The document discusses Schottky barriers and contact resistance at metal-semiconductor junctions. Some key points:
1) A Schottky barrier forms at a metal-semiconductor junction and depends on the barrier height. The barrier height is influenced by the work functions but often does not follow predictions due to interface states.
2) Contact resistance is measured using the transmission line method, where resistance is measured across test structures with varying metal contact lengths. Specific contact resistance is calculated from these measurements.
3) Contact resistance is important to optimize in semiconductor devices and production. It is influenced by temperature and current effects at the metal-semiconductor interface.
1. Hollow waveguides present an alternative to transmission lines at microwave frequencies, as electromagnetic waves reflect from the walls of the waveguide as it travels its length.
2. A waveguide operates most efficiently within modal boundaries, where below a cutoff frequency a signal will not propagate, acting as a filter.
3. Multimode propagation results in different modes traveling at different velocities, causing pulse spreading and interference between closely following pulses.
This document discusses different types of photodetectors. It describes photoconductive detectors like light dependent resistors (LDRs) and junction photodetectors including p-n photodiodes, PIN photodiodes, avalanche photodiodes, and Schottky photodiodes. PIN photodiodes are presented as an improvement over p-n photodiodes by having a larger depletion region for higher quantum efficiency. Avalanche photodiodes provide internal gain through impact ionization. Schottky photodiodes have a high speed due to being majority carrier devices. Phototransistors are also discussed as providing gain. Applications mentioned include fiber optics, cameras, medical devices, barcodes, and security systems
The document summarizes a student group's final design project to build an automated robot to compete in a head-to-head arena style competition based on Star Wars. The group's chosen design, called Alpha, is a stationary robot that uses drawer slides for movement and various subsystems like pneumatics, strings and spools, and mousetraps to complete tasks like retrieving lightsabers, defeating walkers, and escaping the Death Star. Alternative designs considered translation-based drivetrains or gate valves for movement. The robot scored an average of 37.33 points across 3 competition rounds, placing 2nd in its class.
Laser pumping involves transferring energy from an external source into a laser's gain medium, producing excited states in the gain medium's atoms. When there are more excited atoms than unexcited atoms, population inversion occurs, allowing stimulated emission and laser amplification or lasing. Population inversion is achieved after adequate pumping. Continuous wave lasers emit light continuously while pulsed lasers emit light in optical pulses, most commonly nanosecond pulses from Q-switched lasers. Laser-tissue interaction occurs mainly through absorption, with the light energy being transformed into heat. This results in photothermal, photoablative, or photochemical effects depending on laser parameters like intensity and pulse duration.
This document discusses the use of lasers in various medical fields such as dermatology, ophthalmology, dentistry, and gastroenterology. It explains that lasers can be used through four types of tissue interactions: photochemical, photothermal, photoablative, and photomechanical. Specific laser types and their applications in procedures like photocoagulation, photodisruption, and photorefractive keratectomy are outlined. The laser delivery systems of articulated arms, fiber optics, and waveguides are also summarized.
The document discusses optical properties of semiconductors. It begins by introducing Maxwell's equations and how they describe light propagation in a medium with both bound and free electrons. The complex refractive index is then derived, which accounts for changes to the light's velocity and damping due to absorption. Reflectivity and transmission through a thin semiconductor slab are also examined. Key equations for the complex refractive index, reflectivity, and transmission through a thin slab are provided.
The document discusses Schottky barriers and contact resistance at metal-semiconductor junctions. Some key points:
1) A Schottky barrier forms at a metal-semiconductor junction and depends on the barrier height. The barrier height is influenced by the work functions but often does not follow predictions due to interface states.
2) Contact resistance is measured using the transmission line method, where resistance is measured across test structures with varying metal contact lengths. Specific contact resistance is calculated from these measurements.
3) Contact resistance is important to optimize in semiconductor devices and production. It is influenced by temperature and current effects at the metal-semiconductor interface.
1. Hollow waveguides present an alternative to transmission lines at microwave frequencies, as electromagnetic waves reflect from the walls of the waveguide as it travels its length.
2. A waveguide operates most efficiently within modal boundaries, where below a cutoff frequency a signal will not propagate, acting as a filter.
3. Multimode propagation results in different modes traveling at different velocities, causing pulse spreading and interference between closely following pulses.
