Photoluminescent porous silicon surface

MAGNETIC-FIELD-INDUCED MODIFICATION OF POROUS SILICON SURFACE AND PHOTOLUMINESCENCE... 

An influence of a weak magnetic field on the evolution of porous silicon surface species during ageing in air and porous silicon photoluminescence is studied. Magnetic field retards the process of Si surface oxidation and stimulates a breakage of Si-H bonds at the porous silicon surface. It also affects bond energy in silicon complexes witti water molecules. 

Ongoing investigations into the chemistry of porous silicon surfaces seek to develop methods for the preparation of chemically functional interfaces that protect the underlying silicon nanocrystallites from degradation without changing or annihilating their intrinsic behavior. The native, hydride-terminated surface is only metastable under ambient conditions and oxidation of freshly prepared porous silicon commences within minutes when exposed to air. While surface oxide can suitably passivate the nanocrystalline silicon and stabilize its photoluminescence, the electrically insulating and structurally defective character of this oxide layer... 

Platinum ions reduce to metallic Pt by injecting holes into the Si valence band. Thus Pt ions act as an oxidizing agent for silicon, and result in the simultaneous formation of photoluminescent porous silicon under certain conditions. Nickel ions may exchange charge with both the conduction and the valence band. The reduction of Ni ions competes with hydrogen evolution, and the deposition of Ni can only be achieved at high pH where it is kinetically faster. The role of silicon surface states as reaction intermediates is discussed. 

Porous silicon is a desirable surface material for sensors because of its photoluminescence properties. With excitation, the porous silicon surface can luminesce at a variety of easily detected wavelengths. Through various methods, such as quenching, the surface can show some evidence of interaction with a target molecule. However, plain porous silicon lacks the specificity needed to detect target molecules, and is subject to non-specific interferences. 

Wise M, Sneh O, Okada LA, George SM (1996) Reaction kinetics of H2O with chlorinated Si(l 11)— (7 X 7) and porous silicon surfaces. Surf Sci 364 367-379 Xiao L, Gu L, Howell SB, Sailor MJ (2011) Porous silicon nanoparticle photosensitizers for singlet oxygen and their phototoxicity against cancer cells. ACS Nano 5(5) 3651-3659 Xiong ZH, Liao LS, Yuan S, Yang ZR, Ding XM, Hou XY (2001) Effects of O, H andN passivation on photoluminescence from porous silicon. Thin Solid Films 388 271-276 Xu YK, Adachi S (2010) Multiple-peak structure in porous Si photoluminescence. J Appl Phys 107(12) 123520... 

Photoluminescent porous silicon nanoparticles have many potential medical uses if their properties can be optimized. The techniques for both fabricating such particles and their surface chemistry manipulation are reviewed, including recent approaches whereby such nanoparticles are embedded in other biomaterial matrices. 

AUen MJ, Buriak JM (1999) Photoluminescence of porous silicon surfaces stabilized through Lewis acid mediated hydrosilylation. J Lumin 80 29-35 Anglin EJ, Cheng L, Freeman WR, Sailor MJ (2008) Porous silicon in drug delivery devices and materials. Adv Drug Deliv Rev 60 1266-1277... 

A second example concerns another common processing step - chemical passivation of porous silicon surfaces, in particles or patterned wafers. There are three dedicated reviews in the handbook that deal with this Oxidation of mesoporous silicon, Silicon-Carbon Bond Formation for Porous Silicon, and Photoluminescent Nanoparticle Derivatization for Porous Silicon. It can be important to perform these passivation treatments after the particle sizing or patterning process otherwise freshly fractured or patterned porous silicon surfaces will not be passivated. Note that for some applications one can also choose to derivatize the pore walls during anodization (Mattei and Valentini 2003) rather than the more common sequence to derivatize after, or even both during and after anodization to get specific surface chemistries and spatially selective functionalization (Valentini et al. 2007). 

Buriak JM, Allen MJ (1998b) Photoluminescence of porous silicon surfaces stabilized through Lewis acid mediated hydrosilylation. J Luminesc 80 29-35... 

The formation of porous layers in silicon by chemical etching in HF/HNO3 solutions was first reported at about the same time as electrochemical etching [101-104]. These so-called stain etch films are characterized by rough or porous surfaces, typically < 500 A in thickness. Recent work has shown that these stain etch films exhibit strong visible photoluminescence, similar to the emission observed from electrochemically etched porous silicon layers. 

Y. Suda, T. Koizumi, K. Obata, Y. Tezuka, S. Shin, and N. Koshida, Surface electronic structure and photoluminescence mechanism of porous silicon, J. Electrochem. Soc. 143, 2502, 1996. 

Beyond the motivation to fabricate working systems from functionalized porous silicon, there is also more fundamental interest in the reactions of its surfaces. Because the vast surface of nanocrystalline silicon contains a large fraction of the total atoms, the composition and environment of the silicon interface are believed to affect greatly the physical, chemical, and electronic properties of the material. In particular, functionalization of porous silicon with certain organic groups is known to diminish photoluminescence [27] however, the mechanism of quenching has... 

Since the discovery of the intense red photoluminescence of porous silicon [1,2], much work has been devoted to this particular nanostructured material [4, 5] and, in the meantime, also to silicon nanoparticles [6, 7]. An important issue of current studies is the influence of the surface passivation on the photoluminescence properties. It has already been said that, in the quantum confinement model, it is essential that the surface is well passivated to avoid any dangling bonds [8]. Being middle-gap defects, these dangling bonds will quench the PL. On the other hand, the surface itself may lead to surface states that can be the origin of another kind of photoluminescence [9,10]. 

