Characteristics Of Porous Silicon Research Articles

The effective of time etching and different acids on the morphological porous silicon

This paper study the characteristics of nano crystalline silicon prepared with the use of electrochemical etching with etching time (15,20) min for salt and Nitric acid (HNO3) and etching time (15,20) min for Ethanol and Hydrofluoric acid, and study the effect of this solutions on the characteristics of porous silicon (ps) will be produced by electrochemical etching by using electrochemical etching from p-type bulk silicon with resistivity (1-10 Ω.cm) with different time. after that, make a comparison for the morphological properties for porous silicon. Research employing X-ray diffraction and scanning electron microscopy instruments were also performed on the samples that were produced as a result. Micromachining etching uses electrochemical etching of silicon in HF solution. New wafer-etched structures are reported. Wall arrays, hole arrays, meander-shaped structures, spiral-like walls, microtubes, and more are produced. The electrochemical etch process and KOH etching time of the original pattern on final geometries are modelled.

Specific Features of the Optical Characteristics of Porous Silicon and Their Modification by Chemical Treatment of the Surface

Comparative studies of the specific features of the composition and photoluminescence properties of porous silicon with different morphologies are carried out by infrared and photoluminescence spectroscopy. On the basis of the experimental data and commonly accepted theoretical models, the main factors that influence the photoluminescence intensity and its deterioration upon the exposure of porous silicon to directed radiation in the visible region are established. By the example of porous silicon with 50–100 nm pores, the possibility of improving the above characteristics by chemical treatment in polyacrylic acid is shown.

Study of the Effect of Incorporation of CdS Nanoparticles on the Porous Silicon Photodetector

In this study, the influence of embedding cadmium sulfide nanoparticles, synthesised by a chemical method, on the performance of porous silicon matrix photodetectors was investigated. An anodization technique was used to fabricate porous silicon photodetectors at 16 mA/cm2 for 10 min.The characteristics of porous silicon and CdS nanoparticles were investigated by using x-ray diffraction XRD, atomic force microscopy AFM, scanning electron microscopy SEM, and energy dispersive x-ray EDX. Dark and illuminated current-voltage I-V characteristics and spectral responsivity of photodetectors were investigated before and after the incorporation of CdS nanoparticles. Considerable improvement was noticed in responsivity of the porous silicon photodetector after incorporating the CdS nanoparticles into the silicon matrix.

Effect of multiwalled carbon nanotubes incorporation on the performance of porous silicon photodetector

In this study, porous silicon photodetectors incorporated with multiwalled carbon nanotubes MWCNTs were investigated. Anodization technique was used to fabricate porous silicon photodetectors at 16mA/cm2 for 15min. The characteristics of porous silicon and MWCNTs were investigated by using x-ray diffraction XRD, atomic force microscopy AFM, Fourier transformation infrared spectroscopy FT-IR, photoluminescence PL, and scanning electron microscopy SEM, Dark and illuminated current-voltage I-V characteristics, capacitance-voltage characteristics C-V, spectral responsivity, specific detectivity, and minority carrier life time MCLT of photodetectors were investigated before and after incorporation. Significant improvement was noticed in photosensitivity and detectivity of the porous silicon photodetector after incorporating the MWCNTs into the porous matrix.

Effect of SnS Thin Film on the Performance of Porous Silicon Photodiode

In this study, Al/SnS/PS/n-Si/Al photodiode was fabricated and investigated. SnS thin film were prepared by thermal evaporation technique on porous silicon layer which prepared by anodization technique at 32mA/cm2 etching current density and etching time 15min.The characteristics of porous silicon and SnS were investigated by using x-ray diffraction XRD, atomic force microscopy AFM, Fourier transformation infrared spectroscopy FT-IR.Dark and illuminated current-voltage I-V characteristics, spectral responsivity, specific detectivity of photodiode were investigated after depositing. Significant improvement in photosensitivity and detectivity of porous silicon photodiode after SnS deposition on porous silicon was noticed.

Effect of SnS Thin Film on the Performance of Porous Silicon Photodiode

In this study, Al/SnS/PS/n-Si/Al photodiode was fabricated and investigated. SnS thin film were prepared by thermal evaporation technique on porous silicon layer which prepared by anodization technique at 32mA/cm2 etching current density and etching time 15min.The characteristics of porous silicon and SnS were investigated by using x-ray diffraction XRD, atomic force microscopy AFM, Fourier transformation infrared spectroscopy FT-IR.Dark and illuminated current-voltage I-V characteristics, spectral responsivity, specific detectivity of photodiode were investigated after depositing. Significant improvement in photosensitivity and detectivity of porous silicon photodiode after SnS deposition on porous silicon was noticed.