This document discusses different types of photodetectors. It describes photoconductive detectors like light dependent resistors (LDRs) and junction photodetectors including p-n photodiodes, PIN photodiodes, avalanche photodiodes, and Schottky photodiodes. PIN photodiodes are presented as an improvement over p-n photodiodes by having a larger depletion region for higher quantum efficiency. Avalanche photodiodes provide internal gain through impact ionization. Schottky photodiodes have a high speed due to being majority carrier devices. Phototransistors are also discussed as providing gain. Applications mentioned include fiber optics, cameras, medical devices, barcodes, and security systems
The document summarizes a student group's final design project to build an automated robot to compete in a head-to-head arena style competition based on Star Wars. The group's chosen design, called Alpha, is a stationary robot that uses drawer slides for movement and various subsystems like pneumatics, strings and spools, and mousetraps to complete tasks like retrieving lightsabers, defeating walkers, and escaping the Death Star. Alternative designs considered translation-based drivetrains or gate valves for movement. The robot scored an average of 37.33 points across 3 competition rounds, placing 2nd in its class.
Laser pumping involves transferring energy from an external source into a laser's gain medium, producing excited states in the gain medium's atoms. When there are more excited atoms than unexcited atoms, population inversion occurs, allowing stimulated emission and laser amplification or lasing. Population inversion is achieved after adequate pumping. Continuous wave lasers emit light continuously while pulsed lasers emit light in optical pulses, most commonly nanosecond pulses from Q-switched lasers. Laser-tissue interaction occurs mainly through absorption, with the light energy being transformed into heat. This results in photothermal, photoablative, or photochemical effects depending on laser parameters like intensity and pulse duration.
This document discusses the use of lasers in various medical fields such as dermatology, ophthalmology, dentistry, and gastroenterology. It explains that lasers can be used through four types of tissue interactions: photochemical, photothermal, photoablative, and photomechanical. Specific laser types and their applications in procedures like photocoagulation, photodisruption, and photorefractive keratectomy are outlined. The laser delivery systems of articulated arms, fiber optics, and waveguides are also summarized.
The document discusses optical properties of semiconductors. It begins by introducing Maxwell's equations and how they describe light propagation in a medium with both bound and free electrons. The complex refractive index is then derived, which accounts for changes to the light's velocity and damping due to absorption. Reflectivity and transmission through a thin semiconductor slab are also examined. Key equations for the complex refractive index, reflectivity, and transmission through a thin slab are provided.
This document provides information on various topics related to magnetism and magnetic materials:
1. It discusses different types of magnetic behavior such as diamagnetism, paramagnetism, and ferromagnetism. It also discusses the properties of hard and soft magnetic materials.
2. Key magnetic parameters are defined, including magnetic permeability, susceptibility, intensity of magnetization, Curie temperature, magnetic dipole moment, magnetic flux, and relative permeability.
3. The differences between diamagnetic, paramagnetic, and ferromagnetic materials are summarized in a table comparing their behaviors and properties.
4. The document also explains hysteresis loops, hard and soft magnets, and fer
This document discusses the various medical applications of lasers. It begins by defining what a laser is and providing some basic concepts. It then outlines several uses of lasers in medicine such as ophthalmology, dermatology, cancer treatment, surgery, and more. Specific applications discussed in more detail include laser eye surgery to correct vision, using lasers to treat retinal diseases and birthmarks, laser angioplasty, laser hair removal, and laser treatments for cancer. The document also covers laser safety classifications and provides references used.
1) Microwave imaging uses electromagnetic waves in the microwave frequency range (300 MHz to 300 GHz) to evaluate hidden or embedded objects within a structure by reconstructing the distribution of electromagnetic properties like permittivity and conductivity from scattered field data.
2) The inverse problem aims to reconstruct the contrast function χ(r), which represents the difference in electromagnetic properties from a homogeneous background, based on the relationship between the measured scattered fields and χ(r).
3) The total field is calculated using Maxwell's equations and represented as the incident field, determined by the source current and Green's function, plus an additional term accounting for scattering from the contrast χ(r) integrated over the domain.
The document discusses lasers, including their history, characteristics, components, classifications, and uses. It provides details on:
- The invention of the laser by Maiman in 1960 and its influence as a technological achievement.
- The key characteristics of laser light that make it coherent, directional, and monochromatic.
