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.

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.

scholarly journals Luminescence performance of laser synthesized Al2O3:Eu3+ nanophosphors depending on synthesis conditions

2021 ◽  
Vol 2067 (1) ◽  
pp. 012008
Author(s):  
A Kostyukov ◽  
A Nashivochnikov ◽  
M Rakhmanova ◽  
V Snytnikov
Keyword(s):  
Crystallite Size ◽  
Electric Dipole ◽  
Electric Dipole Transition ◽  
Dipole Transition ◽  
Luminescence Properties ◽  
Laser Vaporization ◽  
Red Emission ◽  
Synthesis Conditions ◽  
Chromaticity Coordinates ◽  
Luminescence Performance

Abstract Al2O3:Eu3+ nanophosphors were prepared by laser vaporization method in a flowing mixture of Ar/He and O2. Luminescence properties of Al2O3:Eu3+ nanophosphors are predominantly determined by Eu3+ ions red emission with inhomogeneously broadened bands in the region of 550-750 nm corresponding to 5D0 →7FJ transitions of Eu3+ (J = 0 - 4). Hypersensitive electric dipole transition 5D0 →7F2 dominates in the spectrum and is responsible for the red emission. The effect of crystallite size on luminescence properties of Al2O3:Eu3+ nanocrystals was observed. It was shown that the introduction of oxygen during the synthesis improves the luminescence performance. The obtained chromaticity coordinates and high absolute QY (~ 14%) indicate the possibility of using red nanophosphors based on Al2O3:Eu3+.

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.

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.

Comparative Optical Studies of Chemically Synthesized Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
Gildardo R. Delgado ◽  
Howard W.H. Lee ◽  
Susan M. Kauzlarich ◽  
Richard A. Bley
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Theoretical Calculations ◽  
Dominant Role ◽  
Blue Emission ◽  
Surface States ◽  
Si Nanocrystals ◽  
Optical And Electronic Properties ◽  
Passivation Layers

AbstractWe studied the optical and electronic properties of silicon nanocrystals derived from two distinct fabrication procedures. One technique uses a controlled chemical reaction. In the other case, silicon nanocrystals are produced by ultrasonic fracturing of porous silicon layers. We report on the photoluminescence, photoluminescence excitation, and absorption spectroscopy of various size distributions derived from these techniques. We compare the different optical properties of silicon nanocrystals made this way and contrast them with that observed in porous silicon. Our results emphasize the dominant role of surface states in these systems as manifested by the different surface passivation layers present in these different fabrication techniques. Experimental absorption measurements are compared to theoretical calculations with good agreement. Our results provide compelling evidence for quantum confinement in both types of Si nanocrystals. Our results also indicate that the blue emission from very small Si nanocrystals corresponds to the bandedge emission, while the red emission arises from traps.

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.

Influence of nanostructure size on the luminescence behavior of silicon nanoparticle thin films

1997 ◽  
Vol 12 (12) ◽  
pp. 3386-3392 ◽  
Author(s):  
A. A. Seraphin ◽  
E. Werwa ◽  
K. D. Kolenbrander
Keyword(s):  
Thin Films ◽  
Quantum Confinement ◽  
Room Temperature ◽  
Silicon Nanoparticles ◽  
Excitation Intensity ◽  
Luminescence Properties ◽  
Photoluminescence Intensity ◽  
High Excitation ◽  
Silicon Thin Films ◽  
Processing Techniques

We demonstrate the effect of particle size and quantum confinement on the luminescence properties of nanoscale silicon thin films. Thin films of agglomerated silicon nanoparticles are synthesized using pulsed laser ablation supersonic expansion. Following deposition, standard semiconductor processing techniques are employed to reduce the nanoparticle size. Films are oxidized both in air and chemically to reduce the silicon core dimensions, resulting in a shift of the luminescence emission peak to shorter wavelengths. Removal of the oxide using hydrofluoric acid (HF) results in further blueshifting of the luminescence, as does subsequent reoxidation in air and using nitric acid. The luminescence properties of samples are also studied as a function of excitation intensity. For room temperature excitation with a pulsed 355 nm source, a saturation of the photoluminescence intensity at high excitation intensity is observed, along with a blueshift of the peak PL wavelength. This behavior is found to persist at reduced temperature. A saturation of PL intensity, but no blueshift, is observed for high excitation intensity using a cw 488 nm source at room temperature. At reduced temperatures, no saturation of emission intensity occurs for high intensity 488 nm cw excitation. Both the irreversible shifting of the peak PL wavelength with size reducing treatments and the PL behavior at high excitation intensities indicate that quantum confinement determines the luminescence wavelength.

