scholarly journals Temperature-Dependent Optical Properties of Graphene on Si and SiO2/Si Substrates

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 358
Author(s):  
Sisi Wu ◽  
Lingyu Wan ◽  
Liangmin Wei ◽  
Devki N. Talwar ◽  
Kaiyan He ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Constants ◽  
Near Infrared ◽  
Infrared Region ◽  
Peak Position ◽  
Monolayer Graphene ◽  
Ultraviolet Region ◽  
Si Substrate ◽  
Temperature Dependent ◽  
Si Substrates

Systematic investigations are performed to understand the temperature-dependent optical properties of graphene on Si and SiO2/Si substrates by using a variable angle spectroscopic ellipsometry. The optical constants of graphene have revealed changes with the substrate and temperature. While the optical refractive index (n) of monolayer graphene on Si exhibited clear anomalous dispersions in the visible and near-infrared region (400–1200 nm), the modification is moderate for graphene on SiO2/Si substrate. Two graphene sheets have shown a pronounced absorption in the ultraviolet region with peak position related to the Van Hove singularity in the density of states. By increasing the temperature from 300 K to 500 K, for monolayer graphene on Si, the n value is gradually increased while k decreased. However, the optical constants [n, k] of monolayer graphene on SiO2/Si exhibited unpredictable wave variations. In the wavelength range of 400–1200 nm, an experiential formula of a like-Sellmeier equation is found well suited for describing the dispersions of graphene on Si and SiO2/Si substrates.

scholarly journals Synthesis of Ge1−xSnx Alloy Thin Films by Rapid Thermal Annealing of Sputtered Ge/Sn/Ge Layers on Si Substrates

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2248 ◽  
Author(s):  
Hadi Mahmodi ◽  
Md Hashim ◽  
Tetsuo Soga ◽  
Salman Alrokayan ◽  
Haseeb Khan ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Near Infrared ◽  
Annealing Temperature ◽  
Solid Phase ◽  
Infrared Region ◽  
Alloy Formation ◽  
Phase Mixing ◽  
Si Substrates ◽  
Msm Photodetector

In this work, nanocrystalline Ge1−xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, for 10 s. Then, the effect of thermal annealing on the morphological, structural, and optical characteristics of the synthesized Ge1−xSnx alloys were investigated. The nanocrystalline Ge1−xSnx formation was revealed by high-resolution X-ray diffraction (HR-XRD) measurements, which showed the orientation of (111). Raman results showed that phonon intensities of the Ge-Ge vibrations were improved with an increase in the annealing temperature. The results evidently showed that raising the annealing temperature led to improvements in the crystalline quality of the layers. It was demonstrated that Ge-Sn solid-phase mixing had occurred at a low temperature of 400 °C, which led to the creation of a Ge1−xSnx alloy. In addition, spectral photo-responsivity of a fabricated Ge1−xSnx metal-semiconductor-metal (MSM) photodetector exhibited its extending wavelength into the near-infrared region (820 nm).

scholarly journals Optical properties of spray pyrolysis deposited Cds:Al thin films

2015 ◽  
Vol 39 (1) ◽  
pp. 25-30 ◽  
Author(s):  
A Hasnat Rubel ◽  
J Podder
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Spray Pyrolysis ◽  
Near Infrared ◽  
Visible Region ◽  
Cadmium Sulphide ◽  
Infrared Region ◽  
Photo Detectors ◽  
Direct Energy ◽  
Academy Of Sciences

Aluminium doped cadmium sulphide thin films were prepared on glass substrate using aqueous solution of cadmium sulphide and thiourea salts by spray pyrolysis deposition (SPD) technique. Its optical properties were analyzed as a function of doping concentration. The direct energy band-gap of Al-doped CdS films was estimated in the range of 2.25 to 2.48 eV. The optical spectra of Cd1-xAlxS ternary system exhibit high absorption near visible region and transmission throughout the near-infrared region (600 - 1200 nm). Thus so obtained hetero-junction films are suitable for fabrication of photo detectors, solar cells and other optoelectronics devices.Journal of Bangladesh Academy of Sciences, Vol. 39, No. 1, 25-30, 2015

scholarly journals Enhanced luminescence and tunable magnetic properties of lanthanide coordination polymers based on fluorine substitution and phenanthroline ligand

RSC Advances ◽  
2019 ◽  
Vol 9 (29) ◽  
pp. 16328-16338 ◽  
Author(s):  
Xun Feng ◽  
Yapei Shang ◽  
Heng Zhang ◽  
Rongfang Li ◽  
Weizhou Wang ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Single Molecule ◽  
Near Infrared ◽  
Infrared Region ◽  
Temperature Dependent ◽  
Fluorine Substitution ◽  
Lanthanide Coordination Polymers ◽  
Long Lifetime ◽  
Phenanthroline Ligand ◽  
Phenanthroline Ligands

Lanthanide coordination polymers with F-substituted carboxylate tectonics and phenanthroline ligands exhibit emission from the visible to near-infrared region with long lifetime. Dy(iii) compounds show temperature dependent and field induced single molecule magnetism.

scholarly journals Optical Measurements on Solids of Possible Interstellar Importance