- The basic components and functioning of a laser, including the active medium, excitation mechanism, and optical resonator.
- The various classes of lasers according to output levels and safety standards.
- Applications of lasers in medicine, industry, everyday life, research, and holography.
This document discusses various theories and models of light, including evidence that light behaves as both a wave and particle. It explains Young's double-slit experiment, which showed light can interfere like a wave. However, some experiments like the photoelectric effect are better explained by thinking of light as particles called photons. The document also discusses Snell's law of refraction, how light refracts when passing from one medium to another, total internal reflection, and applications of fiber optics.
The document discusses the medical applications of lasers, including how they interact with tissues and can be used to reduce inflammation, manage pain, and promote healing. It notes that lasers can subside inflammation by reducing cellular activities and physiological effects, while reducing pain through various stages. Lasers also reduce healing time by expediting the stages of tissue healing. In conclusion, the document covers the construction and uses of lasers in medical applications.
This document discusses various types of particle detectors used in high energy physics experiments. It describes semiconductor detectors, solid state detectors, ionization chambers, Geiger-Muller detectors, and photoconductive detectors. It also discusses applications of these detectors at particle physics labs like LHC, CMS, ATLAS, and SLAC. Specific detectors at the BESIII experiment are described, including the drift chamber, electromagnetic calorimeter, and muon counter. In conclusion, the document outlines how these detectors are important for solving physics problems and their applications in high energy physics.
Laser science is principally concerned with quantum electronics, laser construction, optical cavity design, the physics of producing a population inversion in laser media, and the temporal evolution of the light field in the laser. It is also concerned with the physics of laser beam propagation, particularly the physics of Gaussian beams, with laser applications, and with associated fields such as non-linear optics and quantum optics.
This document discusses microwave imaging in the electromagnetic spectrum. It provides background on the microwave band, including its wavelength range from 1 millimeter to 1 meter. The document then discusses:
1) How microwave imaging forms images using the characteristics of microwave radiation and its interaction with different materials.
2) Applications of microwave imaging such as non-destructive testing, medical imaging, concealed weapon detection, and structural health monitoring.
3) Ongoing research on microwave imaging technologies for applications like breast cancer detection, stroke detection, and concealed weapon screening.
Ion implantation of aluminum oxide (alumina) with calcium and yttrium ions results in the formation of aluminum nanoparticles. High temperature annealing or implantation causes implanted ions to precipitate out as nanocrystals by reducing the alumina matrix. Transmission electron microscopy images show particles with the lattice spacing of aluminum embedded in the alumina matrix. Energy loss spectroscopy also indicates the presence of metallic aluminum plasmon peaks, confirming the particles contain aluminum.
This document summarizes lecture notes on electromagnetic wave propagation in free space from a course on electromagnetic theory. It begins with an introduction and lists the course details. It then derives Maxwell's equations in free space and shows that they lead to wave equations for the electric and magnetic fields. It is shown that the electric and magnetic field vectors are perpendicular to each other and the propagation vector. Key concepts discussed include the Poynting vector, energy, impedance, phase velocity, wavelength, and the relation between the electric and magnetic fields. Several examples are worked through.
Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It differs from other sources of light in that it emits light coherently, which allows for a high intensity beam with low divergence. The key components are an amplifying medium that can be pumped to invert a population of atoms or molecules to higher energy levels, and an optical resonator formed by two or more mirrors to provide feedback of the light emitted from the amplifying medium. When the population inversion condition is achieved, stimulated emission produces a cascade of photons with the same phase and wavelength.
The Zeeman effect occurs when spectral lines split into multiple components in the presence of an external magnetic field. In 1896, Zeeman first observed this effect when placing a sodium light source between electromagnets. Normally, lines split into three components, but more complex splitting can occur. Later theories by Lorentz and others explained the polarization and patterns observed. Both classical and quantum mechanics can explain normal Zeeman splitting, while anomalous splitting requires quantum theory accounting for electron spin. Today, the Zeeman effect provides insights into atomic structure and is used in applications like solar magnetic field analysis.
