Conductivity, photoconductivity and optical properties of amorphous GaN films

2001 ◽  
Vol 693 ◽  
Author(s):  
A. Koo ◽  
U. D. Lanke ◽  
B. J. Ruck ◽  
S. A. Brown ◽  
R. Reeves ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Light Emission ◽  
Visible Region ◽  
Green Light ◽  
Complex Form ◽  
Room Temperature Resistivity ◽  
Low Density ◽  
Preparation Conditions ◽  
Gap States

AbstractIt has been predicted that amorphous GaN has a low density of states in the gap, and therefore has potential as a useful opto-electronic material in the blue-green spectral region. We have synthesised amorphous GaN films on various substrates by ion assisted deposition and investigated the effects of sample preparation conditions on the conducting and optical properties. The room temperature resistivity ρ0 of stoichiometric (Ga:N of 1:1) films is above 105 Ω cm, and these films exhibit a complex form for the temperature dependence of the resistivity. Films having an excess of Ga show a much lower ρ0. The optical absorption shows ar 0 band-gap of 3 eV, with the gap falling below that value when the amorphous network incorporates homopolar (Ga-Ga) bonds. The best films are thus transparent across the visible region with a low density of gap states, undetectable in optical absorption. The photoluminescence spectra obtained from these a-GaN films consist of a broad green light emission peaking at 528 nm. Preliminary photoconductivity measurements show sensitivity in the UV.

scholarly journals Tuning the optoelectronic properties of hematite with rhodium doping for photoelectrochemical water splitting using density functional theory approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdur Rauf ◽  
Muhammad Adil ◽  
Shabeer Ahmad Mian ◽  
Gul Rahman ◽  
Ejaz Ahmed ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Optical Absorption ◽  
Water Splitting ◽  
Density Functional ◽  
Formation Energy ◽  
Visible Region ◽  
Photoelectrochemical Water Splitting ◽  
Theory Approach ◽  
Functional Theory

AbstractHematite (Fe2O3) is one of the best candidates for photoelectrochemical water splitting due to its abundance and suitable bandgap. However, its efficiency is mostly impeded due to the intrinsically low conductivity and poor light absorption. In this study, we targeted this intrinsic behavior to investigate the thermodynamic stability, photoconductivity and optical properties of rhodium doped hematite using density functional theory. The calculated formation energy of pristine and rhodium doped hematite was − 4.47 eV and − 5.34 eV respectively, suggesting that the doped material is thermodynamically more stable. The DFT results established that the bandgap of doped hematite narrowed down to the lower edge (1.61 eV) in the visible region which enhanced the optical absorption and photoconductivity of the material. Moreover, doped hematite has the ability to absorb a broad spectrum (250–800) nm. The enhanced optical absorption boosted the photocurrent and incident photon to current efficiency. The calculated results also showed that the incorporation of rhodium in hematite induced a redshift in optical properties.

scholarly journals Green Light Emission ofZnxCd1-xSeNanocrystals Synthesized by One-Pot Method

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Shu-Ru Chung ◽  
Kuan-Wen Wang ◽  
Hong-Shuo Chen
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Light Emission ◽  
Green Light ◽  
Particle Size Effect ◽  
Partial Replacement ◽  
Face Centered Cubic ◽  
One Pot ◽  
Zn Content ◽  
High Emission

We present a facile one-pot synthesis to prepare ternaryZnxCd1-xSe(x= 0.2, 0.5, 0.8, and 1) nanocrystals (NCs) with high emission quantum yield (QY, 45~89%). The effect of Zn content (x) ofZnxCd1-xSeNCs on their physical properties is investigated. The NCs have a particle size of 3.2 nm and face centered cubic structure. However, the actual compositions of the NCs are Zn0.03Cd0.97Se, Zn0.11Cd0.89Se, and Zn0.38Cd0.62Se when Zn content is 0.2, 0.5, and 0.8, respectively. In terms of the optical properties, the emission wavelength shifts from 512 to 545 nm with increasing Zn content from 0 to 0.8 while the QY changes from 89 to 45, respectively. Partial replacement of Cd by Zn is beneficial to improve the QY of Zn0.2and Zn0.5NCs. The optical properties of ternary NCs are affected by compositional effect rather than particle size effect.

OPTICAL SPECTROSCOPY AND NONLINEAR TRANSMITTANCE STUDY OF FULLERENE C60 IN MIXTURES WITH 2-CYCLOOCTYLAMINO-5-NITROPYRIDINE (COANP)

2004 ◽  
Vol 13 (01) ◽  
pp. 113-127 ◽  
Author(s):  
SERGEY S. SARKISOV ◽  
ELENA I. RADOVANOVA ◽  
BURL H. PETERSON ◽  
ALEX LEYDERMAN ◽  
MICHAEL CURLEY ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Spectrum ◽  
Optical Absorption ◽  
Infrared Absorption ◽  
Chemical Bonding ◽  
Infrared Absorption Spectrum ◽  
Visible Region ◽  
Fullerene C60 ◽  
Amino Group

Characterization of the infrared absorption spectrum of the solutions of fullerene C 60 with 2-cyclooctylamino-5-nitropyridine additive has been performed with the focus on possible bonding with the amino-group of the additive. No occurrence of such bonding was found at normal conditions. Also no change of optical absorption in visible region and optical limiting of fullerene due to chemical bonding with the additive was detected. The resulting optical properties of the mixture were simply a sum of the properties of the components for a molar proportion of the additive to fullerene approaching 200:1.

