Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal

2000 ◽  
Vol 72 (1-2) ◽  
pp. 245-255 ◽  
Author(s):  
I. N. Germanenko ◽  
M. Dongol ◽  
Y. B. Pithawalla ◽  
M. Samy El-Shall ◽  
J. A. Carlisle
Keyword(s):  
Quantum Confinement ◽  
Blue Shift ◽  
Laser Vaporization ◽  
Photoluminescence Properties ◽  
Bonding Structure ◽  
Quantum Size ◽  
Si Nanocrystals ◽  
Crystalline Core ◽  
Si Nanoparticles ◽  
Significant Blue Shift

Web-like aggregates of coalesced Si nanocrystals produced by a laser vaporization-controlled condensation technique show luminescence properties that are similar to those of porous Si. The results are consistent with a quantum confinement mechanism as the source of the red photoluminescence (PL) in this system. The oxidized Si nanoparticles do not exhibit the red PL that is characteristic of the surface-oxidized Si nanocrystals. The nanoparticles are allowed to oxidize slowly, and the PL is measured as a function of the exposure time in air. A significant blue shift in the red PL peak is observed as a result of the slow oxidation process. The dependence of quantum size effects on the bonding structure is established by correlating the PL data with the photon-yield electronic structure measurements made at the Advanced Light Source. The results indicate that as the nanoparticles oxidize, the radius of the crystalline core decreases in size, which gives rise to a larger bandgap and consequently to the observed blue-shift in the PL band. The correlation between the PL, SXF, and NEXAFS results provides further support for the quantum confinement mechanism as the origin of the visible PL in Si nanocrystals.

Luminescence Properties of Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
Shoutian Li ◽  
Stuart J. Silvers ◽  
M. Samy El-Shall
Keyword(s):  
Quantum Confinement ◽  
Blue Emission ◽  
Emission Wavelength ◽  
Luminescence Properties ◽  
Raman Shift ◽  
Laser Vaporization ◽  
Emission Characteristic ◽  
Red Emission ◽  
Si Nanocrystals ◽  
Si Nanoparticles

AbstractWeblike aggregates of coalesced Si nanocrystals are produced by a laser vaporization -controlled condensation technique. SEM micrographs show particles with ∼ 10 nm diameters but the Raman shift suggests the presence of particles as small as ∼ 4 nm. FTIR of the freshly prepared particles shows weak peaks due to the stretching, bending and rocking vibrations of the Si-O-Si bonds indicating the presence of a surface oxidized layer SiOx (x<2).The particles show luminescence properties that are similar to those of porous Si and Si nanoparticles produced by other techniques. The nanoparticles do not luminesce unless, by exposure to air, they acquire the SiOx passivated coating. They show a short-lived blue emission characteristic of the SiO2 coating and a biexponential longer-lived red emission. The short lifetime component of the red emission, about 12 μs, does not depend on emission wavelength. The longer-lived component has a lifetime that ranges from 90 to over 130 μs (at 300 K), increasing with emission wavelength. The results are consistent with the quantum confinement mechanism as the source of the red photoluminescence.

Quantum size effects on the optical properties of nc-Si QDs embedded in an a-SiOx matrix synthesized by spontaneous plasma processing

2015 ◽  
Vol 17 (7) ◽  
pp. 5063-5071 ◽  
Author(s):  
Debajyoti Das ◽  
Arup Samanta
Keyword(s):  
Optical Properties ◽  
Size Effects ◽  
Quantum Confinement ◽  
Plasma Processing ◽  
Blue Shift ◽  
Quantum Size Effects ◽  
Confinement Effects ◽  
Quantum Size ◽  
Quantum Confinement Effects ◽  
Stokes Shifts

An energy blue shift due to quantum confinement effects in tiny nc-Si QDs accompanied by larger Stokes shifts in PL at smaller dimensions.

