Measurement of the room temperature band gaps of red HgI2 by a photoconductive technique

This work reports the synthesis, structural characterisation, liquid crystallinity, luminescence and electroluminescence of novel thiophene azomethine polymers. The polymers under study were prepared via oxidative polymerisation of four novel monomers at room temperature using iron (III) chloride. The chemical structures of the prepared monomers and polymers were confirmed by infrared and 1H and 13CNMR spectroscopy. Molecular masses were determined for monomers and polymers by gas/liquid chromatography-mass spectrometry (GC/LC-MS) and by gel-permeation (size exclusion) chromatography (SEC), respectively. Thermal stability studies of the prepared materials were achieved by thermogravimetric analysis (TGA), and the onset of weight loss To and the endset Tmax were calculated from the thermograms. Liquid crystalline mesophases and phase changes of the monomers and polymers were studied by differential scanning calorimetry (DSC) and polarised optical microscopy (POM), and the glass transition temperatures Tg of the polymers were determined from the DSC curves. The electrochemical band gaps, HOMO and LUMO energy levels were measured by cyclic voltammetry. UV-visible absorption-emission spectra (liquid and solid films) of the polymers were obtained at room temperature with different solvents. Optical band gaps were calculated from the absorption edges, and were in good agreement with those estimated from cyclic voltammetry. Mixing the polymers with lanthanide salts such as EuCl3 and YbCl3 gave modified fluorescence, and the light emitted was much more intense than that from the pure polymers. Polymer based light-emitting diodes (PLEDs) were fabricated by spin coating, and their current-voltage characteristics were measured. In preliminary work, the polymer devices were found to produce electroluminescent spectra similar to the PL spectra of the corresponding samples. Molecular modelling studies were performed both on polymer segments and monomer molecules; the absorption spectra of the prepared polymers, HOMO and LUMO energy levels were calculated with ZINDO using AMI geometry optimisation.

Download Full-text

Effects of the Argon Pressure on the Optical Band Gap of Zinc Oxide Thin Films Grown by Nonreactive RF Sputtering

Advances in Condensed Matter Physics ◽

10.1155/2013/970976 ◽

2013 ◽

Vol 2013 ◽

pp. 1-6 ◽

Cited By ~ 8

Author(s):

M. Acosta ◽

I. Riech ◽

E. Martín-Tovar

Keyword(s):

Thin Films ◽

Zinc Oxide ◽

Band Gap ◽

Room Temperature ◽

Optical Band Gap ◽

Rf Sputtering ◽

Argon Pressure ◽

Band Gaps ◽

Zno Thin Films ◽

Optical Band Gaps

Zinc oxide (ZnO) thin films were grown by nonreactive RF sputtering at room temperature under varying argon pressures (PAr). Their optical band gap was found to increase from 3.58 to 4.34 eV when the argon pressure increases from 2.67 to 10.66 Pa. After annealing at 200°C and 500°C, optical band gaps decrease considerably. The observed widening of the band gap with increasingPArcan be understood as being a consequence of the poorer crystallinity of films grown at higher pressures. Measurements of morphological and electrical properties of these films correlate well with this picture. Our main aim is to understand the effects ofPAron several physical properties of the films, and most importantly on its optical band gap.

Download Full-text

Optical Properties of Nd Doped Lead Borotellurite Glass

Materials Science Forum ◽

10.4028/www.scientific.net/msf.846.193 ◽

2016 ◽

Vol 846 ◽

pp. 193-198 ◽

Cited By ~ 1

Author(s):

Azman Kasim ◽

H. Azhan ◽

S. Akmal Syamsyir ◽

Mardhiah Abdullah ◽

M.R.S. Nasuha

Keyword(s):

Optical Properties ◽

Room Temperature ◽

Optical Band Gap ◽

Band Gap Energy ◽

Rare Earth Ions ◽

Band Gaps ◽

Refractive Indices ◽

Excitation Wavelength ◽

Gap Energy ◽

Trivalent Rare Earth

Many trivalent rare earth ions such as Er3+, Tm3+, Ho3+, Pr3+ and Nd3+ were doped as absorption and emission centers in glass hosts. In this work, lead borotellurite (PBT) glass doped with neodymium ion (Nd3+) has been prepared and characterized by mean of their optical properties. The UV-Vis measurement has been carried out in order to determine the optical band gap energy, reflective indices and the polarizability. Optical absorption spectra of the glass samples are recorded in the range 400–900 nm at room temperature From the result, there are six significant absorption peaks that corresponds to 525 nm, 584 nm, 683 nm, 747 nm, 805 nm and 878 nm wavelength have been observed with the most predominant peak to be used as excitation wavelength is found centered at 584 nm. The energy band gaps as well as the refractive indices were found to vary from 2.50eV to 2.59eV and from 1.89 to 1.96 with mol% of Nd content respectively. Meanwhile, the polarizability shows a similar trend of results to refractive indices as it varies from 5.56 x 10-24 cm3 to 5.63 x 10-24 cm3. These results will be discussed further in details.

