Controllability And Homogeneity Of Optical Properties Of Thin Porous Silicon Films

1997 ◽  
Vol 486 ◽  
Author(s):  
S. Uehara ◽  
T. Kubo ◽  
S. Ogata ◽  
T. Sato ◽  
J. Hosono ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Porous Silicon ◽  
Optical Thickness ◽  
Wavelength Dependence ◽  
Effective Medium Approximation ◽  
Electrode Position ◽  
High Porosity ◽  
Optical Homogeneity ◽  
Reflection Spectroscopy

AbstractReflection spectroscopy was applied to evaluate the optical homogeneity and the refractive index of thin porous silicon (PS) layer. Variation in PS layer optical thickness was evaluated by measuring and mapping the reflectance over the surface area. For the circular anodization area of 17 mm diameter, the measured variation was less than 5 % on an area of 11 mm diameter. The anodization electrode position was found to have little influence on the homogeneity. A method to derive refractive index from a reflection spectrum is studied. The wavelength dependence of PS index measured by the method showed fair coincidence with the calculation based on effective medium approximation. In the two layer PS formation, optical thickness was found to change whether high porosity or low porosity layer is formed first.

Investigation of Effect of Chemical Etching and Temperature on Optical Properties of Porous Silicon Layer

2011 ◽  
Vol 311-313 ◽  
pp. 1773-1778
Author(s):  
Yong Fu Long ◽  
Chun Mei Yao ◽  
Li Yun Lei ◽  
Wei Wen Hu ◽  
Bin Fang Cao ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Porous Silicon ◽  
Optical Thickness ◽  
Chemical Etching ◽  
Etching Rate ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Etching Time ◽  
Photoluminescence Spectra

The paper investigated the effect of chemical etching and temperature on the optical properties and microstructures of porous silicon layer fabricated by the pulse electrochemically etching by means of the reflectance spectroscopy and photoluminescence spectroscopy. The relationship between the optical thickness (nd) and refractive index n of porous silicon layer and the chemical etching time and temperature has been detailedly studied. With increasing the chemical etching times, the reflectance spectra exhibit the more intense interference oscillations, which mean the uniformity and interface smoothness of porous silicon layers become better, meanwhile, results in decreasing the optical thickness and refractive index, indicating a higher porosity. Moreover, the intensity of photoluminescence spectra increases, and the envelope curves of photoluminescence spectra exhibit a trend of red-shift, which implied the average diameter of silicon nanocrystallite became larger. The chemical etching rate of the optical thickness intensely increases with the chemical etching temperature.

Optical-Property Profiling of SiO2 Films Containing Si Nanocrystals Formed by Si+ Implantation

2005 ◽  
Vol 23 ◽  
pp. 133-136
Author(s):  
Y. Liu ◽  
T.P. Chen ◽  
M.S. Tse ◽  
P.F. Ho ◽  
A.L.K. Tan ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Optical Property ◽  
Complex Refractive Index ◽  
Effective Medium Approximation ◽  
Sio2 Films ◽  
Depth Profiles ◽  
Si Nanocrystals ◽  
Si Doped

A quantitative approach to determination of depth profiles of optical properties of Si-implanted SiO2 films based on spectroscopic ellipsometry (SE) is presented. From the SE measurements, the depth profiles of the complex refractive index of SiO2 films containing Si nanocrystals (Si-nc) are obtained with an effective medium approximation (EMA) in the wavelength range of 400-1200nm. The optical profiles obtained imply the existence of a wave-guide in the Si-doped SiO2 films.

Optical Properties of Non-Periodic Dielectric Systems Made of Nanostructured Porous Silicon

2009 ◽  
Vol 5 ◽  
pp. 69-78 ◽  
Author(s):  
B. Alvarado Tenorio ◽  
J. Escorcia-Garcia ◽  
Miguel Eduardo Mora-Ramos ◽  
V. Agarwal
Keyword(s):  
Optical Properties ◽  
Porous Silicon ◽  
Optical Thickness ◽  
Periodic Structures ◽  
Period Doubling ◽  
Interference Filters ◽  
Transfer Matrix Approach ◽  
Multilayered Systems ◽  
Random Structures ◽  
Silicon Based

To investigate the optical properties in non-periodic dielectric systems, we study here the reflection of light from nanostructured porous-silicon-based period doubling heterostructures. The multilayered systems are fabricated in such a way that the optical thickness of each layer is one quarter of 650nm. The results for the optical reflectance are presented and compared with that of Fibonacci, Thue-Morse, and random structures fabricated under the same conditions. Numerical simulation for the reflectance along the lines of the transfer matrix approach is performed. In addition, optical reflection from Gaussian porous silicon multilayers is also briefly discussed. We find that porous silicon Period Doubling dielectric multilayers could demonstrate the optical properties similar to the classical periodic Febry-Perot interference filters with one or multiple resonant peaks, but with an advantage of having total optical thickness much lesser than that of the periodic structures.

Optical Properties of Strongly Absorbing Media Determined by External Reflection Spectroscopy

1992 ◽  
Vol 46 (6) ◽  
pp. 1040-1044 ◽  
Author(s):  
J. A. Mielczarski ◽  
M. Milosevic ◽  
S. L. Berets
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Optical Constants ◽  
Infrared Region ◽  
Absorption Index ◽  
Reflection Spectra ◽  
Reflection Spectroscopy ◽  
Butyl Xanthate ◽  
Mid Infrared ◽  
Classical Oscillator

Reflection spectra of opaque samples recorded at different angles of incidence and for both polarizations were used to evaluate the optical constants. A subsequent classical oscillator fitting analysis of these spectra provided the dispersion of the refractive index and the absorption index for cuprous ethyl and butyl xanthate complexes across the mid-infrared region. The advantages of recording spectra under certain conditions are discussed.

