystal ultraviolet emission band is suppressed, and the strongest emission peak is red shifted from 430 ± 10 nm to 489 ± 10 nm which we attribute to base nitrogen 1s transitions. In addition, a strong emission band in the infrared region at 815 ± 10 nm is observed. This clearly resolved strong IR band from the DNA-modified SiNCs may provide a useful luminescence signature in cell-labeling techniques and open up a range of applications for invivo assays.

Controlled oxidative synthesis of Bi nanoparticles and emission centers in bismuth glass nanocomposites for photonic application

Here we demonstrate an oxidative process to control metallic bismuth (Bi 0) nanoparticles (NPs) creation in bismuth glass nanocomposites by using K 2S 2O 8 as oxidant and enhanced transparency of bismuth glasses. Formation of Bi 0 NPs has been monitored by their distinct surface plasmon resonance (SPR) band at 460 nm in the UV–visible absorption spectra. It is further confirmed by the transmission electron microscopy (TEM) images which disclose the formation of spherical Bi 0 NPs whereas the selected area electron diffraction (SAED) pattern reveals their crystalline rhombohedral phase. These glasses are found to exhibit visible and near infrared (NIR) luminescence bands at 630 and 843 nm respectively on excitation at 460 nm of the SPR band. It is realized that the luminescence center of bismuth species is an uncertain issue, however, it is reasonable to consider that the emission band at 630 nm is due to the combination of 2D 5/2 → 4S 3/2 of Bi 0 and 2P 3/2 (1) → 2P 1/2 of Bi 2+ transitions, and that of NIR emission band at 843 nm is attributed to the 2D 3/2 → 4S 3/2 of Bi 0 transition.

Transition metal ions luminescence in neutron irradiated magnesium oxide

The results of investigation of the photoluminescence (PL), its excitation and optical absorption of MgO crystals doped with different concentrations of transition metals exposed to fast neutron irradiation and after annealing are presented. It is suggested that the 440 nm photoluminescence band belongs to the complex V−OH-Fe3+ center with tetragonal symmetry, the ∼730 nm PL band observed in the irradiated MgO crystals is connected with defects, generated as a result of decay of the complex V−OH-Fe3+ centers. The near infrared luminescence bands in MgO crystals are connected with Fe3+-Fe3+ exchange coupled pairs.

EPR, optical absorption and photoluminescence properties of MnO 2 doped 23B 2O 3–5ZnO–72Bi 2O 3 glasses

Electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) spectroscopic measurements are performed on Mn 2+ doped high bismuth containing zinc–bismuth–borate glasses. TEM images reveal homogeneously dispersed Bi o nanoparticles (NPs) of spherical shape with size about 5 nm. EPR spectra exhibit predominant signals at g≈2.0 and 4.3 with a sextet hyperfine structure. The resonance signal at g≈2.0 is due to Mn 2+ ions in an environment close to octahedral symmetry, where as the resonance at g≈4.3 is attributed to the rhombic surrounding of the Mn 2+ ions. The hyperfine splitting constant ( A) indicates that Mn 2+ ions in these glasses are moderately covalent in nature. The zero-field splitting parameter D has been calculated from the allowed hyperfine lines. The optical absorption spectrum exhibits a single broad band centered at 518 nm (19,305 cm −1) is assigned to the 6A 1g(S)→ 4T 1g(G) transition of Mn 2+ ions. The visible and near infrared (NIR) luminescence bands at 548, 652 and 804 nm have been observed when excited at 400 and 530 nm, respectively. These luminescence centers are supposed to be caused by the lower valence state of bismuth, such as Bi 2+ and Bi + ions, generated during melting process.

Optical characterization of InGaN/AlGaN/GaN diode grown on silicon carbide

Electroluminescence (EL) properties of In x Ga 1− x N/Al y Ga 1− y N/GaN/SiC diode were studied. The spectral range for which EL spectra were recorded is 1–3.5 eV. Room temperature EL was obtained for forward bias (3.18 V, 220 μA) at 446.067 nm (blue luminescence band), 606.98 nm (yellow luminescence band) and 893.84 nm (Infrared luminescence band). The EL temperature dependence shows that, BL band is mostly given by e–h recombination corresponding to indium composition equal to 0.17 ± 0.01 and 0.14 ± 0.02 obtained theoretically and experimentally, respectively. The yellow band is generally weak and absent at low temperature. The IRL band is more consistent with the DAP recombination and could be explained by the thermal activation of Mg states. The luminescence bands shift to lower energies is due probably to the larger potential fluctuations effect.

