Porous silicon microstructure

S.-F. Chuang, S. D. Collins, and R. L. Smith, Porous silicon microstructure as studied by transmission electron microscopy, Appl. Phys. Lett. 55(15), 1540, 1989. 

Canham LT, Cullis AG, Pickering C, Dosser OD, Cox TI, Lyneh TP (1994) Lumineseent anodized silicon aerocrystal networks prepared by supercritical drying. Nature 368 133-135 Cao L, Price TP, Weiss M, Gao D (2008) Super water- and oil-repellent surfaces on intrinsically hydrophilic and oleophillic porous silicon films. Langmuir 24(5) 1640-1643 Chao Y (2011) Optical properties of nanostructured silicon. Compr NanoSci Technol 1 543-570 Chuang SF, Collins SD, Smith RL (1989) Porous silicon microstructure as studied by transmission electron microscopy. Appl Phys Lett 55 1540-1543 Costa J, Roura P, Morante JR, Bertran E (1998) Blackbody emission under laser excitation of silicon nanopowder produced by plasma-enhanced chemieal-vapour deposition. J Appl Phys 83(12) 7879-7885... 

Kalinowski T, Rittersma ZM, Benecke W, Binder J (2000) An advanced micromachined fermentation monitoring device. Sens Actuators B 68 281-285 Kronast W, Muller B, Siedel W et al (2001) Single-chip condenser microphone using porous silicon as sacrificial layer for the air gap. Sens Actuators A 87(3) 188-193 Lammel G, Renaud P (2000) Free-standing, mobile 3D porous silicon microstructures. Sens Actuators A 85(l-3) 356-360... 

Garel O et al (2007) Fabrication of free-standing porous silicon microstructures. J Micromech Microeng 17 S164-S167... 

Lammel G, Renaud P (2000) Free standing mobile 3D porous silicon microstructures. Sens Actual A 85(l-3) 356-360... 

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H. Sugiyama and O. Nittono, Microstructure and lattice distortion of anodized porous silicon layers, J. Cryst. Growth 103, 156, 1990. 

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S. Billat, M. Thonissen, R. Arens-Fischer, M. G. Berger, M. Kruger, and H. Luth, Influence of etch stops on the microstructure of porous silicon layers. Thin Solid Films 297, 22, 1997. 

M. L. Ciurea, V. lancu, V. S. Teodorescu, L. C. Nistor, and M. G. Blanchin, Microstructural aspects related to carrier transport properties of nanocrystalline porous silicon films, J. Electrochem. Soc. 146(9), 3516, 1999. 

S. Chattopadhyay and P. W. Bohn, Direct-write patterning of microstructured porous silicon arrays by focused-ion-beam Pt deposition and metal-assisted electroless etching, J. Appl. Phys. 96, 6888-6894 (2004). 

Sun, E, Hu, M., Li, M. and Ma, Sh. Microstructure, electrical and gas sensing properties of meso-porous silicon and macro-porous silicon , (2012) Acta Phys.-Chim. Sin. 28,489-93. 

Although, in structural materials, the pores are generally beheved to cause a deterioration in mechanical reliability, this is not always true. Rather, the pores may cause an improved or even unique mechanical performance of the material which cannot be attained in the dense counterpart, especially when the porous microstructure is carefully tailored. Two examples of porous silicon nitrides are described in the... 

Figure 8.21 Microstructures of porous silicon nitride with large fibrous grain alignment (porosity 14%). Reprinted with permission from Ref [50] 2000, Blackwell Publishing, Inc.

The small dimensions in microreactors imply the presence of laminar flow. This type of flow makes it easier to extract chemical kinetic parameters and fully characterize phenomena. The correct incorporation of the active catalyst onto the surface of the membrane is one of the important aspects of catalytic microreactors. Drott et al. (1997) investigated the use of porous silicon as a carrier matrix in microstructured enzyme reactors. The matrix was created by anodization and the fabrication of the microreactor used flow-through silicon cell comprising 32 channels of 50 pm wide, 250 pm deep and separated by 50 pm. The aim was to increase the surface area on which the enzymes (glucose oxidase) could be coupled. Comparisons were made with the classical non-porous reference device and the glucose turnover rates. The results showed that when compared with the reference reactor the enzyme activity increased 100-fold. 

Other examples are enzymes immobilized on beads which are trapped in a microreactor by etched weirs [88], enzymes encapsulated in hydrogel patches or sol-gel silica [89] and enzymes attached on the surface of (porous) microstructures (for example, on porous silicon manufactured by anodization of single-crystalline silicon see Figure 1.10 [91]), of mesoporous silica or polymer monoliths or directly... 

Chadwick EG, Beloshapkin S, Tanner DA (2012) Microstructural characterisation of metallurgical grade porous silicon nanosponge particles. J Mater Sci 47(5) 2396-2404. doi 10.1007/s10853-011-6060-0... 

