共查询到20条相似文献,搜索用时 15 毫秒
1.
Huabing Song Hao Chen Zhou Yu Zhimei Yang Xiaosong Sun 《Applied Surface Science》2008,254(18):5655-5659
Photoluminescence of porous silicon (PS) is instable due perhaps to the nanostructure modification in air. The controllable structure modification processes on the as-prepared PS were conducted by thermal oxidization and/or HF etching. The PL spectra taken from thermally oxidized PS showed a stable photoluminescence emission of 355 nm. The photoluminescence emission taken from both of PS and oxidized porous silicon (OPS) samples etched with HF were instable, which can be reversibly recovered by the HF etching procedure. The mechanism of UV photoluminescence is discussed and attributed to the transformation of luminescence centers from oxygen deficient defects to the oxygen excess defects in the thermal oxidized PS sample and surface absorbed silanol groups on PS samples during the chemical etched procedure. 相似文献
2.
F. S. Husairi J. Rouhi K. A. Eswar A. Z. Zainurul M. Rusop S. Abdullah 《Applied Physics A: Materials Science & Processing》2014,116(4):2119-2124
Electrical impedance characteristics of porous silicon nanostructures (PSiNs) in frequency function were studied. PSiNs were prepared through photo-electrochemical etching method at various current densities (15–40 mA/cm2) and constant etching time. The atomic force microscope images of PSiNs show that pore diameter and roughness increase when current density increases to 35 mA/cm2. The surface roughness subsequently decreases because of continuous etching of pillars, and a second etching process occurs. Photoluminescence spectra show blue and red shift with increasing applied current density that is attributed to PSiNs size. Variations of electrical resistance and capacitance values of PSiNs were measured using electrochemical impedance spectroscopy analysis. These results indicate that PSiNs prepared at 20 mA/cm2 current density have uniform porous structures with a large number of pillars. Furthermore, this PSiNs structure influences large values of charge transfer resistance and double layer capacitance, indicating potential application in sensors. 相似文献
3.
V. A. Makara N. S. Bolotovets O. V. Vakulenko A. I. Datsenko S. N. Naumenko T. V. Ostapchuk O. V. Rudenko 《Journal of Applied Spectroscopy》1999,66(3):458-463
The effect of chemical treatment of porous silicon samples by HF on its photoluminescence and its evolution with time in sample
aging in air is investigated. It is shown that the effect of HF on the luminescence parameters depends on the duration of
the treatment and the initial photoluminescence intensity of the sample. It is found that chemical etching in HF accelerates
the growth of the total luminescence intensity in aging of the sample in air. The evolution of the photoluminescence spectrum
in aging of the sample in air after chemical etching can be explained within the framework of the quantum-size model of the
luminescence of porous silicon.
Presented at the Fall Meeting of the Material Research Society, December 1–5, 1997, Boston, USA
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 423–427, May–June, 1999. 相似文献
4.
A porous SiC (PSC) layer was fabricated by anodization of a 1.6 μm thin SiC layer deposited onto p-type Si(1 0 0) substrate by pulsed laser deposition (PLD), using a hot-pressed 6H-SiC(p) as sputtered target. p-Type PSC layers were fabricated by anodization in HF/ethylene glycol electrolyte (1:1 by vol.) at different etching times. The properties of the PSC layer formed by this method were investigated by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM) and photoluminescence (PL). The results show, that the growth layer was crystalline and PL spectra exhibit blue band emission centered at 2.95 eV. In addition, the results indicate clearly an increase in PL intensity by ten times of magnitude compared to that exhibited by the unetched sample. 相似文献
5.
Two broad luminescence bands in weakly hydrogenated (glow discharge) undoped amorphous silicon have been observed using time resolved spectroscopy on a nanosecond timescale. Whereas the luminescence decay of the low energy band has been found to be sample independent, the peak position of the luminescence does show a sample dependence. We propose an intrinsic origin of this luminescence. 相似文献
6.