Download Full-text

Biologically encoded magnonics

Nature Communications ◽

10.1038/s41467-019-12219-0 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 4

Author(s):

Benjamin W. Zingsem ◽

Thomas Feggeler ◽

Alexandra Terwey ◽

Sara Ghaisari ◽

Detlef Spoddig ◽

...

Keyword(s):

Room Temperature ◽

Logic Circuits ◽

Band Gaps ◽

Quantum Oscillations ◽

Micromagnetic Simulations ◽

Energy Demands ◽

Local Arrangement ◽

Generation Computing ◽

Band Deformation ◽

Nanoparticle Chains

Abstract Spin wave logic circuits using quantum oscillations of spins (magnons) as carriers of information have been proposed for next generation computing with reduced energy demands and the benefit of easy parallelization. Current realizations of magnonic devices have micrometer sized patterns. Here we demonstrate the feasibility of biogenic nanoparticle chains as the first step to truly nanoscale magnonics at room temperature. Our measurements on magnetosome chains (ca 12 magnetite crystals with 35 nm particle size each), combined with micromagnetic simulations, show that the topology of the magnon bands, namely anisotropy, band deformation, and band gaps are determined by local arrangement and orientation of particles, which in turn depends on the genotype of the bacteria. Our biomagnonic approach offers the exciting prospect of genetically engineering magnonic quantum states in nanoconfined geometries. By connecting mutants of magnetotactic bacteria with different arrangements of magnetite crystals, novel architectures for magnonic computing may be (self-) assembled.

Download Full-text

Influence of Doping Concentration on Dielectric, Optical, and Morphological Properties of PMMA Thin Films

Advances in Materials Science and Engineering ◽

10.1155/2012/605673 ◽

2012 ◽

Vol 2012 ◽

pp. 1-4 ◽

Cited By ~ 4

Author(s):

Lyly Nyl Ismail ◽

Habibah Zulkefle ◽

Sukreen Hana Herman ◽

Mohamad Rusop Mahmood

Keyword(s):

Thin Films ◽

Dielectric Loss ◽

Room Temperature ◽

Sol Gel ◽

Wavelength Region ◽

Band Gaps ◽

Morphological Properties ◽

Dielectric Characteristics ◽

Coating Method ◽

Pmma Powder

PMMA thin films were deposited by sol gel spin coating method on ITO substrates. Toluene was used as the solvent to dissolve the PMMA powder. The PMMA concentration was varied from 30 ~ 120 mg. The dielectric properties were measured at frequency of 0 ~ 100 kHz. The dielectric permittivity was in the range of 7.3 to 7.5 which decreased as the PMMA concentration increased. The dielectric loss is in the range of 0.01 ~ –0.01. All samples show dielectric characteristics which have dielectric loss is less than 0.05. The optical properties for thin films were measured at room temperature across 200 ~ 1000 nm wavelength region. All samples are highly transparent. The energy band gaps are in the range of 3.6 eV to 3.9 eV when the PMMA concentration increased. The morphologies of the samples show that all samples are uniform and the surface roughness increased as the concentration increased. From this study, it is known that, the dielectric, optical, and morphology properties were influenced by the amount of PMMA concentration in the solution.

Download Full-text

Compositional dependence of the direct and indirect band gaps in Ge1−ySnyalloys from room temperature photoluminescence: implications for the indirect to direct gap crossover in intrinsic andn-type materials

Semiconductor Science and Technology ◽

10.1088/0268-1242/29/11/115028 ◽

2014 ◽

Vol 29 (11) ◽

pp. 115028 ◽

Cited By ~ 66

Author(s):

L Jiang ◽

J D Gallagher ◽

C L Senaratne ◽

T Aoki ◽

J Mathews ◽

...

