共查询到20条相似文献,搜索用时 10 毫秒
1.
W. Eichhammer M. Hage-Ali R. Stuck P. Siffert 《Applied Physics A: Materials Science & Processing》1990,50(4):405-410
This work presents direct evidence for a correlation between rapid thermal process-induced recombination centers and co-implanted metallic impurities in ion implanted silicon. Experimental evidence includes the dose dependence of the minority carrier diffusion length measured by the SPV technique, SIMS and RBS analysis of high-dose implantations which show the presence of heavy metals, the dependence of the final diffusion lengths on the mass of the implanted ions, as well as the successful modification of an implantation equipment. 相似文献
2.
Hideki Koyama 《Solid State Communications》2006,138(12):567-570
Linearly-polarized infrared (1.06 μm) laser light with intensities ranging from 5.3 to 97 mW/cm2 has been used to obtain anisotropically luminescent porous silicon (PSi) layers by photoanodic etching in a hydrofluoric acid solution. Remarkably large photoluminescence (PL) anisotropy has been observed in samples prepared with the highest illumination intensity. These samples show very low degrees of linear polarization when the PL excitation light is polarized parallel to the polarization direction of the etching light. When the excitation light is polarized perpendicular to that, we obtain usual degrees of linear polarization of several percent. This result indicates that anisotropic Si nanostructures in PSi layers can be made isotropic with high orientation selectivity by the polarized-light assisted technique. A simple two-dimensional model is presented to explain the observed prominent anisotropy. 相似文献
3.
Y. Kuga S. Isomura K. Takeuchi K. Okuyama 《Applied Physics A: Materials Science & Processing》1996,62(4):373-379
It was demonstrated experimentally for the first time that particle growth of photoproduced UFS was enhanced by ionizing radiation from an -emitting241Am source. A gas mixture of UF6, CH4, and Ar in a reaction cell was irradiated with a single shot of a KrF laser at 248 nm to form UF5 particles. Transmission electron microscope images of the samples indicated that the average size of UF5 particles produced without the -ray source was independent of the laser energy. UFS particles produced with the -ray source were found to be much larger in size than those produced without the a-ray source, and the enhancement of particle growth was marked when the laser energy was low. An explanation was attempted for the anomalous behaviors of particle size distribution from the viewpoint of competition between the second-order coagulation rate and the rate of diffusion from the reaction zone. 相似文献
4.
Marco Antônio da Cunha Sebastião da Costa Paolinelli 《Journal of magnetism and magnetic materials》2008
Low core loss non-oriented silicon steels are produced with high (Si+Al) content to reduce eddy current losses. However, high alloy content has detrimental effect on mechanical properties, saturation polarization and thermal conductivity. A new generation of medium and, particularly, low core loss non-oriented silicon steels was developed, with lower alloy content than the conventional grades, based on improved purity and texture. The development allowed the production of new low loss grades, with maximum core loss (W1.5/50) of 2.30 W/kg at 0.50 mm and 1.95 W/kg at 0.35 mm, with high permeability (J50 of 1.7 and 1.72 T, respectively). Texture improvement was based on hot band structure control and higher boundary mobility. Large hot band grain size and low [1 1 0]∥RD fiber fraction in the hot band texture contribute to reduce the intensity of [1 1 1]∥ND and slightly increase the intensity of [0 0 1]∥RD in the final product. Higher grain boundary mobility and/or a two-stage cold rolling process, with an intermediate annealing, increase the fraction of [0 0 1]∥RD and reduce the fraction of [1 1 1]∥ND on recrystallization and lead to favorable texture evolution on grain growth. 相似文献
5.
Flat layered structure and improved photoluminescence emission from porous silicon microcavities formed by pulsed anodic etching 总被引:2,自引:0,他引:2
Z.H. Xiong L.S. Liao X.M. Ding S.H. Xu Y. Liu L.L. Gu F.G. Tao S.T. Lee X.Y. Hou 《Applied Physics A: Materials Science & Processing》2002,74(6):807-811
Single-mode, highly directional and stable photoluminescence (PL) emission has been achieved from porous silicon microcavities
(PSMs) fabricated by pulsed electrochemical etching. The full width at half maximum (FWHM) of the narrow PL peak available
from a freshly etched PSM is about 9 nm. The emission concentrates in a cone of 10° around the normal of the sample, with
a further reduced FWHM of ∼5.6 nm under angle-resolved measurements. Only the resonant peak is present in such angle-resolved
PL spectra. No peak broadening is found upon exposure of the freshly prepared PSM to a He-Cd laser beam, and the peak becomes
somewhat narrower (∼5.4 nm) after the PSM has been stored in an ambient environment for two weeks. At optimized etching parameters,
even a 4-nm FWHM is achievable for the freshly etched PSM. In addition, scanning electron microscopy (SEM) plane-view images
reveal that the single layer porous Si formed by pulsed current etching is more uniform and flatter than that formed by direct
current (dc) etching, demonstrated by the well-distributed circular pores with small size in the former in comparison with
the irregular interlinking pores in the latter. The SEM cross-section images show the existence of oriented Si columns of
10 nm diameter along the etching direction within the active layer, good reproducibility and flat interfaces. It is thus concluded
that pulsed current etching is superior to dc etching in obtaining flat interfaces within the distributed Bragg reflectors
because of its minor lateral etching.
