scholarly journals Structural and Optical Characteristics of PVA:C-Dot Composites: Tuning the Absorption of Ultra Violet (UV) Region

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 216 ◽  
Author(s):  
Shujahadeen B. Aziz ◽  
Aso Q. Hassan ◽  
Sewara J. Mohammed ◽  
Wrya O. Karim ◽  
M. F. Z. Kadir ◽  
...  
Keyword(s):  
Optical Band Gap ◽  
Ultra Violet ◽  
Photo Luminescence ◽  
Uv Spectra ◽  
Optical Dielectric Constant ◽  
Loss Parameter ◽  
Optical Dielectric ◽  
Scherrer Formula ◽  
Luminescence Behavior ◽  
Composite Samples

: In this work the influence of carbon nano-dots (CNDs) on absorption of ultra violet (UV) spectra in hybrid PVA based composites was studied. The FTIR results reveal the complex formation between PVA and CNDs. The shifting was observed in XRD spectrum of PVA:CNDs composites compared to pure PVA. The Debye-Scherrer formula was used to calculate the crystallite size of CNDs and crystalline phases of pure PVA and PVA:CNDs composites. The FESEM images emphasized the presence and dispersion of C-dots on the surface of the composite samples. From the images, a strong and clear absorption was noticed in the spectra. The strong absorption that appeared peaks at 280 nm and 430 nm can be ascribed to the n-π* and π-π* transitions, respectively. The absorption edge shifted to lower photon energy sides with increasing CNDs. The luminescence behavior of PVA:CNDs composite was confirmed using digital and photo luminescence (PL) measurements. The optical dielectric constant which is related to the density of states was studied and the optical band gap was characterized accurately using optical dielectric loss parameter. The Taucs model was used to determine the type of electronic transition in the samples.

scholarly journals A Comprehensive Review on Optical Properties of Polymer Electrolytes and Composites

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3675 ◽  
Author(s):  
Shujahadeen B. Aziz ◽  
M. A. Brza ◽  
Muaffaq M. Nofal ◽  
Rebar T. Abdulwahid ◽  
Sarkawt A. Hussen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Dielectric Loss ◽  
Band Gap ◽  
Polymer Electrolytes ◽  
Optical Band Gap ◽  
Review Paper ◽  
Good Thermal Stability ◽  
Optical Dielectric Constant ◽  
Loss Parameter ◽  
Optical Dielectric

Polymer electrolytes and composites have prevailed in the high performance and mobile marketplace during recent years. Polymer-based solid electrolytes possess the benefits of low flammability, excellent flexibility, good thermal stability, as well as higher safety. Several researchers have paid attention to the optical properties of polymer electrolytes and their composites. In the present review paper, first, the characteristics, fundamentals, advantages and principles of various types of polymer electrolytes were discussed. Afterward, the characteristics and performance of various polymer hosts on the basis of specific essential and newly published works were described. New developments in various approaches to investigate the optical properties of polymer electrolytes were emphasized. The last part of the review devoted to the optical band gap study using two methods: Tauc’s model and optical dielectric loss parameter. Based on recently published literature sufficient quantum mechanical backgrounds were provided to support the applicability of the optical dielectric loss parameter for the band gap study. In this review paper, it was demonstrated that both Tauc’s model and optical dielectric loss should be studied to specify the type of electron transition and estimate the optical band gap accurately. Other parameters such as absorption coefficient, refractive index and optical dielectric constant were also explored.

scholarly journals Steps Toward the Band Gap Identification in Polystyrene Based Solid Polymer Nanocomposites Integrated with Tin Titanate Nanoparticles

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2320 ◽  
Author(s):  
Ahang M. Hussein ◽  
Elham M. A. Dannoun ◽  
Shujahadeen B. Aziz ◽  
Mohamad A. Brza ◽  
Rebar T. Abdulwahid ◽  
...  
Keyword(s):  
Refractive Index ◽  
Band Gap ◽  
Polymer Nanocomposites ◽  
Absorption Edge ◽  
Optical Band Gap ◽  
Solid Polymer ◽  
Optical Parameters ◽  
Optical Dielectric Constant ◽  
Solution Cast ◽  
Optical Dielectric

In the current study, the film fabrication of polystyrene (PS) based polymer nanocomposites (NCs) with tuned refractive index and absorption edge was carried out using the solution cast method. X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) light characterization techniques were performed. The structural and optical properties of the prepared films were specified. The hump of PS decreased significantly when SnTiO3 nanoparticles (NPs) were introduced. Sharp and high intense peaks of SnTiO3 NPs at a high filler ratio were observed. The crystalline size was determined for SnTiO3 NPs from the sharp crystalline peaks using Debye-Scherrer’s equation and was found to be 25.179 nm, which is close enough to that described by the supplier. Several optical parameters, such as absorption coefficient (α), refractive index (n), and optical dielectric properties, were investigated. The absorption spectra were tuned with increasing SnTiO3NPs. Upon the addition of the NPs to the PS host polymer, the absorption edge undergoes shifting to lesser photon energy sides. The optical dielectric constant (ε′) was correlated to the refractive index. The study of the optical band gap was conducted in detail using both Tauc’s model and the optical dielectric loss (ε″) parameter. The results showed that the ε″ parameter is noteworthy to be measured in the optical band gap study of materials.

