This document analyzes the optical properties of several thin film semiconductors. It characterizes the transmittance, reflectance, and absorption of CdS films deposited at different times, as well as Sb-S-Se films deposited at different temperatures. Key results include the absorption coefficient, transmission and reflection percentages in different wavelength regions, and estimates of photon flux and potential short circuit current density for each film based on their bandgaps. Optical properties were measured using UV-VIS spectroscopy to understand how effectively the materials could absorb light.
This is an example of a formal lab report on Interference and Diffraction done for my Physics class. This document demonstrates my ability to technically report findings from experiments.
3 d single gaas co axial nanowire solar cell for nanopillar-array photovoltai...ijcsa
Nanopillar array photovoltaics give unique advantages over today’s planar thin films in the areas of
optical properties and carrier collection, arising from their 3D geometry. The choice of the material
system, however, is essential in order to gain the advantage of the large surface/interface area associated
with nanopillars. Therefore, a well known Si and GaAs material are used in the design and studied in this
nanowire application. This work calculates and analyses the performance of the coaxial GaAs nanowire
and compared with that of Si nanowire using a semi-classical method. The current-voltage characteristics
are investigated for both under dark and AM1.5G illumination. It is found that GaAs nanowire gives almost
double efficiency with its counterpart Si nanowire. Their TCAD simulations can be validated reasonably
with that of published experimental result.
The document describes the results of an experiment using a Laser-Accelerated Plasma Propulsion System (LAPPS) for spacecraft propulsion. A 1 kJ, 1 μm wavelength laser beam was focused on a 125 μm thick gold foil, generating a proton beam with maximum and average energies of 58 MeV and 5.3 MeV respectively. This proton beam was able to generate a thrust of 1.83x10-2 N when accelerated through 17 GeV/cm electric fields, demonstrating the potential of LAPPS technology for spacecraft propulsion with specific impulses up to 5x106 and repetition rates up to 1000 Hz.
This document summarizes work towards developing a quantum memory for non-classical light using cold atoms. It discusses generating squeezed vacuum light compatible with an atomic memory using an optical parametric oscillator. The light is characterized and techniques for interfacing it with the memory are explored. This includes creating two atomic ensembles for memory applications and characterizing their properties like storage time and efficiency. The goal is to eventually entangle the two memory ensembles.
Attosecond pulses produced by using HHG in gases, it is possible to make a few simple statements: attosecond pulses are unique tools for the investigation of ultrafast electronic processes in atoms, molecules, nano structures and solids. Impressive progress has been demonstrated from the technological point of view, with the possibility to routinely generate attosecond pulses in perfectly reproducible ways.
This document provides a summary of key concepts in nuclear chemistry, including:
1) Nuclear stability and radioactive decay involve the emission of particles like alpha and beta from unstable nuclei. Different types of radiation (alpha, beta, gamma) require different shielding methods.
2) Radioactive decay follows first-order kinetics and half-life is used to describe the rate of decay. Carbon-14 dating and lead-uranium dating use radioactive half-lives to determine the age of materials.
3) Nuclear reactions like fission and fusion release large amounts of energy. Fission is the splitting of heavy nuclei like uranium-235 and is used in nuclear power reactors. Fusion combines light nuclei and occurs in
Laser Pulsing in Linear Compton ScatteringTodd Hodges
This document summarizes a method for calculating the energy spectrum of radiation produced in linear Compton scattering, accounting for the pulsed structure of the incident laser beam. The method involves performing a Lorentz transformation of the Klein-Nishina scattering cross section to calculate the emission from individual electrons in an electron beam, and then summing over all electrons to obtain the total energy spectrum. This approach allows for accurate modeling of effects of electron beam energy spread and emittance. The method is then applied to predict the photon spectrum from a proposed compact inverse Compton scattering x-ray source at Old Dominion University.
This document provides solutions to 10 homework problems about antennas. The problems cover topics like calculating the length of dipole antennas at specific frequencies, efficiency of dipoles, electric field strength from dipoles, gain and beamwidth from plots, EIRP calculations, lengths of quarter-wave antennas, dimensions of discone antennas, calculations for helical antennas, and aperture size for horn antennas to achieve a given gain. The solutions show the relevant equations and step-by-step working to arrive at the final numerical answers.
- Newton's rings are an interference pattern produced when a plano-convex lens rests on a flat glass plate, creating an air gap of variable thickness.
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- Given a 10m radius lens illuminated with 590nm light, over 40 bright rings would be seen within the 4cm diameter, and the sixth ring would have a diameter of around 0.5cm.
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The document proposes using neutrino beams to communicate trading information faster than fiber optics for insider trading purposes. It outlines goals of transmitting information faster than light by hundreds of microseconds using neutrino beams. While an unfeasibly high beam power would be required to achieve the necessary neutrino flux and bit rate, some workarounds are proposed, such as using a larger detector like IceCube or higher neutrino energies. A quaternary communication system using two neutrino flavors could improve speed further.
The document discusses key concepts related to radioactive decay including:
- Radioactive decay is the process by which some atoms spontaneously emit energy through radiation.
