Thermal transport enhancement of hybrid nanocomposites; impact of confined water inside nanoporous silicon

The thermal transport properties of porous silicon and nano-hybrid "porous silicon/water" systems are presented here. The thermal conductivity was evaluated with equilibrium molecular dynamics technique for porous systems made of spherical voids or water-filled cavities. We revealed large thermal conductivity enhancement in the nano-hybrid systems as compared to their dry porous counterparts, which cannot be captured by effective media theory. This rise of thermal conductivity is related to the increases of the specific surface of the liquid/solid interface. We demonstrated that significant difference for more than two folds of thermal conductivity of pristine porous silicon and "porous silicon liquid/composite" is due to the liquid density fluctuation close to "solid/liquid interface" (layering effect). This effect is getting more important for the high specific surface of the interfacial area. Specifically, the enhancement of the effective thermal conductivity is 50 % for specific surface area of 0.3 (1/nm), and it increases further upon the increase of the surface to volume ratio. Our study provides valuable insights into the thermal properties of hybrid liquid/solid nanocomposites and about the importance of confined liquids within nanoporous materials

Characterization of Er in porous Si

The fabrication of porous Si-based Er-doped light emitting devices is a very promising developing field for all-silicon light emitters. However, while luminescence of Er-doped porous silicon devices has been demonstrated, very little attention has been devoted to the doping process itself. We have undertaken a detailed study of this process examining the porous silicon matrix from several points of view, during and after the doping. In particular, we have found that the Er doping process shows a threshold level which, as evidenced by the cross correlation of the various techniques used, does depend on the sample thickness and on the doping parameters

Improved toughness of silicon carbide

Several techniques were employed to apply or otherwise form porous layers of various materials on the surface of hot-pressed silicon carbide ceramic. From mechanical properties measurements and studies, it was concluded that although porous layers could be applied to the silicon carbide ceramic, sufficient damage was done to the silicon carbide surface by the processing required so as to drastically reduce its mechanical strength. It was further concluded that there was little promise of success in forming an effective energy absorbing layer on the surface of already densified silicon carbide ceramic that would have the mechanical strength of the untreated or unsurfaced material. Using a process for the pressureless sintering of silicon carbide powders it was discovered that porous layers of silicon carbide could be formed on a dense, strong silicon carbide substrate in a single consolidation process

AN INVESTIGATION OF THE POROUS SILICON OPTICAL-ABSORPTION POWER-LAW NEAR THE BAND-EDGE

A theoretical investigation of the absorption coefficient of p-type doped porous silicon near the band edge is presented. We assume that the absorption coefficient is constructed by taking an average over a distribution (in terms of band gap) of absorption coefficients of individual crystallites. Exploiting physics fundamental to the crystallite optical absorption process, we derive the relation between the absorption coefficient and the averaged conduction density of states near the band edge for porous silicon. By postulating a specific form for the effective conduction density of states we find excellent agreement with recent optical absorption data for p-type doped porous silicon. We attempt to explain the basis for this postulate phenomenologically by suggesting a certain large-scale behaviour of the particle size distribution. The implication of further experimental verification will be discussed

Tin dioxide sol-gel derived thin films deposited on porous silicon

Undoped and Sb-doped SnO2 sol¿gel derived thin films have been prepared for the first time from tin (IV) ethoxide precursor and SbCl3 in order to be utilised for gas sensing applications where porous silicon is used as a substrate. Transparent, crack-free and adherent layers were obtained on different types of substrates (Si, SiO2/Si). The evolution of the Sn¿O chemical bonds in the SnO2 during film consolidation treatments was monitored by infrared spectroscopy. By energy dispersive X-ray spectroscopy performed on the cross section of the porosified silicon coupled with transmission electron microscopy, the penetration of the SnO2 sol¿gel derived films in the nanometric pores of the porous silicon has been experimentally proved

Role of microstructure in porous silicon gas sensors for NO2_2

Electrical conductivity of porous silicon fabricated form heavily doped p-type silicon is very sensitive to NO$_2$, even at concentrations below 100 ppb. However, sensitivity strongly depends on the porous microstructure. The structural difference between sensitive and insensitive samples is independently confirmed by microscopy images and by light scattering behavior. A way to change the structure is by modifying the composition of the electrochemical solution. We have found that best results are achieved using ethanoic solutions with HF concentration levels between 13% and 15%.Comment: 3 pages, 4 figures, package SIunits require