Keyword(s):

Room Temperature ◽

Band Gaps ◽

Compositional Dependence ◽

Room Temperature Photoluminescence

Download Full-text

Microstructure, Magnetic and Optical Properties of Metal/ Semiconductor Magnetic Granular Film

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.284-286.2207 ◽

2011 ◽

Vol 284-286 ◽

pp. 2207-2210

Author(s):

Bao Xin Huang

Keyword(s):

Room Temperature ◽

Amorphous Matrix ◽

Volume Fraction ◽

Rf Sputtering ◽

Average Diameter ◽

Band Gaps ◽

Localized States ◽

Granular Film ◽

Absorption Process ◽

Granular Films

Fe/In2O3 magnetic granular films have been prepared by rf sputtering method. The results reveal that the nanometersized Fe particles uniformly dispersed in the amorphous matrix In2O3 for the as-deposited samples. At room temperature, the Fe0.35/(In2O3)0.65 film shows a superparamagnetic behavior. The average diameter of particles (d = 5 nm) estimated from the fitting values of the saturation magnetization of Fe particles MFe and magnetic moment mis fitted well with that observed by TEM. The spectra analyses indicate that the indirect photon transitions of granular Fex/ (In2O3)1-x films substitute for the direct photon transition of In2O3 film in the absorption process. The band gaps of magnetic granular films decrease monotonously with the increase of volume fraction of Fe particles in the magnetic granular films, and the tail width of localized states becomes wider in concentration range of Fe studied.

Download Full-text

Prediction Study of Structural, Elastic, Electronic, Optical and Thermodynamic Properties of Cubic Perovskite Bigao3

10.21203/rs.3.rs-275574/v1 ◽

2021 ◽

Author(s):

M. A. Ghebouli ◽

B. Ghebouli ◽

M. Fatmi ◽

T. Chihi ◽

S. I. Ahmed

Keyword(s):

Valence Band ◽

Room Temperature ◽

Elastic Moduli ◽

Band Gaps ◽

Ductile Material ◽

Potential Candidate ◽

Transverse Waves ◽

Equilibrium Pressure ◽

Lattice Constants ◽

G Ratio

Abstract We report computations of all properties cited in title within GGA and LDA for cubic perovskite BiGaO3. Lattice constants, bulk modulus, elastic moduli and band gaps were computed. BiGaO3 is elastically stable at room temperature and equilibrium pressure. We predicted the Debye temperature and longitudinal and transverse waves along [100], [110] ([100], [110], [111]) directions for BiGaO3. Our calculated band gap 1.92 eV predicts the semiconducting nature. The upper valence band is consisted principally of O-2p sites and a little contribution of Ga-4p and Bi-6p states. Hybridization between Ga-4p orbital with O-2p site in the upper valence band traduces that Ga–O bonds have a covalent bonding character. B/G ratio indicates that BiGaO3 is classified as ductile material. We derived mechanical parameters of BiGaO3 using Voigt, Reuss and Hill approximations. The higher absorption value provides a hint that this material is a potential candidate as a photo catalyst in the degradation of chemicals or pollutants.

Download Full-text

Novel up-conversion luminescent rare-earth-doped organic resins for cost-effective applications in 3D photonic devices

Journal of Materials Chemistry C ◽

10.1039/c3tc32476a ◽

2014 ◽

Vol 2 (16) ◽

pp. 2944-2948 ◽

Cited By ~ 6

Author(s):

J. C. Ruiz-Morales ◽

J. Méndez-Ramos ◽

P. Acosta-Mora ◽

M. E. Borges ◽

P. Esparza

Keyword(s):

Rare Earth ◽

Water Splitting ◽

Room Temperature ◽

Laser Excitation ◽

Cost Effective ◽

Photonic Devices ◽

Band Gaps ◽

Photocatalytic Water Splitting ◽

Photonic Structures ◽

Rare Earth Doped

Novel up-conversion luminescent RE-doped organic resins, showing strong UV-Vis emission under infrared 980 nm laser excitation to bridge different band-gaps of main photocatalytic water-splitting semiconductors, with applications to cost-effective, room-temperature and endlessly shaped 3D photonic structures.

Download Full-text

In Air Template-Free Synthesis of In2S3 Hierarchical Nanostructure from InCl3·4H2O and Thiourea

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.152-153.63 ◽

2010 ◽

Vol 152-153 ◽

pp. 63-66

Author(s):

Shi Yin Li ◽

Zhen Ni Du ◽

Yong Cai Zhang

Keyword(s):

Room Temperature ◽

Band Gaps ◽

Cubic Phase ◽

X Ray Diffraction ◽

Scanning Electronic Microscopy ◽

Electronic Microscopy ◽

X Ray ◽

Hierarchical Nanostructure ◽

Optical Band Gaps ◽

Template Free

A novel template-free method, which was based on heating the mixture of InCl3•4H2O and thiourea in air from room temperature to 200 or 250 °C, coupled with a subsequent washing treatment using distilled water and ethanol, was proposed for the synthesis of In2S3 hierarchical nanostructure. X-ray diffraction and field emission scanning electronic microscopy demonstrated that the obtained products were pure cubic phase In2S3 urchin-like clusters built up by mainly nanoflakes (about 12–47 nm thick). UV-vis absorption spectra disclosed that the as-prepared In2S3 urchins had optical band gaps in the range of about 2.18–2.26 eV.

Download Full-text