The Effects of Rapid Thermal Annealing on Photoluminescence Properties of Nanostructures Silicon (original) (raw)
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Effect of Silicon Crystal Size on Photoluminescence Appearance in Porous Silicon
ISRN Nanotechnology, 2011
The photoluminescence (PL) study in porous silicon (PS) with decreasing Si crystallites size among the pores was reported. The PL appearance is attributed to electronic confinement in columnar-like (or dotlike) structures of porous silicon. Three different pore diameter PS samples were prepared by electrochemical etching in HF-based solutions. Changes in porous silicon and Si crystallite size were studied by observing an asymmetric broadening and shift of the optical silicon phonons in Raman scattering. Fourier transform infrared spectroscopy (FTIR) was used to study the role of siloxene or other molecular species, for example, SiH x in the luminescence mechanism. This mechanism was further studied by thermal annealing of PS at different temperatures. The PL of PS sample annealed at ≥300 • C for 1 hr shows that trap electronic states appear in the energy gap of the smaller nano-crystal when Si-O-Si bonds are formed. From the observation of PL, Raman, and FTIR spectroscopy, the origin of PL in terms of intrinsic and extrinsic properties of nanocrystalline silicon was discussed.
Microelectronic Engineering
Photoluminescence properties and surface morphologies of porous silicon were investigated by controlling of etching times and applied current densities. FE-SEM image of porous silicon surface indicated that the porous silicon prepared at currents below 200 mA/cm 2 exhibited very stable and even surface. However the porous silicon prepared at currents above 300 mA/cm 2 displayed the cracked surface of porous silicon. This cracked surface was collapsed to give cracked domains at currents over 500 mA/cm 2 . Photoluminescence of porous silicon was investigated by controlling of etching times and applied current densities in the range from 50 to 900 s and from 50 to 800 mA/cm 2 , respectively. Photoluminescence intensity of porous silicon increased gradually during etching process, reached maximum, and then decreased as the etching time increased. Porous silicon showed the best photoluminescence efficiency was prepared at currents of 200 mA/cm 2 and etching time of 300 s.
Thin Solid Films, 1997
Photoluminescence (PL) spectra of porous silicon (PS) are fitted by a theoretical model based on quantum confinement of electrons in Si nanocrystallites having spherical and cylindrical forms. This model permits one to correlate the PL spectra with the PS structure. It was found that the PS structure is almost independent of the porosity of the PS samples when elaborated in tim same HF solution, but it depends on the composition of the electrolytic solution and post-anodisation treatments such as oxidation. The specific surface area (SSA) was estimated and was found to decrease linearly when the porosity increases. It was pointed out that the SSA plays a key role in the PL behaviour within laser irradiation. The effect of laser irradiation on the PL behaviour has been discussed according to the proposed model, and was shown to be dependent on ambient atmosphere. It was shown that the crystallite size decreases throughout photo-oxidation under laser irradiation in air. © 1997 Elsevier Science S.A.
Materials Science Forum, 2013
Porous silicon (p-Si) is a well-known silicon based material that can emit visible light at room temperature. The radiative recombination that originated from quantum confinement effect shows photoluminescence (PL) in red, while the defect on silicon oxide at the surface of p-Si shows in blue-green region. Porous silicon can be synthesized through two methods; wet-etching and electrochemical anodization using hydrofluoric acid as the main electrolyte. The electrochemical anodization is more favorable due to faster etching rate at the surface than the conventional wetetching method. The objective of this research is to show that both of porous silicons can be synthesized using the same main electrolyte but by varying the reaction environment during anodization/etching process. Here, we shows the wet-etching method that enhanced by polarization concentration will produce porous silicon with silicon oxide defects by means blue-green emission, while direct electrochemical anodization will produce samples that emit red PL signal. The effect of introducing KOH into the electrolyte was also studied in the case of enhanced-wet-etching method. Surface morphology of porous silicon and their photoluminescence were observed by Scanning Electron Microscope and PL spectroscopy, respectively.
Materials Science Forum, 2013
Porous silicon (p-Si) is a well-known silicon based material that can emit visible light at room temperature. The radiative recombination that originated from quantum confinement effect shows photoluminescence (PL) in red, while the defect on silicon oxide at the surface of p-Si shows in blue-green region. Porous silicon can be synthesized through two methods; wet-etching and electrochemical anodization using hydrofluoric acid as the main electrolyte. The electrochemical anodization is more favorable due to faster etching rate at the surface than the conventional wetetching method. The objective of this research is to show that both of porous silicons can be synthesized using the same main electrolyte but by varying the reaction environment during anodization/etching process. Here, we shows the wet-etching method that enhanced by polarization concentration will produce porous silicon with silicon oxide defects by means blue-green emission, while direct electrochemical anodization will produce samples that emit red PL signal. The effect of introducing KOH into the electrolyte was also studied in the case of enhanced-wet-etching method. Surface morphology of porous silicon and their photoluminescence were observed by Scanning Electron Microscope and PL spectroscopy, respectively.