Porous silicon solar cells

We developed a new process for the fabrication of crystalline solar cell, based on an ultrathin silicon membrane, taking advantage of porous silicon technology. The suggested architecture allows the costs reduction of silicon based solar cell reusing the same wafer to produce a great number of membranes. The architectures combines the efficiency of crystalline silicon solar cell, with the great absorption of porous silicon, and with a more efficient way to use the material. The new process faces the main challenge to achieve an effective and not expensive passivation of the porous silicon surface, in order to achieve an efficient photovoltaic device. At the same time the process suggests a smart way to selective doping of the macroporous silicon layers despite the through-going pores. © 2015 IEEE. SciVal Topic Prominence  Topic: Porous silicon | Silicon | macroporous silicon Prominence percentile: 66.984  Author keywords nanofabricationporous siliconsilicon nanoelectronicssolar cells Indexed keywords Engineering controlled terms: Crystalline materialsNanoelectronicsNanostructured materialsNanotechnologyPorous siliconSiliconSilicon wafersSolar cells Engineering uncontrolled terms Crystalline silicon solar cellsCrystalline solar cellsMacro porous siliconPhotovoltaic devicesPorous silicon surfacesPorous silicon technologySilicon nanoelectronicsUltrathin silicon membrane Engineering main heading: Silicon solar cells ISBN: 978-146738155-0 Source Type: Conference Proceeding Original language: English DOI: 10.1109/NANO.2015.7388710 Document Type: Conference Paper Sponsors: Nanotechnology Council Publisher: Institute of Electrical and Electronics Engineers Inc. References (9) View in search results format ▻ All Export  Print  E-mail Save to PDF Create bibliography 1 (2012) International Technology Roadmap for Photovoltaics Results 2012. Cited 24 times. ITRPV, Third Edition, Berlin 2012 www.ITRPV.net 2 Lehmann, V., Honlein, W., Stengl, R., Willer, J., Wendt, H. (1992) Verfahren Zur Herstellung Einer Solarzelle Aus Einer Substratscheibe. Cited 6 times. German patent DE4204455C1; Filing date: 29. 01. 3 Brendel, R., Ernst, M. Macroporous Si as an absorber for thin-film solar cells (2010) Physica Status Solidi - Rapid Research Letters, 4 (1-2), pp. 40-42. Cited 22 times. http://www3.interscience.wiley.com/cgi-bin/fulltext/123215552/PDFSTART doi: 10.1002/pssr.200903372 Locate full-text(opens in a new window) View at Publisher 4 Ernst, M., Brendel, R., Ferré, R., Harder, N.-P. Thin macroporous silicon heterojunction solar cells (2012) Physica Status Solidi - Rapid Research Letters, 6 (5), pp. 187-189. Cited 16 times. doi: 10.1002/pssr.201206113 Locate full-text(opens in a new window) View at Publisher 5 Ernst, M., Brendel, R. Macroporous silicon solar cells with an epitaxial emitter (2013) IEEE Journal of Photovoltaics, 3 (2), art. no. 6472253, pp. 723-729. Cited 7 times. doi: 10.1109/JPHOTOV.2013.2247094 Locate full-text(opens in a new window) View at Publisher 6 Ernst, M., Schulte-Huxel, H., Niepelt, R., Kajari-Schröder, S., Brendel, R. Thin crystalline macroporous silicon solar cells with ion implanted emitter (Open Access) (2013) Energy Procedia, 38, pp. 910-918. Cited 2 times. http://www.sciencedirect.com/science/journal/18766102 doi: 10.1016/j.egypro.2013.07.364 Locate full-text(opens in a new window) View at Publisher 7 Nenzi, P., Kholostov, K., Crescenzi, R., Bondarenka, H., Bondarenko, V., Balucani, M. Electrochemically etched TSV for porous silicon interposer technologies (2013) Proceedings - Electronic Components and Technology Conference, art. no. 6575887, pp. 2201-2207. Cited 2 times. ISBN: 978-147990233-0 doi: 10.1109/ECTC.2013.6575887 Locate full-text(opens in a new window) View at Publisher 8 Perticaroli, S., Varlamava, V., Palma, F. Microwave sensing of nanostructured semiconductor surfaces (2014) Applied Physics Letters, 104 (1), art. no. 013110. Cited 3 times. doi: 10.1063/1.4861424 Locate full-text(opens in a new window) View at Publisher 9 De Cesare, G., Caputo, D., Tucci, M. Electrical properties of ITO/crystalline-silicon contact at different deposition temperatures (2012) IEEE Electron Device Letters, 33 (3), art. no. 6142006, pp. 327-329. Cited 28 times. doi: 10.1109/LED.2011.2180356 Locate full-text(opens in a new window) View at Publisher © Copyright 2017 Elsevier B.V., All rights reserved. ◅ Back to results ◅ Previous 3of10 Next ▻  Top of page Metrics Learn more about article metrics in Scopus (opens in a new window)  0 Citations in Scopus 0 Learn more about Field-Weighted Citation Impact Field-Weighted Citation Impact PlumX Metrics Usage, Captures, Mentions, Social Media and Citations beyond Scopus.  Cited by 0 documents Inform me when this document is cited in Scopus: Set citation alert ▻ Set citation feed ▻ Related documents Thin crystalline macroporous silicon solar cells with ion implanted emitter Ernst, M. , Schulte-Huxel, H. , Niepelt, R. (2013) Energy Procedia Multilayer etching for kerf-free solar cells from macroporous silicon Schäfer, S. , Ernst, M. , Kajari-Schröder, S. (2013) Energy Procedia Macroporous silicon solar cells with an epitaxial emitter Ernst, M. , Brendel, R. (2013) IEEE Journal of Photovoltaics View all related documents based on references Find more related documents in Scopus based on: Authors ▻ Keywords ▻ About Scopus What is Scopus Content coverage Scopus blog Scopus API Privacy matters Language 日本語に切り替える 切换到简体中文 切換到繁體中文 Русский язык Customer Service Help Contact us Elsevier Terms and conditions ↗ Privacy policy ↗ Copyright © 2018 Elsevier B.V ↗. All rights reserved. Scopus® is a registered trademark of Elsevier B.V. We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies. RELX Group We developed a new process for the fabrication of crystalline solar cell, based on an ultrathin silicon membrane, taking advantage of porous silicon technology. The suggested architecture allows the costs reduction of silicon based solar cell reusing the same wafer to produce a great number of membranes. The architectures combines the efficiency of crystalline silicon solar cell, with the great absorption of porous silicon, and with a more efficient way to use the material. The new process faces the main challenge to achieve an effective and not expensive passivation of the porous silicon surface, in order to achieve an efficient photovoltaic device. At the same time the process suggests a smart way to selective doping of the macroporous silicon layers despite the through-going pores