Optical properties of low-phonon-energy Ge30Ga5Se65:Dy2Se3 chalcogenide glasses

Homogeneous pure and dysprosium-doped (Ge30Ga5Se65)100−x(Dy2Se3)x glasses, x=0, 0.01, 0.05, 0.1, 0.2, 0.3, 0.5, were synthesized. From the room temperature absorption spectra, the experimental oscillator strengths of six f–f electron transitions of Dy3+ ions and Judd–Ofelt intensity parameters were evaluated. The Dy3+ induced absorption bands were assigned to electron transition from the ground level 6H15/2 to the 6H13/2, 6H11/2, 6H9/2, 6F11/2, 6F9/2, 6H7/2, 6F7/2 and 6F5/2 energy levels of Dy3+ ions. High values of the oscillator strengths and of the intensity parameter, Ω2, originate apparently from the high covalence of chemical bonds in studied glasses. Using the Judd–Ofelt theory, the spontaneous emission probabilities, the branching ratios and the emission cross-sections were calculated. In the emission spectra of (Ge30Ga5Se65)100−x(Dy2Se3)x glasses, seven infrared luminescence bands (1150, 1340, 1560, 1760, 2170, 2470 and 2950nm) were observed when pumped by 808nm light. Using 905nm excitation light, five emission bands at 1150, 1340, 1760, 2470 and 2950nm were found. Only three luminescence bands were identified (1760, 2470 and 2950nm) when excited by 1300nm light. The bands were assigned to the individual electron transitions. The long-wawelength absorption edge (∼700cm−1) corresponds to multiphonon Ge–Se bonds vibrations.

Photoluminescence of copper-doped porous silicon

In this letter, we report the results of copper-doped porous silicon. In the photoluminescence spectrum of porous silicon without Cu doping, only one red luminescence band appears with a peak at 676.5 nm; while in the photoluminescence spectrum of Cu-doped porous silicon, red and near infrared luminescence bands appear with peaks at 660.6 and 802.2 nm, respectively. Energy dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy indicate the near infrared luminescence band is related to copper impurity in porous silicon. We assign the red luminescence band to band-to-band emission, and the near infrared luminescence band to band-to-acceptor emission.

The relation between the visible and the infrared luminescence bands in porous silicon. Comparison with amorphous Si alloys

The energy positions of the visible and the infrared luminescence bands in porous Si are related. Their dependence on different parameters is examined. They are both blue-shifted (from 1.0 eV to 2.1 eV for the visible and from 0.8 eV to 1.3 eV for the infrared band) due to a reduced crystallite size. However, the visible band can be red-shifted by up to 300 meV by surface effects. The observed behaviour is characteristic of neither pure quantum systems nor amorphous alloys. It is typical for porous Si containing surface states.

Infrared-luminescence diagnostics of an industrial fast-flow CO2 laser with a crossed electrode system

Infrared-luminescence diagnostics, based on vibrational—rotational bands of the CO2 molecule with the wavelengths 2.7 and 4.3 μm, was used in a study of the spatial structure of the characteristics of the active medium of an industrial fast-flow CO2 laser excited by a self-sustained glow discharge with orthogonally sectioned electrodes. The distributions of the infrared luminescence intensity were determined along and across the gas flow in the gas-discharge chamber at various heights above the anode. The experimental infrared luminescence data were used to calculate the spatial distribution of the vibrational temperatures of the coupled and asymmetric modes of the CO2 molecule in the downstream direction. The feasibility of monitoring the output power of an industrial laser on the basis of the 4.3 μm infrared luminescence band was demonstrated.

Infrared luminescence of residual iron deep level acceptors in gallium nitride (GaN) epitaxial layers

A characteristic infrared luminescence band, dominated by a zero-phonon line at 1.30 eV has been consistently detected in gallium nitride (GaN) epitaxial layers. It is assigned to the intra-3d-shell transitions 4T1(G)→6A1(S) of omnipresent iron trace impurities, Fe3+Ga(3d5). Another infrared emission is often also observed at 1.19 eV. This is tentatively assigned to chromium trace impurities, Cr4+Ga(3d2). The role of iron and chromium as minority-carrier lifetime killers in GaN-based optoelectronic devices is suggested from these data.

