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Scattering characteristics from porous silicon
R. Sabet-Dariani,A. Morteza Ali & H Nurani
Iranian Journal of Physics Research , 2000,
Abstract: Porous silicon (PS) layers come into existance as a result of electrochemical anodization on silicon. Although a great deal of research has been done on the formation and optical properties of this material, the exact mechanism involved is not well-understood yet. In this article, first, the optical properties of silicon and porous silicon are described. Then, previous research and the proposed models about reflection from PS and the origin of its photoluminescence are reveiwed. The reflecting and scattering, absorption and transmission of light from this material, are then investigated. These experiments include,different methods of PS sample preparation their photoluminescence, reflecting and scattering of light determining different characteristics with respect to Si bulk.
Effect of Nd:YAG laser irradiation on the characteristics of porous silicon photodetector
Raid A Ismail and Marwa K Abood
International Nano Letters , 2013, DOI: 10.1186/2228-5326-3-11
Abstract: Electrical and photoresponse properties of a Al/porous silicon/crystalline silicon/Al structure (Al/PSi/Si/Al) are investigated under irradiation of Nd:YAG laser pulses. The effect of Nd-YAG laser irradiation on the morphological and structural properties of a porous silicon layer is also demonstrated. The porous Si layer is synthesized on a single crystalline p-type Si using electrochemical etching in aqueous hydrofluoric acid at a current density of 20 mA/cm2 for a 40-min etching time. The structure of the porous layer is investigated using atomic force microscopy and optical microscopy. The electrical properties and photodetector figures of merit (responsivity, detectivity, and carrier lifetime) are found to be dependent on the laser fluence.
Photodetectors on the Basis of Porous Silicon  [PDF]
Journal of Nano- and Electronic Physics , 2012,
Abstract: The paper studies the electrical characteristics of photodiode structures porous silicon – silicon substrates modified with molecules of iodine. Changes the nature of current-voltage characteristics obtained structures with symmetrical for straightening result of adsorption of iodine are revealed. It is studied the spectral characteristics of photoresponse in the 450-1100 nm wavelength range, its temperature dependence in the 125-325 K range and energy characteristics of photovoltaic structures based on porous silicon. A possible mechanism of influence of iodine adsorption on the electrical and photoelectrical properties of the structures of porous silicon – silicon substrates is proposed. The results extend the perspectives of porous silicon in photoelectronics.
Structural, Optical and Electrical Properties of ZnS/Porous Silicon Heterostructures
WANG Cai-Feng,LI Qing-Shan,LV Lei,ZHANG Li-Chun,QI Hong-Xia,CHEN Hou,

中国物理快报 , 2007,
Abstract: ZnS films are deposited by pulsed laser deposition on porous silicon (PS) substrates formed by electrochemical anodization of p-type (100) silicon wafer. Scanning electron microscope images reveal that the surface of ZnS films is unsmoothed, and there are some cracks in the ZnS films due to the roughness of the PS surface. The x-ray diffraction patterns show that the ZnS films on PS surface are grown in preferring orientation along cubic phase β-ZnS (111) direction. White light emission is obtained by combining the blue-green emission from ZnS films with the orange-red emission from PS layers. Based on the I-V characteristic, the ZnS/PS heterojunction exhibits the rectifying junction behaviour, and an ideality factor n is calculated to be 77 from the I-V plot.
Oxygen Absorption in Free-Standing Porous Silicon: A Structural, Optical and Kinetic Analysis  [cached]
Cisneros Rodolfo,Pfeiffer Heriberto,Wang Chumin
Nanoscale Research Letters , 2010,
Abstract: Porous silicon (PSi) is a nanostructured material possessing a huge surface area per unit volume. In consequence, the adsorption and diffusion of oxygen in PSi are particularly important phenomena and frequently cause significant changes in its properties. In this paper, we study the thermal oxidation of p+-type free-standing PSi fabricated by anodic electrochemical etching. These free-standing samples were characterized by nitrogen adsorption, thermogravimetry, atomic force microscopy and powder X-ray diffraction. The results show a structural phase transition from crystalline silicon to a combination of cristobalite and quartz, passing through amorphous silicon and amorphous silicon-oxide structures, when the thermal oxidation temperature increases from 400 to 900 °C. Moreover, we observe some evidence of a sinterization at 400 °C and an optimal oxygen-absorption temperature about 700 °C. Finally, the UV/Visible spectrophotometry reveals a red and a blue shift of the optical transmittance spectra for samples with oxidation temperatures lower and higher than 700 °C, respectively.