Spectroscopy is the study of the quantized interaction of energy with the matter. In the electromagnetic spectrum, there are radiations of different energy which lead to a wide range of spectroscopy techniques like UV-Vis, Infrared, NMR etc. The spectral range from around 3.3 cm-1 to 333.6 cm-1 was mostly unexplored before 30 years and known as “terahertz gap” due to unavailability of Terahertz (THz) generators and detectors but in the last two decades, this has emerged as a field of great potential and various applications like THz imaging, chemical analysis and molecular spectroscopy, applications in biology, medicines, protein analysis and pharmaceuticals, in solid state where it can be an alternative to XRD, NMR, DSC, in radio astronomy, in environmental control, in explosive detection. The combination of all these applications falls under THz spectroscopy.
This document provides information on various topics related to magnetism and magnetic materials:
1. It discusses different types of magnetic behavior such as diamagnetism, paramagnetism, and ferromagnetism. It also discusses the properties of hard and soft magnetic materials.
2. Key magnetic parameters are defined, including magnetic permeability, susceptibility, intensity of magnetization, Curie temperature, magnetic dipole moment, magnetic flux, and relative permeability.
3. The differences between diamagnetic, paramagnetic, and ferromagnetic materials are summarized in a table comparing their behaviors and properties.
4. The document also explains hysteresis loops, hard and soft magnets, and fer
This document discusses the various medical applications of lasers. It begins by defining what a laser is and providing some basic concepts. It then outlines several uses of lasers in medicine such as ophthalmology, dermatology, cancer treatment, surgery, and more. Specific applications discussed in more detail include laser eye surgery to correct vision, using lasers to treat retinal diseases and birthmarks, laser angioplasty, laser hair removal, and laser treatments for cancer. The document also covers laser safety classifications and provides references used.
1) Microwave imaging uses electromagnetic waves in the microwave frequency range (300 MHz to 300 GHz) to evaluate hidden or embedded objects within a structure by reconstructing the distribution of electromagnetic properties like permittivity and conductivity from scattered field data.
2) The inverse problem aims to reconstruct the contrast function χ(r), which represents the difference in electromagnetic properties from a homogeneous background, based on the relationship between the measured scattered fields and χ(r).
3) The total field is calculated using Maxwell's equations and represented as the incident field, determined by the source current and Green's function, plus an additional term accounting for scattering from the contrast χ(r) integrated over the domain.
The document discusses lasers, including their history, characteristics, components, classifications, and uses. It provides details on:
- The invention of the laser by Maiman in 1960 and its influence as a technological achievement.
- The key characteristics of laser light that make it coherent, directional, and monochromatic.
- The basic components and functioning of a laser, including the active medium, excitation mechanism, and optical resonator.
- The various classes of lasers according to output levels and safety standards.
- Applications of lasers in medicine, industry, everyday life, research, and holography.
This document discusses various theories and models of light, including evidence that light behaves as both a wave and particle. It explains Young's double-slit experiment, which showed light can interfere like a wave. However, some experiments like the photoelectric effect are better explained by thinking of light as particles called photons. The document also discusses Snell's law of refraction, how light refracts when passing from one medium to another, total internal reflection, and applications of fiber optics.
The document discusses the medical applications of lasers, including how they interact with tissues and can be used to reduce inflammation, manage pain, and promote healing. It notes that lasers can subside inflammation by reducing cellular activities and physiological effects, while reducing pain through various stages. Lasers also reduce healing time by expediting the stages of tissue healing. In conclusion, the document covers the construction and uses of lasers in medical applications.
This document discusses various types of particle detectors used in high energy physics experiments. It describes semiconductor detectors, solid state detectors, ionization chambers, Geiger-Muller detectors, and photoconductive detectors. It also discusses applications of these detectors at particle physics labs like LHC, CMS, ATLAS, and SLAC. Specific detectors at the BESIII experiment are described, including the drift chamber, electromagnetic calorimeter, and muon counter. In conclusion, the document outlines how these detectors are important for solving physics problems and their applications in high energy physics.
Laser science is principally concerned with quantum electronics, laser construction, optical cavity design, the physics of producing a population inversion in laser media, and the temporal evolution of the light field in the laser. It is also concerned with the physics of laser beam propagation, particularly the physics of Gaussian beams, with laser applications, and with associated fields such as non-linear optics and quantum optics.
This document discusses microwave imaging in the electromagnetic spectrum. It provides background on the microwave band, including its wavelength range from 1 millimeter to 1 meter. The document then discusses:
1) How microwave imaging forms images using the characteristics of microwave radiation and its interaction with different materials.
