Silicon nanocrystallites

The temperature dependence of meso PS resistivity can be understood if Coulomb blockade effects are taken into account. For a silicon nanocrystallite to become conducting, it must first overcome the Coulomb blockade barrier, EB [Lel4, Hal4, Mi8] ... 

P. M. Fauchet, Porous Silicon Photoluminescence and Electroluminescent Devices C. Delerue, G. Allan, and M. Lannoo, Theory of Radiative and Nonradiative Processes in Silicon Nanocrystallites L. Bros, Silicon Polymers and Nanocrystals... 

G. Polisski, B. Averboukh, K. Kovalev, and F. Koch, Control of silicon nanocrystallite shape asymmetry and orientation anisotropy by light-assisted anodization, App/. Phys. Lett. 70(9), 1116, 1997. 

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... 

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. 

B. Sweryda et al., A Comparison of Porous Sflicon and Silicon Nanocrystallite Pho-toluminescence Quenching with Amines, J. Phys. Chem. 1996,100(32), 13 776-13 780, and reference therein. 

Moretti L, De Stefano L, Rendina I (2007) Quantitative analysis of capillary condensation in fiuctal-like porous silieon nanostructures. J Appl Phys 101 024309 Nyehyporuk T, Lysenko V, Barbier D (2005) Fractal nature of porous silicon nanocrystallites. APS J Phys Rev B 71 115 02... 

Guo D-J, Wang J, Tan W, Xiao S-J, Dai Z-D (2009) Macroporous silicon templated from silicon nanocrystallite and functionalized Si-H reactive group for grafting organic monolayer. J Colloid Interface Sci 336 723-729... 

Sailor MJ, Lee EJ (1997) Surface chemistry of luminescent silicon nanocrystallites. Adv Mater 9 783-793... 

Sweryda-Krawiek B, Chandler-Henderson RR, Coffer JL, Rho YG, Pinizzotto RF (1996) A comparison of porous silicon and silicon nanocrystallite photoluminescence quenching with amines. J Phys Chem 100 13776-13780... 

Sweryda-Krawiec B, Cassagneau T, Fendler JH (1999) Surface modification of silicon nanocrystallites by alcohols. J Phys Chem B 103 9524—9529 Takasuka E, Kamei K (1994) Microstmcture of porous silicon and its correlation with photolumi-nescence. Appl Phys Lett 65 484—486... 

By controlling the structural and electronic properties of sNPS which are related to the nanocrystallite dimensions and porosity, their surface selectivity and sensitivity to different gases (nitrogen and carbon oxide, vapors of water and organic substances) can be adjusted. This approach for the effective detection of acetone, methanol and water vapor in air was described in [13-15].The minimal detectable acetone concentration was reported to be 12 pg/mL. Silicon sensors for detection of SO2 and some medicines such as penicillin were created [16-18]. sNPS were used for the development of a number of immune biosensors, particularly using the photoluminescence detection. Earlier we developed similar immune biosensors for the control of the myoglobin level in blood and for monitoring of bacterial proteins in air [19-23]. 

REDISTRIBUTION OF CrSiz NANOCRYSTALLITES IN SILICON CAP LAYERS DURING MBE GROWTH ON Si(lll)... 

Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy (RDE) of 0.6 nm Cr at 500, 550 and 600 C. The NCs were covered by epitaxial silicon at 700 °C with different thickness. It was observed that CrSi2 is localized nearthe surface in the form of 20 nm 2D nanoislands and 40-80 nm 3D NCs. The 2D nanoisland concentration is found to be reduced by the Si cap growth, while the large 3D NCs appear at the depth of Cr deposition and they also appear at the surface. 

THE MORPHOLOGY AND OPTICAL PROPERTIES OF Fe, Cr AND Mg SILICIDE NANOCRYSTALLITES BURIED IN SILICON BY ION IMPLANTATION, PULSED TREATMENTS AND Si OVERGROWTH... 

McHale JM, Auroux A, Perrotta AJ, Navrotsky A (1997) Surface energies and thermodynamic phase stability in nanocrystalline aluminas. Science 277 788-791 Molteni C, Martonak R, Parrinello M (2001) First principles molecular dynamics simulations of pressure-induced stiuctural transformations in silicon clusters. J Chem Phys 114 5358-5365 Murray CB, Norris DJ, Bawendi MG (1993) Synthesis and characterization of nearly monodisperse CdE (E = S, Se, Te) semiconductor nanocrystallites. J Am Chem Soc 115 8706-8715 Onodera A (1972) Kinetics of polymorphic transitions of cadmium chalcogenides under high pressure. Rev Phys Chem Japan 41 1... 

