Optical properties porous silicon

Qiu T, Wu XL, Siu GG, Chu PK (2005) Self-assembled growth and green emission of gold nano whiskers. Appl Phys Lett 87 223115-1-223115-3 Qu Y, Liao L, Li Y, Zhang H, Huang Y, Duan X (2009) Electrically conductive and optically active porous silicon nanowires. Nano Lett 9(12) 4539 543 Qu Y, Zhong X, Li Y, Liao L, Huang Y, Duan X (2010) Photocatalytic properties of porous silicon nanowires. J Mater Chem 20(18) 3590-3594... 

Loni A (1997) Capping of porous silicon. In Canham L (ed) Properties of porous silicon. INSPEC, London, p 51 Ludwig MH (1996) Optical properties of silicon-based materieils a comparison of porous and spark-processed silicon. 

Snow, P. A. Squire, E. K. Russell, P. S. J. Canham, L. T., Vapor sensing using the optical properties of porous silicon bragg mirrors, J. Appl. Phys. 1999, 86, 1781 1784... 

Octasilacubanes were used as a model in an attempt to understand the optical properties of porous silicon because both porous silicon and octasilacubane show a broad photoluminescence spectra and large Stokes shifts52. 16 for example, shows an absorption edge at ca 3.2 eV and a broad photoluminescence spectrum with a peak at 2.50 eV. 

In a Si zero-dimensional system the strong quantum confinement can increase the optical infrared gap of bulk Si and consequently shift the optical transition energies towards the visible range [65,66]. This is the reason for which silicon nanocrystals (Si-NCs) with a passivated surface are used as the natural trial model for theoretical simulations on Si based light emitting materials, such as porous Si or Si nanocrystals dispersed in a matrix. In this section we present a comprehensive analysis of the structural, electronic and optical properties of Si-NCs as a function of size, symmetry and surface passivation. We will also point out the main changes induced... 

Non-Debye dielectric relaxation was also observed in porous silicon (PS) [25,160,161], PS has attracted much attention recently, mainly due to its interesting optical and electro-optical properties that can be utilized for device applications [164,165], So far, most of the activity in this field has focused on the intense visible photoluminescence (PL) from nano-PS and the underlying physical mechanism that is responsible for the generation of light. In addition, transport and dielectric relaxation phenomena in PS have also attracted... 

The optical properties of porous silicon have given rise to renewed interest in the processes leading to pore formation and the relationship between the structure and characteristic properties of porous layers. Indeed, porous semiconductors may be considered a new class of materials, since pore formation is not limited to silicon and has been observed for a wide range of compound semiconductors. 

Cubic Si-skeleton clusters were used to model the optical properties of porous silicon (40). In the octasilacubane 15, the absorption edge is observed at approxiamtely 3.2 eV, and a broad photoluminescence spectrum is also observed with a peak of 2.50 eV. Both porous silicon and octasilacubane show broad photoluminescence spectra and large Stokes shifts. 

C. Pichering, M. I. J. Beal, and D. J. Robins (Optical properties of Porous silicon films), Thin Solid Films 125, 157, 1984. 

Evolution of reflectivity signals over time has been used to temporally resolve the constituents of a binary vapor mixture [102]. Since the studied solvents (ethanol and acetone) have identical refractive indices, changes in the optical reflectance of porous silicon exposed to these vapors were shown to depend upon the rates of diffusion and adsorption of these species into the material. Time-resolved refrac-tometry revealed that an equimolar mixture of acetone and ethanol vapors exhibited markedly different condensation within porous silicon than did the pure mixture constituents (figure 16.14). This method is comparable to gas chromatography in that the vapor mixture interacts with the matrix in a manner dependent upon the physical properties of its components, but the porous silicon device... 

Optical properties of dielectrics can be modified by incorporating nanosize clusters of foreign materials. Recently Si nanoclusters were shown to excite rare-earth element Er in the silica glass host [1,2]. The favorable effect of Si nanoclusters on the photoluminescence of Er in oxidized porous silicon (OPS) was also demonstrated [3], In silica hosts doped with Si nanoclusters it was shown that the excitation energy can be transferred from nanoclusters to Er ions located in a silicalike environment near the clusters. Nowadays, there is a principal interest to incorporate Er ions inside clusters due to influence on the excitation process. 

The study of small and intermediate-sized clusters has become an important research field because of the role clusters play in the explanation of the chemical and physical properties of matter on the way from molecules to solids/ Depending on their size, clusters can show reactivity and optical properties very different from those of molecules or solids. The great interest in silicon clusters stems mainly from the importance of silicon in microelectronics, but is also due in part to the photoluminescence properties of silicon clusters, which show some resemblance to the bright photoluminescence of porous silicon. Silicon clusters are mainly produced in silicon-containing plasma as used in chemical vapor deposition processes. In these processes, gas-phase nucleation can lead to amorphous silicon films of poor quality and should be avoided.On the other hand, controlled production of silicon clusters seems very suitable for the fabrication of nanostructured materials with a fine control on their structure, morphological, and functional properties. ... 

Porous silicon (por-Si) formed by electrochemical etching of (llO)-oriented p-type Si wafers is an example of novel nanostructured medium with controllable optical properties. It was found to exhibit the strong in-plane birefringence (up to 18 %) and free-carrier dichroism [1-5]. Both phenomena originate from the form anisotropy of Si nanocrystals and voids assembling the material [3-5]. Below, we report the analysis of the dichroism in por-Si on the basis of the generalized effective-medium approximation (EMA) [7] as well as prominent anisotropy of absorption by silicon-hydrogen surface bonds. 

Structural and Optical Properties of Porous Silicon Nanostructures, (Eds. G. Amato, C. Delerue H. J. von Bardeleben), Gordon and Breach, Amsterdam, 1997. 

To enhance the specificity towards target molecules, specific sites for interaction have been developed. A select group of enzymes show selectivity towards organophosphorus compounds, including nerve agents, through the action of hydrolysis. These enzymes present potential for detection if they can be immobilized on the surface of the porous silicon and the enzymatic activity affects the optical properties of the porous silicon. Hart and coworkers have... 

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