Porous silicon (PS) exhibits several photoluminescence (PL) bands, whose spectral position and intensity depend strongly on the actual conditions of preparation of PS, its treatment, and subsequent use. The PS PL band peaking at about 1.8 eV and usually assigned to the intrinsic emission of silicon nanocrystals was studied. It was shown that the temperature-induced variation of the PL kinetics in the 80 to 300-K interval follows a complex pattern and depends noticeably on the actual point on the band profile. The temperature behavior of PL decay in the 1.8-eV band is determined by the electron-hole recombination rate within a nanocrystal and the cascade carrier transitions from small to large nanocrystals, with an attendant decrease in energy. 相似文献
7.
Porous silicon (PS) layers based on crystalline silicon (c-Si) n-type wafers with (1 0 0) orientation were prepared using electrochemical etching process at different etching times. The optimal etching time for fabricating the PS layers is 20 min. Nanopores were produced on the PS layer with an average diameter of 5.7 nm. These increased the porosity to 91%. The reduction in the average crystallite size was confirmed by an increase in the broadening of the FWHM as estimated from XRD measurements. The photoluminescence (PL) peaks intensities increased with increasing porosity and showed a greater blue shift in luminescence. Stronger Raman spectral intensity was observed, which shifted and broadened to a lower wave numbers of 514.5 cm−1 as a function of etching time. The lowest effective reflectance of the PS layers was obtained at 20 min etching time. The PS exhibited excellent light-trapping at wavelengths ranging from 400 to 1000 nm. The fabrication of the solar cells based on the PS anti-reflection coating (ARC) layers achieved its highest efficiency at 15.50% at 20 min etching time. The I-V characteristics were studied under 100 mW/cm2 illumination conditions. 相似文献
8.
Photoluminescence (PL) analysis is used to study porous layers elaborated by electrochemical etching of n+ Si-doped GaAs substrate with different etching times. Temperature and power dependence photoluminescence (PL) studies were achieved to characterize the effect of the etching time on the deep levels of the n+ Si-doped GaAs. The energy emission at about 1.46 eV is attributed to the band-to-band (B-B) (e-h) recombination of a hole gas with electrons in the conduction band. The emission band is composed of four deep levels due to the complex of (VAsSiGaVGa), a complex of a (Ga vacancy - donor - As vacancy), a (SiGa-VGa3−) defect or Si clustering, and a (gallium antisite double acceptor-effective mass donor pair complex) and which peaked, respectively, at about (0.94, 1, 1.14, and 1.32 eV). The PL intensity behavior as function of the temperature is investigated, and the experimental results are fitted with a rate equation model with double thermal activation energies. 相似文献
9.
Nanostructured porous silicon (NPSi) is versatile nanomaterials, and attractive area in device application after visible luminescence
was observed from NPSi by Canham (1990). NPSi has been prepared by electrochemical techniques with silicon wafer as a based
material. The electrolyte solution consists of ethanol and hydrofluoric acid at volume ratio of 1:1. The etching time was
varied while other preparation parameters were fixed to produce different porosity of NPSi samples. The structural properties
of samples were measured using field emission scanning electron microscope and Raman spectrometer. The surface structural
study has shown the surface roughness increase at inertial stage but decrease gradually with longer etching time. However,
nanostructured surface was decreased with increasing of etching time. From side view measurement, the nanopillar of NPSi becomes
smaller size while increase of etching time. The crystallinity of PSi is observed by Raman scattering varied with different
etching time. The photoluminescence measurement will be carried out to study the correlation between optical and structural
properties. 相似文献
10.
11.
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
12.
V. F. Agekyan A. M. Aprelev R. Laiho Yu. A. Stepanov 《Physics of the Solid State》2000,42(8):1431-1434
A study has been made of the transformation of photoluminescence (PL) spectra of porous silicon (PS) induced by its ageing, including the early stages of contact with air. The sample was prepared under conditions that minimized this contact, and spectral measurements were carried out in a high vacuum or in liquid nitrogen. The PS PL spectra obtained under continuous measurement in high vacuum are always dominated by one emission band of PS nanoelements, which shifts toward shorter wavelengths with ageing by 150 nm. At 80 K, the band intensity is considerably higher than at 300 K, and this difference grows with ageing. Exposure of a sample to air for a few tens of seconds is long enough to strongly transform its time-resolved PL spectra, which is evidence of a change in the sample surface. The effect of immersion of PS samples in liquid nitrogen on PL spectra is associated not only with their cooling, but also with the field of adsorbed nitrogen molecules, whose influence becomes weaker with increasing thickness of the oxidized near-surface layer. The variation of the spectral properties and kinetics of the long-wavelength PS PL band with temperature, medium (liquid nitrogen or vacuum), and exposure time suggest that these factors affect carrier migration between silicon nanoelements. 相似文献
13.
