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

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

Comparative Analysis of the Methods for the Calculations of the Stability of Soil Slopes

The article discusses various methods for calculating the coefficient of slope stability on three options of soil slopes. The results of the calculations in the software systems PLAXIS and FSS-PSU are provided. The conclusion is made concerning the discrepancy of the obtained results

КРЕМНИЙ-ГЕРМАНИЕВЫЕ ПРИБОРНЫЕ НАНОСТРУКТУРЫ ДЛЯ ПРИМЕНЕНИЯ В ОПТОЭЛЕКТРОНИКЕ

Influence of technological parameters (temperature of substrate, number of Ge layers, ion treatment) on optical properties of Si/Ge nanostructures with Ge quantum dots have been studied. The Raman scattering lines related to the Si-Si, Ge-Ge and Si-Ge vibration modes have been detected in the Raman spectra of Si/Ge nanostructures. A significant enhancement of intensity of luminescence band at 0.8 eV related with radiative recombination on Ge quantum dots is observed after hydrogen-plasma ion treatment of Si-Ge nanostructures. It is important for increasing of the luminescence quantum efficienty of devices on the base of Si nanolayer with Ge quantum dots.Исследовано влияние технологических параметров (температура подложки, количество слоев Ge, ионная обработка) на оптические свойства Si/Ge наноструктур с квантовыми точками Ge. В спектрах комбинационного рассеянии света Si/Ge наноструктур наблюдались линии, связанные с Si-Si, Ge-Ge и Si-Ge колебательными модами. Обработка Si/Ge наноструктур в плазме водорода приводит к изменению спектральной формы и значительному увеличению интенсивности полосы люминесценции в области энергии 0,8 эВ, связанной с излучательной рекомбинацией неравновесных носителей заряда (электронов, дырок) на квантовых точках Ge, что важно для повышения квантового выхода люминесценции приборных структур, создаваемых на основе нанослоев Si и квантовых точек Ge

Reaction of human metallothionein-3 with cisplatin and transplatin

Human metallothioneins, small cysteine- and metal-rich proteins, play an important role in the acquired resistance to platinum-based anticancer drugs. These proteins contain a M(II)4(CysS)11 cluster and a M(II)3(CysS)9 cluster localized in the alpha-domain and the beta-domain, respectively. The noninducible isoform metallothionein-3 (Zn7MT-3) is mainly expressed in the brain, but was found overexpressed in a number of cancer tissues. Since the structural properties of this isoform substantially differ from those of the ubiquitously occurring Zn7MT-1/Zn7MT-2 isoforms, the reactions of cis-diamminedichloridoplatinum(II) (cisplatin) and trans-diamminedichloridoplatinum(II) (transplatin) with human Zn7MT-3 were investigated and the products characterized. A comparison of the reaction kinetics revealed that transplatin reacts with cysteine ligands of Zn7MT-3 faster than cisplatin. In both binding processes, stoichiometric amounts of Zn(II) were released from the protein. Marked differences between the reaction rates of cisplatin and transplatin binding to Zn7MT-3 and the formation of the Pt-S bonds suggest that the binding of both Pt(II) compounds is a complex process, involving at least two subsequent binding steps. The electrospray ionization mass spectrometry characterization of the products showed that whereas all ligands in cisplatin were replaced by cysteine thiolates, transplatin retained its carrier ammine ligands. The 113Cd NMR studies of Pt1 113Cd6MT-3 revealed that cisplatin binds preferentially to the beta-domain of the protein. The rates of reaction of cisplatin and transplatin with Zn7MT-3 were much faster than those of cisplatin and transplatin with Zn7MT-2. The biological consequences of a substantially higher reactivity of cisplatin toward Zn7MT-3 than Zn7MT-2 in the acquired resistance to platinum-based drugs are discussed

Structural and optical properties of CdS/Cu(In,Ga)Se-2 heterostructures irradiated by high energy electrons

Thin films of Cu(In, Ga)Se-2 (CIGS) with a Ga/(Ga + In) ratio of similar to 0.27 corresponding to the standard elemental composition for solar-energy transducers were grown on Mo-coated glass substrates by the Cu, In, Ga, and Se co-evaporation technique from different sources. Transmission (T), photoluminescence (PL), and photoluminescence excitation (PLE) spectra at 4.2 K were used to analyze electronic properties in the asgrown and electron-irradiated CIGS films. The band-gap energy (E-g) of the CIGS films measured using both transmission and PLE methods was found to be about 1.28 eV at 4.2 K. Two deep bands in the PL spectra of the irradiated CIGS films, P-1 at similar to 0.91 eV and P-2 at similar to 0.77 eV, have been detected. These bands are tentatively associated with copper atoms substituting indium (Cu-In) and indium vacancies V-In, respectively, as the simplest radiation-induced defects