Optical Properties and Electronic Structures of Sexithiophene

2010 ◽  
Vol 428-429 ◽  
pp. 475-478 ◽  
Author(s):  
Bao Gai Zhai ◽  
Yuan Ming Huang
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Ultraviolet Light ◽  
Organic Semiconductor ◽  
Electronic Structures ◽  
Light Emission ◽  
Visible Spectroscopy ◽  
Time Resolved ◽  
Pump And Probe ◽  
Green Photoluminescence

The optical properties and electronic structures of an organic semiconductor sexithiophene have been investigated with ultraviolet-visible spectroscopy, cw photospectroscopy and time-resolved photospectroscopy, respectively. Sexithiophene in dilute tetrahydrofuran solutions can absorb photons at 400 nm while it can give off strong green photoluminescence at 550 nm under the excitation of 325 nm ultraviolet light. With the assistance of calculated electronic structures and pump-and-probe characterization, our results indicate that both the optical absorption and the light emission of the sexithiophene are controlled by the p-conjugation of the oligothiophene.

STRUCTURAL, ELECTRICAL AND OPTICAL PROPERTIES OF TiO2THIN FILM DEPOSITED ON THE NANO POROUS SILICON TEMPLATE

2017 ◽  
Vol 24 (Supp02) ◽  
pp. 1850017
Author(s):  
MAHMOOD BAHAR ◽  
ENSIEH KHALILI DERMANI
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Porous Silicon ◽  
Light Emission ◽  
Electrochemical Etching ◽  
Green Light ◽  
Blue Emission ◽  
Band Gap Energy ◽  
X Ray Diffraction ◽  
Green Light Emission

The porous silicon (PSi), which is produced by the electrochemical etching, has been used as a substrate for the growth of the titanium oxide (TiO2) thin films. By using the EBPVD method, TiO2thin films have been deposited on the surface of the PSi substrate. TiO2/PSi layers were annealed at the temperature of 400[Formula: see text]C, 500[Formula: see text]C and 600[Formula: see text]C for different tests. The morphology and structures of layers were investigated by the scanning electron microscopy (SEM) and X-ray diffraction (XRD). The current–voltage characteristic curves of samples and the ideality factor of heterojunction were studied. The results showed that the electrical properties of the samples change with increase in the annealing temperature. The optical properties of the prepared samples were investigated by using UV–Vis and photoluminescence (PL) spectroscopy. Green light emission of the PSi combined with the blue light and violet–blue emission obtained from the TiO2/PSi PL spectra. The results showed that the optical band gap energy of the PSi has increased from 1.86[Formula: see text]eV to 2.93[Formula: see text]eV due to the deposition of TiO2thin film.

Variations in the optical properties of TiO2 with Pb doping using ab initio calculations

2021 ◽  
Author(s):  
Hamid Khan ◽  
Yaseen Iqbal ◽  
Matiullah Khan ◽  
S. N. Ahmad ◽  
Yi Zeng
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Density Functional ◽  
Separation Efficiency ◽  
Computational Study ◽  
Visible Region ◽  
Solar Spectrum ◽  
High Rate ◽  
Practical Applications ◽  
Pb Doping

Titanium dioxide (TiO2) is one of the most promising photocatalysts for photoelectrochemical applications due to its high chemical as well as photochemical stability. Its efficiency in practical applications is limited due to its wide bandgap, a high rate of recombination of electron–hole pairs and the weak photo-carriers separation efficiency. In this computational study, a path was followed to find out the redshift of the TiO2 light absorption edge via lead (Pb) doping. The density functional theory (DFT) results revealed that the doped TiO2 bandgap was decreased to the lower edge (2.1 eV) in the visible region resulting in a relatively better optical absorption of the material. Furthermore, doped TiO2 was found to absorb a large part of the solar spectrum. The improvement in optical absorption resulted in good photo response. The calculated results also showed a redshift in optical properties produced through the doping of Pb in TiO2.