- Activity is a measure of the amount of radioactive material and is quantified using the unit Becquerel (Bq).
- The law of radioactive decay states that the rate of decay is proportional to the amount of radioactive material present.
- Half-life refers to the time it takes for half the atoms in a sample to decay and is unique for each radioactive isotope.
This document discusses simulating UV-vis spectra of methyl viologen and its radical cation using time-dependent density functional theory (TD-DFT). It optimizes the geometries of methyl viologen and its radical cation using DFT and discusses using TD-DFT with a 6-311G** basis set to simulate the UV-vis spectra. It also plans to simulate the UV-vis spectra using a multi-reference method called CASPT2.
Los días 22 y 23 de junio de 2016 organizamos en la Fundación Ramón Areces un simposio internacional sobre 'Materiales bidimensionales: explorando los límites de la física y la ingeniería'. En colaboración con el Massachusetts Institute of Technology (MIT), científicos de este prestigioso centro de investigación mostraron las propiedades únicas de materiales como el grafeno, de solo un átomo de espesor, y al mismo tiempo más resistente que el acero y mucho más ligero.
Aeroacoustic simulation of bluff body noise using a hybrid statistical methodCon Doolan
The document summarizes a presentation on aeroacoustic simulation of bluff body noise using a hybrid statistical method. It discusses limitations of conventional computational fluid dynamics methods for noise prediction and introduces a new statistical correction method to improve noise simulation results from unsteady Reynolds-averaged Navier Stokes simulations. Key results from applying the statistical correction to simulations of circular cylinder noise are also summarized.
A Hybrid Approach for Real-time Room Acoustic Response Simulationa3labdsp
Reverberation is a well known effect particularly important for music listening especially for recorded and live music. Generally, there are two approaches for artificial reverberation: the desired signal can be obtained by convolving the input signal with a measured impulse response (IR) or a synthetic one. Taking into account the advantages of both approaches, a hybrid artificial reverberation algorithm is presented. The early reflections are derived from a real IR, truncated considering the calculated mixing time, and the reverberation tail is obtained considering the Moorer's structure. The parameters defining this structure are derived from the analyzed IR, using a minimization criteria based on Simultaneous Perturbation Stochastic Approximation (SPSA). The obtained results showed a high-quality reverberator with a low computational load.
Flow and Noise Simulation of the NASA Tandem Cylinder Experiment using OpenFOAMCon Doolan
The document summarizes flow and noise simulations of the NASA tandem cylinder experiment using OpenFOAM software. It aims to present URANS aerodynamic simulations comparing results to experimental data, and to predict noise using a statistical method. Surface pressures are used to calculate noise by Curle's theory with temporal and spatial phase dispersion models. Mean flow results agree reasonably well with PIV experiments, while acoustic predictions are assessed against experimental noise data.
L. Venturino, C. Risi, A. Zappone and S. Buzzi, "Green Joint User Scheduling and Power Control in Downlink Multi-Cell OFDMA Network" 2013 Future Networks and mobile Summit, Lisbon, July 2013.
New folderelec425_2016_hw5.pdfMar 25, 2016 ELEC 425 S.docxcurwenmichaela
The document discusses omnidirectional reflection from a one-dimensional photonic crystal structure. It presents the following key points:
1) A one-dimensional photonic crystal, such as a multilayer film, can exhibit complete reflection of light within a frequency range for all incident angles and polarizations, even without a full photonic bandgap.
2) The criterion for omnidirectional reflection is that there exists a frequency range where the projected band structures of the photonic crystal and surrounding medium do not overlap, rather than there being no propagating states within the crystal itself.
3) As an example, a multilayer film with refractive indices of n1 = 1.7 and n2 = 3.4
TSSB Brain Initiative - Overview of Nano and Molecular Communications and Bra...Walton Institute
This was a presentation given by Dr. Sasitharan Balasubramaniam, Director of Research at TSSG, in which he presented his current research in developing miniature devices for Brain implants. The talk focused on two types of implants, which includes (i) nanoelectronics that are used to stimulate neutrons, (ii) engineered cells that transfect and communicate to neurons. The talk will also touch on the potential applications for these types of devices.
This document provides an introduction to lasers and their applications. It begins with recommended textbooks on the subject, then provides a chart showing the laser spectrum and examples of different laser types and their wavelengths. The remainder of the document discusses the basic components and functioning of lasers, including the gain medium that provides stimulated emission, the pump source to create population inversion, and the optical cavity formed by mirrors. It also provides brief histories of the development of masers and the first ruby laser.
This research article investigates the surface roughness and electrical conductivity of ultra-thin tin dioxide (SnO2) layers deposited by spray pyrolysis. Two sets of samples with different precursor concentrations and volumes were analyzed using X-ray reflectivity. XRR analysis revealed that increasing the precursor volume led to thicker layers with higher electron densities. Higher precursor concentration resulted in denser layers with larger thicknesses. Sheet resistance measurements showed lower values for thicker layers, correlated with their higher electron densities from XRR analysis.