Sensitivity of the optical properties of porous silicon layers to the refractive index of liquid in the pores

2003 ◽  
Vol 197 (2) ◽  
pp. 528-533 ◽  
Author(s):  
M. A. Anderson ◽  
A. Tinsley-Bown ◽  
P. Allcock ◽  
E. A. Perkins ◽  
P. Snow ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Porous Silicon

scholarly journals Caracterización óptica y estructural de monocapas de silicio poroso por medio de reflectancia en la región visible y rayos X

2018 ◽  
pp. 66-70
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Porous Structure ◽  
Visible Region ◽  
Wavelength Dependence ◽  
Optical Methods ◽  
X Ray ◽  
Cylindrical Pores

Caracterización óptica y estructural de monocapas de silicio poroso por medio de reflectancia en la región visible y rayos X Danilo Roque Huanca Instituto de Física e Química da Universidade Federal de Itajubá, Avenida B. P. S, 1303, Pinheirinho, Itajubá - MG, Brasil Recibido el 15 de noviembre del 2018. Aceptado el 21 de noviembre del 2018. DOI: https://doi.org/10.33017/RevECIPeru2018.0010/ Resumen Una monocapa de silicio poroso con porosidad variable a lo largo del espesor fue caracterizando usando diferentes técnicas ópticas. Los resultados muestran que las técnicas basadas en reflectancia en la región visible divergen en aproximadamente 20% de aquellas encontradas por medio de los métodos basados en rayos X. Esa divergencia es una consecuencia de la variación del índice de refracción con la longitud de onda, tanto de la estructura porosa como del líquido empleado para el análisis. Los resultados sugieren que la estructura porosa puede ser modelada como un conjunto de poros esféricos con radio que varía entre 3.0 nm a 4.4 nm, en adición a los poros con forma cilíndrica con radio entre 22 nm y 42 nm, mientras su altura lo hace entre 55 y102 nm. La porosidad de la estructura varia a lo largo del espesor entre 65-81 %. Descriptores: silicio poroso, reflectancia de rayos X, GISXASX, espectroscopia por infiltración de líquidos Abstract A porous silicon monolayer with porosity varying in depth was characterized using different optical methods. The results show that techniques based on reflectance in the visible region diverge in approximately 20% of those found by means of X-ray based methods. This divergence is associated to the wavelength dependence of the refractive index of both the porous structure and the infiltrated liquid inside the pores. The results suggest that the porous structure can be modeled as a set of spherical pores with radius ranging from 3.0 to 4.4 nm, in addition to cylindrical pores with radius and length varying between 22 and 42 nm, while its length does between 55 -102 nm. The porosity of the structure varies in depth between 65-81%.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

Stress Whitening in Polypropylene. I. Light Scattering Theory and Model Experiments

1995 ◽  
Vol 60 (11) ◽  
pp. 1875-1887 ◽  
Author(s):  
Jaroslav Holoubek ◽  
Miroslav Raab
Keyword(s):  
Refractive Index ◽  
Light Scattering ◽  
Incident Light ◽  
Polymeric Materials ◽  
Wavelength Dependence ◽  
Theoretical Background ◽  
Surrounding Matrix ◽  
Embedded Particles ◽  
The One ◽  
Stress Whitening

Theoretical background for an optical method is presented which makes it possible to distinguish unambiguously between voids and particles as light scattering sites in polymeric materials. Typical dependences of turbidity as a function of diameter of scattering elements, their volume fractions and also turbidity curves as a function of the wavelength of the incident light were calculated, based both on the Lorenz-Mie theory and the fluctuation theory. Such dependences calculated for polypropylene-containing voids on the one hand and particles, differing only slightly from the surrounding matrix in their refractive index, on the other hand, are markedly different. The most significant results are: (i) Turbidity is at least by two orders of magnitude larger for voids in comparison to embedded particles of ethylene-propylene (EPDM) rubber of the same size, concentration and at the same wavelength. (ii) The wavelength dependence of turbidity for EPDM particles and the inherent refractive index fluctuations in the polypropylene matrix is much steeper as compared to voids for all considered diameters (0.1-10 μm). Thus, the nature of stress whitening in complex polymeric materials can be determined from turbidity measurements.

scholarly journals Broadband spectroscopy of astrophysical ice analogues

2019 ◽  
Vol 629 ◽  
pp. A112 ◽  
Author(s):  
B. M. Giuliano ◽  
A. A. Gavdush ◽  
B. Müller ◽  
K. I. Zaytsev ◽  
T. Grassi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Far Infrared ◽  
Infrared Region ◽  
Thz Radiation ◽  
The Real ◽  
Thz Range ◽  
The Time Domain

Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.

scholarly journals Synthesis of PVA/CeO2 Based Nanocomposites with Tuned Refractive Index and Reduced Absorption Edge: Structural and Optical Studies

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1570
Author(s):  
Shujahadeen B. Aziz ◽  
Elham M. A. Dannoun ◽  
Dana A. Tahir ◽  
Sarkawt A. Hussen ◽  
Rebar T. Abdulwahid ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Absorption Edge ◽  
Ceo2 Nanoparticles ◽  
Poly Vinyl Alcohol ◽  
Optical Parameters ◽  
Single Oscillator Model ◽  
Vis Spectroscopy ◽  
The Impact ◽  
Host Polymer

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO2 on optical properties of PVA. On the insertion of CeO2 nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO2 nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO2 content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ɛ” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.

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