Synthesis and Characterization of Si Nanoparticles Obtained on Sonication of Porous Silicon Multilayer Films

2012 ◽  
Vol 17 ◽  
pp. 13-25 ◽  
Author(s):  
Paresh G. Kale ◽  
Sharma Pratibha ◽  
Chetan S. Solanki
Keyword(s):  
Surface Modification ◽  
Porous Silicon ◽  
Current Density ◽  
Quantum Confinement ◽  
Blue Shift ◽  
Vis Spectroscopy ◽  
Si Nanoparticles ◽  
Confinement Behavior ◽  
Si Quantum Dots

Synthesis of Si quantum dots (QDs), useful for multi-junction crystalline Si solar cells, using porous Silicon (PS) is presented in this paper. Four types of freestanding PS structures are fabricated by anodization method with modulation of current density between two levels. The level-1 current density is kept constant at 20 mA/cm2 (for reference monolayer structure - sample A) and 10 mA/cm2 (for all multilayer structures samples B, C, D). The level-2 is varied between 0 to 50 mA/cm2 (0, 20, 30, 50 mA/cm2 as sample A, B, C and D respectively). In order to obtain Si QDs from PS films, the films are subjected to sonication (120 W, 42 kHz) for 6 hours. HRTEM images confirm presence of Si nanoparticles in the range of 2 to 8 nm. Various spectroscopic analyses of Si nanoparticles are performed in order to evaluate quantum confinement behavior and surface modification observed during sonication. Analysis of de-convoluted Raman peaks shows frequency downshift and increase in full width half maximum due to formation of QDs. After sonication, PL spectroscopy indicates blue shift from 2.54 eV (sample A) to 2.85 eV (sample D_6HR), similar to the observations made by UV-Vis spectroscopy. FTIR spectra show oxidation of Si QDs during sonication. Spectroscopic and microscopic results are explained using quantum confinement and surface modification phenomenon.

Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers

2003 ◽  
Vol 775 ◽  
Author(s):  
Suk-Ho Choi ◽  
Jun Sung Bae ◽  
Kyung Jung Kim ◽  
Dae Won Moon
Keyword(s):  
Quantum Confinement ◽  
Radiative Recombination ◽  
Ion Beam ◽  
Quantum Confinement Effect ◽  
Visible Range ◽  
Ion Beam Sputtering ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Beam Sputtering ◽  
Microscopy Images

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.

The Emission Property of Phosphors LEDs Based on ZnCuInS/ZnSe/ZnS Quantum Dots

2014 ◽  
Vol 989-994 ◽  
pp. 623-625
Author(s):  
Ke Bi ◽  
Wen Yan Liu ◽  
Tian Yue Xu ◽  
Tie Qiang Zhang ◽  
Yu Zhang
Keyword(s):  
Quantum Dots ◽  
Photoluminescence Spectrum ◽  
Stokes Shift ◽  
Core Shell ◽  
Photoluminescence Properties ◽  
Red Emission ◽  
Light Emitting ◽  
Quantum Size ◽  
Gan Led ◽  
Photoluminescence Peak

.In this research, ZnCuInS/ZnSe/ZnS quantum dots (QDs) have been studied as an excellent red emitting source for blue GaN LED because of its non-toxic deep red emmission, and large Stokes shift properties. In the paper ZnCuInS/ZnSe/ZnS core/shell quantum dots were prepared with the particle size of 4.5nm. According to the measurement of photoluminescence spectrum emitted by ZnCuInS/ZnSe/ZnS core/shell quantum dots, the emitting peak of 700 nm and the full was achieved as red emitter.It was found that absorption edge and photoluminescence peak shifted to shorter wavelength with decreasing the nanocrystal size due to quantum size effect.Meanwhile, we were prepared ZnCuInS/ZnSe/ZnS core/shell quantum dot light emitting diodes and their photoluminescence properties were studied. After the suitable bias was applied on the films, increasing the ZnCuInS/ZnSe/ZnS QDs concentration in the blue GaN chips, red emission increased with decreasing LED’s blue light.

Laser Induced Etching for Generation of Si Nanocrystals and Spectroscopic Investigation of Morphology

2005 ◽  
Vol 23 ◽  
pp. 43-46
Author(s):  
H.S. Mavi ◽  
S. Rath ◽  
Arun Shukla
Keyword(s):  
Quantum Confinement ◽  
Silicon Nanocrystals ◽  
Laser Wavelength ◽  
Interconnected Network ◽  
Substrate Type ◽  
Argon Ion Laser ◽  
Si Nanocrystals ◽  
Ion Laser ◽  
Laser Induced Etching ◽  
Argon Ion

Laser-induced etching of silicon is used to generate silicon nanocrystals. The pore structure depends on the substrate type and etching laser wavelength. Porous silicon (PS) samples prepared by Nd:YAG laser (1.16 eV) etching of n-type substrate showed a fairly uniform and highly interconnected network of nearly circular pores separated by thin columnar boundaries, while no circular pits were produced by argon- ion laser (2.41 eV) etching under similar conditions. The size and size distribution of the nanocrystals are investigated by Raman and photoluminescence spectroscopies and analyzed within the framework of quantum confinement models.

Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Tsu ◽  
L. Ioriatti ◽  
J. F. Harvey ◽  
H. Shen ◽  
R. A. Lux
Keyword(s):  
Dielectric Constant ◽  
Porous Silicon ◽  
Size Effects ◽  
Quantum Confinement ◽  
Electrochemical Etching ◽  
Index Of Refraction ◽  
Quantum Size Effects ◽  
Quantum Size ◽  
Quantum Confinement Effects ◽  
Shallow Impurities

ABSTRACTThe reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.

Influence of the Dispersion of the Size of the Si Nanocrystals on their Emission Spectra

1994 ◽  
Vol 358 ◽  
Author(s):  
J. B. Khurgin ◽  
E. W. Forsythe ◽  
S. I. Kim ◽  
B. S. Sywe ◽  
B. A. Khan ◽  
...  
Keyword(s):  
Systematic Study ◽  
Quantum Confinement ◽  
Emission Spectra ◽  
Emission Peak ◽  
Nanocrystal Size ◽  
Pl Spectra ◽  
Si Nanocrystals ◽  
Average Size ◽  
Size Dispersion ◽  
Confinement Model

ABSTRACTA systematic study of the PL spectra of Si quantum nanocrystals in the SiO2 matrix has been performed. The results have been fitted to a quantum-confinement model that includes the nanocrystal size dispersion rather than a specific size of the nanocrystal. This serves as a strong confirmation of the confinement-induced nature of the PL. It has been shown that if the dispersion is taken into account, the position of the emission peak as well as the PL width can always be correlated with the average size of the nanocrystal.

Effect of Thermal Annealing on the Photoluminescence Properties of a GaInNAs/GaAs Single Quantum Well

2000 ◽  
Vol 639 ◽  
Author(s):  
Laurent Grenouillet ◽  
Catherine Bru-Chevallier ◽  
Gérard Guillot ◽  
Philippe Gilet ◽  
Philippe Ballet ◽  
...  
Keyword(s):  
Quantum Well ◽  
Thermal Annealing ◽  
Low Temperatures ◽  
Blue Shift ◽  
Emission Peak ◽  
Single Quantum ◽  
Photoluminescence Properties ◽  
Single Quantum Well ◽  
Peak Energy ◽  
Strong Blue Shift

ABSTRACTWe report on the effect of thermal annealing on the photoluminescence properties of a Ga0.65In0.35N0.02As0.98/GaAs single quantum well. Thermal annealing is shown to decrease the strong nitrogen-induced localization effects observed at low temperatures and to reduce the full width at half maximum of the emission peak. It also induces a strong blue shift of the emission peak energy, which is thought not to arise from an In-Ga interdiffusion alone, as it is much larger than in a nitrogen-free reference single quantum well.

scholarly journals Properties and Analysis of Transparency Conducting AZO Films by Using DC Power and RF Power Simultaneous Magnetron Sputtering

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Neng-Fu Shih ◽  
Jin-Zhou Chen ◽  
Yeu-Long Jiang
Keyword(s):  
Incident Light ◽  
Blue Shift ◽  
Light Wavelength ◽  
Rf Power ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dc Power ◽  
Incident Light Wavelength ◽  
Significant Blue Shift ◽  
Sputtering System

DC power and RF power were introduced into the magnetic controlled sputtering system simultaneously to deposit AZO films in order to get an acceptable deposition rate with high quality transparency conducting thin film. The resistivity decreases with the RF power for the as-deposited samples. The resistivity of 6 × 10−4 Ω-cm and 3.5–4.5 × 10−4 Ω-cm is obtained for the as-deposited sample, and for all annealed samples, respectively. The transmittance of the AZO films with higher substrate temperature is generally above 80% for the incident light wavelength within 400–800 nm. The transmittance of the as-deposited samples reveals a clear blue shift phenomenon. The AZO films present (002) oriented preference as can be seen from the X-ray diffraction curves. All AZO films reveal compressive stress. The annealing process improves the electrical property of AZO films. A significant blue shift phenomenon has been found, which may have a great application for electrode in solar cell.

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