Reaction cured glass and glass coatings

The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF)

Interfacial thermal resistance between porous layers: impact on thermal conductivity of a multilayered porous structure

Features of thermal transport in multilayered porous silicon nanostructures are considered. Such nanostructures were fabricated by electrochemical etching of monocrystalline Si substrates by applying periodically changed current density. Hereby, the multilayered structures with specific phononic properties were formed. Photoacoustic (PA) technique in gas-microphone configuration was applied for thermal conductivity evaluation. Experimental amplitude-frequency dependencies were adjusted by temperature distribution simulation with thermal conductivity of the multilayered porous structure as a fitting parameter. The experimentally determined values of thermal conductivity were found to be significantly lower than theoretically calculated ones. Such difference was associated with the presence of thermal resistance at the interfaces between porous layers with different porosities arising because of elastic parameters mismatch (acoustical mismatch). Accordingly, the magnitude of this interfacial thermal resistance was experimentally evaluated for the first time. Furthermore, crucial impact of the resistance on thermal transport perturbation in a multilayered porous silicon structure was revealed

Multi-walled microchannels: free-standing porous silicon membranes for use in µTAS

Electrochemically formed porous silicon (PS) can be released from the bulk silicon substrate by underetching at increased current density. Using this technique, two types of channels containing free-standing layers of PS were constructed, which were failed multi-walled microchannels (MW µCs). They can be used in devices like microsieves, microbatteries, and porous electrodes. Two types of MWµC were made: the 'conventional' version, consisting of two or more coaxially constructed microchannels separated by a suspended PS membrane, and the buried variety, where a PS membrane is suspended halfway in an etched cavity surrounded by silicon nitride walls. The latter is more robust. The pore size of the PS was measured using transmission electron microscopy and field emission gun scanning electron microscopy (FEGSEM) and found to be of the order of 7 n