The Influence of the Film Deposition of Metals on the Composition and Optical Characteristics of Porous Silicon for Use in Hydrogen Energy

The paper studies the composition and optical properties of advanced composites based on porous silicon with deposited transition metals and indium and tin by a sol-gel process. It is shown that the deposition of films of metals of the iron group enhances the photoluminescence intensity and stabilizes it in time, while the deposition of tin and indium has virtually no effect on the optical characteristics of the porous layer. The paper shows coating the surface of the sample by metal oxide film saves hydrogen in the pores.

Electrolyte composition dependence of the morphological and nanostructural features of porous silicon prepared by electrochemical anodic etching

Porous silicon layers were formed by electrochemical anodic etching of p-type Si wafers. The electrostatic condition at the interface between the Si wafers and electrolytes was affected sensitively by the addition of isopropyl alcohol (IPA) in the etchant. As the IPA ratio was varied in the range of 0 to 75%, the ideality factor in the ln I-V relationships and the viscosity of the electrolytes changed from 27.2 to 16.0, and from 1.0 to 3.3 cp, respectively. The etched surface exhibited three different morphologies, such as ‘turtle-back’-, ‘column’-, and ‘mountain’-like structures depending on the electrolyte composition. The etched layers contained Si nanocrystallites, ~5.5 to ~2.6 nm in size, which exhibited photoluminescence features in the wavelength range, 733 to 624 nm. The variation of the band gap was determined by size of the nanocrystallites, whereas the nanostructural and morphological features were dependent on the IPA ratios of the etchants.

Effect of ion irradiation on the structure and luminescence characteristics of porous silicon impregnated with tungsten-telluride glass doped by Er and Yb impurities

Using transmission electron microscopy and elemental analysis, it has been shown that tungsten telluride glass (TTG) containing erbium and ytterbium as impurities penetrates into pores of porous silicon (PS) when melted in vacuum at 500°C. It has been found that the intensity of photoluminescence (PL) of erbium at the wavelength of 1.54 μm in PS: TTG layers increases by a factor of up to 5 in the layers irradiated by P+ and Ar+ ions. This is assigned to ion mixing which favors interaction among the Er ions and PS-embedded Si nanocrystals initiating sensitization of the PL, as well as to broadening of the glass-impregnated PS region. Implantation of the lighter Ne+ ions affects only weakly the PL of erbium ions.

Impact of the Variability in the Current Density on the Porous Silicon Characteristics

Porous silicon (PS) in comparison to the bulk silicon shows new features such as shifting of the absorption edge into the short wavelength and photoluminescence visible region, it shows a new characteristics such as larger surface to volume ratio, high-intensity of nano porous structure and low refractive index which can be used as an anti-reflection coating in solar cells. In this paper, PS has been p epared from n-type silicon wafer of (100) orientation. The influence of varying current density (J) in the anodizing solution, on the performance of PS has been investigated. Scanning electron microscope (SEM), atomic force microscope (AFM), and dark, forward and reverse bias I-V measurement have been used to morphologically characterize structure and electrical propert es of PS. Best results achieved when the current density is (60) mA/cm2.

Structural Characteristics of Porous Silicon

Silicon wafers (p-type) were etched under continuous flow of HF vapors in a reaction chamber at standard temperature and pressure. Etched surface of the silicon wafer was found emitting red luminescence when exposed to ultra violet (UV) light. XRD and Atomic Force Microscopy of the etched samples were carried out to study the surface of the etched silicon. It is noticed that etching has removed the stress induced atomic layers of silicon at grain boundaries and layer of porous silicon has been formed at the surface of silicon wafer which has higher inter planer distance than the silicon itself. The size of dots observed on the surface of etched silicon is of the order of few nm. The red emission from the surface of etched silicon appears to be due to the energy states induced by quantum confinement.

Influence of Current Density on Porous Silicon Characteristics

Porous silicon structures have been fabricated by electrochemical etching using different current density. From field emission scanning electron microscope images (FE-SEM) it was observed that more uniform distribution of pores is obtained when the current density was increased from 20mA/cm2to30 mA/cm2. The porosity is estimated based on the analysis of FE-SEM and gravimetric analysis, the results were confirmed by reflectivity measurements which show that the high current density and porous samples have low reflection for wide spectrum. Results show good improvement in the solar cell efficiency.

