共查询到20条相似文献,搜索用时 609 毫秒
1.
J.M. Hvam 《Solid State Communications》1978,27(12):1347-1350
The M-band emission in ZnO at 1.7 K is investigated by tuning the excitation light through the A-B exciton region. Externally stimulated two-photon emission from excitonic molecules is observed when the pump photon energy is resonant with the upper B-polariton. The experiments suggest two excitonic molecule levels separated by 4.6 meV and with a ground state energy EM = 6.7394 eV. 相似文献
2.
Masahino Ojima Takashi Kushida Yuichi Tanaka Shigeo Shionoya 《Solid State Communications》1977,24(12):841-844
Time-resolved luminescence spectra of excitonic molecules in CuCl created by the two-photon resonance excitation are studied at 4.2 K with a time resolution of ~ 60 psec. Two sharp emission lines observed are ascribed to the radiative decay of “cold” excitonic molecules with k ~ 2K0. Stimulated emission process gives a considerable influence on luminescence properties. 相似文献
3.
Y. Toda O. Moriwaki M. Nishioka Y. Arakawa 《Physica E: Low-dimensional Systems and Nanostructures》2000,8(4)
We have investigated the carrier relaxation mechanism in InGaAs/GaAs quantum dots by photoluminescence excitation (PLE) spectroscopy. Near-field scanning optical microscope successfully shows that a PLE resonance at a relaxation energy of 36 meV can be seen in all single-dot luminescence spectra, and thus can be attributed to resonant Raman scattering by a GaAs LO phonon to the excitonic ground state. In addition, a number of sharp resonances observed in single-dot PLE spectra can be identified as resonant Raman features due to localized phonons, which are observed in the conventional Raman spectrum. The results reveal the mechanism for the efficient relaxation of carriers observed in self-assembled quantum dots: the carriers can relax within the continuum states, and make transitions to the excitonic ground state by phonon emission. 相似文献
4.
We develop the theory of multi-polariton scattering via excitonic molecules under strong excitation. New emission lines, denoted by X- and L-bands, were observed at slightly lower energy side of two-photon Raman line in CuCl under strong excitation. In terms of the present theory, these lines can be for the first time assigned to the multi-polariton scatterings associated with the coherently (virtually) and incoherently (realy) created excitonic molecules, respectively. 相似文献
5.
Two-photon resonant Raman scattering via excitonic molecule in CuCl is studied with using dye laser excitation of different band widths. The yield of the Raman scattering is found to drop remarkably at resonant excitation and luminescence line of 0.3 meV half-width comes out. The predominance of the Raman or luminescence or their coexistence depends on the intensity and energy band width of excitation light. 相似文献
6.
Hiroto Kuroda Shigeo Shionoya Hiroshi Saito Eiichi Hanamura 《Solid State Communications》1973,12(6):533-536
It is observed that excitonic molecules in CdSe exhibit the Bose condensation when excitation is given at 1.8–4.2 K by pico-second light pulses from a mode-locked glass laser. Strong evidence is provided by the appearance of an extremely sharp luminescence line produced from the excitonic molecules condensed to the k = 0 state. 相似文献
7.
High energy resolution KL23L23 Auger spectra of polycrystalline Cu and Ni were measured using photon energies up to about 50 eV above the K-absorption edge and down to 5 eV (Cu KLL) and 4 eV (Ni KLL) below threshold. The spectra show strong satellite structures varying considerably as a function of the photon energy. In the sub-threshold region the linear dispersion of the diagram line energy positions and a distortion of the line shape as a function of photon energy, attributable to the Auger resonant Raman process, is clearly observed, indicating the one-step nature of the Auger emission. These changes in the resonant spectra are interpreted using a simple model based on resonant scattering theory in combination with partial density of states obtained from cluster molecular orbital (DV-Xα) calculations. 相似文献
8.