We provide a literature survey of a number of classical techniques used to quantify the chemical composition of porous silicon, highlighting their general merits and potential limitations with the material. Much of the early literature was focused on photoluminescent material, but increasingly there are studies on nanocomposites where chemical composition analysis is required to assess the degree and uniformity of impregnation or surface attachment. 

Du XW, Jin Y, Zhao NQ, Fu YS, Kulinich SA (2008) Controlling surface states and photoluminescence of porous silicon by low-energy-ion irradiation. Appl Surf Sci 254(8) 2479-2482 El Houichet H, Oueslati M, Bessais B, Ezzaouia H (1997) Photoluminescence enhancement and degradation in porous silicon evidence for nonconventional photoinduced defects. J Lumin... 

Takeda E, Nakamura T, Fujii M, Miura S, Hayashi S (2006) Surface plasmon polariton mediated photoluminescence from excitons in silicon nanocrystals. Appl Phys Lett 89(10) 101907 Tsybeskov L, Duttagupta SP, Fauchet PM (1995) Photoluminescence and electroluminescence in partially oxidized porous silicon. Solid State Commun 95(7) 429-433 Tsybeskov L, Duttagupta SP, Hirschman KD, Fauchet PM (1996) Stable and efficient electroluminescence from a porous silicon-based bipolar device. Appl Phys Lett 68(15) 2058-2060 Valenta J, Lalic N, Linnros J (2004) Electroluminescence of single silicon nanocrystals. Appl Phys Lett 84(9) 1459-1461... 

Porous silicon (pSi) at atomic scale is a crystalline material however, it presents a random porous distribution with branches of different morphologies and sizes, as discussed along this book. The description of this disordered porous structure is one of the main theoretical challenges. Due to the fabrication process, pSi presents different surface saturations and internal stmctural strains, both should be adequately simulated. In addition, the inhomogeneity of pSi produces broadening of the photoluminescence response that could be caused by a spread of local bandgaps if there is only a partial interconnection between the nanostructures (Calcott 1977). 

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... 

Low SP, Williams KA, Canham LT, Voelcker NH (2006) Evaluation of mammalian cell adhesion on surface-modified porous silicon. Biomaterials 27 4538 Makara VA, Klyui NI, Rozhin AG, Litovchenko VG, Piryatinskii YP, Kometa OB (2003) Porous silicon photoluminescence modification by surface treatments and impregnation of carbon based nanoclusters. Phys Status Solidi A-Appl Res 197 355 Makila E, Bimbo LM, Kaasalainen M, Herranz B, Airaksinen AJ, Heinonen M, Kukk E, Hirvonen J, Santos HA, Salonen J (2012) Amine modification of thermally carbonized porous silicon with silane coupling. Langmuir 28 14045... 

Kim Y, Tsao A, Lee DH, Maboudian R (2012) Solvent-induced formation of unidirectionally curved and tilted Si nanowires during metal-assisted chemical etching. J Mater Chem C 1 220-224 Kiraly B, Yang S, Huang TJ (2013) Multifunctional porous silicon nanopillar arrays antireflection, superhydrophobicity, photoluminescence, and surface-enhanced Raman scattering. Nanotechnology 24 245704... 

Lauerhaas JM, Sailor MJ (1993) The effects of halogen exposure on the photoluminescence of porous silicon. Mater Res Soc Symp Proc (USA) 298 259-263 Lees IN, Lin H, Canaria CA, Miskelly GM et al (2003) Chemical stability of porous silico surfaces electrochemically modified with functional alkyl species. Langmuir 19 9812-9817 Li K, Diaz DC, He Yet al (1994) Electroluminescence Ifom porous silicon with conducting polymer film contacts. Appl Phys Lett 64(18) 2394-2396... 

Petrova-Koch V, Muschik T, Kux A et al (1992) Rapid-thermal-oxidized porous Si-the superior photoluminescent Si. Appl Phys Lett 61 943-945 Porter LA, Choi HC, Ribbe AE et al (2002) Controlled electroless deposition of noble metal nanoparticle films on germanium surfaces. Nano Lett 2 1067-1071 Rabinal MK, Mulimani BG (2007) Transport properties of molecularly stabilized porous silicon schottky junctions. New J Phys 9 440-448... 

Kochergin V, Christophersen M, Foil H (2004) Effective medium approach for calculations of optical anisotropy in porous materials. Appl Phys B 79(6) 731-739 Kochergin V, Christophersen M, Foil H (2005) Surface plasmon enhancement of an optical anisotropy in porous silicon/metal composite. Appl Phys B 80(l) 81-87 Kovalev D et al (1995) Porous Si anisotropy from photoluminescence polarization. Appl Phys Lett 67(11) 1585-1587... 

Squire EK, Snow PA, Russell PS, Canham LT, Simons AJ, Reeves CL (1998) Light emission from porous silicon single and multiple cavities. J Lumin 80(1 ) 125-128 Sun J, Lu YW, Du XW, Kulinich SA (2005) Improved visible photoluminescence from porous silicon with surface Si-Ag bonds. Appl Phys Lett 86(17) 171905, Artn 171905, doi 10.1063/ 1.19240426... 

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