Microanalysis in Science and Engineering – Electron Microscopy

فهرست عناوین اصلی در این پاورپوینت

فهرست عناوین اصلی در این پاورپوینت

● Microanalysis in Science and Engineering – Electron Microscopy
● What will we learn
● What is electron microscopy?
● I’ve heard other terms used…
● How are electrons generate?
● Thermionic emissions
● Electron flux (current density)
● Field emissions
● The requirement of high vacuum
● Focusing a beam of electrons
● How does the e- beam interact with matter?
● Learning about secondary electrons.
● Learning about electron interactions
● Inelastic emissions
● How is a secondary image generated?
● Elastic collisions
● Detecting BS electrons
● What are some unique properties of BS electrons?
● Summary
● Some web links

نوع زبان: انگلیسی حجم: 0.81 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 21 صفحه
سطح مطلب: نامشخص پسوند فایل: ppt
گروه موضوعی: زمان استخراج مطلب: 2019/05/10 01:26:06

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عبارات مهم استفاده شده در این مطلب

عبارات مهم استفاده شده در این مطلب

electron, ., sem, http, secondary, curriculum, lecturecw, emal, emalwww.engin.umich.edu, course, emission, collision,

توجه: این مطلب در تاریخ 2019/05/10 01:26:06 به صورت خودکار از فضای وب آشکار توسط موتور جستجوی پاورپوینت جمع آوری شده است و در صورت اعلام عدم رضایت تهیه کننده ی آن، طبق قوانین سایت از روی وب گاه حذف خواهد شد. این مطلب از وب سایت زیر استخراج شده است و مسئولیت انتشار آن با منبع اصلی است.

http://www.cae.tntech.edu/~jbiernacki/electronmicroscopy.ppt

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عبارات پرتکرار و مهم در این اسلاید عبارتند از: electron, ., sem, http, secondary, curriculum, lecturecw, emal, emalwww.engin.umich.edu, course, emission, collision,