This document summarizes the results of a simulation study investigating light absorption in organic solar cells with smooth and pyramidal textured surfaces. The study first optimized a flat organic solar cell structure by simulating the effects of varying each layer's thickness on short-circuit current and quantum efficiency. The optimized flat cell achieved 13.65 mA/cm2 short-circuit current and 84% quantum efficiency at 640 nm. It then proposed a pyramid textured surface to enhance light trapping and absorption compared to a smooth surface. The effects of period and height of the pyramids were analyzed to validate the light trapping model.
Numerical ray tracing through a modified cladding fiber optic segment sensorsRadhi Chyad
1) The document investigates light transmission through an optical fiber with a modified cladding segment using 3D geometric optics modeling.
2) It analyzes how the intensity of transmitted light is affected by the refractive index and length of the modified cladding segment.
3) The modeling shows that if the modified cladding has a higher refractive index than the core, light transmission is very low due to partial reflection and losses. But if the modified cladding has a lower refractive index, transmission reaches saturation after a short segment length, making it suitable for sensor applications.
1. Microwave diagnostics techniques such as interferometry, reflectometry, scattering and electron cyclotron emission (ECE) have been powerful tools for diagnosing magnetically confined plasmas.
2. Recent advances in electronics and computer technology have enabled the development of advanced microwave diagnostic systems that can measure 2D and 3D profiles of plasma density, temperature, and fluctuations.
3. Key microwave diagnostic techniques discussed in the document are interferometry, reflectometry, and ECE. Interferometry measures line integrated density, reflectometry measures local density, and ECE measures local electron temperature. These techniques provide important information for understanding issues in plasma physics like stability, waves, and transport.
This document summarizes research into using laser excitation of cesium ions to enhance the performance of thermionic energy converters (TECs). The researchers have developed a particle-in-cell model of a planar diode discharge to simulate TEC operation and are using it to model the effects of laser excitation on current-voltage characteristics. They have also designed a laboratory test cell to experimentally validate the effects of laser excitation on TEC performance. Initial results suggest laser excitation could substantially improve TEC current density and efficiency over conventional ignited or triode configurations.
This document summarizes research into using laser excitation to enhance the production of cesium ions in thermionic energy converters (TECs). The researchers have developed a particle-in-cell model of a planar diode discharge to simulate TEC performance with and without laser ionization. They have also designed a laboratory test cell to experimentally validate the effect of laser excitation on TEC current-voltage characteristics. Future work will include refining the models, procuring parts for the test cell, and conducting experimental studies to analyze how laser excitation can increase TEC efficiency and be used in energy systems to reduce carbon emissions.
This document summarizes research into using laser excitation to enhance the production of cesium ions in thermionic energy converters (TECs). The researchers have developed a particle-in-cell model of a planar diode discharge to simulate TEC performance with and without laser ionization. They have also designed a laboratory test cell to experimentally validate the effect of laser excitation on TEC current-voltage characteristics. Future work will include refining the models, procuring parts for the test cell, and conducting experimental studies to characterize optimized TEC performance with optical modulation. The goal is to increase TEC efficiency for applications in solar and combustion energy systems to reduce greenhouse gas emissions.
This document summarizes research into using laser excitation of cesium ions to enhance the performance of thermionic energy converters (TECs). The researchers have developed a particle-in-cell model of a planar diode discharge to simulate TEC operation and are using it to model the effects of laser excitation on current-voltage characteristics. They have also designed a laboratory test cell to experimentally validate the effects of laser excitation on TEC performance. Initial results suggest laser excitation could substantially improve TEC current density and efficiency over conventional ignited or triode configurations.
This document is a thesis submitted by Liam A. Young to the Pennsylvania State University for a baccalaureate degree in Engineering Science. The thesis investigates defects in cadmium telluride (CdTe) solar cell samples using electron paramagnetic resonance (EPR) spectroscopy. EPR spectroscopy is used to detect electron spin resonances in the samples, which can provide information about defects. The thesis will examine CdTe samples at temperatures of 300K, 80K, 50K, and 5K using an EPR spectrometer to analyze defects. The lower temperatures are expected to increase signal strength and reveal more defining features of any defects present.
Laser trapped mirrors could enable the construction of large, lightweight optical systems in space. A laser traps microscopic particles at the interference fringes created by its reflection between two deflectors, arranging the particles into a reflective mirror surface. Key challenges include maintaining the trap against particle evaporation from infrared background photons and understanding optical binding forces between particles. Further experiments and simulations are needed to evaluate particle design, collective behavior, trap loading and damping mechanisms to develop this technology.
The document describes a lifetime calculator tool developed at ALBA to calculate the beam lifetime based on machine parameters like beam current, coupling, RF voltage, and pressure. It summarizes the calculation methods for Touschek lifetime due to electron-electron scattering and gas lifetime due to collisions with residual gas. The tool integrates these calculations into ALBA's control system to continuously compare calculated and measured lifetimes as a diagnostic. It allows simulating the lifetime for different machine conditions to predict changes.
Infrared spectroscopy involves measuring the absorption or emission of electromagnetic radiation by molecules as they undergo transitions between different energy states. Infrared spectroscopy analyzes the infrared region of the electromagnetic spectrum, where molecules absorb radiation based on the vibrational and rotational motions of their bonds. The positions and intensities of absorption bands in an infrared spectrum provide information about the types of bonds in a molecule and can be used to determine its structure.
