Anisotropy of the Porous Silicon Photoluminescence

1996 ◽  
Vol 452 ◽  
Author(s):  
G. Polisski ◽  
B. Averboukh ◽  
D. Kovalev ◽  
F. Koch
Keyword(s):  
Porous Silicon ◽  
Memory Effect ◽  
Linear Polarization ◽  
Polarized Light ◽  
Optical Excitation ◽  
Polarization Degree ◽  
Porous Si ◽  
Si Substrate ◽  
Plane Distribution

AbstractPolarization memory effect in the porous Si photoluminescence is studied. The anisotropy of the linear polarization degree is found in the samples etched with polarized light-assistance. The effect is explained by the anisotropie in plane distribution of the elongated Si crystallites. Under resonant optical excitation four-fold anisotropy of the photoluminescence polarization, linked to the crystalline axes of the bulk Si substrate, is observed.

Auger Ionization of Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
B. Averboukh ◽  
D. Kovalev ◽  
M. Ben Chorin ◽  
F. Koch ◽  
Al.L. Efros ◽  
...  
Keyword(s):  
Low Temperature ◽  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Polarized Light ◽  
Optical Excitation ◽  
Porous Si ◽  
Auger Process ◽  
Linearly Polarized

AbstractPhotoluminescence saturation under intense CW optical excitation and optical degradation of photoluminescence from porous Si are studied. The anisotropy of the luminescence is observed under intense linearly polarized illumination at room temperature and after polarized light induced degradation at low temperature. The Auger process is shown to be responsible for these observations.

scholarly journals Formation and Evaluation of Silicon Substrate with Highly-Doped Porous Si Layers Formed by Metal-Assisted Chemical Etching

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yijie Li ◽  
Nguyen Van Toan ◽  
Zhuqing Wang ◽  
Khairul Fadzli Bin Samat ◽  
Takahito Ono
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Contact Resistance ◽  
Power Factor ◽  
Chemical Etching ◽  
Porous Si ◽  
Si Substrate ◽  
Si Substrates ◽  
Output Performance ◽  
Metal Assisted Chemical Etching

AbstractPorous silicon (Si) is a low thermal conductivity material, which has high potential for thermoelectric devices. However, low output performance of porous Si hinders the development of thermoelectric performance due to low electrical conductivity. The large contact resistance from nonlinear contact between porous Si and metal is one reason for the reduction of electrical conductivity. In this paper, p- and n-type porous Si were formed on Si substrate by metal-assisted chemical etching. To decrease contact resistance, p- and n-type spin on dopants are employed to dope an impurity element into p- and n-type porous Si surface, respectively. Compared to the Si substrate with undoped porous samples, ohmic contact can be obtained, and the electrical conductivity of doped p- and n-type porous Si can be improved to 1160 and 1390 S/m, respectively. Compared with the Si substrate, the special contact resistances for the doped p- and n-type porous Si layer decreases to 1.35 and 1.16 mΩ/cm2, respectively, by increasing the carrier concentration. However, the increase of the carrier concentration induces the decline of the Seebeck coefficient for p- and n-type Si substrates with doped porous Si samples to 491 and 480 μV/K, respectively. Power factor is related to the Seebeck coefficient and electrical conductivity of thermoelectric material, which is one vital factor that evaluates its output performance. Therefore, even though the Seebeck coefficient values of Si substrates with doped porous Si samples decrease, the doped porous Si layer can improve the power factor compared to undoped samples due to the enhancement of electrical conductivity, which facilitates its development for thermoelectric application.

Comparison of linear polarization degree in healthy and wounded rat skin

2001 ◽  
Author(s):  
Martha S. Ribeiro ◽  
Anderson Z. Freitas ◽  
Daniela F. Silva ◽  
Denise M. Zezell ◽  
Cleusa M. R. Pellegrini ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Polarization Degree ◽  
Rat Skin

Enhancement of efficiency in graphene/porous silicon solar cells by co-doping graphene with gold nanoparticles and bis(trifluoromethanesulfonyl)-amide

2017 ◽  
Vol 5 (35) ◽  
pp. 9005-9011 ◽  
Author(s):  
Ju Hwan Kim ◽  
Dong Hee Shin ◽  
Ha Seung Lee ◽  
Chan Wook Jang ◽  
Jong Min Kim ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Solar Cells ◽  
Porous Silicon ◽  
Au Nanoparticles ◽  
Silicon Solar Cells ◽  
Porous Si ◽  
Co Doping ◽  
Si Solar Cells ◽  
First Time

The co-doping of graphene with Au nanoparticles and bis(trifluoromethanesulfonyl)-amide is employed for the first time to enhance the performance of graphene/porous Si solar cells.