Peculiarities of Photoluminescence in Porous Silicon Prepared by Metal-Assisted Chemical Etching
ISRN Optics, 2012
Photoluminescent (PL) porous layers were formed on p-type silicon by a metal-assisted chemical etching method using H2O2 as an oxidizing agent. Silver particles were deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. The morphology of the porous silicon (PS) layer formed by this method was investigated by atomic force microscopy (AFM). Depending on the metal-assisted chemical etching conditions, the macro- or microporous structures could be formed. Luminescence from metal-assisted chemically etched layers was measured. It was found that the PL intensity increases with increasing etching time. This behaviour is attributed to increase of the density of the silicon nanostructure. It was found the shift of PL peak to a green region with increasing of deposition time can be attributed to the change in porous morphology. Finally, the PL spectra of samples formed by high concentrated solution of AgNO3 showed two narrow peaks of emission at 520 and 550 nm. Th...
Strong white light emission from a processed porous silicon and its photoluminescence mechanism
Journal of Luminescence, 2011
We have prepared various porous silicon (PS) structures with different surface conditions (any combination of oxidation, carbonization as well as thermal annealing) to increase the intensity of photoluminescence (PL) spectrum in the visible range. Strong white light (similar to daylight) emission was achieved by carrying out thermal annealing at 1100 1C after surface modification with 1-decene of anodic oxidized PS structures. Temperature-dependent PL measurements were first performed by gradually increasing the sample temperature from 10 to 300 K inside a cryostat. Then, we analyzed the measured spectrum of all prepared samples. After the analysis, we note that throughout entire measured spectrum, only two main peaks corresponding to blue and green-orange emission lines (which can be interpreted by quantum size effect and/or configuration coordinate model) were seem to be predominant for all temperature range. To further reveal and analysis these peaks, finally, measured data were inputted into the formula of activation energy of thermal excitation. We found that activation energies of blue and green-orange lines were approximately 49.3 and 44.6 meV, respectively.
Correlation of photoluminescence spectra and structure of porous silicon
Semiconductor Science and Technology, 1996
Porous silicon (PS) layers emitting red photoluminescence (PL) have been prepared by anodization of p-type (100) monocrystalline silicon substrate in aqueous HF solutions. PS layers oxidized in free air exhibit under UV photoirradiation an intense yellow-orange PL, whilst as-prepared samples emit red PL. Our aim is to explain the PL behaviour and its origin in both unetched and HF etched as-prepared and oxidized PS layers according to calculated PL based on quantum confinement formalism and to infrared spectroscopy (IRS). It was found that the PL behaviour is associated with a quantum size effect and concentration change in quantum dots and wires. It was observed that HF etching of oxidized PS may induce a preponderance of dots or wires in the PS structure, depending on the oxidation degree, and produce a PL blueshift or redshift respectively. By correlating PL spectra of unetched and HF-etched oxidized PS, we found that highly oxidized PS transforms into an SiO 2 matrix in which photoluminescent nanocrystalline Si quantum dots are embedded.
Photoluminescence Emission Control of Porous Silicon
Soft Nanoscience Letters
This paper reports the feasibility of synthesis and characterization of nano-porous silicon (NPS) powder and (Nickel/nano-porous silicon, Ni/NPS) nano-composite prepared using dual techniques (alkaline chemical etching process and ultra-sonication technique). The structural and the optical properties of the fabricated structures are inspected using X-ray Diffraction, Fourier Transform Infrared Spectrophotometer, Raman Spectroscopy, and Fluorescence Spectrophotometer Photoluminescence. All the results have agreed that NPS is one of the most suitable materials used as active material in the LED fabrication; by changing the main factors in the preparation process, so the different physical and chemical properties are obtained. NPS produces two emission regions that correspond to orange-red and dark red; on the other hand, (Ni/NPS) produce the yellow emission. So, the photoluminescence emission is controllable by adjusting the preparation conditions. The optical data recorded here are useful for the production of the nanoscale optical devices.
Influence of light intensity on the photoluminescence of silicon nanostructures
Journal of Applied Physics, 2002
The strong visible photoluminescence ͑PL͒ of nanostructured silicon, such as porous Silicon and silicon nanocrystals, is studied as a function of the power and the wavelength of the excitation laser source. The position of the PL peak is a function of the fluence: when the incident fluence is increased, the PL peak is blueshifted, and it is redshifted to its initial position when the fluence is decreased back. The PL yield is strongly attenuated with the increasing fluence and this decrease is partially irreversible. The behavior is also found to be a function of the wavelength of excitation: the shorter the excitation wavelength, the stronger the fluence effect. The PL temporal behavior has also been studied and appears to be weakly sensitive to the fluence. Fluence effects are compared to temperature effects and both are noticeably different, proving the absence of heating effects in our experiment for a wide range of incident power. Auger effect and state filling are discussed in order to understand the experimental results in the framework of the quantum confinement process.