scholarly journals Optical characterization of Ga2SeS layered crystals by transmission, reflection and ellipsometry

2015 ◽  
Vol 29 (18) ◽  
pp. 1550088 ◽  
Author(s):  
Mehmet Isik ◽  
Nizami Gasanly
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Optical Constants ◽  
Optical Characterization ◽  
Second Derivative ◽  
Derivative Spectra ◽  
Layered Crystals ◽  
Second Derivative Spectra ◽  
Transmission And Reflection

Optical properties of [Formula: see text] crystals grown by Bridgman method were investigated by transmission, reflection and ellipsometry measurements. Analysis of the transmission and reflection measurements performed in the wavelength range of 400–1100 nm at room temperature indicated the presence of indirect and direct transitions with 2.28 eV and 2.38 eV band gap energies. Ellipsometry measurements were carried out in the 1.2–6.0 eV spectral region to get information about optical constants, real and imaginary parts of the pseudodielectric function. Moreover, the critical point (CP) analysis of the second derivative spectra of the pseudodielectric constant in the above band gap region was accomplished. The analysis revealed the presence of five CPs with energies of 3.87, 4.16, 4.41, 4.67 and 5.34 eV.

Structural and Optical Characterization of CdSe Films Grown by Chemical Bath Deposition

2011 ◽  
Vol 691 ◽  
pp. 119-126 ◽  
Author(s):  
J.R. Aguilar-Hernández ◽  
A. Espinosa-Bustamante ◽  
M.A. Hernández-Pérez ◽  
G.S. Contreras-Puente ◽  
M. Cárdenas-García ◽  
...  
Keyword(s):  
Band Gap ◽  
Cadmium Selenide ◽  
Chemical Bath Deposition ◽  
Room Temperature ◽  
Bulk Material ◽  
Optical Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Radiative Emission

We present in this work experimental results and their analysis concerning the structural and optical characterization of cadmium selenide (CdSe) films grown by the Chemical Bath Deposition (CBD) technique, at different bath temperaturesTd: 0≤Td≤80 °C. Structural characterization was carried out by using X-ray diffraction, whereas optical characterization was done by using optical absorption and photoluminescence spectroscopies. X-ray results showed a change of the crystalline structure as a function ofTd, from the zincblende to wurzite one whenTdincreases from 0 to 80 °C. The respective band-gap,Eg,was calculated from the absorption spectrum giving rise to values in the range 1.85 to 2.30 eV, as a function also ofTd. Thses values are higher than the well accepted value of 1.75 eV for the CdSe bulk material. The radiative emission was analyzed throughout the photoluminescence (PL) spectra. All samples showed radiative emission above the band-gap, at room temperature, this radiative emission having a dependence on the pressure inside the cryostat. A quenching of the PL signal is observed when the pressure is decreased at values as low as 60 mTorr.

Second‐Derivative Spectra for Estimating Crop Residue Cover

1994 ◽  
Vol 86 (2) ◽  
pp. 349-354 ◽  
Author(s):  
Haiping Su ◽  
Michel D. Ransom ◽  
Edward T. Kanemasu ◽  
Tanvir H. Demetriades‐Shah
Keyword(s):  
Crop Residue ◽  
Second Derivative ◽  
Derivative Spectra ◽  
Second Derivative Spectra

scholarly journals Machine learning powered ellipsometry

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinchao Liu ◽  
Di Zhang ◽  
Dianqiang Yu ◽  
Mengxin Ren ◽  
Jingjun Xu
Keyword(s):  
Machine Learning ◽  
Optical Constants ◽  
Optical Characterization ◽  
Superior Performance ◽  
Trial And Error ◽  
Powerful Method ◽  
Human In The Loop ◽  
Ill Posed ◽  
Fully Automatic

AbstractEllipsometry is a powerful method for determining both the optical constants and thickness of thin films. For decades, solutions to ill-posed inverse ellipsometric problems require substantial human–expert intervention and have become essentially human-in-the-loop trial-and-error processes that are not only tedious and time-consuming but also limit the applicability of ellipsometry. Here, we demonstrate a machine learning based approach for solving ellipsometric problems in an unambiguous and fully automatic manner while showing superior performance. The proposed approach is experimentally validated by using a broad range of films covering categories of metals, semiconductors, and dielectrics. This method is compatible with existing ellipsometers and paves the way for realizing the automatic, rapid, high-throughput optical characterization of films.

Thermo-Optical Properties of Perfluorinated Sulfonic Acid Membranes: An Investigation of Hydration Based on Absorption Spectra

2017 ◽  
Vol 71 (11) ◽  
pp. 2504-2511 ◽  
Author(s):  
Daniele T. Dias ◽  
Guy Lopes ◽  
Tales Ferreira ◽  
Ivanir L. Oliveira ◽  
Caroline D. Rosa
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Water Retention ◽  
Structural Changes ◽  
Optical Characterization ◽  
Scanning Calorimetry ◽  
Experimental Procedure ◽  
Nafion Membranes ◽  
Perfluorinated Sulfonic Acid

The Nafion membranes are widely used in electrochemical applications such as fuel cells, chlor-alkali cells, and actuators–sensors. In this work, the thermal-optical characterization of Nafion in acid form was performed by photoacoustic spectroscopy, thermogravimetry, and differential scanning calorimetry. In the experimental procedure three distinct hydration levels were considered: (1) pristine membrane (λ ≅ H2O/–SO3H ≅ 5.6); (2) swelling process (λ ≅ 17.4); and (3) drying at controlled room temperature after swelling process (λ ≅ 6.5). The discovered behaviors showed significant irreversible structural changes induced by water retention in the membrane. These structural changes depend on the water population present in the clusters and also affect the directional thermal diffusivity of the membrane irreversibly.