Received: 7 March 2001 / Accepted: 23 July 2001 / Published online: 30 October 2001 相似文献
6.
A. Elior B. D. Barmashenko E. Lebiush S. Rosenwaks 《Applied physics. B, Lasers and optics》1995,61(1):37-47
We report on detailed experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser. The laser has a 5 cm long active medium and utilizes a simple sparger-type O2(1
) chemical generator and a medium-size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 25 W of cw laser emission at 1.315 µm are obtained in the present experiments. The small size and the simple structure of the laser system and its stable operation for long times make it a convenient tool for studying parameters important for high-power supersonic iodine lasers and for comparison to model calculations. The lasing power is studied as a function of the molar flow rates of the various reagents, and conditions are found for optimal operation. Good agreement is found between the experimental results and calculations based on a simple one-dimensional semi-empirical model, previously developed in our laboratory and modified in the present work. The model is used to predict optimal values for parameters affecting the laser performance that are difficult to examine in the present experimental system. 相似文献
7.
The time resolved polarized CARS technique has been used to detect Cl atoms produced by photolysis of ICl in the presence and absence of O2. A population inversion was observed between the ground state electronic levels Cl(2
P
1/2) and Cl(2
P
3/2). The rate constant for Cl(2
P
1/2) decay (quenching + reaction) in ICl was determined to be (3.2±0.2)×10–13 cm3/molecule×s; the rate constant for Cl(2
P
3/2) reaction with ICl was determined to be (7.8±0.5)×10–12 cm3/molecule×s; and the rate constant for Cl(2
P
1/2) quenching by O2 was determined to be (1.9±0.2)×10–13 cm3/molecule×s. 相似文献
8.
Laser-induced wet chemical etching of stainless steel 304 and Ti in phosphoric acid, sulfuric acid and aqueous KOH has been investigated using cw Ar and cw Nd : YAG lasers. Two different phases of laser-induced etching of Ti in phosphoric acid were found by electrochemical investigations. Laser-enhanced electrochemical dissolution of stainless steel was observed in the passivation and transpas sivation region. In the latter case, laser heating accelerates the metal dissolution. In the passivation region, laser heating results in a breakthrough of the passivation layer near the Flade potential. By multiple scanning microstructures of high quality and an aspect ratio > 10 have been produced. By EDX analysis the laser-etching process was found to be practically free of chemical residues on etched surfaces. 相似文献
9.
R. Käsmaier S. Lätsch H. Hiraoka 《Applied Physics A: Materials Science & Processing》1996,63(4):305-313
A thin solid C60 film has been irradiated under a fix incident angle with pulsed UV light at the wavelength of 266 nm. With scanning electron microscopy and atomic force microscopy, a surface transformation of the irradiated films has been observed to a periodic surface structure at low laser fluences in air as well as in vacuum and to strong morphology changes at higher laser fluences only in air. For both structural transformations the occuring surface chemistry has been studied with Raman spectroscopy and X-ray photoelectron spectroscopy. In the case of the periodical lines, these results in addition to a detailed discussion of the existing models for laser induced surface structures have shown that the C60 film remains a van der Waals solid but with much oxygen incorporation in the lattice and does not polymerize as it is known to happen during continuous wave irradiation. The case of strong morphology changes could be explained by detailed comparison of the obtained Raman and X-ray photoelectron spectroscopy data as the formation of a new carbon phase with diamond-like sp3 bondings through an oxygen-assisted fullerene cage opening. 相似文献
10.