Influence of processing parameters on structural characteristics of porous calcium phosphate samples: a study using an experimental design method
Ugarte, José Fernandes de Oliveira;Sena, Lidia ágata de;Pérez, Carlos André de Castro;Aguiar, Paula Fernandes de;Rossi, Alexandre Malta;Soares, Glória Almeida;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000100013
Abstract: synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. the aim of this work is to correlate process parameters with scaffolds structural characteristics. the factorial 2 level experimental design was chosen to study the effect of the ca/p ratio (1.58 or 1.67), calcination temperature (1000 or 1150 °c) and porogen content (20 or 40%) on the calcium phosphate samples characteristics. the influence of such parameters was determined by x-ray diffraction, infrared spectroscopy and image analysis. it was observed that phase composition was basically a function of the ca/p ratio of the raw material. the use of the porogen did not alter the hydroxyapatite (ha)/tricalcium phosphate (tcp) content, but induced changes in the relative content of tcp phase (a or b). it is possible to design a porous sample with defined characteristics, and the model herein used can be considered as having a good predictive power.
Fabrication and Characteristics of Fast Photo Response ZnO/Porous Silicon UV Photoconductive Detector  [PDF]
Hanan A. Thjeel, Abdulla. M. Suhail, Asama N. Naji, Qahtan G. Al-zaidi, Ghaida S. Muhammed, Faten A. Naum
Advances in Materials Physics and Chemistry (AMPC) , 2011, DOI: 10.4236/ampc.2011.13012
Abstract: Fast response time UV photoconductive detector was fabricated based on ZnO film prepared by thermal chemical spray pyrolysis technique. The ZnO nanofilms are grown on the porous silicon (PS) nanosurface which has drastically reduced the response time of the ZnO UV detector from few seconds to few hundreds of microseconds. The surface functionalization of the ZnO film deposited on porous silicon (PS) layer by polyamide nylon has highly improved the photoresponsivity of the detector to 0.8 A/W. The normalized de-tectivity (D*) of the fabricated ZnO UV detector at wavelength of 385 nm is found to be about 2.12 × 1011 cm Hz1/2 W–1. The ZnO film grown on the porous silicon layer was oriented in the c-axis and it is found to be a p-type semiconductor, which is referred to the compensation of the excess charge carriers in the ZnO film by the nanospikes silicon layer.
Morphological and optical characteristics of porous silicon produced by anodization process in HF-acetonitrile and HF-ethanol solutions
Miranda, Cláudia R. B.;Baldan, Maurício R.;Beloto, Antonio F.;Ferreira, Neidenêi G.;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000400022
Abstract: porous silicon (ps) samples were obtained by anodization etching process of n-type silicon wafer phosphorus-doped. electrochemical oxidation of ps was investigated in aqueous hydrofluoric acid (hf) containing additive such as ethanol or acetonitrile. pore formation was studied with the variation of type and resistivity of the silicon wafer, taking into account the most important anodization process parameters such as: acid concentration, current density and anodization time. scanning electron microscopy (sem) and raman scattering spectroscopy measurements were used to characterize the macropore morphology changes and sample photoluminescense responses, respectively. ps layer formed in hf-acetonitrile solution showed more uniform and homogeneous macropore distributions with different shapes and sizes. behavior may be explained because acetonitrile surface tension is greater than that of ethanol. therefore, acetonitrile molecules might passivate the silicon surface dissolved during the anodization process.
Role of microstructure in porous silicon gas sensors for NO$_2$  [PDF]
Zeno Gaburro,Paolo Bettotti,Massimo Saiani,Lorenzo Pavesi,Lucio Pancheri,Claudio J. Oton,Nestor Capuj
Physics , 2003, DOI: 10.1063/1.1775887
Abstract: 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%.
Interfacial polaron in quantum dots and luminescent porous silicon
Bingsuo Zou,Sishen Xie
Chinese Science Bulletin , 2001, DOI: 10.1007/BF03182821
Abstract: Polaronic effect is important in the current researches on quantum dots (QD). This paper reported a new concept of the “confined polaron”, their size dependent formation possibilities and energy variation in different QD systems, with an indication of contribution from both intrinsic and/or extrinsic phonons. To understand the spectroscopic characteristics of porous silicon (PS), we find that luminescence behavior of oxidized porous silicon is in good agreement with the model of interfacial confined polaron in QDs. This conclusion is useful to unveiling the mechanmism of PS luminescence.
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