14.
The photoluminescence of porous silicon with and without carbon deposition fabricated by plasma-enhanced chemical vapor deposition technique has been investigated. After the deposition, the rapid thermal processes in the temperature ranging from 500 to 1100 °C have been carried out. It was found that after the carbon deposition a new intense blue emission appeared. The rapid thermal processes at 800and 900 °C could enhance the blue emission, while the other rapid thermal processes quenched it. Finally, the mechanism for the effect of carbon deposition and rapid thermal processes on photoluminescence properties of porous silicon was discussed. 相似文献
15.
16.
Results of studies of the photoluminescence of porous silicon with different prehistories have revealed the mechanism and
nature of the instability of the luminescence properties of freshly prepared samples. It was established that the initial
quenching and subsequent rise of the photoluminescence is attributable to the intermediate formation of silicon monoxide (photoluminescence
degradation) and subsequent additional oxidation to form SiO2 (photoluminescence rise). Ultraviolet laser irradiation accelerates this process by a factor of 200–250 compared with passive
storage of the samples in air. Plasma-chemical treatment in an oxygen environment merely results in a subsequent rise in the
photoluminescence as a result of the formation of monoxide on the porous silicon surface. A kinetic model is proposed for
this process.
Zh. Tekh. Fiz. 69, 135–137 (June 1999) 相似文献
17.
18.
《Solid State Communications》1998,106(4):211-214
β-Silicon carbide layers have been prepared by high temperature pyrolysis of polyimide Langmuir-Blodgett films on porous silicon substrate in vacuum. The formation of silicon carbide is confirmed by the IR and XRD spectra. It is found that photoluminescence still exists and appears in the blue-green and ultraviolet regions after thermal treatment at 900°C. These results indicate that the silicon carbide layers, which are formed, are responsible for the blue-green luminescence. 相似文献
19.
Effects of vacuum and ambient thermal annealing and ageing on the photoluminescence (PL) spectra of porous silicon (po-Si) have been investigated. Isochronal anneals up to 300°C were done and PL spectra were recorded and compared to the un-annealed specimens. Minimal changes are induced for anneals below approximately 125°C; however, significant reduction in PL intensity occurs following anneals at T?≥?200°C. Deconvolution of the PL spectra into five distinct Gaussian bands reveals that at least two of the bands are attributable to non-quantum confinement mechanisms. Specifically, bands appearing at 1.58 and 1.78?eV are ascribed to non-bridging oxygen hole related defects. Recovery of PL intensity following thermal annealing occurs over a period of several days at a rate that is dependent upon annealing temperature and environment. Passivation of Si dangling bonds on the po-Si surface via effusion of hydrogen and incorporation of oxygen is responsible for the observed variations in PL intensity. 相似文献
20.
W. Dimassi I. Haddadi R. Bousbih S. Slama M. Ali Kanzari M. Bouaïcha H. Ezzaouia 《Journal of luminescence》2011,131(5):829-833
A new method has been developed to improve the photoluminescence intensity of porous silicon (PS), which is first time that LiBr is used for passivation of PS. Immersion of the PS in a LiBr solution, followed by a thermal treatment at 100 °C for 30 min under nitrogen, leads to a nine fold increase in the intensity of the photoluminescence. The atomic force microscope (AFM) shows an increase of the nanoparticle dimension compared to the initial dimension of the PS nanostructure. The LiBr covers the nanoparticles of silicon without changing the wavelength distribution of the optical excitation and emission spectra. Moreover, a significant decrease of reflectivity was observed for the wavelength in the range of 350-500 nm. 相似文献