Raman and Optical Characterization of Porous Silicon

ABSTRACTRaman spectra from electrochemically etched porous silicon are correlated with photoluminescence (PL) data from the same spots of the sample. This correlation is consistent with optical properties of quantum confinement. The dielectric constant determined from angle resolved ellipsometry gives values far below that of bulk silicon. This reduction is due to the combined effects of voids as well as quantum confinement. The PL spectrum shows a weak high energy peak around 2.8eV in addition to the strong broad peak at 1.5 to 1.9eV. The temperature dependence of PL resembles that of bound excitons such as Si:S, having a thermal dissociation energy of 100 meV near room temperature. The radiation life time changes from tens of microseconds near room temperature to a few milliseconds at liquid helium temperatures. The rapid increase in lifetime and decrease in PL intensity at low temperatures indicates that phonons are probably involved.

Download Full-text

Fabrication and characterization of magnetic porous silicon with curie temperature above room temperature

Journal of Porous Materials ◽

10.1007/s10934-016-0353-2 ◽

2017 ◽

Vol 24 (5) ◽

pp. 1139-1144 ◽

Cited By ~ 2

Author(s):

Mansour Aouassa ◽

Imen Jadli ◽

Mohammad Ali Zrir ◽

Hassen Maaref ◽

Ridha Mghaieth ◽

...

Keyword(s):

Porous Silicon ◽

Curie Temperature ◽

Room Temperature ◽

Fabrication And Characterization

Download Full-text

Preparation and Characterization of ZnS/ZnO Compound Grown on Porous Silicon Substrate Using CVD Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.393 ◽

2010 ◽

Vol 663-665 ◽

pp. 393-396

Author(s):

Fu Ru Zhong ◽

Xiao Yi Lv ◽

Zhen Hong Jia

Keyword(s):

Electron Microscopy ◽

Porous Silicon ◽

Room Temperature ◽

Zinc Sulphide ◽

Cvd Method ◽

Peak Energy ◽

Porous Silicon Substrate ◽

Photoluminescence Peak ◽

Scanning Electron

We have investigated the morphology and photoluminescence (PL) of Zinc Oxide (ZnO) and Zinc sulphide (ZnS) compound grown on porous silicon at room temperature. Under different excitation wavelengths (320 nm, 340nm, 370 nm), the photoluminescence (PL) spectra of PS-ZnS-ZnO composites were different, and at 550nm there is a strong photoluminescence peak. Energy dispersive spectroscopy (EDS) has been carried out to evaluate the existing of ZnO/ZnS compound. In addition, the scanning electron microscopy (SEM) observation shows that the morphology of the PS-ZnS-ZnO composites was well grown on porous silicon.

Download Full-text

Synthesis of Phosphorescent Platinum Complexes with 3-Aryl Pyridazine as Prominent Emitting Materials in Organic Light-Emitting Device

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.277-279.1006 ◽

2005 ◽

Vol 277-279 ◽

pp. 1006-1010

Author(s):

Seung Hee Lee ◽

Won Hee Han ◽

Hyun Seo Shin ◽

Sang Jin Lee

Keyword(s):

Room Temperature ◽

General Structure ◽

Platinum Complexes ◽

Life Time ◽

Molecular Orbital Calculation ◽

Ancillary Ligands ◽

Light Emitting ◽

Organic Light ◽

Square Planar

The synthesis and characterization of a series of square planar Pt(II) complexes, which are luminescent at room temperature, are reported. The complexes have the general structure of (C^N)Pt(O^O), where HC^N is 3-phenylpyridazine (ppdz), 3-(4’-biphenyl)pyridazine (4’phppdz), 3-(2’-naphthyl)pyridazine (2’napdz), or 3-(1’-naphthyl)pyridazine (1’napdz), and HO^O is acetylacetone (Hacac). The reaction of K2PtCl4 with HC^N forms the chloro-bridged dimer, (C^N)Pt( µ-Cl)2Pt(C^N), which are cleaved with an ancillary ligand to give the corresponding monomeric (C^N)Pt(O^O) complexes. The emission bands of these complexes are governed by the structure of the cyclometalating ligands, with emission band (lem) ranging from 516 to 645 nm. The two emission bands at (515 and 550 nm) of (ppdz)Pt(acac) complex have 7 and 6 ms of life time which imply those bands are due to phosphorescence decay. The conjugating ring on the pyridazine makes the emission more red shifted which is expected based on molecular orbital calculation. In addition to the alteration of cyclometalating ligands, ancillary ligands also change. These results can be compared with the corresponding Ir(III) complexes.

