Excitation power and temperature dependence of excitons in CuInSe2

Excitonic recombination processes in high quality CuInSe2 single crystals have been studied by photoluminescence (PL) and reflectance spectroscopy as a function of excitation powers and temperature. Excitation power dependent measurements confirm the identification of well-resolved A and B free excitons in the PL spectra and analysis of the temperature quenching of these lines provides values for activation energies. These are found to vary from sample to sample, with values of 12.5 and 18.4meV for the A and B excitons, respectively, in the one showing the highest quality spectra. Analysis of the temperature and power dependent PL spectra from the bound excitonic lines, labelled M1, M2, and M3 appearing in multiplets points to a likely assignment of the hole involved in each case. The M1 excitons appear to involve a conduction band electron and a hole from the B valence band hole. In contrast, an A valence band hole appears to be involved for the M2 and M3 excitons. In addition, the M1 exciton multiplet seems to be due to the radiative recombination of excitons bound to shallow hydrogenic defects, whereas the excitons involved in M2 and M3 are bound to more complex defects. In contrast to the M1 exciton multiplet, the excitonic lines of M2 and M3 saturate at high excitation powers suggesting that the concentration of the defects involved is low. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709448

Diamagnetic shift of the A free exciton in CuGaSe2 single crystals

Single crystals of CuGaSe2 were studied using magnetophotoluminescence inmagnetic fields up to 20 T at 4.2 K. The rate of the diamagnetic shift in the A free exciton peak was determined to be 9.82 x 10(-6) eV/T-2. This rate was used to calculate the reduced mass as 0.115m(0), the binding energy as 12.9 meV, the Bohr radius as 5.1 nm and an effective hole mass of 0.64m(0) (m(0) is the free electron mass) of the free A exciton using a low-field perturbation approach and the hydrogenic model

Excited states of the free excitons in CuInSe2 single crystals

High-quality CuInSe2 single crystals were studied using polarization resolved photoluminescence (PL) and magnetophotoluminescence (MPL). The emission lines related to the first (n=2) excited states for the A and B free excitons were observed in the PL and MPL spectra at 1.0481 meV and 1.0516 meV, respectively. The spectral positions of these lines were used to estimate accurate values for the A and B exciton binding energies (8.5 meV and 8.4 meV, respectively), Bohr radii (7.5 nm), band gaps (E-g(A)=1.050 eV and E-g(B)=1.054 eV), and the static dielectric constant (11.3) assuming the hydrogenic model

Characterization of carbon contamination under ion and hot atom bombardment in a tin-plasma extreme ultraviolet light source

Molecular contamination of a grazing incidence collector for extreme ultraviolet (EUV) lithography was experimentally studied. A carbon film was found to have grown under irradiation from a pulsed tin plasma discharge. Our studies show that the film is chemically inert and has characteristics that are typical for a hydrogenated amorphous carbon film. It was experimentally observed that the film consists of carbon (~70 at. %), oxygen (~20 at. %) and hydrogen (bound to oxygen and carbon), along with a few at. % of tin. Most of the oxygen and hydrogen are most likely present as OH groups, chemically bound to carbon, indicating an important role for adsorbed water during the film formation process. It was observed that the film is predominantly sp3 hybridized carbon, as is typical for diamond-like carbon. The Raman spectra of the film, under 514 and 264 nm excitation, are typical for hydrogenated diamond-like carbon. Additionally, the lower etch rate and higher energy threshold in chemical ion sputtering in H2 plasma, compared to magnetron-sputtered carbon films, suggests that the film exhibits diamond-like carbon properties.Comment: 18 pages, 10 figure

Numerical and experimental studies of the carbon etching in EUV-induced plasma

We have used a combination of numerical modeling and experiments to study carbon etching in the presence of a hydrogen plasma. We model the evolution of a low density EUV-induced plasma during and after the EUV pulse to obtain the energy resolved ion fluxes from the plasma to the surface. By relating the computed ion fluxes to the experimentally observed etching rate at various pressures and ion energies, we show that at low pressure and energy, carbon etching is due to chemical sputtering, while at high pressure and energy a reactive ion etching process is likely to dominate

The research program of the Liquid Scintillation Detector (LSD) in the Mont Blanc Laboratory

A massive (90 tons) liquid scintillation detector (LSD) has been running since October 1984 in the Mont Blanc Laboratory at a depth of 5,200 hg/sq cm of standard rock. The research program of the experiment covers a variety of topics in particle physics and astrophysics. The performance of the detector, the main fields of research are presented and the preliminary results are discussed

Statistics of a noise-driven Manakov soliton

We investigate the statistics of a vector Manakov soliton in the presence of additive Gaussian white noise. The adiabatic perturbation theory for Manakov soliton yields a stochastic Langevin system which we analyze via the corresponding Fokker-Planck equation for the probability density function (PDF) for the soliton parameters. We obtain marginal PDFs for the soliton frequency and amplitude as well as soliton amplitude and polarization angle. We also derive formulae for the variances of all soliton parameters and analyze their dependence on the initial values of polarization angle and phase.Comment: Submitted to J.Phys.A: Mathematical and Genera

Optical properties of high quality Cu2ZnSnSe4 thin films

Cu2ZnSnSe4 thin films, fabricated on bare or molybdenum coated glass substrates by magnetron sputtering and selenisation, were studied by a range of techniques. Photoluminescence spectra reveal an excitonic peak and two phonon replicas of a donor-acceptor pair (DAP) recombination. Its acceptor and donor ionisation energies are 27 and 7 meV, respectively. This demonstrates that high-quality Cu2ZnSnSe4 thin films can be fabricated. An experimental value for the longitudinal optical phonon energy of 28 meV was estimated. The band gap energy of 1.01 eV at room temperature was determined using optical absorption spectr

On-line recognition of supernova neutrino bursts in the LVD detector

In this paper we show the capabilities of the Large Volume Detector (INFN Gran Sasso National Laboratory) to identify a neutrino burst associated to a supernova explosion, in the absence of an "external trigger", e.g., an optical observation. We describe how the detector trigger and event selection have been optimized for this purpose, and we detail the algorithm used for the on-line burst recognition. The on-line sensitivity of the detector is defined and discussed in terms of supernova distance and electron anti-neutrino intensity at the source.Comment: Accepted for pubblication on Astroparticle Physics. 13 pages, 10 figure

Muon diffusion and trapping in chalcopyrite semiconductors

The diffusion parameters of diamagnetic muons in chalcopyrites CuInSe2, CuInS2, CuInTe2, CuGaTe2 and (Ag0.25Cu0.75)InSe2 were obtained by [mu]SR methods. The variations among the different compositions were found to validate the anion-antibonding localization model. The application of a two-state model to the zero-field data revealed muon trapping by defects. The dipolar width at the trap and the number of jumps before trapping were determined. The Cu vacancy is identified as the trapping center in CuInSe2 and the energy depth of the trap has been determined.http://www.sciencedirect.com/science/article/B6TVH-47K37XD-1/1/c6039f1a6212b2c9af977ddf9c54886