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1.
Porous silicon is usually formed by means of the anodization under constant current density. In order to study the role of the applied voltage during the anodization, we formed porous silicon on condition that the applied voltage was constant. The current density was not always large when the applied voltage was large. We have found that the thickness of the formed porous layer correlated with the current density while photoluminescent intensity depended on the applied voltage. When the anodization was performed with a comparatively large current density, the constant-voltage condition caused unstable current density accompanied by partial peeling of the surface. 相似文献
2.
Porous silicon (PS) layers were fabricated by anodization of low resistive (highly doped) p-type silicon in HF/ethanol solution, by varying current density, etching time and HF concentration. Atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM) analyses were used to investigate the physical properties and reflection spectrum was used to investigate the optical behavior of PS layers in different fabrication conditions. Vertically aligned mesoporous morphology is observed in fabricated films and with HF concentration higher than 20%. The dependence of porosity, layer thickness and rms roughness of the PS layer on current density, etching time and composition of electrolyte is also observed in obtained results. Correlation between reflectivity and fabrication parameters was also explored. Thermal oxidation was performed on some mesoporous layers that resulted in changes of surface roughness, mean height and reflectivity of the layers. 相似文献
3.
The properties of porous silicon prepared at different illumination and electrochemical conditions were studied. The preparation procedure was based on the electrochemical etching in HF containing electrolyte. In the dissolution of n-type silicon, an external source of light is necessary to obtain a sufficient holes flux density. Here, illumination was applied from the backside of the wafer (the side not immersed in the electrolyte), from topside (the side immersed in the electrolyte), and for the highly doped silicon, etching proceeds without illumination. The electrolyte contains HF in the range 2–50 wt%. The highest current density flows with topside assisted illumination. Backside illumination and etching in the dark resulted in a reduction in the current density. In the dark the current density significantly increased at a higher anodic bias. These conditions gave rise to pores formation with a diameter from 20 nm up to 3 μm. The smallest pore size was obtained for highly doped n-Si (111) wafers, etched without illumination. The present paper confirms the possibility of porous silicon formation in the dark and with backside illumination, these being alternative methods for topside assisted illumination etching methods. 相似文献
4.
电化学法制备的多孔硅发光 总被引:4,自引:1,他引:3
在(111)晶向的n型单晶硅片上,用电化学腐蚀的方法成功地制备出多孔硅膜,室温下,在344nm波长的光激发时用肉眼观察到明亮的桔红色荧光(577nm)研究了HF浓度,光照强度,电流密度和电化学腐蚀时间对多孔硅膜的发射波长和发光强度的影响,相应的多孔硅量子线度为1.5nm。 相似文献
5.
Structural and optical features of nanoporous silicon prepared by electrochemical anodic etching 总被引:1,自引:0,他引:1
D. -A. Kim S. -I. Im C. M. Whang W. -S. Cho Y. -C. Yoo N. -H. Cho J. -G. Kim Y. -J. Kwon 《Applied Surface Science》2004,230(1-4):125-130
Nanoporous silicon (NPS) samples were prepared by electrochemical anodic etching of p-type (0 0 1) silicon wafers in HF solution, and some of them were aged in air. The nanostructural, optical and chemical features of the NPS were investigated in terms of etching and aging conditions. The surface of the porous Si exhibits an etched layer with a thickness of 30–40 nm; this layer appears to consist of aggregates of 5–10 nm size nano-crystallites. The NPS exhibited broad photoluminescence (PL) spectra with its peak in the red light region (740 nm). After aging the porous samples for 4 weeks in air, we observed the PL intensity became approximately a fifth of that of the as-prepared one, along with a blue shift. It is very likely that the blue shift of the PL peak was caused by the shrinkage of the Si nano-crystallites due to the oxidation in the surface of the nano-crystallites. 相似文献
6.
M. Balucani V. Bondarenko N. Vorozov A. Ferrari 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):574
We studied the influence of the thickness and porosity of the buffer layer on the guiding properties of oxidized porous silicon waveguides (OPSWG). It is demonstrated how a modified anodization process acts on the porosity of the final oxidized porous silicon. In this way, it is possible to control the refractive index jump between the core of OPSWG made of compact silicon dioxide and the bottom buffer layer made of porous silicon dioxide. The adoption of a double-step anodization process decreases the propagation losses to 0.5 dB/cm against the 8 dB/cm measured for the waveguide realized using a single-step anodization. The main reason seems not to be the increase of the difference of refractive index values but the more homogeneous buffer layer obtained along the core of the waveguide. This homogeneous layer permits a better lateral confinement of the light as demonstrated by spatial refractive index profile measurement. 相似文献
7.
The photoluminescence (PL) of the annealed and amorphous silicon passivated porous silicon with blue emission has been investigated. The N-type and P-type porous silicon fabricated by electrochemical etching was annealed in the temperature range of 700-900 °C, and was coated with amorphous silicon formed in a plasma-enhanced chemical vapor deposition (PECVD) process. After annealing, the variation of PL intensity of N-type porous silicon was different from that of P-type porous silicon, depending on their structure. It was also found that during annealing at 900 °C, the coated amorphous silicon crystallized into polycrystalline silicon, which passivated the irradiative centers on the surface of porous silicon so as to increase the intensity of the blue emission. 相似文献
8.