Metal Contacts on a-GaN

1996 ◽  
Vol 1 ◽  
Author(s):  
T. U. Kampen ◽  
W. Mönch
Keyword(s):  
Tight Binding ◽  
Image Force ◽  
Schottky Contacts ◽  
Metal Contacts ◽  
Zero Bias ◽  
Barrier Heights ◽  
Current Voltage ◽  
Optical Dielectric Constant ◽  
Optical Dielectric ◽  
Gap States

The Schottky barrier heights of silver and lead contacts on n-type GaN (0001) epilayers were determined from current-voltage characteristics. The zero-bias barrier heights and the ideality factors were found to be linearly correlated. Similar observations were previously reported for metal contacts on Si (111) and GaAs (110) surfaces. The barrier heights of ideal Schottky contacts are characterized by image force lowering of the barrier only. This gives an ideality factor of 1.01. From our data we obtain barrier heights of 0.82 eV and 0.73eV for ideal Ag and Pb contacts on GaN, respectively. The metal-induced gap states (MIGS) model predicts the barrier heights of ideal Schottky contacts on a given semiconductor to be linearly correlated with the electronegativities of the metals. The two important parameters of this MIGS-and-electronegativity model are the charge neutrality level (CNL) of the MIGS and a slope parameter. The CNL may be calculated from the dielectric band gap and using the empirical tight-binding method. The slope parameters are given by the optical dielectric constant of the respective semiconductor. The predictions of the MIGS model for metal/GaN contacts are confirmed by the results presented here and by barrier heights previously reported by others for Au, Ti, Pt, and Pd contacts on GaN.

Energy gap and optical dielectric constant of Pb1−Cd Se films

1987 ◽  
Vol 27 (6) ◽  
pp. 389-397 ◽  
Author(s):  
M. Baleva ◽  
M. Maksimov ◽  
M. Sendova
Keyword(s):  
Dielectric Constant ◽  
Energy Gap ◽  
Optical Dielectric Constant ◽  
Optical Dielectric

Optical and dielectric properties of lead perovskite and iodoplumbate complexes: an ab initio study

2020 ◽  
Vol 22 (33) ◽  
pp. 18423-18434
Author(s):  
Malladi Srikanth ◽  
Mailde S. Ozório ◽  
Juarez L. F. Da Silva
Keyword(s):  
Density Functional Theory ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Optical Dielectric Constant ◽  
Energetic Stability ◽  
Optical Dielectric

Optical and dielectric properties, and energetic stability orders of black phase of perovskites and yellow phase of iodoplumbates have been studied using density functional theory; where the optical dielectric constant varies with the polymorphic phase and nature of cation.

Optical Band Gap of Wurtzite Zinc Sulphide Doped with Lanthanum Ions

2012 ◽  
Vol 622-623 ◽  
pp. 752-756
Author(s):  
George Varughese ◽  
Sreeja R. Aswathy ◽  
K.T. Usha ◽  
A.S. Kumar
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Light Transmission ◽  
Photo Luminescence ◽  
Chemical Precipitation ◽  
High Refractive Index ◽  
Zinc Sulphide ◽  
Zns Nanoparticles ◽  
Visible Absorption ◽  
Lanthanum Ions

Pure and doped Zinc Sulfide (ZnS) quantum dots have attracted increasing interest from researchers working on various scientific and engineering applications in electronics, nonlinear optical devices for communication, and optical computers. In this study, ZnS nanoparticles doped with lanthanum (ZnS:La) with approximately 11 nm size was produced at 150°C by chemical precipitation route. Zinc Sulphide is an extensively studied group II-VI semiconductor with wide application in field of Photo Luminescence (PL),Electro Luminescence(EL) and Cathodo Luminescence (CL). It is an excellent light transmission material with high refractive index 2.27. XRD, SEM, FTIR UV-Vis and EDS characterize the samples.In this study, the UV–Visible absorption spectra of ZnS:La showed a red shift in the absorption shoulder compared with the spectra of undoped samples. ZnS nanoparticles could be doped with lanthanum ions during synthesis without altering the X-ray diffraction (XRD) patterns of ZnS. Also, the XRD pattern of the powders showed cubic crystal structures for ZnS:La. The Optical band gap has been found to be 2.7 eV. It was found that energy Band gap Eg decreases with doping of La.

D.C. electrical and optical properties of vacuum-deposited organic semiconductor FePcCl thin films

2005 ◽  
Vol 83 (11) ◽  
pp. 1151-1159 ◽  
Author(s):  
K R Rajesh ◽  
C S Menon
Keyword(s):  
Thin Film ◽  
Room Temperature ◽  
Hole Concentration ◽  
Hole Mobility ◽  
Optical Parameters ◽  
Trap Level ◽  
72.80 Le ◽  
Planar Structures ◽  
Optical Dielectric Constant ◽  
Optical Dielectric

Sandwich and planar structures are fabricated by a vacuum deposition method using iron phthalocyanine chloride (FePcCl) as an active layer and gold (Au) as electrodes. The permittivity ε of FePcCl is determined from the dependence of capacitance on film thickness. The current density – voltage characteristics characteristics of the Au/FePcCl/Au structure at room temperature are found. Thermally generated hole concentration p0, hole mobility µp, total trap concentration Nt, and depth of the trap level are estimated. The activation energies of FePcCl films are determined from Arrhenious plots of ln σ versus 1000/T. The absorption and reflectance spectra of a FePcCl thin film deposited at room temperature are recorded in the spectral range 300–900 nm. The optical band gap of a FePcCl thin film is determined from the α2 versus hν graph. The optical constants n and k are found. The real and imaginary parts of the optical dielectric constant ε1 and ε2 are calculated. These optical parameters are plotted against photonenergy. PACS Nos.: 72.80.Le, 73., 78.20.–e

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