Visible Electro- and Photoluminescence from Porous Silicon and its Related Optoelectronic Properties

1991 ◽  
Vol 256 ◽  
Author(s):  
Nobuyoshi Koshida ◽  
Hideki Koyama
Keyword(s):  
Porous Silicon ◽  
Optical Absorption ◽  
Size Effect ◽  
Band Gap ◽  
Visible Region ◽  
Optoelectronic Properties ◽  
Porous Si ◽  
Quantum Size ◽  
Effect Model ◽  
Injection Type

ABSTRACTThe optoelectronic properties of porous Si (PS) are presented in terms of electroluminescence (EL), photoluminescence (PL), photoconduction (PC), and optical absorption. Observations of injection-type EL, efficient PL, band-gap widening, and photosensitivities In the visible region are consistent with the quantum size effect model in PS.

scholarly journals Morphology and FT IR spectra of porous silicon

2017 ◽  
Vol 68 (7) ◽  
pp. 53-57 ◽  
Author(s):  
Martin Kopani ◽  
Milan Mikula ◽  
Daniel Kosnac ◽  
Jan Gregus ◽  
Emil Pincik
Keyword(s):  
Porous Silicon ◽  
Ir Spectra ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Layer Formation ◽  
Porous Si ◽  
Ft Ir ◽  
P Type ◽  
Type Sample ◽  
Ftir Investigation

AbstractThe morphology and chemical bods of p-type and n-type porous Si was compared. The surface of n-type sample is smooth, homogenous without any features. The surface of p-type sample reveals micrometer-sized islands. FTIR investigation reveals various distribution of SiOxHycomplexes in both p-and n-type samples. From the conditions leading to porous silicon layer formation (the presence of holes) we suggest both SiOxHyand SiFxHycomplexes in the layer.

scholarly journals Polarization perception in humans: on the origin of and relationship between Maxwell’s spot and Haidinger’s brushes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Gary P. Misson ◽  
Shelby E. Temple ◽  
Stephen J. Anderson
Keyword(s):  
Linear Polarization ◽  
Light Absorption ◽  
Polarized Light ◽  
Retinal Images ◽  
Clinical Use ◽  
Differential Absorption ◽  
Model Simulations ◽  
Eye Disorders ◽  
Absorption Of Light ◽  
Linearly Polarized

AbstractUnder specific conditions of illumination and polarization, differential absorption of light by macular pigments is perceived as the entoptic phenomena of Maxwell’s spot (MS) or Haidinger’s brushes (HB). To simulate MS and HB, an existing computational model of polarization-dependent properties of the human macula was extended by incorporating neuronal adaptation to stabilized retinal images. The model predicted that polarized light modifies the appearance of MS leading to the perception of a novel phenomenon. The model also predicted a correlation between the observed diameters of MS and HB. Predictions were tested psychophysically in human observers, whose measured differences in the diameters of each entoptic phenomenon generated with depolarized and linearly polarized light were consistent with the model simulations. These findings support a common origin of each phenomenon, and are relevant to the clinical use of polarization stimuli in detecting and monitoring human eye disorders, including macular degeneration. We conclude: (i) MS and HB both result from differential light absorption through a radial diattenuator, compatible with the arrangement of macular pigments in Henle fibres; (ii) the morphology of MS is dependent on the degree of linear polarization; (iii) perceptual differences between MS and HB result from different states of neural adaptation.

scholarly journals Exciton-to-trion conversion as a control mechanism for valley polarization in room-temperature monolayer WS2

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Joris J. Carmiggelt ◽  
Michael Borst ◽  
Toeno van der Sar
Keyword(s):  
Room Temperature ◽  
Polarized Light ◽  
Optical Excitation ◽  
Equation Model ◽  
Chemical Doping ◽  
Transition Metal Dichalcogenide ◽  
Net Charge ◽  
Circularly Polarized Light ◽  
Valley Polarization

Abstract Transition metal dichalcogenide (TMD) monolayers are two-dimensional semiconductors with two valleys in their band structure that can be selectively addressed using circularly polarized light. Their photoluminescence spectrum is characterized by neutral and charged excitons (trions) that form a chemical equilibrium governed by the net charge density. Here, we use chemical doping to drive the conversion of excitons into trions in $$\text {WS}_{2}$$ WS 2 monolayers at room temperature, and study the resulting valley polarization via photoluminescence measurements under valley-selective optical excitation. We show that the doping causes the emission to become dominated by trions with a strong valley polarization associated with rapid non-radiative recombination. Simultaneously, the doping results in strongly quenched but highly valley-polarized exciton emission due to the enhanced conversion into trions. A rate equation model explains the observed valley polarization in terms of the doping-controlled exciton-trion equilibrium. Our results shed light on the important role of exciton-trion conversion on valley polarization in monolayer TMDs.

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