In the present paper, several samples of porous silicon monolayers and multilayers were prepared at different anodization
conditions with fixed HF concentration. The room temperature photoluminescence wavelength observed to be increased with increased
etching time and current density respectively. By Raman measurement it has been observed that as the size of silicon crystallites
decreased with increased etching time, the silicon optical phonon line shifted somewhat to lower frequency from 520.5 cm−1 and became broader asymmetrically. The surface roughness and pyramid like hillocks surface was confirmed by AFM measurement.
In SEM images, the porous silicon layers were clearly observed by white and black strips. It was also observed that the reflectivity
increased as the number of porous silicon layers was increased. 相似文献
9.
G. A. Melikjanyan Kh. S. Martirosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2012,47(3):133-136
Porous silicon layers on the p-type silicon substrate with different porosity and thickness have been obtained by electrochemical anodization method. Dependences
of porosity and thickness of the layers on the content of HF in solution, anodization current density and anodization time
were analyzed. The obtained experimental results are approximated by analytical expressions for revealing the regimes at which
porous silicon layers with desired parameters can be produced. 相似文献
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A series of porous silicon samples prepared at different etching parameters, namely etchant composition, etching time and current density, was investigated as substrates for surface-enhanced Raman scattering (SERS). Silver nanostructures were deposited on porous silicon by immersion plating method and Rhodamine 6G was used as analyte. The relation between the etching parameters, morphology of porous silicon surface and its SERS efficiency after silver deposition is examined. We show that a high HF content in the etchant allows the formation of a film with close-packed silver nanocrystals, which possess strong surface enhancement properties. 相似文献
12.
硅发光对于在单一硅片上实现光电集成是至关重要的.目前已有的使硅产生发光的方法有:掺杂深能级杂质、掺稀土离子、多孔硅、纳米硅以及Si/SiO2超晶格.声空化所引发的特殊的物理、化学环境为制备光致发光多孔硅薄膜提供了一条重要的途径.实验表明,声化学处理对于改善多孔硅的微结构,提高发光效率和发光稳定性都是一项非常有效的技术.超声波加强阳极电化学腐蚀制备发光多孔硅薄膜,比目前通用的常规方法制备的样品显示出更优良的性质.这种超声波的化学效应源于声空化,即腐蚀液中气泡的形成、生长和急剧崩溃.在多孔硅的腐蚀过程中,由于超声波的作用增加了孔中氢气泡的逸出比率和塌缩,有利于孔沿垂直方向的腐蚀,使多孔硅光致发光峰的半峰全宽压缩到了3.8nm. 相似文献
13.
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
14.
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
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采用双槽电化学腐蚀法以电阻率为10-15 Ω·cm的p型<100>晶向的单晶硅片制备了孔径约为1.5 μm, 孔深约为15-20 μm的p型多孔硅, 并以此多孔硅作为基底采用无电沉积法通过调控沉积时间在其表面沉积了不同厚度的银纳米颗粒薄膜. 采用扫描电子显微镜和X 射线衍射仪表征了银纳米颗粒/多孔硅复合材料的形貌和微观结构, 结果表明银纳米颗粒较均匀的分布于多孔硅的表面上且沉积时间对产物的形貌有重要影响. 采用静态配气法在室温下研究了银纳米颗粒/多孔硅复合材料对NH3的气敏性能. 气敏测试结果表明沉积时间对产物的气敏性能影响较大. 当沉积时间较短时, 适量银纳米颗粒掺杂的多孔硅复合材料由于其较高的比表面积以及特殊的形貌和结构, 对NH3气体表现出较高的灵敏度、优良的响应/恢复性能. 室温下, 其对50 ppm 的NH3气体的气敏灵敏度可以达到5.8左右. 相似文献
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Yunsen Zhang Donglai Liu Xue Bai Huabing Song Wenyu Li Xiaosong Sun 《Journal of luminescence》2010,130(6):1005-1473
This very paper is focusing on the investigation of porous silicon preparation with n-type silicon wafer by means of electrochemical anodization in the dark and, particularly, on its stable ultraviolet photoluminescence emission. A lateral electrical potential was applied, for this purpose, on silicon wafers, driving the electrons away and letting holes appear on the surface of the silicon wafer to enhance the electrochemical etching process. Characterizations have been made with scanning electronic microscope, fluorescence spectrophotometer and Fourier transform infrared spectroscope. An ultraviolet photoluminescence emission of 370 nm is found in the as-prepared n-type porous silicon, which seems to be well associated with the formation of oxygen-related species (twofold coordinated silicon defect) during the anodic oxidation. The result characterized by photo-bleaching performance indicates that the ultraviolet photoluminescence emission is so stable—only 7% reduction within 3600 s. Meanwhile the morphology of as-prepared n-type porous silicon is investigated. 相似文献
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The Au-assisted electroless etching of p-type silicon substrate in HF/H2O2 solution at 50 °C was investigated. The dependence of the crystallographic orientation, the concentration of etching solution and the silicon resistivity on morphology of etched layer was studied. The layers formed on silicon were investigated by scanning electron microscopy (SEM). It was demonstrated that although the deposited Au on silicon is a continuous film, it can produce a layer of silicon nanowires or macropores depending on the used solution concentration. 相似文献