A Front Surface Optimization Study for Photovoltaic ApplicationTELKOMNIKA JOURNAL
This document summarizes a study on optimizing the front surface of silicon solar cells to reduce reflectance through antireflection coatings and surface texturing. Silicon nitride films were deposited using plasma-enhanced chemical vapor deposition and hot-wire chemical vapor deposition on silicon substrates, and showed weighted average reflectances of 1.5% and 1.8% respectively. Random pyramid surface textures were formed on silicon using potassium hydroxide etching for 30 minutes, achieving low reflectance. Combining the optimized silicon nitride coatings with the textured surfaces further reduced weighted average reflectances to 1.5% for PECVD and 1.8% for HWCVD coatings.
DEVELOPMENT OF OPTICAL PARAMETER CALCULATIONS OF THE PROBES IN WATERDr. Ved Nath Jha
This document describes the development of optical parameter calculations for probes used in water sensing. Three probes (a, b, c) of varying nanoparticle size were developed and their plasma and collision wavelengths were calculated based on experimental measurements in water and air. The probes showed decreasing collision wavelength but nearly constant plasma wavelength with increasing nanoparticle size. Models were developed to calculate output intensity based on the dielectric constant of the surrounding medium. Distinct dips in output intensity correlated with different dielectric components when mixtures were tested, showing ability to detect multiple impurities simultaneously. The probes function best for dielectric constants between 1.4-2.0 and silver nanoparticles provide sensitivity towards targeted impurities in water quality monitoring.
This document summarizes the design, fabrication, and testing of a microfluidic chip prototype for manipulating particles using dielectrophoresis (DEP). Finite element modeling was used to simulate the electric field distributions around quadrupole and comb electrode geometries. A prototype was fabricated containing these electrode designs in two separate microchannels. Silica microspheres were successfully manipulated within the chip using positive and negative DEP sequences, concentrating particles in the electrode areas. Testing demonstrated the potential of this technique for manipulating and separating microparticles in integrated microfluidic devices.
This document summarizes research on characterizing crosstalk in dense Geiger-mode avalanche photodiode arrays. The researchers measured crosstalk probability (PCT) using different experimental setups and calculation methods. Key findings include:
1) PCT decreases with increasing pixel distance and decreases with lower bias voltages.
2) PCT increases with higher pixel capacitance, extrapolating to a value of 0.05% for a capacitance of 100fF.
3) PCT decay time was measured to be a few microseconds to investigate crosstalk origins.
Similar to Optical Absoprtion of Thin Film Semiconductors (20)
All-domain Anomaly Resolution Office Supplement to Oak Ridge National Laborat...Sérgio Sacani
In 2022, The All-domain Anomaly Resolution Office (AARO) contracted with Oak Ridge
National Laboratory (ORNL) to conduct materials testing on a magnesium (Mg) alloy specimen.
This specimen has been publicly alleged to be a component recovered from a crashed
extraterrestrial vehicle in 1947, and purportedly exhibits extraordinary properties, such as
functioning as a terahertz waveguide to generate antigravity capabilities. In April 2024, ORNL
produced a summary of findings documenting the laboratory’s methodology to assess this
specimen’s elemental and structural characteristics, available on AARO’s website.
ORNL assessed this specimen to be terrestrial in origin and that it does not meet the theoretical
requirements to function as a terahertz (THz) waveguide. AARO concurs with ORNL’s
assessment and provides this supplementary material to add historical context to account for its
likely origin. The specimen’s characteristics are consistent with Mg alloy research and
development projects and experimental manufacturing methods in the mid-20th century.
Complementary interstellar detections from the heliotailSérgio Sacani
The heliosphere is a protective shield around the solar system created by the Sun’s interaction with the local interstellar medium (LISM) through the solar wind, transients, and interplanetary magnetic field. The shape of the heliosphere is directly linked with interactions with the surrounding LISM, in turn affecting the space environment within the heliosphere. Understanding the shape of the heliosphere, the LISM properties, and their interactions is critical for understanding the impacts within the solar system and for understanding other astrospheres. Understanding the shape of the heliosphere requires an understanding of the heliotail, as the shape is highly dependent upon the heliotail and its LISM interactions. The heliotail additionally presents an opportunity for more direct in situ measurement of interstellar particles from within the heliosphere, given the likelihood of magnetic reconnection and turbulent mixing between the LISM and the heliotail. Measurements in the heliotail should be made of pickup ions, energetic neutral atoms, low energy neutrals, and cosmic rays, as well as interstellar ions that may be injected into the heliosphere through processes such as magnetic reconnection, which can create a direct magnetic link from the LISM into the heliosphere. The Interstellar Probe mission is an ideal opportunity for measurement either along a trajectory passing through the heliotail, via the flank, or by use of a pair of spacecraft that explore the heliosphere both tailward and noseward to yield a more complete picture of the shape of the heliosphere and to help us better understand its interactions with the LISM.