Download Full-text

Silver Nanocrystals at Cavities Created by High Energy Helium Implantation in Bulk Silicon

MRS Proceedings ◽

10.1557/proc-0994-f11-06 ◽

2007 ◽

Vol 994 ◽

Cited By ~ 1

Author(s):

Rachid El Bouayadi ◽

Gabrielle Regula ◽

Maryse Lancin ◽

Eduardo Larios ◽

Bernard Pichaud ◽

...

Keyword(s):

Room Temperature ◽

High Energy ◽

Nickel Silicide ◽

Bulk Silicon ◽

Shape Characteristic ◽

Transmission Electron ◽

Helium Implantation ◽

Ag Deposition ◽

First Time ◽

Good Agreement

AbstractHigh resolution transmission electron microscopy observations show for the first time the presence of two orientations of pure silver precipitates in nanocavities induced in bulk silicon by implantation at 1.6 MeV with a dose of 5×1016 He+ cm−2 and a two hour annealing at 1050°C. These precipitates were called A and B to refer to the two well-known nickel silicide (NiSi2) precipitates or Ag films on a {111} silicon surface. Thus, the A precipitate corresponds to a growth of silver nanocrystal on {111} cavity walls in epitaxy with the Si matrix with an orientation relationship Ag(-111)[211]||Si(-111)[211]. The B precipitate develops on a {111} plane parallel to a {111} cavity wall as well, but in a twin orientation with respect to the Si matrix defined by Ag(-111)[211]||Si(-111)[-2-1-1]. The Ag nanocrystals have a size ranging from a few nm to 50 nm. Most of them have the faceted-shape characteristic of “clean” cavities. They are either A precipitates or they contain alternatively A and B bands in good agreement with both the low stacking fault energy of silver and the two types of nanocrystal orientations obtained by Ag deposition on (111) Si substrate at room temperature. Some Ag precipitates were also found at dislocations located at the He+ projection range, but these trapping sites were found thermally unstable as compared to the cavity ones. Indeed, during a second identical annealing, the precipitates grow in cavities whereas they fade at dislocations.

Download Full-text

Epitaxy of Aluminium Films on Semiconductors by Ionized Cluster Beam

MRS Proceedings ◽

10.1557/proc-37-401 ◽

1984 ◽

Vol 37 ◽

Cited By ~ 16

Author(s):

I. Yamada ◽

C. J. Palmstrøm ◽

E. Kennedy ◽

J. W. Mayer ◽

H. Inokawa ◽

...

Keyword(s):

Heat Treatment ◽

Room Temperature ◽

Depth Profiling ◽

Electrical Characterization ◽

Life Time ◽

Cluster Beam ◽

Clean Surface ◽

Si Substrate ◽

Thermal Stability Of

AbstractEpitaxial Al films have been deposited onto the clean surface of single-crystal Si by ionized cluster beam (ICB) at room temperature. Thermal stability of the film has been examined by SEM, AES depth profiling, ion backscat. tering/channeling, and electrical characterization of the Al-Si interface. It was found that the ICB Al film on Si substrate was remarkably stable up to 550°C although pure Al was used. Alloy penetration at the interface, shift of barrier height, degradation of crystalline quality and development of annealing hillocks on the surface were not observed after the heat treatment. Extremely long electromigration life time was also confirmed. Epitaxial growth on GaAs(100) substrate was attempted and preliminary results are given.

Download Full-text

Preparation and Characterization of Water-Soluble CdSe/CdS Core/Shell Quantum Dots

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.549.212 ◽

2012 ◽

Vol 549 ◽

pp. 212-215

Author(s):

Ming Li Li ◽

Qiong Yu ◽

Ying Xu ◽

Chun Jiang Zhou ◽

Qing Guo Lu

Keyword(s):

Quantum Dots ◽

Energy Band ◽

Xrd Analysis ◽

High Energy ◽

Water Soluble ◽

Excitation Wavelength ◽

Core Shell ◽

Electron Hole ◽

Energy Peak

Cadmium Selenide/Cadmium Sulfide (CdSe/CdS) core/shell quantum dots (QDs) in aqueous solution were prepared by solve-separate method using CdSe as core and mercapto-acetate acid as stabilizer and surfactants. The results of experiments indicate that the size of the CdSe/CdS QDs was about 5nm estimated by FE-TEM, which is accordant with that calculated from the XRD data by the Scherer equation after emendation. The QDs belong to the cubic structure (zinc blende) by XRD analysis. The intensity of luminescence of the quantum dots was greatly improved after the surface was coated with CdS shell. With increasing the time of refluence, the intensity of photoluminescence was promoted correspondingly. The excitation wavelength was 350nm, two emission peaks were clearly observed, the first high-energy peak was at 600nm and the second one located in 700nm. The first high-energy band was attributed to electron–hole recombination after relaxation and the second energy band was to deep traps in quantum-confined systems.

