Search query: Porous silicon a useful imperfection

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abstract: Abstract When semiconductor developers noticed in the 1950s that electropolishing of bulk silicon left certain areas rougher than the rest and somewhat porous, they regarded these simply as imperfect areas. It was not until Leigh Canham, a scientist with DERA (the UK's Defence Evaluation and Research Agency) discovered in 1990 that porous silicon (PSi) emits visible light when activated by external ultraviolet sources 1 that this morphological state of the material came to attract significant research interest. Elementary photonic sensors were soon proposed. In 1992 researchers discovered that PSi also emits light when an electric current is applied, a finding that raised prospects for new optronic sensors and other devices coupling light to electronics, including future high speed computers. Technology extensions have since been found that make the material chemi and bio luminescent as well as photo and electro luminescent. In sight by the mid to late 1990s, therefore, was a whole new class of solid state sensors offering significant advantages over solid state gas and other sensors. Many of these were based on bulk silicon and semiconducting oxides such as tin or indium oxide and alumina. Compared with them, PSi offers a high surface area to volume ratio and hence high reactivity and, as researchers have established, a porous structure whose morphology could be engineered for high selectivity to particular molecules. Along with high sensitivity and selectivity, comes a rapid response time.
author_names: G Marsh
title: Porous silicon a useful imperfection
year: 2002

abstract: As subwavelength nanostructures are receiving increasing attention for photonic and plasmonic applications, we grew nanostructured porous silicon (n PS) and hybrid n PS/Ag layers onto silicon substrates and measured their reflection and absorption characteristics as functions of the wavelength, angle of incidence, and polarization state of incident light. The experimental results show that the absorption characteristics of the hybrid n PS/Ag layer can be controlled by selecting the appropriate combination of its thickness and porosity, together with the density of infiltrant silver nanoparticles. The observed wideband optical absorption characteristics of the hybrid n PS/Ag layers might be useful in light harvesting devices and photodetectors, since the overall efficiency will be increased as a result of increased field of view for both s and p polarization states of incident light.
author_names: Raul Jose Martin-Palma

Patrick D Mcatee

Rehab Ramadan

Akhlesh Lakhtakia
title: Hybrid Nanostructured Porous Silicon Silver Layers for Wideband Optical Absorption
venue: Scientific Reports
year: 2019

abstract: a b s t r a c t This review is devoted to summarising the hydrogen assisted properties and applications of porous silicon (PS) The role of hydrogen as an intermediate product in silicon porosification technology is accentuated. The regularities of hydrogen bonding in PS and its applications for hydrogen storage are listed. The models of hydrogen influence on luminescence and electrical properties of PS are analysed. The corresponding applications of PS for H2 gas sensors and pH metres are illustrated. Hydrogen assisted explosion and grafting of PS are discussed. Such a review can be useful for the tailoring of PS properties.
author_names: Anton I Manilov

Valeriy A Skryshevsky
title: Hydrogen in porous silicon A review
year: 2013

abstract: Abstract Porous silicon (PSi) has a high chemical energy, which has the potential to be converted to mechanical energy very quickly through ignition. Here we investigate a means to convert this mechanical energy to electrical energy via a piezoelectric cantilever and rectifying circuit. This current could be used to power sensors, devices, or store charge, and this type of system could be useful in ignition systems for munitions. The efficiency of this system is critical to realizing the potential for PSi as a one time electrical energy source. A mechanical to electrical efficiency of 4.1 was achieved, but the chemical to electrical efficiency was much less than 1
author_names: Louis B Levine

Matthew H Ervin

Wayne A Churaman
title: Energy Harvesting from Energetic Porous Silicon
year: 2016

abstract: Abstract An express technique to define the thickness and rate of porous silicon (PS) layer growth during the electrochemical etching of silicon wafers is proposed. The method is based on the in situ measurement of reflected laser beam from PS layer in electrochemical cell during the etching process. Numerical simulation of the wavelength dependent interference data obtained from the reflectivity showed the possibility of the selectivity improvement of thin layer PS sensors by the use of a set of PS layers with defined thicknesses and porosities. The different behavior of the reflection coefficients, shape and position of the maxima of the interference peaks during desorption of water ethanol solutions and wines from the PS films were observed. The differences in the peak shape indicated the presence of inhomogeneity in the distribution of the film porosity with depth. On the other hand, the differences in the interaction modes between the adsorbed molecules and the pore surface caused differences in the kinetics of the optical characteristics during the desorption. The obtained results could be useful for development of selective optical sensors based on porous materials.
author_names: Nickolai I Klyui

I I Ivanov

Oleksandr S Kyslovets

Lyubov V Avksentyeva

Valeriy A Skryshevsky
title: Features of the use of optical reflection from thin porous silicon for detection of organic liquids
year: 2017

abstract: Abstract We report a detailed study on the concentration profiles and ion irradiation induced desorption of hydrogen from porous silicon (pSi) by on line elastic recoil detection analysis (ERDA) 100 MeV Ag ions have been employed to analyze the pSi samples prepared at different etching current densities. The observed blue shift in the photoluminescence of pSi with increase in etching current density is consistent with previous reports. Here we find that the concentration of hydrogen in near surface regions decreases with increase in etching current density. It is also observed that the concentration of hydrogen is greater in the near surface region and decreases rapidly as a function of depth in porous silicon. Further, the ion irradiation induced desorption of hydrogen from pSi has been characterized by the second order decay, indicating that the hydrogen desorbs in molecular form. The rate of desorption is found to be higher from the deeper layers when compared to that of near surface regions, possibly due to higher diffusivity of elemental hydrogen within the deeper layer. Strong electronic excitations produced by probing beam are expected to be responsible for the observed non thermal dissociation of Si H bonds and consequent desorption of hydrogen from the surface of pSi in molecular form. These results provide useful information to elucidate 1) the role of hydrogen in determining the optical properties of porous/nano crystalline silicon and 2) mechanisms that govern the non thermal dissociation of Si H bonds.
author_names: V S Vendamani