مشاهده محتوای متنیِ این اسلاید ppt

مشاهده محتوای متنیِ این اسلاید ppt

microanalysis in science and engineering electron microscopy a workshop for middle and high school teachers sponsored by tennessee technological university center for manufacturing research departments of chemical mechanical earth sciences and curriculum and instruction and the national science foundation faculty joseph j. biernacki chemical engineering june ۱۶ ۲ ۳ what will we learn what is electron microscopy how are electrons generated how are electrons focused how do electrons interact with matter how are the electron matter interactions used to generate images what linkages can be made between the technology fundamentals and the middle high school science curriculum what is electron microscopy electron microscopy is an imaging technology that uses the properties of electrons rather than light. a bit of history von ardenne ۱۹۳۸ – earliest recognizable work describing scanning electron microscope sem zworykin hillier and snyder ۱۹۴۲ – basis for modern sem cambridge scientific instruments ۱۹۶۵ – introduction of first commercial instrument http mse.iastate.edu microscopy path.html http mse.iastate.edu microscopy elementary.html i’ve heard other terms used… electron probe microanalyzer epma an electron probe microanalyzer utilizes x rays emitted due to electron bombardment to obtain qualitative and quantitative microanalysis. electron microprobe same as epma transmission electron microscope tem uses transmitted electrons instead of emitted electrons. scanning transmission electron microscope stem combines aspects of both sem and tem. environmental scanning electron microscope esem similar to a sem but does not require the high vacuum. scanning auger microscope sam similar to an sem only it uses auger electron emissions instead of secondary electron emissions for imaging and compositional analysis. http emalwww.engin.umich.edu emal courses sem lecturecw sem microscopes.html how are electrons generate thermionic emission tungsten w filament lanthanum hexaboride lab۶ filament field emission the amount of electrons flux or current density determines resolution. the size of the electron beam spot size determines resolution. http mse.iastate.edu microscopy source.html thermionic emissions electrons will escape from heated metals when the thermal energy of the electron is greater than the work function. ef lowest free energy state highest free energy state fermi level e ew recall that the work function is the amount of energy required to remove an electron from its highest free energy state to infinity. ew e ef suggested curriculum links chemistry and physics work function electron flux current density current density act۲e ew kt ac a constant that depends on the material to increase the current density at constant t either ac must increase of ew must decrease. material ew ev w ۴.۵ lab۶ ۲.۴ suggested curriculum links physics current density flux concept field emissions suggested curriculum links physics e field near a sharp object electron tunneling effect an extremely high field is produced at the sharp tip of the cathode. this reduces the potential barrier and permits electrons to tunnel out. benjamin franklin discovered that static discharges are attracted to the sharp tip of a conductor. he used this phenomena to invent the lightning rod which he gave as his gift to the world. the requirement of high vacuum electrons have extremely low mass ~۱ ۱ that of a proton and easily give up their energy in collisions with gas atoms and molecules. sem technology is not possible without a high vacuum in at least the source and focusing column of the machine. column vacuum ~۱ ۷ torr sample chamber vacuum ~ ۱ ۵ torr esem technology permits sample chamber vacuum ~ ۲ torr suggested curriculum links chemistry and physics absolute and relative pressure scales focusing a beam of electrons a magnetic field exerts a force perpendicular to the plane formed by the vector velocity and the magnetic field vector. suggested curriculum links physics force on a moving charged particle in an b field http mse.iastate.edu microscopy electro lens.html http mse.iastate.edu microscopy path۲.html http emalwww.engin.umich.edu emal courses sem lecturecw sem focus.html how does the e beam interact with matter incident electrons interact with matter in two ways elastic collisions inelastic collisions from these interactions information regarding shape composition crystal structure electronic structure internal electric or magnetic fields … http mse.iastate.edu microscopy beaminteractions.html http emalwww.engin.umich.edu emal courses sem lecturecw sem interaction.html suggested curriculum links chemistry and physics kinetic theory collision dynamics probability flux concept q collision cross section probability n num of collisions unit volume nt number of targets unit volume ni number of incident particles unit area flux http biology.udayton.edu sem principle ۲ imaging.htm learning about secondary electrons. use the internet page below and any other web based resource available to you and what you have learned thus far to answer the following questions about secondary electrons do secondary electrons originate only from the sample surface what is the kinetic energy of secondary electrons what type of interaction produces a secondary electron what type of information can be obtained from secondary electron emissions why is secondary electron emission independent of atomic number http emalwww.engin.umich.edu emal courses sem lecturecw sem se۱.html learning about electron interactions download the software below and use it to answer the following questions what affect does atomic weight have on the interaction volume what is the nominal shape of the interaction volume what affect does beam voltage have on the interaction volume design a computational experiment to answer each question. state your design briefly one or two sentences with a table etc. be prepared to present your results in some understandable form. casino a software for performing monte carlo simulation of electron matter interactions. inelastic emissions inelastic interactions result in a wide variety of emissions secondary electrons characteristic x rays bremsstarahlung continuum x rays cathodluminescence radiation ir uv and visible light how is a secondary image generated emitted electrons are not assembled by the electron microscope in the way that light visible photons are assembled by the human eye. light reflecting from a given spot enters the eye. many points of such reflected light are assembled in a pattern on the eye that exactly mimics the reflecting source. this is not the case for electrons in the electron microscope. suggested curriculum links physics electrostatic phenomena http emalwww.engin.umich.edu emal courses sem lecturecw sem basics۲.html how is a secondary image generated secondary electrons are generated by the interaction of the incident electron beam and the sample. the secondary electrons emerge at all angles. these electrons gathered by electrostatically attracting them to the detector. knowing both the intensity of secondary electrons emitted and position of the beam an image is constructed electronically. http emalwww.engin.umich.edu emal courses sem lecturecw sem se۲.html http emalwww.engin.umich.edu emal courses sem lecturecw sem basics۳.html http emalwww.engin.umich.edu emal courses sem lecturecw sem basics۱.html suggested curriculum links across the curriculum computers and information processing elastic collisions elastic collisions produce backscattered electrons bs . http emalwww.engin.umich.edu emal courses sem lecturecw sem bse۱.html http emalwww.engin.umich.edu emal courses sem lecturecw sem bse۲.html http emalwww.engin.umich.edu emal courses sem lecturecw sem bse۳.html in elastic scattering ei~ eo. the elastic collision is with the nuclei of an atom partly obscured by the electron cloud. suggested curriculum links chemistry and physics kinetic theory collision dynamics z the atomic number e electron energy kev fo scattering …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: electron, ., sem, http, secondary, curriculum, lecturecw, emal, emalwww.engin.umich.edu, course, emission, collision,

این فایل پاورپوینت شامل 21 اسلاید و به زبان انگلیسی و حجم آن 0.81 مگا بایت است. نوع قالب فایل ppt بوده که با این لینک قابل دانلود است. این مطلب برگرفته از سایت زیر است و مسئولیت انتشار آن با منبع اصلی می باشد که در تاریخ 2019/05/10 01:26:06 استخراج شده است.

http://www.cae.tntech.edu/~jbiernacki/electronmicroscopy.ppt

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