Porous silicon surface modification stability

In most of these applications, silica has the role of a support material. The popularity of silicon-based supports for multiple modification applications is well summarized by Mottola.1 Chemical modification requires seemingly paradoxal support properties (a) supports need to have a surface hydrophilic in nature but also to be insoluble in aqueous solutions and polar solvents (b) supports are required, in many instances, to be porous but retain mechanical stability and (c) they must be chemically stable but easily derivatized. Silica gel meets all of these requirements. 

Porous silicon (PS) is one of the nanoscale modifications of silicon. There are various approaches to PS producing that are now in use. The technique most generally employed today is known as wet anodization of a crystalline silicon. With this technique, yield parameters of porous material (porosity, pore size and shape, interpore distance) may be readily varied by anodization regimes. However, it is well known the problem of the PS stability influencing the physical properties of the PS layers. P S instability is c onditioned b y very large specific surface area of the porous material. 

A number of studies has been attempted to stabilize porous silicon low-temperature oxidation in a controlled way [1-3], surface modification of silicon nanocrystallites by chemical [4] or electrochemical [5] procedures etc. Rapid thermal processing (RTP) is thought to be a shortcut method of the PS stabilization for a number of purposes. However, there is no data about RTP influence on the PS structure. Therefore, the study of lattice deformations of PS layers after RTP is of great interest. In the present work. X-ray double-crystal diffractometry was used to measure lattice deformations of PS after RTP of millisecond and second durations. 

Ohmic and rectifying contacts to porous silicon are important and challenging for the commercial applications of PS-based electronic, optoelectronic, and sensor devices. The choice of contact materials and the nature of PS surface (including porosity) are the prime factors for the successful achievement in the contact formation with the desired specific contact resistance. Surface modification of porous silicon by Pd improves both ohmic and rectifying contacts along with the stability as it was verified by intermittent I-V studies. Verification of specific contact resistance at regular intervals can be an alternative method to study the junction stability. 

Mahmoudi BE, Gabouze N, Guerbous L, Haddadi M, Beldjilali K (2007b) Long-time stabilization of porous silicon photoluminescence by surface modification. J Lumin 127 534-540 McLellan RB (1997) The kinetic and thermodynamic effects of vacancy interstitial interactions in Pd-H solutions. Acta Mater 45 1995-2000... 

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