Pico-second time-resolved measurements of the two-photon resonant Raman scattering via excitonic molecules in CuCl were carried out for the first time. The Raman scattering leaving transverse excitons decays as fast as the laser light. When the energy of the incident light falls in the vicinity of the two-photon resonant absorption, both Raman and luminescence lines are simultaneously observed. In case of just resonant excitation, the transient response indicates that the secondary radiation can be decomposed into the Raman and the luminescence components as regards its temporal and spectral behavior. 相似文献
9.
The stimulated emission from ZnSe under one photon or two photon excitation has been investigated in the temperature range between 20 and 100 K. The spectra obtained under quasi-resonant one photon pumping show a dominant P line, ascribed to exciton-exciton scattering on the basis of its intensity dependence and its optical gain spectrum. The role of many-body processes under non-resonant one photon excitation is discussed. Under two photon pumping the LO-phonon assisted free exciton recombination is shown to be the dominant lasing mechanism. 相似文献
10.
R. Thangavel Mohammad Tariq Yaseen Yia Chung Chang Chia-Hao Hsu Kuo-Wei Yeh Maw Kuen Wu 《Journal of Physics and Chemistry of Solids》2013
Transparent conducting polycrystalline Al-doped ZnO (AZO) films were deposited on sapphire substrates at substrate temperatures ranging from 200 to 300 °C by pulsed laser deposition (PLD). X-ray diffraction measurement shows that the crystalline quality of AZO films was improved with increased substrate temperature. The electrical and optical properties of the AZO films have been systematically studied via various experimental tools. The room-temperature micro-photoluminescence (µ-PL) spectra show a strong ultraviolet (UV) excitonic emission and weak deep-level emission, which indicate low structural defects in the films. A Raman shift of about 11 cm−1 is observed for the first-order longitudinal-optical (LO) phonon peak for AZO films when compared to the LO phonon peak of bulk ZnO. The Raman spectra obtained with UV resonant excitation at room temperature show multi-phonon LO modes up to third order. Optical response due to free electrons of the AZO films was characterized in the photon energy range from 0.6 to 6.5 eV by spectroscopic ellipsometry (SE). The free electron response was expressed by a simple Drude model combined with the Cauchy model are reported. 相似文献
11.
12.
Nikolay Vasilyev 《Journal of luminescence》2012,132(5):1215-1219
Intra-center luminescence of Cd1?xMnxTe semi magnetic semiconductors under low excitation density was investigated both experimentally and by Monte-Carlo simulation. Experimental time-resolved spectra of 2 eV-band under different photon energy for excitation were used. The approach revealed that Mn2+–Mn2+excitation energy transfers take place by means of resonant dipole–dipole interaction. Besides energy transfer dynamics is strongly influenced by hopping-assisted quenching. Having been intra-center excitation selective-, mixed- and non-selective types of excitation are proved to occur if photon energy for excitation is increased. This is originated from overlapping of 4T1- and 4T2-states. Under inter-band excitation it was established that Mn2+-ion excitation takes place with the aid of excitonic energy transfer, with excitation energy being centered at exciton energy. Under temperature rise the transfer rate vigorously enhances due to great increase of overlap integral of Mn2+- ions' side-bands. The quenching is proved to be limited in accordance with existing theory. Inhomogeneous broadening diminishes as a result of fast fluctuation rate of excited ions' energy. 相似文献
13.
Ryota Ishii Rei Fukuta Fumitaro Ishikawa Masafumi Matsushita Hiroaki Ohfuji Toru Shinmei 《高压研究》2020,40(1):140-147
ABSTRACTDeep-ultraviolet continuous-wave photoluminescence spectroscopy is performed for nano-polycrystalline diamond (NPD) synthesized by a high pressure high-temperature technique. NPD exhibits clear deep-ultraviolet emissions, which originate from intrinsic excitonic transitions assisted by a momentum-conserving phonon with a photon. Surprisingly, the peak emission energy is about 30?meV higher than that of the single-crystalline diamond. Raman scattering spectroscopy indicates that the energy difference should originate from the excitonic properties of the NPD and not the phonon. Hence, NPD has a large bandgap compared to single-crystalline diamond. 相似文献
14.