Chao Song Jun Xu Guran Chen Yu Liu Ling Xu Kunji Chen 《Applied Surface Science》2010,257(4):1337-1341
Intrinsic, P- and B-doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique. As-deposited samples were thermally annealed at the temperature of 800 °C to obtain the doped nanocrystalline silicon (nc-Si) films. The microstructures, optical and electronic properties have been evaluated for the undoped and doped nanocrystalline films. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron and phosphorous in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the activation of dopant by annealing increased the room temperature dark conductivity from 3.4 × 10−4 S cm−1 to 5.3 S cm−1 for the P-doped films and from 1.28 × 10−3 S cm−1 to 130 S cm−1 for the B-doped films. Meanwhile, the corresponding value of conductivity activation energies was decreased from 0.29 eV to 0.03 eV for the P-doped films and from 0.3 eV to 5.6 × 10−5 eV for the B-doped films, which indicated the doped nc-Si films with high conductivity can be achieved with the present approach. 相似文献
11.
《Superlattices and Microstructures》1995,17(2):155-157
The mechanism by which porous silicon luminesces when excited by UV radiation is still unknown. As opposed to de-localized models, proposed by other researchers, in which conduction band carriers are believed to recombine with traps during luminescence, we show evidence for and argue ha favour of a localized structure in which, on excitation, electrons are promoted to higher energy levels within a luminescence center but are not given up to the conduction band. Luminescence occurs when they relax to a lower level in the center. 相似文献
12.
Fully processed non-oriented silicon steel samples 0.50 mm thick were sheared and submitted to stress relief annealing under different conditions of temperature and atmosphere to investigate the effect of this treatment on the recovery of magnetic properties. Two different compositions were used, with different Si and Al contents. Temperature was varied in the range of 600–900 °C and four atmospheres were used: N2 and N2+10%H2 combined with dew points of −10 and 15 °C. The results showed that annealing atmosphere has very important effect on the magnetic properties and that the beneficial effect of stress relief annealing can be overcome by the detrimental effect of the atmosphere under certain conditions, due to oxidation and nitration. 相似文献
13.
Elena Froner Roberta Adamo Zeno Gaburro Benno Margesin Lorenzo Pavesi Adelio Rigo Marina Scarpa 《Journal of nanoparticle research》2006,8(6):1071-1074
Aqueous solutions of silicon nanocrystals have been obtained, by sonication, from porous Si (p-Si) aged in air for various times. The photoluminescence of these solutions changes with the aging time of p-Si. These changes correlate with nanocrystal core dimensions, i.e. with the oxidation of the nanocrystals. Infrared spectra show that the reaction with water depends on the age of the starting p-Si sample, since the native superficial oxide layer on p-Si inhibits these reactions. 相似文献
14.
《Current Applied Physics》2008,8(2):206-211
In recent years, the photoluminescence and the photoconductivity of porous silicon were comprehensively studied. But the photoluminescence and the photoconductivity of porous polycrystalline silicon have not been wholely studied. In this paper, the results showed that luminescent property of the samples prepared by poly-crystal silicon wafers may be related to the defects on Si complexes surface, which can be proved by microwave-detected photoconductivity decay measurements. Furthermore, the luminescence of samples was disappeared under the external illumination, which may be related to the elimination of luminescent-centers. In addition, the conductivities of the samples were dependent on etched time and current density, and the large porosity of samples led to isotropic photoconductivity, which may be related to the change of energy band structure of the devices. 相似文献
15.
The possible construction of a self-contained and compact pulsed chemical HF-laser based on an auto-wave photon-branched chain
reaction initiated in a gaseous disperse medium composed of H2-F2-O2-He and Al particles by focused external IR radiation is theoretically substantiated. It is shown that an autonomous system
and minimization of the parameters of the main pulsed HF-laser units are achievable due to both the effect of ignition of
the laser-chemical reaction in an auto-wave regime under the condition of external beam focusing and the effect of a huge
laser energy gain of 1011. These effects provide strong reduction of the input pulse energy necessary for initiation up to ∼10-8 J, and make it possible to construct a self-contained laser with kilojoule output energy, which can be initiated by a small
submicrojoule master oscillator powered by an accumulator. Due to an increase in the general pressure of working gases up
to P=2.3 bar and optimization of the parameters of the dispersed component (Al particles with radius r0=0.09 μm and concentration N0=1.4×109 cm-3) and the composition of the working mixture, the HF-laser system will ensure an output energy up to ∼1.5 kJ in a pulse from
the rather small volume of ∼2 L of the active medium.
Received: 18 April 2000 / Revised version: 21 August 2000 / Published online: 8 November 2000 相似文献
16.