Detection of the elusive dangling OH ice features at ~2.7 μm in Chamaeleon I ...Sérgio Sacani
Ascertaining the morphology and composition of the icy mantles covering
dust grains in dense, cold regions of the interstellar medium is essential to
developing accurate astrochemical models, determining conditions for
ice formation, constraining chemical interactions in and on icy grains and
understanding how ices withstand space radiation. The widely observed
infrared spectroscopic signature of H2O ice at ~3 μm discriminates crystalline
from amorphous structures in interstellar ices. Weaker bands seen only in
laboratory ice spectra at ~2.7 μm, termed ‘dangling OH’ (dOH), are attributed
to water molecules not fully bound to neighbouring water molecules and
are often considered as tracing the degree of ice compaction. We exploit
the high sensitivity of JWST NIRCam to detect two dOH features at 2.703 and
2.753 μm along multiple lines of sight probing the dense cloud Chamaeleon
I, attributing these signatures to unbound dOH in cold water ice and dOH in
interaction with other molecular species. These detections open a path to
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AlgaeBrew project - Unlocking the potential of microalgae for the valorisation of brewery waste products into omega-3 rich animal feed and fertilisers
Carmen Gabriela Constantin, University of Agronomic Sciences and Veterinary Medicine (USAMV), Romania
atom, elements, molecule and compounds in telugu.pptxManjulaVani3
Classification of Matter
Matter can be classified into pure substances and mixtures:
Pure Substances
Elements: Consist of only one type of atom (e.g., Iron (Fe), Nitrogen (N2)).
Compounds: Consist of two or more types of atoms chemically bonded in a fixed ratio (e.g., Water (H2O), Carbon dioxide (CO2)).
Mixtures
Homogeneous Mixtures (Solutions): Uniform composition throughout (e.g., Saltwater, Air).
Heterogeneous Mixtures: Non-uniform composition, components are distinguishable (e.g., Salad, Sand and iron filings).
Atom
Definition: The smallest unit of matter that retains the identity of a chemical element. Example: A single helium atom.Element
Definition: A pure substance consisting of only one type of atom, distinguished by its atomic number (the number of protons in the nucleus).Example: Oxygen (02)Molecule
Definition: Two or more atoms chemically bonded together. Molecules can consist of atoms of the same element or different elements.
Types:
Diatomic Molecules: Two atoms, either of the same element (e.g., 02)or different elements (e.g.,
CO).
Polyatomic Molecules: More than two atoms
Example: Water (H2O), Carbon dioxide (CO2). Compound
Definition: A substance formed when two or more different types of atoms chemically bond in a fixed ratio.
Properties: Compounds have properties different from their constituent elements.
Example: Sodium chloride (NaCl), Glucose (C6H12O6).
•
A hot-Jupiter progenitor on a super-eccentric retrograde orbitSérgio Sacani
Giant exoplanets orbiting close to their host stars are unlikely to have formed in
their present confgurations1
. These ‘hot Jupiter’ planets are instead thought to have
migrated inward from beyond the ice line and several viable migration channels
have been proposed, including eccentricity excitation through angular-momentum
exchange with a third body followed by tidally driven orbital circularization2,3
. The
discovery of the extremely eccentric (e = 0.93) giant exoplanet HD 80606 b (ref. 4)
provided observational evidence that hot Jupiters may have formed through
this high-eccentricity tidal-migration pathway5
. However, no similar hot-Jupiter
progenitors have been found and simulations predict that one factor afecting the
efcacy of this mechanism is exoplanet mass, as low-mass planets are more likely to
be tidally disrupted during periastron passage6–8
. Here we present spectroscopic and
photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter
with an extreme orbital eccentricity of e = 0.94. The orbit of TIC 241249530 b is
consistent with a history of eccentricity oscillations and a future tidal circularization
trajectory. Our analysis of the mass and eccentricity distributions of the transitingwarm-Jupiter population further reveals a correlation between high mass and high
eccentricity.
Speed-accuracy trade-off for the diffusion modelssosukeito
The presentation of Frontiers in Nonequilibrium Physics at YITP about the preprint https://arxiv.org/abs/2407.04495.
Thermodynamic trade-off between the accuracy of the data generation and the diffusion speed for the diffusion models. We show thermodynamically that the optimal transport provides the most accurate data generation.
Types of Hypersensitivity Reactions.pptxIsha Pandey
Hypersensitivity as an immunological dysfunction is defined as exaggerated or inappropriate response of the immune system. Hypersensitivity can be classified into four types; namely, type I (Immediate), type II (antibody-mediated), type III (immune complex-mediated), and type IV (cell-mediated or delayed-type) hypersensitivity.
Type I hypersensitivity or allergy, the most common immune disorder, is mainly mediated by immunoglobulin (Ig)E and mast cells. It can cause anaphylaxis, food allergy, and asthma.
Type II hypersensitivity can lead to tissue damage by three main mechanisms: (1) direct cellular destruction (e.g., autoimmune hemolytic anemia and immune thrombocytopenia, (2) inflammation (e.g., Goodpasture's syndrome and acute rheumatic fever), and (3) disrupting cellular function (e.g., myasthenia gravis and Graves’ disease).
