Porosity superlattices: a new class of Si heterostructures

Berger, M.; Dieker, C.; Thönissen, M.; Vescan, L.; Lüth, H.; Münder, H.; Theiß, W.; Wernke, M.; Große, Peter

doi:10.1088/0022-3727/27/6/035

Cited by 163 publications

(63 citation statements)

References 8 publications

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“…Estimated thickness of the basic layer was about six times the thickness of the auxiliary layer. Calculations of geometry and porosity of the layers were based on data depending on density of the dc current and duration of etching [14,15]. Contacts were made by vacuum evaporation of aluminium and subsequent annealing at temperature of 450 • C in nitrogen atmosphere.…”

Section: Methodsmentioning

confidence: 99%

Effect of microwave radiation on conductivity of porous silicon nanostructures

Shatkovskis¹

2007

Lithuanian J. Phys.

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An attempt was made to find out the possible influence of microwave radiation on the conductivity of structures containing porous silicon layers. Samples have been made of boron doped p-type, (100) oriented, ρ = 0.4 Ω·cm specific resistance silicon wafers by technology involving electrochemical etching in HF : ethanol = 1 : 2 electrolyte, and subsequent preparation of contacts. Two kinds of prepared samples have been characterized by nonlinear and linear current-voltage characteristics. Electric conductivity of the samples was investigated under the action of 10 GHz frequency microwave radiation. Activation nature of porous silicon conductivity was revealed. Model of hopping conductivity in the vicinity of Fermi level in the lattice of a porous silicon grid, considering the fractal character of porous silicon skeleton, has been applied to explain experimental results. Three activation energies were found: E 0 , E 0 , and E 0 (E 0 < E 0 < E 0 ), caused by fractal character of a porous silicon grid. Activation of conductivity occurs because of charge carrier heating in porous silicon structure by microwave radiation.

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Section: Methodsmentioning

confidence: 99%

Effect of microwave radiation on conductivity of porous silicon nanostructures

Shatkovskis¹

2007

Lithuanian J. Phys.

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“…More dense auxiliary PSi * layer was formed in the first phase. From the density of anodic current [9], the porosity of the auxiliary layer was estimated to be about 55%, and its thickness was about 3-5 µm. The basic layer of porous silicon (PSi * * ) was formed in the second phase.…”

Section: Methodsmentioning

confidence: 99%

Studies of Response of Metal - Porous Silicon Structures to Microwave Radiation

et al. 2006

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Structures containing layers of porous silicon with two metal contacts are investigated. Porous silicon is manufactured by anodizing p-type crystalline silicon plates of resistivity of 0.4 Ω cm. Contacts for the samples are made by additional boron doping of the surface and by thermal evaporation of aluminium. Resistance and current-voltage characteristics are investigated. Response of the porous silicon layer containing structures under action of pulsed microwave radiation was investigated for the first time. The origin of the response is discussed.

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“…The light passed at normal incidence through the grating sample in the chamber. [1][2][3][4][5][6][7][8] The new glasses constitute a significant extension of silicate glass compositions and also show high chemical flexibility. Samples have been prepared with high concentrations of alkaline-earth and rare-earth elements such as Ca, Sr, Ba, La, Pr, and Sm (higher than 50 % cations; hereafter cation %).…”

Section: Methodsmentioning

confidence: 99%

“…For example, highly reflective porous silicon microcavities can be generated by using controlled etching, resulting in layers of alternating porosities. [2,3] Recently, excellent progress has been made in creating porous silicon films, [4,5] microcavities, [6,7] and arrays of microstructures [8] useful for optical sensing. Generally, these devices rely on the changes in the optical resonance that occur when the porous structure is occupied by the analyte species, allowing for simple and effective detection schemes.…”

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confidence: 99%

Organic Solvent Vapor Detection Using Holographic Photopolymer Reflection Gratings

et al. 2005

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Significant research efforts have focused on the development of effective means for the detection of organic molecules. These efforts can be divided, very crudely, into those focusing on either electrical-or optical-sensing mechanisms. To date, sensors based on optical measurements have generally proven to be faster, safer, and easier to implement than those employing electrical measurements.[1] In particular, porous materials are well suited for use as templates for optical sensing. Porous silicon is an especially appealing material for these applications due largely to the fact that it can be readily structured using electrochemical etching and/or photolithography. For example, highly reflective porous silicon microcavities can be generated by using controlled etching, resulting in layers of alternating porosities. [2,3] Recently, excellent progress has been made in creating porous silicon films, [4,5] microcavities, [6,7] and arrays of microstructures [8] useful for optical sensing. Generally, these devices rely on the changes in the optical resonance that occur when the porous structure is occupied by the analyte species, allowing for simple and effective detection schemes. However, the versatility of porous silicon is tempered by its instability. As an alternative, porous polymer nanostructures produced from an oxidized porous silicon template have been demonstrated as a way for sensing applications.[9] Micropatterned polymeric gratings have also been demonstrated as a relevant sensing material for detecting organic solvents. For example, instead of using a porous layer-by-layer geometry of a reflection grating, a micropatterning transmission grating (array design) was shown to have the ability to identify a mixture of chemical analytes. [10] In the work reported in this communication, we demonstrate a simple method for optical detection of different organic-solvent vapors based on the holographic fabrication of high-porosity polymer Bragg reflection gratings. Furthermore, these results demonstrate that this photopolymer fabrication technique could potentially be used to create structures suitable for biological applications in aqueous environments. The typical method used to produce periodic porous silicon structures is relatively complicated, requiring a controlled electrochemical etching process in a hydrofluoric acid solution. [1±3,5±9] In contrast, it has recently been demonstrated that organic polymeric materials can yield high-efficiency reflection gratings through a fast and inexpensive holographic photopolymerization technique. [11] In this technique, a prepolymer syrup containing a monomer, a photoinitiator, a co-initiator, and a liquid crystal (LC) is sandwiched between two pieces of glass, and a periodic structure is then formed by applying an optical interference pattern generated using a simple one-beam setup. [12] We have recently demonstrated that porous acrylate polymer grating structures can be created in a similar manner by simply adding a non-reactive solvent, such as acetone or toluene,...

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Porosity superlattices: a new class of Si heterostructures

Cited by 163 publications

References 8 publications

Effect of microwave radiation on conductivity of porous silicon nanostructures

Effect of microwave radiation on conductivity of porous silicon nanostructures

Studies of Response of Metal - Porous Silicon Structures to Microwave Radiation

Organic Solvent Vapor Detection Using Holographic Photopolymer Reflection Gratings

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