L-cysteine functionalized graphene quantum dots for sub-ppb detection of As (III)

2021 ◽  
Author(s):  
Md. Farhan Naseh ◽  
Neelam Singh ◽  
Jamilur R. Ansari ◽  
Ashavani Kumar ◽  
Tapan Sarkar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Room Temperature ◽  
Graphene Quantum Dots ◽  
Optical Characterization ◽  
Functionalized Graphene ◽  
Transmission Electron ◽  
Sensitivity And Selectivity ◽  
Structural Characterizations

Abstract Here, we report functionalized graphene quantum dots (GQDs) for the optical detection of arsenic at room temperature. GQDs with the fluorescence of three fundamental colors (red, green, and blue) were synthesized and functionally capped with L-cysteine (L-cys) to impart selectively towards As (III) by exploiting the affinity of L-cys towards arsenite. The optical characterization of GQDs was carried out using UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectrometry and the structural characterizations were performed using transmission electron microscopy. The fluorescence results showed instantaneous quenching in intensity when the GQDs came in contact with As (III) for all test concentrations over a range from 0.025 ppb to 25 ppb, which covers the permissible limit of arsenic in drinking water. The experimental results suggested excellent sensitivity and selectivity towards As (III).

Multi-wavelength analyses of second-derivative spectra for rapid determination of acetaminophen in serum.

1988 ◽  
Vol 34 (6) ◽  
pp. 1119-1121 ◽  
Author(s):  
B Dingeon ◽  
M A Charvin ◽  
M T Quenard ◽  
H Thome
Keyword(s):  
Phosphate Buffer ◽  
Rapid Determination ◽  
Turnaround Time ◽  
Second Derivative ◽  
Derivative Spectra ◽  
Multi Wavelength ◽  
Precision And Accuracy ◽  
Second Derivative Spectra ◽  
Method Of Extraction

Abstract Measurement of acetaminophen by analysis of the second derivative of its spectrum is specific and sensitive. The method of extraction and the use of just one phosphate buffer as reagent makes this method very convenient. Readings are reliable from 10 to 1500 mg/L. A turnaround time of 20 min makes this method well suited for emergency cases. Precision and accuracy of the method are presented. Results are not biased by interferences, not even from N-acetylcysteine.

MORPHOLOGY CONTROLLING AND OPTICAL CHARACTERIZATION OF ZnO NANOMATERIALS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3635-3639
Author(s):  
YUZHEN LV ◽  
CHUNPING LI ◽  
PING CHE ◽  
LIN GUO ◽  
HUIBIN XU
Keyword(s):  
Room Temperature ◽  
Optical Characterization ◽  
Visible Emission ◽  
Ultraviolet Emission ◽  
Synthetic Process ◽  
Uv Emission ◽  
Zno Nanomaterials ◽  
Solution Route ◽  
Pl Spectrum

Wurtzite ZnO nanomaterials including nanoparticles, nanocolumns and nanorods were successfully synthesized by a solution route. Concentrations of modifying reagent and differences of solvent employed in the synthetic process can effectively adjust the morphologies of the as-grown products. Photoluminescence measurements of the ZnO nanocolumns and nanorods have been carried out at room temperature. A sharp Ultraviolet emission at 386 nm and a weak visible emission centered at 515 nm were observed in the PL spectrum of the nanocolumns, while a UV emission of the nanorods was observed at 377 nm.

scholarly journals Green Synthesis and Characterization of Gallium(III) Sulphide (α-Ga2S3) Nanoparicles at Room Temperature

Nano Hybrids ◽  
2014 ◽  
Vol 6 ◽  
pp. 37-46 ◽  
Author(s):  
Tansir Ahamad ◽  
Saad M. Alshehri
Keyword(s):  
Green Synthesis ◽  
Band Gap ◽  
Raman Spectra ◽  
Room Temperature ◽  
Optical Band Gap ◽  
Blue Shift ◽  
Synthesis And Characterization ◽  
Spectroscopic Techniques ◽  
Sodium Thiosulphate

Two different batches of Gallium (III) sulphide nanocrystals, (α-Ga2S3)1 and (α-Ga2S3)2 were synthesized at room temperature by the reaction of Gallium (III) chloride with sodium thiosulphate in water for 10 and 20 min respectively. The resultant nanoparticles were characterized by different spectroscopic techniques. TEM micrographs showed well-defined, close to hexagonal particles, and the lattice fringes in the HRTEM images confirmed their nanocrystalline nature. The sizes of (α-Ga2S3)1 and (α-Ga2S3)2 were 12 and 35 nm respectively with similar morphologies. Optical band gap energies (3.43 eV/3.41 eV) and photoluminescence peaks 635/641 nm (red shift) and 414/420 nm (blue shift) of the synthesized α-Ga2S3 nanocrystals suggest that they may be promising photocatalysts. Raman spectra for the α-Ga2S3, shows very sharp bands at 119, 135 and 148 cm-1 due to Ga-S2 scissoring.

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