Type III hypersensitivity is caused by excess production of immune complexes or impaired clearance of them and includes serum sickness, systemic lupus erythematosus, and post-streptococcal glomerulonephritis.
Type IV hypersensitivity is mediated by T cells and macrophages, causing diseases like multiple sclerosis and rheumatoid arthritis.
Introduction to Space (Our Solar System)vanshgarg8002
Space is tremendous, apparently endless span that exists past earth and its environment. It is a locale up with endless heavenly bodies,
including stars, planets, moons, space rocks, and comets, all represented by the gravity. Space investigation has extended how we might interpret the universe, uncovering the excellence and intricacy of far off cosmic system, the secret of dark openings, and the potential for life past our planet. An outskirts keeps of motivating interest, logical request, and a feeling of marvel about our spot in the universe. Space is immense, largely unexplored expanse beyond Earth's atmosphere, home to countless celestial bodies likes stars, planets, and asteroids. Human exploration began with the launch of Sputnik in 1957 followed by significant achievements such as the Moon landing in 1969.
Burn child health Nursing 3rd year presentation..pptx
Optical Absoprtion of Thin Film Semiconductors
1. UNAM Instituto de Energ´ıas Renovables
Universidad Nacional
Aut´onoma de M´exico
Instituto de Energ´ıas Renovables
Semiconductores
Optical properties of thin film semiconductors
Autores:
Castro Grespan Enrico
Profesor:
Dr. Karunakaran Nair Padmanabhan
Pankajakshy
Temixco, Morelos, M´exico
18 de abril del 2017
IER Semiconductores 1
3. UNAM Instituto de Energ´ıas Renovables
1 Introduction
Band gap is one of the most important concepts that has to be clear to develop solar cells. In a
nutshell band gap is the minimum amont of energy required for an electron to jump to a state with
higher energy. To excite an electron that is stuck in its bound state into a free one, energy is requiered,
in this new state the electron can participate in conduction. When the energy of a photon is equal
to or greater than the band gap of the material, the photon is absorbed by the material and excites
an electron into the conduction band. A pair hole-electron is formed a photon is absorbed. The
generation of charge carriers by photons is the basis of the photovoltaic production of energy.
A photon is characterized by either a wavelength, denoted by λ or equivalently an energy, denoted
by E. There is an inverse relationship between the energy of a photon (E) and the wavelength of the
light (λ) given by the Eq.(1)
E =
hc
λ
(1)
where h is Planck’s constant and c is the light velocity.
h = 6.626 × 10−34
J s
c = 2.998 × 108
m/s
It can be demostrated by substituting those constants and converting Joules in electronvolts that
Eq.(1) can be written as
E(eV ) =
1240
λ(nm)
(2)
Optical absorption can be defined has the process where the energy of a photon is removed or
stole by matter, more precisely the electrons of an atom. The absorption coefficient determines how
far into a material light of a particular wavelength can penetrate before it is absorbed. Semiconductor
materials have a sharp edge in their absorption coefficient, since light which has energy below the band
gap does not have sufficient energy to excite an electron into the conduction band from the valence
band.
In order to calculate the optical absorption of a certain material, measurements of optical trans-
mittance and reflectance are needed. As we can see in Fig.(1) by measuring the transmittance and the
reflectance, in a sample with ceratin composition, it is possible to calculate the absorptance according
to the following.
A(λ) = 1 − (Tλ + Rλ)
IER Semiconductores 3
4. UNAM Instituto de Energ´ıas Renovables
Figure 1: Diagram of the optical processes in a thin film.
As it is known solar cells are complex devices, the semiconductors that are used need to have a
substrate and elements to collect the free carriers. There are a couple of ways to do that; one way is
using metal contacts as in common silicion solar cells and other is with Transparent Conductive Oxides
(TCO). Since these materials are on top of our semiconductor film, the need to know the transmission,
reflection and absorption is requiered. In this work we analyse Tec7 and Tec15 as well as the normal
substrate glasses. Likewise, with those values and the solar spectral irradiance is possible to estimate
the amount of power per unit area that goes through our film, as well as the amount that gets reflected
in each region.
2 Characterization
In thin films the absorption coefficient (α) can be yield from Eq.(3) obtained by doing the analysis of
the transmittion and considering multiple reflections within the thin film, that obeys Beer-Lambert
law, in a film with thickness d.
T(λ) =
(1 − Rλ)2e−αλd
1 − R2
λe−2αλd
(3)
α =
1
d
ln
(1 − R)2 + (1 − R)2 + 4RT2
2T
(4)
Another important parameter is photon flux; which determines the number of photons that interact
with the material generating free electrons, and hence the current produced by the solar cell. This
parameter does not have the information about the energy (or wavelength) of the photons. The
solar photon flux can be calculated using Eq.(5) in order to estimate the photon flux s−1m−2 by a
semiconductor with bandgap Eg.
Nph(λ) =
Iλ
Eλq
(5)
Furthermore, by knowing the number of photons with enough energy to excites an electron into
the conduction band (those with energy greater than the band gap). By applying Eq.(6) the upper
limit of the shortcircuit current density can be estimated for each semiconductor.