Sebastião da Costa Paolinelli Marco Antônio da Cunha André Barros Cota 《Journal of magnetism and magnetic materials》2008
The presence of shear bands in the deformed material before final annealing is very important for Goss and Cube textures formation in silicon steel [S.C. Paolinelli, M.A. Cunha, J. Magn. Magn. Mater. 255 (2003) pp. 379. [1]; J.T. Park, J.A. Szpunar, Acta Mater., 51 (2003) 3037. [2]]. The increase of the hot-band grain size can increase the number of shear bands, which favor the nucleation of these orientations. In this work, the effect of the hot band grain size variation, promoted by varying the hot rolling finishing temperature, on final structure and magnetic properties was investigated for 3% Si alloy. It was found that the increase of the hot-band grain size increases the occurrence of shear bands and promotes an increase of η fiber fraction and a reduction of γ fiber fraction, improving the magnetic induction. On the other hand, the final grain size is reduced when the hot-band grain size is larger than 190 μm, deteriorating the core loss values in spite of the texture benefits. The reduction of final grain size was explained by the increase of the number of nuclei at the beginning of the recrystallization caused by the increase of shear bands in the deformed material. 相似文献
17.
V. V. Filippov V. P. Bondarenko P. P. Pershukevich V. S. Khomenko 《Journal of Applied Spectroscopy》1997,64(4):514-517
We obtained porous silicon films modified at room temperature by an Eu3+-containing polymer complex. The most intense photoluminescence of Eu3+ implanted in the porous silicon was observed at the wavelengths of 611, 618, 691, and 704 nm. In this case, the intensity
of the intrinsic photoluminescence of strongly irradiated specimens of porous silicon decreased, while the intensity of weakly
emitting films multiply increased. An investigation of the photoexcitation spectra made it possible to establish the effect
of Eu3+-containing complexes on the mechanism underlying the excitation of photoluminescence of porous silicon.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 499–501, July–August, 1997. 相似文献
18.
S.A. Basun A.A. Kaplyanskii A.B. Kutsenko V. Dierolf T. Troester S.E. Kapphan K. Polgar 《Applied physics. B, Lasers and optics》2001,73(5-6):453-461
Low-temperature luminescence spectra of stoichiometric Cr:LiNbO3, congruent Cr:LiNbO3 and congruent Cr,Mg:LiNbO3 were studied. Dominant low-field and minor high-crystal-field optical centers are the Cr3+ impurity ions that preferentially occupy Li+ sites (CrLi) in the Cr:LiNbO3 crystals. Low-field centers related to Cr3+ substitution of Nb5+ (CrNb) occur in addition to CrLi in co-doped Cr,Mg:LiNbO3 samples. Application of high hydrostatic pressure leads to the transformation of dominant Cr3+ centers from low- to high-field type due to strong pressure-induced blue shift of the 4
T
2 state, resulting in its crossing with the 2
E state of Cr3+. This level-crossing effect was observed for the dominant Cr3+
Li and Cr3+
Nb centers at pressures that correlate well with estimations based on the 4
T
2-2
Eenergy gap (230 cm-1 and 1160 cm-1) and on the rate of their pressure-induced change (14.35 and 11.4 cm-1/kbar, respectively). We also studied inhomogeneous broadeningof the 2
E?4
A
2transitions at ambient pressure for the minor high-field “defect” Cr3+
Li centers in congruent LiNbO3. A fine structure in the spectral response of these centers was observed. The obtained results are discussed on the basis
of a microscopic hierarchic model for perturbed Cr3+ ions in the LiNbO3 lattice.
Received: 25 June 2001 / Published online: 2 November 2001 相似文献
19.
One hundred and fifty-seven nanometers irradiation of LiF crystals accelerates the penetration of C, O, N, Si and other contaminants within the crystal bulk. New bonding between the contaminant elements in both the irradiated and the non-irradiated areas of the crystal was identified. The chemical changes eventually form inhomogeneous nano/micro-islands, which further agglomerate to larger structures in the form of an interfacial layer. The concentration and diffusion (∼100 nm) of contaminants in the irradiated part of the crystal is higher than for the non-irradiated one. The accelerated diffusion is due to a force perpendicular to the crystal surface. This force is generated by the laser's electric field gradient in the direction of beam propagation due to the inhomogeneous absorption at the interfacial layer. A theoretical diffusion model in the presence of the laser field allows rationalizing and interpreting the experimental results. 相似文献
20.
The paper describes a new generation of the high permeability fully processed silicon steel grades developed by Acesita, with core loss (W1.5/60) in range of 3.10–4.20 W/kg and polarisation (J50) from 1.71 to 1.75 T, respectively. The new grades have lower (Si+Al) content and a better crystallographic texture, with lower fractions of [1 1 1]||ND fibre and higher fractions of [0 0 1]||RD fibre. The new grades have better mechanical and magnetic properties than conventional grades. 相似文献