Dynamics of formation of the mosaic structure of porous silicon during prolonged anodic etching in electrolytes with an internal current source

So far, while producing porous silicon (PSi) with anodic etching of silicon in an aqueous solution of hydrofluoric acid, many researchers (including us) have obtained the crack-into-pieces (or mosaic) structure. Most of the authors believed that the cause of this structure is the collapse and the cracking of the porous, especially highly porous, silicon layer which took place during the drying of PSi after fabrication. However, our study showed that the mosaic structure was formed right during the course of silicon anodization at high anodic current density. Furthermore, our study also showed that at high anodic current density the real silicon etching has been replaced by the growth of a silicon oxide layer. This is a layer of another substance that grows on silicon, so when the layer is too thick (which is obtained when the anodic current density is too high and/or the anodization time is too long) it will crack, creating mosaic pieces. When the silicon oxide layer is cracked, the locations around the cracks will be etched more violently than elsewhere, creating trenches. Thus, the mosaic structure with mosaic pieces emerged between the trenches has formed.

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Fabrication of Luminescent Porous Silicon with Stain Etches and Evidence that Luminescence Originates in Amorphous Layers

MRS Proceedings ◽

10.1557/proc-256-165 ◽

1991 ◽

Vol 256 ◽

Cited By ~ 9

Author(s):

R. W. Fathauer ◽

T. George ◽

A. Ksendzov ◽

T. L. lin ◽

W. T. Pike ◽

...

Keyword(s):

Porous Silicon ◽

Anodic Oxidation ◽

Oxidation Reaction ◽

Porous Si ◽

Anodic Etching ◽

Si Films

Stain films on Si wafers produced in solutions of HF:HNO3:H2O have been studied for over 30 years [1], and have been suggested [1] to be similar in nature to the anodically-etched porous Si films first demonstrated by Uhlir [2]. More recently, it was shown that stain films produced by etching Si in solutions of NaNO2 in HF and CrO3 in HF were similar in structure to porous Si films produced by anodic etching [3]. In fact, in the etching of Si by HF:HNO3:H3O solutions, the oxidation reaction chemistry is recognized to be the same as that of anodic oxidation, with points on the Si surface behaving randomly as localized anodes and cathodes [4]

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Radial microstructure and optical properties of a porous silicon layer by pulse anodic etching

Journal of Semiconductors ◽

10.1088/1674-4926/32/4/043003 ◽

2011 ◽

Vol 32 (4) ◽

pp. 043003 ◽

Cited By ~ 1

Author(s):

Yongfu Long

Keyword(s):

Optical Properties ◽

Porous Silicon ◽

Silicon Layer ◽

Porous Silicon Layer ◽

Anodic Etching

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Fabrication of Macroporous on No-Mask Silicon Substrate for Application to Microsystems

2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems ◽

10.1115/micronano2008-70323 ◽

2008 ◽

Cited By ~ 4

Author(s):

Gyoko Nagayama ◽

Ryuji Ando ◽

Kei Muramatsu ◽

Takaharu Tsuruta

Keyword(s):

Fuel Cell ◽

Porous Silicon ◽

Pore Size ◽

Silicon Wafer ◽

Silicon Substrate ◽

Electrochemical Etching ◽

Cell System ◽

Back Side ◽

Ambient Conditions ◽

Anodic Etching

We applied the anodic etching (i. e. photo assisted electrochemical etching) to the n type silicon substrate of orientation (100) without masking to fabricate macropores penetrated Si substrate. The anodic etching conditions of the macroporous formation were discussed and the effects of the resistivity, voltage, current density, electrolyte concentration and illumination etc. on the pore size and the porosity were investigated. The pores in high aspect ratio through the cross section of the silicon wafer were obtained with polishing and RIE (reactive ion etching) from the back side. It is found that the pore size at the back side is about 1.5 to 2 times larger than that of the front side. Also, as one example of the applications of porous silicon to microsystems, we demonstrate the results obtained in a micro fuel cell system using a porous silicon membrane (PSM). The PSM was fabricated by a porous silicon wafer which was filled with Nafion dispersion solution with ultrasonic vibrations. It was used as a proton conduction membrane by assembling into the H2 / air feed fuel cell at ambient conditions using conventional electrodes. We found that the Nafion filled PSM worked well and a maximum power density of 89.2 mW/cm2 were achieved under the flow rate of 100ml/min for H2 and 200ml/min for air.

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Light-Emitting Porous Silicon Prepared by Pulsed Anodic Etching

10.7567/ssdm.1995.pd-l1-l5 ◽

1995 ◽

Author(s):

Xiaoyuan Hou ◽

Honglei Fan ◽

Fulong Zhang ◽

Mingren Yu ◽

Xun Wang

Keyword(s):

Porous Silicon ◽

Light Emitting ◽

Anodic Etching

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STRUCTURAL AND OPTICAL FEATURES OF POROUS SILICON PREPARED BY ELECTROCHEMICAL ANODIC ETCHING

Surface Review and Letters ◽

10.1142/s0218625x09012342 ◽

2009 ◽

Vol 16 (01) ◽

pp. 93-97 ◽

Cited By ~ 2

Author(s):

L. S. CHUAH ◽

Z. HASSAN ◽

F. K. YAM ◽

H. ABU HASSAN

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Porous Silicon ◽

Raman Scattering ◽

Raman Spectra ◽

Raman Peak ◽

Sem Images ◽

Anodic Etching ◽

Etching Duration ◽

Scanning Electron

Porous silicon (PS) samples were prepared by electrochemical anodic etching of n-type (111) silicon wafers in HF solution. The structural, optical, and chemical features of the PS were investigated in terms of different etching durations. The porous samples were investigated by scanning electron microscopy (SEM), photoluminescence (PL), and Raman scattering. SEM images indicated that the pores increased with the etching duration; however, the etching duration has significant effect on the shape of the pores. PL measurements revealed that the porosity-induced PL intensity enhancement was only observed in the porous samples. Raman spectra showed shifting of PS Raman peak to lower frequency relative to non-porous silicon Raman peak.

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