The Oxidation Behavior of Silicon Nanocrystals in the Submonolayer Region

1997 ◽  
Vol 486 ◽  
Author(s):  
J. Diener ◽  
M. Ben-Chorin ◽  
D. I. Kovalev ◽  
G. Polisski ◽  
F. Koch
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Oxidation Behavior ◽  
Surface Oxidation ◽  
Square Root ◽  
Mesoporous Silicon ◽  
Si Nanocrystals ◽  
Evolution Of Oxygen

AbstractFourier transform infrared spectroscopy is used to determine the time evolution of oxygen incorporation onto the surface of silicon nanocrystals. Oxygen concentrations up to one monolayer are investigated. The temporal progress of surface oxidation of Si nanocrystals in porous silicon shows a linear dependence on the square root of the oxidation time. This is similar to the oxidation of bulk Si and mesoporous silicon.

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.

Grains of Porous Silicon Embedded in SiO2:Studies of Optical Gain and Electroluminescence

2004 ◽  
Vol 99-100 ◽  
pp. 31-36 ◽  
Author(s):  
K. Dohnalová ◽  
K. Luterová ◽  
J. Valenta ◽  
Jiří Buršík ◽  
M. Procházka ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Visible Region ◽  
Optical Gain ◽  
Intrinsic Property ◽  
Stimulated Emission ◽  
Silicon Nanostructures ◽  
Porous Si ◽  
Si Nanocrystals ◽  
Excitation Spot

Recent reports on experimental observation of optical gain in silicon nanostructures in the visible region, performed at several laboratories all over the world, have triggered an extraordinary surge of interest in silicon lasing. However, attempts aimed at reproducing the red stimulated emission from „standard“silicon nanocrystals (sized 3-5 nm) at some other laboratories either failed, or. did not come to definite conclusions. Therefore, more detailed measurements of optical gain in a wider variety of samples containing Si nanocrystals are required in order to unravel whether or not the observation of optical gain is an intrinsic property of Si nanocrystals. We have performed a detailed study of optical gain in layers of densely packed Si nanocrystals in SiO2, prepared on the basis of porous Si, using the variable-stripe-length (VSL) method in combination with the shifted-excitation-spot (SES) method. In selected samples we have observed a distinct difference in behaviour between VSL and SES curves, indicating the occurrence of positive optical gain of ~ 24 cm-1. Preliminary reports on transport and electroluminescence measurements in thin films of SiO2 doped with porous silicon grains, prepared by spin-coating technique, are also discussed.

scholarly journals Stabilization of porous silicon nanoparticles by PEGalization in water

2021 ◽  
Vol 2058 (1) ◽  
pp. 012013
Author(s):  
A S Eremina ◽  
A Yu Kharin ◽  
Yu V Kargina ◽  
V Yu Timoshenko
Keyword(s):  
Electron Microscopy ◽  
Drug Delivery ◽  
Scanning Electron Microscopy ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Ball Mill ◽  
Silicon Nanoparticles ◽  
Mechanical Grinding ◽  
Mesoporous Silicon ◽  
Scanning Electron

Abstract Mesoporous silicon (mPSi) nanoparticles (NPs) are stabilized by polyethylene glycol (PEG) chains during mechanical grinding in a ball mill that is used to form mPSi-PEG-NPs. The structure, composition, and properties of the obtained samples are studied by means of the dynamic light scattering, scanning electron microscopy and Fourier-transform infrared spectroscopy. The proposed PEGalization procedure is an effective way of regulating the dissolution of mPSi-NPs in water and it is promising for potential application of mPSi-NPs in drug delivery.

FTIR Studies of CH3OH on Porous Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
John A. Glass ◽  
Edward A. Wovchko ◽  
John T. Yates
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Porous Silicon ◽  
Fourier Transform Infrared Spectroscopy ◽  
Porous Layer ◽  
Fourier Transform Infrared ◽  
Surface Species ◽  
Carbon Incorporation ◽  
Oxygen Incorporation ◽  
Ftir Studies

ABSTRACTFourier transform infrared spectroscopy (FTIR) was used to investigate the reaction of methanol with porous silicon and hydrogen passivated porous silicon. At 300 K methanol adsorbs onto hydrogen free porous silicon by cleavage of the O-H bond. Both of the resulting surface species, Si-H and Si-OCH3, were determined to be stable up to ∼500 K. Above 500 K the Si-OCH3 moiety decomposes by breakage of the C-O and C-H bonds. The resulting carbon and oxygen were incorporated into the porous layer and additional Si-H surface species were detected. Further heating to 900 K removed the Si-H surface species. Adsorption of methanol onto hydrogen-passivated porous silicon did not occur until 600 K. At temperatures beyond 600 K, oxygen and carbon incorporation into the porous layer and Si-OCH3, Si-CH3, and Si-H surface species were seen. The previously unseen Si-CH3 surface species is believed to be stabilized by oxygen incorporation.

Modification of Visible Light Emission from Silicon Nanocrystals as a Function of Size, Electronic Structure, and Surface Passivation

1998 ◽  
Vol 536 ◽  
Author(s):  
M.V. Wolkin ◽  
J. Jorne ◽  
P.M. Fauchet ◽  
G. Allan ◽  
C. Delerue
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Light Emission ◽  
Electrochemical Etching ◽  
Theoretical Calculations ◽  
Surface Oxidation ◽  
Stain Etching ◽  
Visible Light Emission ◽  
Effect Of Surface

AbstractThe effect of surface passivation and crystallite size on the photoluminescence of porous silicon is reported. Oxygen-free porous silicon samples with medium to ultra high porosities have been prepared by using electrochemical etching followed by photoassisted stain etching. As long as the samples were hydrogen-passivated the PL could be tuned from the red (750nm) to the blue (400nm) by increasing the porosity. We show that when surface oxidation occurred, the photoluminescence was red-shifted. For sizes smaller than 2.8nm, the red shift can be as large as 1eV but for larger sizes no shift has been observed. Comparing the experimental results with theoretical calculations, we suggest that the decrease in PL energy upon exposure to oxygen is related to recombination involving an electron or an exciton trapped in Si=O double bonds. This result clarifies the recombination mechanisms in porous silicon.

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