1973 ◽  
Vol 52 ◽  
pp. 297-301 ◽  
Author(s):  
Donald R. Huffman ◽  
James L. Stapp
Keyword(s):  
Optical Properties ◽  
Wavelength Range ◽  
Optical Constants ◽  
Near Infrared ◽  
Large Change ◽  
Optical Measurements ◽  
Ultraviolet A ◽  
Peculiar Characteristic ◽  
Far Ultraviolet

Optical constants of olivine – (Mg, Fe)2SiO4 and magnetite – Fe3O4 are presented for the wavelength range from near infrared to far ultraviolet. A feature occurs in the optical constants of olivine at about 1460 Å, but no structure that could give rise to a 2200 Å interstellar feature is found. The most peculiar characteristic of the magnetite results is the large change of optical properties with temperature in the infrared.

Optical constants of silicon in near infrared region

2008 ◽  
Vol 93 (13) ◽  
pp. 131916 ◽  
Author(s):  
V. Ya. Mendeleyev ◽  
S. N. Skovorodko ◽  
E. N. Lubnin ◽  
V. M. Prosvirikov
Keyword(s):  
Optical Constants ◽  
Near Infrared ◽  
Infrared Region ◽  
Near Infrared Region

scholarly journals First principles DFT calculations of the optical properties of A4BX6 group crystals

2021 ◽  
Vol 22 (1) ◽  
pp. 117-122
Author(s):  
H. Ilchuk ◽  
M. Solovyov ◽  
I. Lopatynskyi ◽  
F. Honchar ◽  
F. Tsyupko
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Energy Band ◽  
Density Functional ◽  
Near Infrared ◽  
Infrared Region ◽  
Energy Structure ◽  
Generalized Gradient ◽  
Reflection Index ◽  
Functional Theory

The results of investigating of the electron band energy structure and optical properties of A4BX6 (Tl4HgI6 and Tl4CdI6) group crystals are presented. The energy band structures of Tl4HgI6 and Tl4CdI6 crystals are calculated from the first principles within generalized gradient approximation (GGA). The band structure and reflection index were calculated using a pseudopotential method in the framework of density functional theory. Optical absorption edge in Tl4HgI6 and Tl4CdI6 is formed by direct optical transitions. The spectral dependence of the reflection index was calculated on the basis of the energy band results with using the Kramers–Kronig method. The spectra show pronounced anisotropy in E||a(b) and E||c polarizations. It was found the anomalous by large values of the birefringence (Δn > 0.18 for Tl4HgI6 and Δn > 0.03 for Tl4CdI6) in the visible and near infrared region.

scholarly journals Experimental constraints on the ordinary chondrite shock darkening caused by asteroid collisions

2020 ◽  
Vol 639 ◽  
pp. A146 ◽  
Author(s):  
T. Kohout ◽  
E. V. Petrova ◽  
G. A. Yakovlev ◽  
V. I. Grokhovsky ◽  
A. Penttilä ◽  
...  
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Infrared Region ◽  
Shock Pressure ◽  
Ordinary Chondrite ◽  
Second Stage ◽  
Shock Experiment ◽  
Induced Changes ◽  
Spherical Shock ◽  
Characteristic Pressure

Context. Shock-induced changes in ordinary chondrite meteorites related to impacts or planetary collisions are known to be capable of altering their optical properties. Thus, one can hypothesize that a significant portion of the ordinary chondrite material may be hidden within the observed dark C/X asteroid population. Aims. The exact pressure-temperature conditions of the shock-induced darkening are not well constrained. Thus, we experimentally investigate the gradual changes in the chondrite material optical properties as a function of the shock pressure. Methods. A spherical shock experiment with Chelyabinsk LL5 was performed in order to study the changes in its optical properties. The spherical shock experiment geometry allows for a gradual increase of shock pressure from ~15 GPa at a rim toward hundreds of gigapascals in the center. Results. Four distinct zones were observed with an increasing shock load. The optical changes are minimal up to ~50 GPa. In the region of ~50–60 GPa, shock darkening occurs due to the troilite melt infusion into silicates. This process abruptly ceases at pressures of ~60 GPa due to an onset of silicate melting. At pressures higher than ~150 GPa, recrystallization occurs and is associated with a second-stage shock darkening due to fine troilite-metal eutectic grains. The shock darkening affects the ultraviolet, visible, and near-infrared region while changes to the MIR spectrum are minimal. Conclusions. Shock darkening is caused by two distinct mechanisms with characteristic pressure regions, which are separated by an interval where the darkening ceases. This implies a reduced amount of shock-darkened material produced during the asteroid collisions.

Temperature-dependent optical constants of water ice in the near infrared: new results and critical review of the available measurements

2001 ◽  
Vol 40 (25) ◽  
pp. 4449 ◽  
Author(s):  
Bhavani Rajaram ◽  
David L. Glandorf ◽  
Daniel B. Curtis ◽  
Margaret A. Tolbert ◽  
Owen B. Toon ◽  
...  
Keyword(s):  
Critical Review ◽  
Optical Constants ◽  
Near Infrared ◽  
Temperature Dependent ◽  
Water Ice
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