Nph × q (6)
IER Semiconductores 4
5. UNAM Instituto de Energ´ıas Renovables
3 Results and discussion
According to Eq.(4) the thickness of the films is needed to calculate the value of the absorption
coefficient. A profilometer is used, in this work, to obtein those measurements; these instruments
measure surfaces profile. A reference, for example, the substrate, works as the step up or down.
However this devices are not very precise. Nevertheless thickness can also be estimated using Eq.(7)
which needs the wavelength of two adjascent maxima of our transmittance measurements that will be
discussed later on.
d =
λ1 λ2
2 n(λ1 − λ2)
(7)
Thickness (nm)
Sample Measure Calculated
CdS 55 min 80 105
CdS 90 min 182 266
Sb2S − S3 250◦C 188 n.d
Sb2S − S3 270◦C 140 n.d
Tec15 200 n.d
Optical transmittance (T) and specular reflectance (R, measured at an angle of incidence of 5◦)
spectra of the films were measured in the cell structure using 3101PC Shimadzu UV-VIS-NIR spec-
trophotometer. For the CdS samples remove the film from one side is required. With these measure-
ments it is possible, using the solar spectral irradiance, calculate the amount of light that is transmited
or reflected and also; estimate the number of photons that are absorbed in each film. Eq.(??) give us
the power per square meter that is transmitted through the film in the UV region; Similarly for the
reflectance Eq.(??) and for other spectral regions Eq.(?? - ??).
380 nm
λ=300 nm
Iλ Tλ ∆λ (8)
380 nm
λ=300 nm
Iλ Rλ ∆λ (9)
780 nm
λ=380 nm
Iλ Tλ ∆λ (10)
780 nm
λ=380 nm
Iλ Rλ ∆λ (11)
4000 nm
λ=780 nm
Iλ Tλ ∆λ (12)
4000 nm
λ=780 nm
Iλ Rλ ∆λ (13)
Weighing those values with the solar radiation, as shown in Eq.(14 and 15), the percentage of
radiation transmitted and reflected are calculated.
Tvis = 100 ×
780 nm
λ=380 nm
Iλ Tλ ∆λ
780
λ=380
Iλ ∆λ
(14)
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Rvis = 100 ×
780 nm
λ=380 nm
Iλ Rλ ∆λ
780 nm
λ=380 nm
Iλ ∆λ
(15)
3.1 CdS 55 min
Region % Transmitted % Reflected % Absorbed
UV 14.17 5.23 80.6
Vis 69.85 11.94 18.21
NIR 72.60 21.43 5.97
Photon flux s−1m−2 for CdS 55 min, with a Eg = 2.84 eV , is 1.984 × 1020 which is 3.83% of the
available resource. Short circuit current density equal to 3.178 mA/cm2
R
T
500 1000 1500 2000
20
40
60
80
CdS55min
wavelength (nm)
%
Figure 2: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plots for
CdS deposited at 80◦C during 55 min from a
chemical bath containing cadmium-citrate com-
plex.
A
T+R
500 1000 1500 2000
20
40
60
80
100
CdS55min
wavelength (nm)
%
Figure 3: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plots for CdS deposited at 80◦C
during 55 min from a chemical bath containing
cadmium-citrate complex.
3.2 CdS 90 min
Region % Transmitted % Reflected % Absorbed
UV 0.43 5.20 94.37
Vis 52.26 14.75 32.99
NIR 76.40 14.21 9.39
Photon flux s−1m−2 for CdS 90 min, with a Eg = 2.47 eV , is 4.596 × 1020 which is 8.87% of the
available resource. Short circuit current density equal to 7.363 mA/cm2
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2.0 2.5 3.0 3.5 4.0 4.5 5.0
Energy (eV)
200000
400000
600000
800000
1×106
α/cm-1
CdS55min
Figure 4: Absorption coefficient (α) corrected by a T + R = 0.93 versus wavelength plots for CdS
deposited at 80oC during 55 min from a chemical bath containing cadmium-citrate complex.
R
T
500 1000 1500 2000
20
40
60
80
100
CdS90min
wavelength (nm)
%
Figure 5: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plots for
CdS deposited at 80oC during 90 min from a chem-
ical bath containing cadmium-citrate complex.
T+R
A
0 500 1000 1500 2000
20
40
60
80
100
CdS90min
wavelength (nm)
%
Figure 6: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plots for CdS deposited at 80oC
during 90 min from a chemical bath containing
cadmium-citrate complex.
3.3 Sb-S-Se 250 o
C
Region % Transmitted % Reflected % Absorbed
UV 0.00 49.94 50.06
Vis 0.77 51.80 47.43
NIR 41.74 46.50 11.76
Photon flux s−1m−2 for SbSSe3 at 250oC, with a Eg = 1.33 eV , is 9.461 × 1020 which is 18.25%
of the available resource. Short circuit current density equal to 15.156 mA/cm2
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2.0 2.5 3.0 3.5 4.0
Energy (eV)
50000
100000
150000
200000
α/cm-1
CdS90min
Figure 7: Absorption coefficient (α) corrected by a T + R = 0.93 versus wavelength plots for CdS
deposited at 80oC during 90 min from a chemical bath containing cadmium-citrate complex.