An important attraction of porous silicon (PS) has been its customizable morphology which can be tailored to change its optoelectronic properties to suit the required apphcation. In case of luminescence, an important property of PS, morphology can be modified to tune the intensity and the peak position of luminescence over a wide range of wavelengths (Marsh 2002). However, the versatile microstructural nature of porous sihcon that imparts to it these exciting possibilities is also the main hindrance in the studies of its electrical properties. 

Chan S, Kwon S, Koo TW, Lee LP, Berlin AA (2003) Surface-enhanced Raman scattering of small molecules from silver-coated silicon nanopores. Adv Mater 15 1595 Chen LL, Tang ZK, Shi MJ (2013) Microstructures and photoluminescence of electrochemically-deposited ZnO films on porous silicon and silicon. Key Eng Mater 538 30 Chiboub N, Boukherroub R, Gabouze N, Moulay S, Naar N, Lamouri S, Sam S (2010a) Covalent grafting of polyaniline onto aniline-terminated porous silicon. Opt Mater 32 748... 

Frascella F, Mandracci P, Venturello A, Sciacca B, Giorgis F, Geobaldo F (2009) Microstructure and optical properties of porous silicon after plasma assisted nitridation. Phys Status Solidi C 6 1661... 

Bengtsson M, Ekstrom S, Drott J, Collins A, Csoregi E, Marko-Varga G, Laurell T (2000) Applications of microstructured porous silicon as a biocatalytic surface. Phys Stat Sol 182 495-504 Bimer A, Li A-P, Muller F, Gdsele U, Kramper P, Sandoghdar V, Mlynek J, Busch K, Lehmann V (2000) Transmission of a microcavity structure in a two-dimensional photonic crystal based on macroporous silicon. Mat Sci Semicon Proc 3 487-491 Carstensen J, Christophersen M, Foil H (2000) Pore formation mechanisms for the Si-HF system. Mat Sci Eng B 69/70 23-28... 

Lehmann V, Stengl R, Luigart A (2000) On the morphology and the electrochemical formation mechanism of mesoporous silicon. Mater Sci Eng B 69 11-22 Li MD, Hu M, Liu QL, Ma SY, Sun P (2013) Microstructure characterization and N02-sensing properties of porous silicon with intermediate pore size. Appl Surf Sci 268 188-194 Lysenko V, Vitiello J, Remaki B, Barbier D (2004) Gas permeability of porous silicon nanostructures. Phys Rev E 70(1) 017301... 

Barthelemy P, Ghulinyan M, Gaburro Z, Toninelli C, Pavesi L, Wiersma DS (2007) Optical switching by capillary condensation. Nat Photonics 1(3) 172-175 Billat S, Thonissen M, ArensFischer R, Berger MG, Kruger M, Luth H (1997) Influence of etch stops on the microstructure of porous silicon layers. Thin Solid Films 297(l-2) 22-25 Bisi O, Ossicini S, Pavesi L (2000) Porous silicon a quantum sponge structure for silicon based optoelectronics. Surf Sci Rep 38(1-3) 1-126... 

Bruska A, Chemook A, Schulze S, Hietschold M (1996) Cathodoluminescence and writing of optical patterns on porous silicon by scanning electron microscopy. Appl Phys Lett 68(17) 2378 Canham LT (1997) Properties of porous silicon. Institution of Engineering and Technology, London Cole MW, Harvey JF (1992) Microstructure of visibly luminescent porous silicon. Appl Phys Lett 60(22) 2800-2802... 

Fig. 5 SEM images of polypyrrole nano- and microstructures after selective removal of porous silicon templates. Images (a-e) are related to polypyrrole, image (f) is for polyaniline, (d) is a magnified image of (b). Image (e) eorresponds to partially filled pores. Templates used are (a) ordered macropores and (c) mesopores while (b, d, e, f) medium-sized pores...

Table 1 summarizes some microstructural and electrochemical properties of porous Si anode materials, as pertaining to the second approach mentioned above, collected from the literature published since 2005. Several synthesis methods have been identified for preparing the porous Si anode materials (column 1, Table 1). One of the two most adopted methods is known as the metal-assisted chemical etching (MACE denoted as E in Table 1). The fundamental principle of this method can be found in the handbook chapter Porous Silicon Formation by Metal Nanoparticle Assisted Etching. Figure 2 shows an example of the MACE-derived porous Si particle. The other most adopted method is magnesiothermic reduction (denoted as M in Table 1). In this method (see handbook chapter Porous Silicon Formation by Porous Silica Reduction ), porous Si oxide materials are reduced by magnesium vapor under high-temperature thermal treatment. The porous Si oxide precursors may be synthesized via the conventional sol-gel processes. Porous Si particles with unique pore structures, such as hollow interior and ordered mesoporosity, may be obtained from Si oxides having the same pore structures which are achieved by using proper templates.

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