P type porous silicon resistivity and carrier transport
TL;DR: In this paper, the porosity of porous silicon (PS) was found to be the major contributor to the PS resistivity (ρPS), and ρPS increases exponentially with P%.
Abstract: The resistivity of p type porous silicon (PS) is reported on a wide range of PS physical properties. Al/PS/Si/Al structures were used and a rigorous experimental protocol was followed. The PS porosity (P%) was found to be the major contributor to the PS resistivity (ρPS). ρPS increases exponentially with P%. Values of ρPS as high as 1 × 109 Ω cm at room temperature were obtained once P% exceeds 60%. ρPS was found to be thermally activated, in particular, when the temperature increases from 30 to 200 °C, a decrease of three decades is observed on ρPS. Based on these results, it was also possible to deduce the carrier transport mechanisms in PS. For P% lower than 45%, the conduction occurs through band tails and deep levels in the tissue surrounding the crystallites. When P% overpasses 45%, electrons at energy levels close to the Fermi level allow a hopping conduction from crystallite to crystallite to appear. This study confirms the potential of PS as an insulating material for applications such as power e...
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TL;DR: In this paper, the electrical properties of meso-porous silicon films were explored and optimized through fabrication conditions and surface treatment, and the experimental results showed that a low value of resistance along with high value of TCR can be obtained by altering porosity and surface passivation in single and multi-layer porous silicon films.
15 citations
TL;DR: In this paper, the influence of oxidation properties such as oxygen content and its distribution gradient on the electron emission characteristics of porous silicon (PS) emitters was investigated, and the most favorable results occurred for the PS emitter with the smallest oxygen distribution gradient and the highest level of oxygen content, with an emission current density of 212.25μA/cm 2 and efficiency of 59.21
12 citations
TL;DR: In this article, the 1/f noise in porous silicon films in conjunction with temperature coefficient of resistance (TCR) was characterized for high sensitivity thermal sensors, and the results confirmed great promise of porous silicon for low manufacturing cost, and higher sensitivity of the thermal sensors.
11 citations
TL;DR: In this article, film resistivity and current-voltage relationship were measured with a sandwich metal/porous silicon/silicon/metal structure, and it was shown that the porosity induced low modulus (low modulus) of high porosity films is the dominant contribution to the measurement.
10 citations
TL;DR: In this paper, the performance of polyaniline deposition in an oxidized porous matrix was analyzed using AT-FTIR and Raman spectroscopy, and it was shown that the polymer layer is non-homogeneous in depth, which was confirmed by electrical measurements of currentvoltage and electrochemical impedance at different points between the polymer surface and silicon substrate.
Abstract: Macroporous silicon layer was passivated by chemical oxidation and then polyaniline was deposited chemically within the porous structure in order to fabricate a heterostructure to be used as chemical sensor. The structural characterization of this device by scanning electron microscopy reveals the effectiveness of the chemical method for polyaniline deposition in oxidized porous matrix. The analysis by AT-FTIR and Raman spectroscopy shows that polyaniline was deposited in its emeraldine state, which is the most conductive phase, forming a well-defined replica of the porous structure. However, according to the EDS analysis, this polymer layer is non-homogeneous in depth. This feature was also confirmed by electrical measurements of current-voltage and electrochemical impedance at different points between the polymer surface and silicon substrate. In spite of this fact, the immersion of this structure in an ethanolic solution containing low amounts of naphthalene shown that this structure is excellent to be used as chemical sensor for the detection of low concentrations of naphthalene in the order of 30 ppb.
6 citations
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TL;DR: In this paper, the structure of the porous layers that emit red light under photoexcitation was revealed, which constitutes direct evidence that highly porous silicon contains quantum-size crystalline structures responsible for the visible emission.
Abstract: LIGHT-emitting devices based on silicon would find many applications in both VLSI and display technologies, but silicon normally emits only extremely weak infrared photoluminescence because of its relatively small and indirect band gap1. The recent demonstration of very efficient and multicolour (red, orange, yellow and green) visible light emission from highly porous, electrochemically etched silicon2,3 has therefore generated much interest. On the basis of strong but indirect evidence, this phenomenon was initially attributed to quantum size effects within crystalline material2, but this interpretation has subsequently been extensively debated. Here we report results from a transmission electron microscopy study which reveals the structure of the porous layers that emit red light under photoexcitation. Our results constitute direct evidence that highly porous silicon contains quantum-size crystalline structures responsible for the visible emission. We show that arrays of linear quantum wires are present and obtain images of individual quantum wires of width <3 nm.
1,285 citations
TL;DR: In this paper, the mesopore morphology and its dependence on formation parameters, such as HF concentration, current density, bias, and substrate doping density, is investigated in detail.
Abstract: Electrochemical pore formation in silicon electrodes is a well-known phenomenon. While micropore formation is commonly understood as due to quantum size effects, the formation of larger pores is dominated by the electric field of the space charge region. In contrast to the macropore regime which is well understood, little is known about the morphology and formation mechanism of mesopores. In this report mesopore morphology and its dependence on formation parameters, such as HF concentration, current density, bias, and substrate doping density, is investigated in detail. In addition, a simulation of the breakdown conditions at the pore tip is performed which shows that mesopore formation is dominated by charge carrier tunneling, while avalanche breakdown is found to be responsible for the formation of large etchpits.
357 citations
TL;DR: In this paper, a real-space pseudopotential method was used to calculate quasiparticle gaps, self-energy corrections, exciton Coulomb energies, and optical gaps in Si quantum dots.
Abstract: Quasiparticle gaps, self-energy corrections, exciton Coulomb energies, and optical gaps in Si quantum dots are calculated from first principles using a real-space pseudopotential method. The calculations are performed on hydrogen-passivated spherical Si clusters with diameters up to 27.2 \AA{} ( $\ensuremath{\sim}800\mathrm{Si}$ and H atoms). It is shown that (i) the self-energy correction in quantum dots is enhanced substantially compared to bulk, and is not size independent as implicitly assumed in all semiempirical calculations, and (ii) quantum confinement and reduced electronic screening result in appreciable excitonic Coulomb energies. Calculated optical gaps are in very good agreement with absorption data.
332 citations
TL;DR: In this article, conductometric porous silicon gas sensors consisting of a sensitive surface layer which is conducive to the rapid and reversible transduction of sub-ppm levels of analyte gas have been developed.
Abstract: Conductometric porous silicon gas sensors consisting of a sensitive surface layer which is conducive to the rapid and reversible transduction of sub-ppm levels of analyte gas have been developed. Several new fabrication and testing methods allow the detection of a number of analytes including CO (
225 citations
TL;DR: In this paper, a wide range of pore and crystallite sizes can be formed easily due to the doping sensitivity of the porous silicon formation and the high surface-to-volume ratio.
183 citations