Effect of bromine adsorption on the charge transport in porous silicon-silicon structures

We studied the electrophysical characteristics of porous silicon (PS) layers formed on single-crystalline silicon substrates with both n-type and p-types of conductivity under conditions of adsorption of bromine molecules. An increase in the conductivity of PS-p-Si nanostructures is observed with increasing bromine concentration. The adsorption of bromine is shown to give rise to ‘diode-like’ current-voltage characteristics of the PS formed on the silicon substrate with the electronic conductivity. This can be caused by inversion of the conductivity type occurring in nanocrystals of the porous layer. Spectral characteristics of photovoltage for our structures subjected to bromine adsorption have been studied in the range of 450 — 1100 nm. We suggest a possible mechanism for the influence of bromine adsorption on the electrical and photoelectrical properties of the PS-silicon structures.

The nature of emission of porous silicon produced by chemical etching

The structural and luminescence characteristics of porous silicon produced by chemical etching are studied. From analysis of the behavior of luminescence spectra with temperature, it is shown that the luminescence band of porous silicon samples produced by chemical etching presents a superposition of two bands. It is concluded that one of the bands is due to excitonic recombination in amorphous silicon nano-clusters smaller than 3 nm in dimensions and the other band corresponds to recombination of charge carriers via defects in silicon oxide. At room temperature, the latter band prevails.

Some characteristics of porous silicon (Reflection, scattering, refractive index, microhardness)

A porous layer formed on the surface of a silicon single crystal as a result of the electrochemical erosion represents a composite material, in which the energy band structure of silicon is deformed and the refractive index is much smaller compared to that of the single crystal.

Influence of preparation and storage conditions on photoluminescence of porous silicon powder with embedded Si nanocrystals

The time changes of photoluminescence (PL) characteristics of porous silicon (porSi) powder during storing in different ambients have been reported. A porous silicon material with embedded Si nanocrystals of size of few nanometers was prepared by an electrochemical method from 10 to 20 Ωcm p-type Si wafers, and both constant and pulse current anodization regimes were used. A powder with a submicron average particle size was obtained by simple mechanical lift-off of the porous layer followed by additional manual milling. The air, hexane, and water as storage media were used, and modification by a nonionic surfactant (undecylenic acid) of the porSi surface was applied in the latter case. Dependence of PL characteristics on preparation and storage conditions was then studied. A remarkable blue shift of a position of PL maximum was observed in time for porSi powders in each storage media. In water suspension a many-fold build-up (10–30) of PL intensity in a time scale of few days was accompanied by an observed blue shift. Photoluminescence time behavior of porSi powders was described by a known mechanism of the change of porSi PL from free exciton emission of Si nanocrystals to luminescence of localized oxidized states on the Si nanocrystal surface.

Morphological and optical characteristics of porous silicon produced by anodization process in HF-acetonitrile and HF-ethanol solutions

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.

Electronic Processes in the Porous Silicon-Conducting Polymer Heterostructures

The effect of an integrated polymer on the luminescence characteristics of porous silicon (PS)-conducting polymer (CP) heterostructures has been studied. Both n-(100) and p-type (111) PS has been employed in order to prepare the heterostructures. To obtain the integrated polymer layers (polyaniline, polymethoxyaniline, polyphenylacetylene, poly-para-phenylene, poly-N-epoxy-propylcarbazol), the methods of electrochemical polymerization, vacuum deposition, and spin coating have been used. The obtained structures were studied using atom force microscopy and were examined as to the capability to photoluminescence (PL) and cathodoluminescence (CL). It has been found that the presence of a CP layer on the PS surface preserves the “red” PL, but weakens it to 50–90%. The CL spectra of the obtained heterostructures allow us to suggest their capability of electroluminescence in the visible region of the spectrum.

Electron field emission from porous silicon prepared at low anodisation currents

The dependence of electron field emission (FE) characteristics of porous silicon (por-Si) prepared by anodisation at low current density without external bias is investigated. Effective electron FE from por-Si on p-Si flat surface was revealed. With growth of anodisation current (from 1 mA/cm² to 5 mA/cm²) the electron FE efficiency was decreased. Resonance tunnelling at electron field emission from por-Si was observed. The por-Si coating with thin diamond-like carbon film allowed the increase of the efficiency and stability of electron emission current significantly. The obtained experimental results on electron FE from por-Si on flat p-Si silicon surface were explained on the basis of electrical field enhancement coefficient growth, existence of dipole Si-H layer, lowering of por-Si electron affinity and growth of native SiO2 oxide on silicon surface. The model for explanation of resonance tunnelling from por-Si was proposed.

Electrical properties study of porous silicon layer prepared by electrochemical etching

Abstract This paper considers an AC and DC electrical features of porous silicon (PSi) layers prepared by electrochemical etching. Measurements of capacitance–frequency ( C – f ), conductance–frequency ( G – f ), photoconductivity (PC) and current–voltage ( I – V ) were used for the investigation of the electrical properties of these structures.