Two-phonon resonant, coherent Raman scattering (four-photon degenerate coherent scattering) via excitonic molecules has been studied as a function of intensity of incident light in CuCl and CuBr. Observed line-shaped of coherent scattering spectra broadens as excitation intensity is raised. This broadening is found to be closely correlated with that of the two-photon absorption. These results are qualitatively explained by taking account of the excitation intensity-dependence of χ(3), but cannot be explained by the autoinization model. 相似文献
15.
S.S. Sussman R. Alben M. Selders R.K. Chang R.H. Callender 《Solid State Communications》1973,13(7):799-802
We present measurement of the resonant Raman effect in the alloy system CdS1?xSex for laser photon energies both above and below the concentration-dependent energy gap. Our data show that the Raman intensities are not simply functions of the difference between the photon energy and the gap energy. These results may be partially understood in terms of a simple theoretical model which elucidates the role of local electric fields in determining Raman intensities in alloys. 相似文献
16.
An investigation of resonant Raman scattering in mixed crystals of AgBr:Cl at 1.8 K shows that the zero-phonon and LO phonon-assisted exciton luminescence excited in the free indirect exciton absorption, exhibits an anomalous dependence on the exciton photon energy EL. Close to the exciton gap, the bands show a Raman-like behaviour with their peaks at constant energetic distance from EL. As EL is tuned further into the absorption, the bands gradually develop into normal photoluminescence. The effect is explained by taking into account exciton relaxation via scattering by long-wavelength acoustic phonons, a process which is strongly energy dependent. In addition, resonant Raman scattering observed for excitation in the zero-phonon absorption suggests study for the first time of the mode behaviour of certain off-zone center phonons in this system. 相似文献
17.
Masahiro Ojima Yasuo Oka Takashi Kushida Shigeo Shionoya 《Solid State Communications》1977,24(12):845-848
Luminescence spectra of excitonic molecules in CuCl resonantly created by nano-second dye laser excitation are measured at 4.2 K changing the lenghts of the excited region. The spectra are dominated by stimulated emission. The gain coefficient for the MT line is saturated more easily than that for ML, though the former is larger under unsaturated conditions. These gain characteristics explain well various stimulated emission effects observed. 相似文献
18.
Takashi Kushida 《Solid State Communications》1979,32(3):209-212
The origin of the narrow secondary emission lines under two-photon just- resonance excitation of the excitonic molecule in CuCl is discussed. Luminescence due to cold, but not Bose-condensed excitonic molecules is concluded to be dominant. Recent experiments to discriminate between Raman scattering and luminescence by picosecond spectroscopy on these emissions are criticized. 相似文献
19.
G. Kurtze C. Klingshirn B. Hönerlage E. Tomzig H. Scholz 《Journal of luminescence》1979,20(2):151-161
The luminescence of red HgI2 is investigated as a function of temperature, excitation intensity and wavelength. At high excitation intensity and low temperature an “M-band” emission dominates. This M-band is assigned to biexciton decay and bound exciton scattering with acoustic phonons (“acoustic wing”), this assumption being supported by the results of excitation spectroscopy. The energy of the biexciton is determined to be (4661 ± 1) meV. From the evaluation of Raman spectra, the phonon energies (1.9, 3.1 and 14.0 ± 0.2) meV are found. At higher temperatures two lines are observed, one of which is ascribed to exciton-free carrier scattering. Position and line shape are in good agreement with theoretical results. The other emission line is found to be due to scattering involving excitons or carriers bound to lattice defects. 相似文献
20.
Laser-induced desorption of P from GaP at various photon energies near the absorption edge has been measured. The desorption yield is found to start increasing above a certain threshold laser fluence, of which the dependence on the photon energy exhibits a sharp dip near the indirect band gap besides a gradually decreasing component from the indirect band gap to the direct band gap energy. The sharp dip is ascribed to desorption induced by dense excitation of the surface states. 相似文献