Download Full-text

Effect of Preparation Conditions on the Silicon L-Edge In Electrochemically Prepared Porous Silicon

MRS Proceedings ◽

10.1557/proc-298-283 ◽

1993 ◽

Vol 298 ◽

Author(s):

T. Van Buuren ◽

T. Tiedje ◽

W. Weydanz

Keyword(s):

Electronic Structure ◽

High Resolution ◽

Porous Silicon ◽

Quantum Confinement ◽

Light Exposure ◽

Blue Shift ◽

Bulk Silicon ◽

Preparation Conditions ◽

P Type ◽

Confinement Model

AbstractHigh resolution measurements of the silicon L-edge absorption in electrochemically prepared porous silicon show that the absorption threshold is shifted to higher energy relative to bulk silicon, and that the shift is dependent on how the porous silicon is prepared. When the porous silicon is made from n-type material with light exposure, the blue shift increases logarithmically with the anodizing current. Porous silicon prepared by anodizing p-type silicon exhibits a blue shift in the L-edge which increases with the time spent in the HF solution after the anodizing potential is turned off. The data are consistent with the quantum confinement model for the electronic structure of porous silicon.

Download Full-text

Optical Studies of Electroluminescent Structures from Porous Silicon

MRS Proceedings ◽

10.1557/proc-283-395 ◽

1992 ◽

Vol 283 ◽

Cited By ~ 4

Author(s):

J. F. Harvey ◽

R. A. Lux ◽

D. C. Morton ◽

G. F. McLane ◽

R. Tsu

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Room Temperature ◽

Light Emitting Diode ◽

Spectral Peak ◽

Electrical Excitation ◽

Silicon Structure ◽

Electrical Measurements ◽

Optical Studies ◽

Light Emitting

ABSTRACTTwo components of the electroluminescence (EL) from porous silicon light emitting diode (LED) devices have been observed. A slower component and a faster component have been identified. The slower component has a spectral peak shifted to the red from the corresponding photoluminescence (PL) spectrum. The faster component has a spectral peak well in the infrared (IR). Optical and electrical measurements of these two components are discussed. The temperature dependence of the two EL components are presented and contrasted. Our measurements demonstrate that the two EL components and the PL result from recombination in different parts of the porous silicon structure. As the temperature is reduced below room temperature the slower EL exhibits a decrease in intensity at relatively high temperatures, suggesting a freeze out of electrical carriers due to quantum confinement, resulting in a much reduced electrical excitation of the EL.

Download Full-text

Room Temperature PL Characterization of Polycrystalline Diamond Prepared by HPHT

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.178.265 ◽

2010 ◽

Vol 178 ◽

pp. 265-269

Author(s):

Zhi Hong Li ◽

Kai Gao ◽

Xue Song Li ◽

Yu Mei Zhu ◽

Peng Fei Wang

Keyword(s):

Excitation Energy ◽

Room Temperature ◽

Energy Intensity ◽

Polycrystalline Diamond ◽

High Energy ◽

Excitation Wavelength ◽

High Energy Region ◽

Half Height ◽

Peak Location

Diamond polycrystalline composites with some different elements were prepared by HPHT (high pressure and high temperature). The dependence between emission energy and excitation energy was characterized by PL technique. The results showed that the photoluminescence of diamond polycrystalline composites was not affected by additives, only related to the excitation. The emission wavelengths of composites decreased with excitation, at the same time, emission peaks shifted to high energy region and the peak width at half-height decreased relatively. The energy of emission had a linear relationship with that of excitation. The emission band peak location shifted from 1.57 (790nm) to 1.97eV (628nm) as the excitation wavelength changed from 2.34 (530nm) to 2.95eV (420nm). Emission intensity decreased linearly with the decrease of excitation energy intensity. However, this linear dependence disappeared as excitation wavelength was below 400nm.

Download Full-text