RT
0 500 1000 1500 2000
20
40
60
80
100
Sb-S-Se 250ºC
wavelength (nm)
%
Figure 8: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plots for
Sb-S-Se film deposited at 250oC by thermal evap-
oration.
A
T+R
0 500 1000 1500 2000
20
40
60
80
100
Sb-S-Se 250ºC
wavelength (nm)
%
Figure 9: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plots for Sb-S-Se film deposited
at 250◦C by thermal evaporation.
3.4 Sb-S-Se 270 o
C
Region % Transmitted % Reflected % Absorbed
UV 0.00 49.98 50.02
Vis 0.38 51.44 48.18
NIR 32.62 48.49 18.89
Photon flux s−1m−2 for SbSSe3 at 270◦C, with a Eg = 1.4 eV ,is 1.034 × 1021 which is 19.95% of
the available resource. Short circuit current density equal to 24.23 mA/cm2
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1.0 1.5 2.0 2.5 3.0
Energy (eV)
100000
200000
300000
400000
500000
600000
α/cm-1
Sb-S-Se 250ºC
Figure 10: Absorption coefficient (α) versus wavelength plot for Sb-S-Se film deposited at 250◦C by
thermal evaporation.
T
R
500 1000 1500 2000
20
40
60
80
100
Sb-S-Se 270ºC
wavelength (nm)
%
Figure 11: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plot for
Sb-S-Se film deposited at 270◦C by thermal evap-
oration.
A
T+R
500 1000 1500 2000
20
40
60
80
100
Sb-S-Se 270ºC
wavelength (nm)
%
Figure 12: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plot for Sb-S-Se film deposited
at 270◦C by thermal evaporation.
3.5 Tec 7
The table show the result of the analyzed data to see which light is able to surpass Tec 7 film and
reach the semiconductor material.
Region % Transmitted % Reflected % Absorbed
UV 3.01 0.65 96.34
Vis 61.46 4.98 33.56
NIR 62.19 6.76 31.05
For the conductive films we measure optical tranittance and reflectance to also calculate absorption.
Absorption coefficient in this cases is not needed.
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1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
Energy (eV)
5.0×106
1.0×107
1.5×107
2.0×107
2.5×107
3.0×107
α/cm-1
Sb-S-Se 250ºC
Figure 13: Absorption coefficient (α) versus wavelength plot for Sb-S-Se film deposited at 270◦C by
thermal evaporation.
R
T
500 1000 1500 2000
20
40
60
80
100
Tec 7
wavelength (nm)
%
Figure 14: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plot for
Tec 7 film.
A
T+R
500 1000 1500 2000
20
40
60
80
100
Tec 7
wavelength (nm)
%
Figure 15: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plot for Tec 7 film.
3.6 Tec 15
Region % Transmitted % Reflected % Absorbed
UV 2.34 9.40 88.26
Vis 74.79 12.48 12.73
NIR 61.76 11.55 26.69
With the data shown in the table for Tec 15 and the previous one for Tec 7, we can conclude that
UV light can not reach the absorber film but this tecnologies present good transmission mostly in the
visible spectrum.
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T
R
500 1000 1500 2000
20
40
60
80
100
Tec 15
wavelength (nm)
%
Figure 16: Optical transmittance (T) in blue and
reflectance (R) in red versus wavelength plot for
Tec 15 film.
T+R
A
0 500 1000 1500 2000
20
40
60
80
100
Tec 15
wavelength (nm)
%
Figure 17: Optical transmittance (T) plus re-
flectance (R) in pink and absorption (A) in green
versus wavelength plot for Tec 15 film.
3.7 Glass 2.5 mm
Region % Transmitted % Reflected % Absorbed
UV 8.59 6.32 85.09
Vis 89.07 9.47 1.46
NIR 85.24 8.21 6.55
For the Corning Glass, the values are close to the TCO wich is precise for solar applications.
R
T
500 1000 1500 2000
20
40
60
80
100
Vidrio 2.5 mm
wavelength (nm)
%
Figure 18: Optical transmittance (T) in blue and
reflectance (T) in red versus wavelength plot for
2.5 mm glass.
A
T+R
500 1000 1500 2000
20
40
60
80
100
Vidrio 2.5 mm
wavelength (nm)
%
Figure 19: Optical transmittance (T) plus re-
flectance (R) in pink and absortion (A) in green
versus wavelength plot for 2.5 mm glass.
4 Conclusions
We analyzed the optical response of the elements that compound a antimony sulfide-selenide solar
cell. Through simple calculations we arrived at shortcircuit current values by optical measurements
and applying the concepts reviewed in lectures. As we can observed not all the photons form the sun
create free electron and not only because of their energy, also as a result of the layer on top of our
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absorber material as it is the conductive glass and the CdS film. There is a balance to be made to
yield the best results becuase thickness control band gap of the CdS but also result in a change of
the absorption. Further analyses need to be done in order to see why different temperatures in the
Sb-S-Se films give us different band gaps.
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