Effects of Red and Green Laser Irradiations on the Optical Properties of an Azo-Containing Bent-Core Liquid Crystal

2010 ◽  
Vol 428-429 ◽  
pp. 588-592
Author(s):  
Yuan Ming Huang ◽  
Fu Fang Zhou ◽  
Bao Gai Zhai
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Optical Absorption ◽  
Laser Irradiation ◽  
Ethyl Alcohol ◽  
Irradiation Time ◽  
Green Light ◽  
Green Laser ◽  
Time Dependent ◽  
532 Nm

With the ultraviolet-visible spectrophotometry, we have investigated the effects of red laser (633 nm) and green laser (532 nm) irradiations on the optical absorption of the ethyl alcohol solutions of an azo-containing bent-core liquid crystal. As the irradiation duration increases, the optical absorptions at about 360 nm of the bent-core compound exhibit concentration dependent and irradiation-time dependent features. The absorptions of dilute solutions (~2.2 mg/litter) are not sensitive to the laser irradiation duration whereas the absorptions of higher concentrations (~10 mg/litter) decrease as the laser irradiation continues. Our results have demonstrated that laser irradiation induced thermolysis is responsible for the dissociation of the azo-linkages in azo-containing bent-core compound. The mechanisms on the red and green light irradiations are discussed.

scholarly journals Optical Properties and Conductivity of PVA–H3PO4 (Polyvinyl Alcohol–Phosphoric Acid) Film Blend Irradiated by γ-Rays

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1065
Author(s):  
Susilawati Susilawati ◽  
Saiful Prayogi ◽  
Muhamad F. Arif ◽  
Noor Maizura Ismail ◽  
Muhammad Roil Bilad ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiation Dose ◽  
Optical Absorption ◽  
Phosphoric Acid ◽  
Polyvinyl Alcohol ◽  
Polymer Film ◽  
Energy Gap ◽  
Visible Region ◽  
Ultraviolet Region ◽  
Γ Rays

This study assesses the optical properties and conductivity of PVA–H3PO4 (polyvinyl alcohol–phosphoric acid) polymer film blend irradiated by gamma (γ) rays. The PVA–H3PO4 polymer film blend was prepared by the solvent-casting method at H3PO4 concentrations of 75 v% and 85 v%, and then irradiated up to 25 kGy using γ-rays from the Cobalt-60 isotope source. The optical absorption spectrum was measured using an ultraviolet–visible spectrophotometer over a wavelength range of 200 to 700 nm. It was found that the absorption peaks are in three regions, namely two peaks in the ultraviolet region (310 and 350 nm) and one peak in the visible region (550 nm). The presence of an absorption peak after being exposed to hυ energy indicates a transition of electrons from HOMO to LUMO within the polymer chain. The study of optical absorption shows that the energy band gap (energy gap) depends on the radiation dose and the concentration of H3PO4 in the polymer film blend. The optical absorption, absorption edge, and energy gap decrease with increasing H3PO4 concentration and radiation dose. The interaction between PVA and H3PO4 blend led to an increase in the conductivity of the resulting polymer blend film.

Fluorescent Nanotechnology: An Evolution in Optical Sensors

2020 ◽  
Vol 17 ◽  
Author(s):  
Dilawar Hassan ◽  
Hadi Bakhsh ◽  
Asif M. Khurram ◽  
Shakeel A. Bhutto ◽  
Nida S. Jalbani ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Sensors ◽  
Light Emission ◽  
Environmental Contaminants ◽  
Fluorescent Nanoparticles ◽  
Sensing Applications ◽  
Properties Of Materials ◽  
Optical Properties Of Materials ◽  
Fluorescent Nanomaterials

Background: The optical properties of nanomaterials have evolved enormously with the introduction of nanotechnology. The property of materials to absorb and/or emit specific wavelength has turned them into one of the most favourite candidates to be effectively utilized in different sensing applications e.g organic light emission diodes (OLEDs) sensors, gas sensors, biosensors and fluorescent sensors. These materials have been reported as a sensor in the field of tissue and cell imaging, cancer detection and detection of environmental contaminants etc. Fluorescent nanomaterials are heling in rapid and timely detection of various contaminants that greatly impact the quality of life and food, that is exposed to these contaminants. Later, all the contaminants have been investigated to be most perilous entities that momentously affect the life span of the animals and humans who use those foods which have been contaminated. Objective: In this review, we will discuss about various methods and approaches to synthesize the fluorescent nanoparticles and quantum dots (QDs) and their applications in various fields. The application will include the detection of various environmental contaminants and bio-medical applications. We will discuss the possible mode of action of the nanoparticles when used as sensor for the environmental contaminants as well as the surface modification of some fluorescent nanomaterials with anti-body and enzyme for specific detection in animal kingdom. We will also describe some RAMAN based sensors as well as some optical sensing-based nanosensors. Conclusion: Nanotechnology has enabled to play with the size, shape and morphology of materials in the nanoscale. The physical, chemical and optical properties of materials change dramatically when they are reduced to nanoscale. The optical properties can become choosy in terms of emission or absorption of wavelength in the size range and can result in production of very sensitive optical sensor. The results show that the use of fluorescent nanomaterials for the sensing purposes are helping a great deal in the sensing field.

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