The Visible and the Infrared Luminescence Bands as a Tool for Characterization of the Porous Silicon Bandstructure

ABSTRACTThe visible and the infrared photoluminescence bands in porous Si have been studied at low temperature for two series of samples: one in which the size of the crystallites has been varied and another in which the degree of surface degradation has been changed. It is shown that the relation of the two bands can be explored for characterization of the porous Si bandstructure. The size- and the surface dependence of the valence band and of the conduction band related states is discussed. A model is proposed for explanation.

Photoluminescence and optically detected magnetic resonance investigations on porous silicon

Photoluminescence, electron paramagnetic resonance and optically detected magnetic resonance spectroscopy are used to study the defect properties of as-etched porous silicon. Both, the visible and the infrared luminescence bands are investigated. The paramagnetic defects observed in ODMR on the infra-red emission are closely related to the P b0-centers known from studies in crystalline Si. The luminescence and defect properties of meso- and nano-porous silicon are compared.

Luminescence of ZnS and ZnSe Window and Filter Materials

The visible and infrared cathodoluminescence spectra of undoped polycrystalline and single-crystal ZnSe and ZnS have been measured at 295, 78, and 10 K. Infrared luminescence bands were detected at 1.8, 2.4, 3.2, and 3.8 pm in IRTRAN 4 (ZnSe) and single-crystal ZnSe, but not in Raytran ZnSe. Similarly, bands at 1.4, 1.6, and 1.9 am were detected in IRTRAN 2 (ZnS) and single-crystal ZnS, but not in Raytran ZnS. The infrared luminescence in ZnSe materials is accompanied by edge emission and the copper red band, in addition to the copper green band appearing in IRTRAN 4. Self-activated luminescence was observed in Raytran ZnSe. The power law decay of the 1.8 and 3.8 pm bands in IRTRAN 4 suggests a bimolecular kinetic reaction. A model is proposed to account for the transitions involved.

The influence of adsorption on the luminescence of semiconductors Part II. Exciton luminescence

A theoretical and experimental investigation of the influence of adsorption on the exciton luminescence of semiconductors has been carried out. Exciton luminescence arises from the annihilation of excitons produced by light at unionized impurity centres in the bulk of a crystal. Measurements have been made in the infrared luminescence band of Cu 2O (λ max = 0.96 μm). It has been found that the adsorption of water and oxygen on Cu 2O leads to a considerable quenching of luminescence. Parallel studies of the change of the conductivity of crystals on adsorption permitted the determination of the sign of the change of the bending of bands during adsorption. A comparative analysis of the change of luminescent properties with an equal bending of the bands caused by adsorption on the one hand, and an electric field on the other, enable us to conclude that the principal mechanism of the influence of adsorption on the exciton luminescence of Cu 2O is the increase of the rate of surface annihilation of excitons because of the appearance of centres of radiationless annihilation of an adsorption origin.

Infrared cathodoluminescence of AlN

Measurements were made of cathode-ray excited infrared luminescence band of AlN powder in the temperature range 110 K to 535 K. The form of the temperature-dependent luminescence band and the temperature dependence of the band half-width were used in the determination of the value of the Huang-Rhys factor (S ≈ 2) as well as of the frequency of phonons (441 cm−1) interacting with electron transition. A discussion is presented of the possibility of interaction between an infrared luminescence centre and branch of natural transverse acoustic vibrations of the AlN lattice.

Luminescence of the Tetrachloroferrate(III) Ion

Excitation of a series of compounds containing the FeCl4− ion with ultraviolet or blue radiation at 85°K gave in each case a broad featureless luminescence band in the near infrared. Analysis of the decay curves obtained by using monochromatic excitation pulses and different observation wavelengths indicates that two emissive processes contribute to the emission. Excitation into a d→ d absorption band produces 4T1(G)→6A1 luminescence, whereas excitation into the low energy tail of the charge transfer absorption gives a second luminescence process, there being little or no tendency for the ion to cross from this luminescent state to the 4T1(G) although the latter is probably the lowest excited state. The FeBr4− ion under similar conditions gives a broad, near infrared luminescence band which also appears to consist of two transitions.