Formation Mechanism of Microporous Silicon: Predictions and Experimental Results

1992 ◽  
Vol 283 ◽  
Author(s):  
V. Lehmann ◽  
U. Gösele
Keyword(s):  
Porous Silicon ◽  
Formation Mechanism ◽  
Quantum Confinement ◽  
Experimental Results ◽  
Porous Region ◽  
Formation Conditions ◽  
Porous Morphology

ABSTRACTRecently we presented a formation mechanism for micro-porous silicon which is based on a depletion of holes in the porous region due to quantum confinement. This theory allows predictions concerning the dependence of the porous morphology on the formation conditions. It is the purpose of this work to check whether these predictions are in accordance with experimental observations.

Picosecond Decay Dynamics in Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
T. Matsumoto ◽  
T. Futagi ◽  
H. Mimura ◽  
Y. Kanemitsu
Keyword(s):  
Porous Silicon ◽  
Quantum Confinement ◽  
Streak Camera ◽  
Luminescence Decay ◽  
Experimental Results ◽  
Porous Si ◽  
Emission Energy ◽  
Localized State ◽  
Hydrogen Termination

ABSTRACTPicosecond decay dynamics of luminescent porous silicon has been studied using the second harmonics (SH) of a cw modelocked YLF laser and a synchroscan streak camera. Picosecond luminescence decay shows nonexponential behavior that becomes large with decreasing emission energy. When increasing hydrogen termination on the surface of a Si microcrystal occurs, this picosecond luminescence decay becomes faster. Our experimental results indicate that there are two luminescent states in porous Si : a weak luminescent quantum confinement state and a strong luminescent surface localized state.

Can Oxidation and Other Treatments Help Us Understand the Nature of Light-Emitting Porous Silicon?

1993 ◽  
Vol 298 ◽  
Author(s):  
P.M. Fauchet ◽  
E. Ettedgui ◽  
A. Raisanen ◽  
L.J. Brillson ◽  
F. Seiferth ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Quantum Confinement ◽  
Room Temperature ◽  
Vacuum Annealing ◽  
Surface States ◽  
Careful Analysis ◽  
Experimental Results ◽  
Dangling Bonds ◽  
Light Emitting ◽  
Confinement Model

AbstractUsing a careful analysis of the properties of light-emitting porous silicon (LEpSi), we conclude that a version of the “smart” quantum confinement model which was first proposed by F. Koch et al [Mat. Res. Soc. Symp. Proc. 283, 197 (1993)] and allows for the existence of surface states and dangling bonds, is compatible with experimental results. Among the new results we present in support of this model, the most striking ones concern the strong infrared photoluminescence that dominates the room temperature cw spectrum after vacuum annealing above 600 K.

New Results on Electroluminescence from Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
Peter Steiner ◽  
Frank Kozlowski ◽  
Hermann Sandmaier ◽  
Walter Lang
Keyword(s):  
Porous Silicon ◽  
Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Uv Light ◽  
Green Light ◽  
Light Emitting ◽  
Porous Region ◽  
First Results

ABSTRACTFirst results on light emitting diodes in porous silicon were reported in 1991. They showed a quantum efficiency of 10-7 to 10-5 and an orange spectrum. Over the last year some progress was achieved:- By applying UV-light during the etching blue and green light emitting diodes in porous silicon are fabricated.- When a p/n junction is realized within the porous region, a quantum efficiency of 10-4 is obtained.

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.

scholarly journals Depth-Resolved Microspectroscopy of Porous Silicon Multilayers

1999 ◽  
Vol 588 ◽  
Author(s):  
S. Manotas ◽  
F. Agulló-Rueda ◽  
J. D. Moreno ◽  
R. J. Martín-Palma ◽  
R. Guerrero-Lemus ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Quantum Confinement ◽  
Silicon Nanocrystals ◽  
Phonon Frequency ◽  
Lattice Mismatch ◽  
High Porosity ◽  
Phonon Confinement ◽  
Heating Effects ◽  
Average Size ◽  
Good Agreement

AbstractWe have measured micro-photoluminescence (PL) and micro-Raman spectra on the cross section of porous silicon multilayers to sample different layer depths. We find noticeable differences in the spectra of layers with different porosity, as expected from the quantum confinement of electrons and phonons in silicon nanocrystals with different average sizes. The PL emission band gets stronger, blue shifts, and narrows at the high porosity layers. The average size can be estimated from the shift. The Raman phonon band at 520 cm−1 weakens and broadens asymmetrically towards the low energy side. The line shape can be related quantitatively with the average size by the phonon confinement model. To get a good agreement with the model we add a band at around 480 cm−1, which has been attributed to amorphous silicon. We also have to leave as free parameters the bulk silicon phonon frequency and its line width, which depend on temperature and stress. We reduced laser power to eliminate heating effects. Then we use the change of frequency with depth to monitor the stress. At the interface with the substrate we find a compressive stress in excess of 10 kbar, which agrees with the reported lattice mismatch. Finally, average sizes are larger than those estimated from PL.