Hydrothermal synthesis is one of the important methods for producing fine powders of oxides. A hydrothermal system is usually maintained at a temperature beyond 100 °C and the autogenous pressure of water exceeds the ambient pressure, which is favorable for the crystallization of products. Recent research indicates that the hydrothermal method is also a practical means for preparing chal-cogenide and phosphide nanomaterials, and hydrothermal treatment is an effective method for passivating porous silicons. Similar to hydrothermal synthesis, in a solvothermal process, a non-aqueous solvent, which is sealed in an autoclave and maintained in its superheated state, is the reaction medium, where the reactants and products are prevented effectively from oxidation and volatilization and the reaction and crystallization can be realized simultaneously. Furthermore, organic solvents may be favorable for the dispersion of non-oxide nanocrystallites and may stabilize some metastable phases. 

Porous silicon is comprised of interconnected zero-dimensional nanocrystallites and one-dimensional nanowires produced through the chemical [7], photochemi-... 

SiHs) moieties comprising the surfaces of the nanocrystallites. Silicon hydride bending modes appear below 1000 cm Silicon oxide, which absorbs near 1100 cm is conspicuously absent. 

The native properties of high surface area, luminescence, tunable biostability, and reactive surface chemistry identify porous silicon as a potentially useful substrate for a variety of tasks. Presented below are several uses that have been developed by exploiting the chemical reactivity or changes effected by chemical interactions with the nanocrystallites. These applications range from use as a material or structural implant to use as a sensor or analytical support. 

Highly monodisperse ZnSe nanocrystallites (NCs) were deposited on free-standing porous silieon. Optical phonons confined in nearly spherical ZnSe QDs have been studied theoretically and experimentally. Spatially quantized phonon modes are considered in the framework of the continuum model. Raman scattering and absorption of far-infrared (FIR) radiation in ZnSe quantum dots have been studied. Experimental FTIR transmittance spectra of porous silicon free layers containing nearly spherical ZnSe nanocrystals show a broad band between the bulk TO and LO phonon frequencies. 

The next two chapters deal with investigations concerning solid silicon monoxide. The application of thin films of this material is based on its unique mechanical, chemical, and dielectric properties. It is related to Si-Si systems in so far as solid SiO consists of small particles of Si and Si02. Depending on the conditions for synthesis, the material has different local structures. In the contribution of U. Schubert and T. Wieder (Chapter 18), the structure and reactivity of a special SiO modification (Patinal ) is described. This material consists of Si and Si02 regions of 0.25 - 0.5 nm in diameter, which are connected by a thin interface. Most of the SiO reactions are also observed for elemental silicon. H. Hofineister and U. Kahler (Chapter 19) show that thermal processing of solid SiO (from BALZERS) up to 1300°C leads to phase separation into Si nanocrystallites embedded in an SiOx matrix. Their internal structure is determined by solid-phase crystallization processes. 

SEMICONDUCTOR SILICIDE NANOCRYSTALLITES IN SILICON MATRIX GROWTH AND OPTICAL PROPERTIES... 

In this work a growth and study of optical properties of monolithic silicon -silicide heteronanostructures with multilayers of buried semiconductor silicide (FeSi2 and CrSi2) nanocrystallites (NC s) have been performed. 

For a growth of monolithic silicon structures with few buried layers of CrSi2 nanocrystallites the substrate temperature of 750 °C and silicon layer thickness of 35 nm were selected. Three samples with two, four and six layers of buried CrSi2 nanocrystallites were grown. Si(l 11)7x7 patterns were preserved for all cases that corresponds to a formation of monolithic heteronanostructures based on silicon. A study of morphology has shown that a fdm surface consists of... 

Since a depth of burying of silicide nanocrystallites does not exceed 100 nm, a light with a penetration depth of one micron is enough for registration of another phase inside silicon matrix. Therefore, new information about existing of semiconductor silicide nanocrystallites inside silicon matrix can be obtained from DRS-spectra in the narrow range of photon energy (1.1-2.8 eV). As a reference a monocrystalline silicon substrate can be used. 

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