Structural, Morphological, Vibrational, Thermal and Optical Properties of ZnS Quantum Dots in the Polymer Matrix

2019 ◽  
Vol 3 (1) ◽  
pp. 50-58
Author(s):  
Feroz A. Mir ◽  
Owais I. Mir ◽  
Rayees A. Zargar
Keyword(s):  
Polymer Matrix ◽  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Visible Region ◽  
Blue Emission ◽  
Confinement Effect ◽  
Optical Data ◽  
Drying Time ◽  
Zinc Blend ◽  
Ft Ir

<P>Background: Nanotechnology is believed to be a future for new human generations. Among different emerging materials, the Nanocomposites (NCs) would be on front line. The aim of the current study is provide a way to synthesis the ZnS-polyacrylamide NCs with emphasizes on the effect of aging in polymer on its various physical properties. </P><P> Objectives: To prepare and study the properties of ZnS-Polymer NCs with drying time in polymer matrix. </P><P> Methods: ZnS-polyacrylamide NCs samples were synthesized by adding aqueous suspension of ZnS Nanoparticles (NPs) in Sol of acrylamide: bisacrylamide copolymer. These samples were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), UV-Vis, and Photoluminescence (PL) spectroscopy. </P><P> Results: From XRD data analysis, nano phase and zinc blend structure of the material is confirmed. From SEM images, the pristine ZnS NPs show spherical morphology, and this texture is still preserved in the polymer composites. FT-IR confirms that there is strong interaction between polymer chain and ZnS NPs. The TGA results indicate that the incorporation of the NPs impacts the thermal properties of the ZnS-polymer NCs and displaying higher thermal stability than the pure polymer matrix. The optical data predicts the band gap and Quantum Confinement Effect (QCE) and reduction of ZnS NPs within the polymer matrix. These NCs show emission in blue region with decreases in intensity with drying time. </P><P> Conclusion: ZnS NPs incorporated in polyacrylamide ware prepared by copolymer technique. Structural analysis confirms zinc blend structure. The vibration spectra of composites samples predicts an interaction between different functional groups of polymer with the metal sulfide. These NCs show an enhanced thermally stability. The observed optical band show a red shift and quantum confinement effect. Size calculated by XRD and optical data shows good correlation with each other. The PL spectra of the NCs exhibits a broad blue emission with excitation (λex = 320 nm). The visible region emission could be originating from the radiative recombination involving defect states within the ZnS nanocrystals energy band.</P>

A new langbeinite-type phosphate K2GdHf(PO4)3: synthesis, crystal structure, band structure and luminescence properties

2020 ◽  
Vol 76 (8) ◽  
pp. 771-778
Author(s):  
Hua Nan ◽  
Li Chen ◽  
Rui-Juan Zhang ◽  
Dan Zhao
Keyword(s):  
Optical Transition ◽  
Blue Emission ◽  
Large Family ◽  
Luminescence Properties ◽  
X Ray Diffraction ◽  
Blue Emission Band ◽  
Light Emitting ◽  
Direct Band ◽  
Cie Chromaticity ◽  
White Light Emitting Diodes

Langbeinite-type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite-type compound, K2GdHf(PO4)3 [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single-crystal X-ray diffraction. Theoretical studies reveal that K2GdHf(PO4)3 is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O-2p→Hf-5d transition. A Ce3+-doped phosphor, K2Gd0.99Ce0.01Hf(PO4)3, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d 1→4f 1 transition of Ce3+. The average luminescence lifetime was calculated to be 5.437 µs and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K2Gd0.99Ce0.01Hf(PO4)3 can be used as a good blue phosphor for three-colour white-light-emitting diodes (WLEDs).

Sign in / Sign up

Export Citation Format

Share Document