scholarly journals THE STRATIFIED MEDIEVAL HORIZON IN THE NIZHNIY NOVGOROD KREMLIN: FORMATION CONDITIONS AND PRELIMINARY CHARACTERISTICS

2019 ◽  
Author(s):  
Н.Н. Грибов
Keyword(s):  
Formation Mechanism ◽  
Medieval Period ◽  
Preliminary Results ◽  
Bank Slope ◽  
Formation Conditions

В статье публикуются предварительные результаты изучения культурных отложений, вскрытых раскопками в зоне воссоздания храма Святого Симеона Столпника в кремле г. Нижнего Новгорода в 2018 г. Охарактеризован механизм формирования стратифицированного сухого культурного слоя на оползневой террасе в пределах берегового склона. Средневековый горизонт датирован XIII - началом XV в. В нем выделено пять разновременных слоев с археологическими находками, отделенными друг от друга стерильными склоновыми отложениями. Отмечена смена характера использования исследованного участка после завершения средневекового периода. Позднейший этап освоения (конец XV - начало XVIII в.) связан с функционированием монастырского некрополя. The paper reports on preliminary results of examining the occupational deposits discovered by the 2018 excavations conducted on the site where the Cathedral of St. Simeon Stylite in the Nizhny Novgorod Kremlin will be rebuilt. The paper characterizes the formation mechanism of the stratified dry occupation layer on the landslip terrace within the bank slope. The medieval horizon dates to the 13th - early 15th centuries. Five layers with archaeological finds separated by sterile slope detritus dating to different periods are singled out. It is noted that after the medieval period the examined site was used for a different purpose. The latest stage of its occupation (late 15th - early 18th centuries) is related to the operation of a monastery necropolis.

The formation mechanism, improved photoluminescence and LED applications of red phosphor K2SiF6:Mn4+

2014 ◽  
Vol 2 (20) ◽  
pp. 3879-3884 ◽  
Author(s):  
Lifen Lv ◽  
Xianyu Jiang ◽  
Shaoming Huang ◽  
Xi'an Chen ◽  
Yuexiao Pan
Keyword(s):  
Formation Mechanism ◽  
Manganese Oxides ◽  
Experimental Results ◽  
Red Phosphor ◽  
White Leds ◽  
Luminescence Efficiency

The formation mechanism of red phosphor K2SiF6:Mn4+ free of manganese oxides has been discussed based on detailed experimental results. Significant improvements in the luminescence efficiency make it a good candidate for applications in “warm” white LEDs.

Effects of nano-copper particles on the properties of Sn58Bi composite solder pastes

2017 ◽  
Vol 34 (1) ◽  
pp. 40-44 ◽  
Author(s):  
Hao Zhang ◽  
Yang Liu ◽  
Fenglian Sun ◽  
Gaofang Ban ◽  
Jiajie Fan
Keyword(s):  
Formation Mechanism ◽  
Composite Solder ◽  
Defect Formation ◽  
Void Formation ◽  
Experimental Results ◽  
Solder Paste ◽  
Content Type ◽  
Weight Percentage ◽  
Copper Particles ◽  
Solder Pastes

Purpose This paper aimed to investigate the effects of nano-copper particles on the melting behaviors, wettability and defect formation mechanism of the Sn58Bi composite solder pastes. Design/methodology/approach In this paper, the mechanical stirring method was used to get the nano-composite solder pastes. Findings Experimental results indicated that the addition of 3 wt.% (weight percentage) 50 nm copper particles showed limited effects on the melting behaviors of the Sn58Bi composite solder paste. The spreading rate of the Sn58Bi composite solder paste showed a decreasing trend with the increase of the weight percentage of 50 nm copper particles from 0 to 3 wt.%. With the addition of copper particles of diameters 50 nm, 500 nm or 6.5 μm into the Sn58Bi solder paste, the porosities of the three types of solder pastes showed a similar trend. The porosity increased with the increase of the weight percentage of copper particles. Based on the experimental results, a model of the void formation mechanism was proposed. During reflow, the copper particles reacted with Sn in the matrix and formed intermetallic compounds, which gathered around the voids produced by the volatilization of flux. The exclusion of the voids was suppressed and eventually led to the formation of defects. Originality/value This study provides an optimized material for the second and third level packaging. A model of the void formation mechanism was proposed.

Influence of the formation conditions on the microstructure of porous silicon layers studied by spectroscopic ellipsometry

1995 ◽  
Vol 255 (1-2) ◽  
pp. 5-8 ◽  
Author(s):  
U. Rossow ◽  
U. Frotscher ◽  
M. Thönissen ◽  
M.G. Berger ◽  
S. Frohnhoff ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Spectroscopic Ellipsometry ◽  
Formation Conditions
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