2) Applications of microwave imaging such as non-destructive testing, medical imaging, concealed weapon detection, and structural health monitoring.
3) Ongoing research on microwave imaging technologies for applications like breast cancer detection, stroke detection, and concealed weapon screening.
Ion implantation of aluminum oxide (alumina) with calcium and yttrium ions results in the formation of aluminum nanoparticles. High temperature annealing or implantation causes implanted ions to precipitate out as nanocrystals by reducing the alumina matrix. Transmission electron microscopy images show particles with the lattice spacing of aluminum embedded in the alumina matrix. Energy loss spectroscopy also indicates the presence of metallic aluminum plasmon peaks, confirming the particles contain aluminum.
This document summarizes lecture notes on electromagnetic wave propagation in free space from a course on electromagnetic theory. It begins with an introduction and lists the course details. It then derives Maxwell's equations in free space and shows that they lead to wave equations for the electric and magnetic fields. It is shown that the electric and magnetic field vectors are perpendicular to each other and the propagation vector. Key concepts discussed include the Poynting vector, energy, impedance, phase velocity, wavelength, and the relation between the electric and magnetic fields. Several examples are worked through.
Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It differs from other sources of light in that it emits light coherently, which allows for a high intensity beam with low divergence. The key components are an amplifying medium that can be pumped to invert a population of atoms or molecules to higher energy levels, and an optical resonator formed by two or more mirrors to provide feedback of the light emitted from the amplifying medium. When the population inversion condition is achieved, stimulated emission produces a cascade of photons with the same phase and wavelength.
The Zeeman effect occurs when spectral lines split into multiple components in the presence of an external magnetic field. In 1896, Zeeman first observed this effect when placing a sodium light source between electromagnets. Normally, lines split into three components, but more complex splitting can occur. Later theories by Lorentz and others explained the polarization and patterns observed. Both classical and quantum mechanics can explain normal Zeeman splitting, while anomalous splitting requires quantum theory accounting for electron spin. Today, the Zeeman effect provides insights into atomic structure and is used in applications like solar magnetic field analysis.
Spectroscopy is the study of the quantized interaction of energy with the matter. In the electromagnetic spectrum, there are radiations of different energy which lead to a wide range of spectroscopy techniques like UV-Vis, Infrared, NMR etc. The spectral range from around 3.3 cm-1 to 333.6 cm-1 was mostly unexplored before 30 years and known as “terahertz gap” due to unavailability of Terahertz (THz) generators and detectors but in the last two decades, this has emerged as a field of great potential and various applications like THz imaging, chemical analysis and molecular spectroscopy, applications in biology, medicines, protein analysis and pharmaceuticals, in solid state where it can be an alternative to XRD, NMR, DSC, in radio astronomy, in environmental control, in explosive detection. The combination of all these applications falls under THz spectroscopy.
استكشاف كيمياء إمسات_ رؤية جديدة في مراقبة البيئة.pdfelmadrasah
في مجال العلوم البيئية، تكمن أهمية مراقبة الملوثات وتقييم صحة البيئة. مع تقدم التكنولوجيا، ظهرت طرق جديدة لتعزيز فهمنا وإدارتنا للتحديات البيئية. واحدة من هذه الابتكارات هي كيمياء امسات، وهي نهج مبتكر يحدث ثورة في مراقبة البيئة. يستكشف هذا المقال المبادئ والتطبيقات والأهمية لكيمياء امسات في حماية صحة كوكبنا،التسجيل للأمسات.
كثر حديث الناس عن أخطار تلوث السلع الغذائية والمشروبات ببعض مكونات المواد البلاستيكية بسبب كثرة استخدامها في صناعة عبواتها وتغليف الكثير منها، ويعزى ذلك إلى
التركيب الكيماوي المعقد للبلاستيك
تنوع المركبات المستعملة في صناعته واستخدام المركبات المضافة Additives المستعملة في تحسين صفاته
تأثير طول فترة تخزين الأغذية فيه وتاثير درجة الحرارة ورقم حموضة على لونه ودرجة تسرب بعض مكوناتها إلى السلع الغذائية والأدوية المعبأة فيه
ويؤثر بلا شك نوع البوليمر المستعمل في البلاستيك وطريقة تحضير عبواته ودرجة فاذيته للضوء على سلامة استخدامه