S A Khan

M Dhanunjaya

A P Pathak

S V S Nageswara Rao
title: Energetic ion induced desorption of hydrogen from porous silicon studied by on line elastic recoil detection analysis
year: 2017

abstract: A systematic study of nanoenergetic films consisting of nanostructured porous silicon impregnated with sodium perchlorate is carried out. The explosive properties of these films are investigated as a function of thickness, porosity, and confinement. The films' burning rates are investigated using fiber optic velocity probes, demonstrating that flame front velocities vary between approximately 1 and 500 m s( 1) and are very sensitive to the films' structural characteristics. Analysis of the flame profile by high speed video is also presented, suggesting that the reaction type is a deflagration rather than a detonation. A strong plume of flame is emitted from the surface, indicating the potential for this material to perform useful work either as an initiator or as a propellant. The shape of the flame front transitioned from an inverted V at thin film thicknesses to a neat square shaped front once the material became self confining at 50 mm.
author_names: Andrew Plummer

Valerian A Kuznetsov

Timothy Joyner

Joseph G Shapter

Nicolas Hans Voelcker
title: The burning rate of energetic films of nanostructured porous silicon.
venue: Small
year: 2011

abstract: A capacitive sensor based on porous silicon (PSi) for detection of various polar (ethanol, methanol, acetone, acetonitrile, chloroform) and non polar organic solvents (n hexane, toluene) was described. The meso PSi layer with an average pore size of 30 nm was prepared by a galvanostatic electrochemical etching of crystalline silicon in HF based solution. Surface passivation was conducted by anodic oxidation process and the electrical contacts were made exclusively onto the front porous structure. The as fabricated sensor exhibits highly sensitive and reversible response toward polar organic molecules during the real time measurements of capacitance, whereas the capacitive sensing behavior was irreversible and opposite in direction in case of non polar solvents. The response time was in the order of acetone methanol acetonitrile ethanol chloroform. The observed response could be understood as the impact of charge redistribution on the pore walls upon organic infiltration, along with changes in the dielectric constant of the porous layer. A comparative study of such different responses is provided. Excellent repeatability of the device was obtained after twelve cyclic tests of acetone, demonstrating stability of the sensor. Long term stability for the sensor was also observed after four weeks storage. The present approach is useful for the development of a simple, cost effective sensor for detection of various chemical analytes.
author_names: Farid A Harraz

Adel A Ismail

Houcine Bouzid

Saleh A Al-Sayari

Ali Al-Hajry

M Al-assiri
title: A capacitive chemical sensor based on porous silicon for detection of polar and non polar organic solvents
year: 2014

abstract: The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self assembly of nanostructures. The widespread implementation of self assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures' morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic active surfaces for surface enhanced Raman spectroscopy based detection of ultra low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam.
author_names: Dzmitry V Yakimchuk

Victoria D Bundyukova

Jon Ustarroz

Herman Terryn

Kitty Baert

Artem L Kozlovskiy

Maxim V Zdorovets

Soslan A Khubezhov

Alexey Trukhanov

Sergei V Trukhanov

Larissa V Panina

Grigory M Arzumanyan

Kahramon Z Mamatkulov

Daria I Tishkevich

Egor Y Kaniukov

Vladimir Sivakov
title: Morphology and Microstructure Evolution of Gold Nanostructures in the Limited Volume Porous Matrices
venue: Sensors
year: 2020

abstract: There are a vast number of applications for biosensors ranging from medical monitoring and control, to release of drugs [1] and biosecurity [2] The goblal market for biosensors in 2012 is estimated to reach 8.5 billion USD and projected to reach 16.8 billion by 2018 [3] Po rous silicon (p Si) offers several advantages for its use as a biosensor such as a large specific surface area (of the order of 500 m 2 cm 3) [4] visible luminescence at room temperature [5] and biocompatibility [6] The p Si was accidentally discovered when, in 1956 at the U.S. Bell Laboratories, Arthur Uhlir Jr. and Ingeborg Uhlir observed a red green film formed on the wafer surface while trying a new technique for polishing silicon (Si) crystalline wafers. At the time however, it was not considered an interesting material. But when Leigh Canham in 1990 [5] discovered its visible luminescence properties, researchers started studying its non linear optical, electric and mechanical properties. These academic and technological efforts have permitted the fabrication of uniform porous layers with diameters as small as one nanometer, permitting an enormous inner surface density, which is useful for biosensing ap plications. Several techniques exist to form this structure from a pure silicon crystalline wa fer. The most popular is the electrochemical etching of crystalline silicon wafers (c Si) [5] Anodization begins when a constant current is applied between the c Si wafer and the elec trolyte by means of an electronic circuit controlling the anodization process [6]
author_names: M B de la Mora

Miguel A Ocampo

Rafael Doti

Jesus Eduardo Lugo

Jocelyn Faubert
title: Chapter 6 Porous Silicon Biosensors
year: 2013