Qhov zoo ntawm electron microscopy tshaj optical microscopy
Lub tshuab ntsuas hluav taws xob yog ib qho cuab yeej uas siv cov kab hluav taws xob thiab cov khoom siv hluav taws xob tsis siv lub teeb ci thiab lub teeb pom kev zoo raws li cov hauv paus ntsiab lus ntawm electron optics kom pom cov qauv zoo ntawm cov teeb meem loj heev.
Kev daws lub zog ntawm lub tshuab ntsuas hluav taws xob yog qhia los ntawm qhov deb me me ntawm ob lub ntsiab lus uas nws tuaj yeem daws tau. Hauv xyoo 1970s, qhov kev daws teeb meem ntawm kev xa hluav taws xob tshuab hluav taws xob yog li ntawm 0.3 nanometers (qhov kev daws teeb meem ntawm tib neeg lub qhov muag yog li 0.1 millimeters). Niaj hnub no, qhov siab tshaj plaws magnification ntawm electron microscopes tshaj 3 lab lub sij hawm, thaum lub siab tshaj plaws magnification ntawm optical microscopes yog hais txog 2, 000 zaug. Yog li ntawd, atoms ntawm qee cov hlau hnyav thiab cov txheej txheem atomic lattice hauv cov pob zeb zoo nkauj tuaj yeem pom ncaj qha los ntawm electron microscopes.
Txawm hais tias qhov kev daws teeb meem ntawm electron microscopes yog qhov zoo dua li ntawm optical microscopes, electron microscopes yuav tsum tau ua haujlwm nyob rau hauv lub tshuab nqus tsev, yog li nws nyuaj rau kev soj ntsuam cov kab mob nyob, thiab irradiation ntawm cov kab hluav taws xob kuj tuaj yeem ua rau hluav taws xob puas tsuaj rau cov qauv lom. Lwm yam teeb meem, xws li kev txhim kho qhov ci ntsa iab ntawm rab phom electron thiab qhov zoo ntawm lub lens electron, kuj yuav tsum tau kawm txuas ntxiv mus.
Lub zog daws teeb meem yog qhov taw qhia tseem ceeb ntawm lub tshuab hluav taws xob hluav taws xob, uas cuam tshuam nrog qhov xwm txheej ntawm lub khob hliav qab thiab lub voj voog ntawm lub teeb hluav taws xob dhau los ntawm cov qauv. Lub wavelength ntawm pom lub teeb yog li 300 mus rau 700 nanometers, thiab lub wavelength ntawm lub electron beam muaj feem xyuam rau lub accelerating voltage. Thaum qhov nrawm nrawm yog 50 txog 100 kilovolts, lub teeb hluav taws xob hluav taws xob wavelength yog kwv yees li 0.0053 txog 0.0037 nanometers. Txij li thaum lub wavelength ntawm lub electron beam yog ntau me dua lub wavelength ntawm pom lub teeb, txawm yog hais tias lub khob hliav qab ntawm lub electron beam tsuas yog 1% ntawm cov optical microscope, qhov kev daws teeb meem ntawm electron microscope tseem nyob deb tshaj qhov ntawd. ntawm optical microscope.
Lub tshuab hluav taws xob hluav taws xob muaj peb ntu: lub lens raj, lub tshuab nqus tsev thiab lub hwj chim txee. Lub lens fwj feem ntau suav nrog cov khoom siv xws li rab phom electron, lub lens electron, tus qauv tuav, lub vijtsam fluorescent, thiab lub koob yees duab mechanism. Cov khoom no feem ntau yog sib sau ua ke rau hauv lub tog raj kheej los ntawm sab saum toj mus rau hauv qab; lub tshuab nqus tsev muaj lub tshuab nqus tsev twj tso kua mis, lub twj tso kua mis diffusion, lub tshuab nqus tsev vacuum, thiab lwm yam, thiab yog nqus los ntawm cov kav dej roj txuas nrog lub lens raj; lub hwj chim txee yog tsim los ntawm high-voltage generator, ib tug excitation tam sim no stabilizer thiab ntau yam kev hloov kho units.
Lub lens electron yog ib qho tseem ceeb ntawm lub tshuab electron microscope chim. Nws siv lub spatial electric teb los yog magnetic teb uas yog symmetrical rau lub axis ntawm lub chim los khoov lub electron trajectory mus rau lub axis los ua kom pom tseeb. Nws muaj nuj nqi zoo ib yam li cov iav convex lens kom pom cov nqaj, yog li nws hu ua electron lens. . Niaj hnub nimno electron microscopes feem ntau siv cov lo ntsiab muag electromagnetic. Cov hlau nplaum muaj zog uas tsim los ntawm qhov ruaj khov DC excitation tam sim no dhau los ntawm lub kauj nrog ncej khau tsom rau cov electrons.
Cov phom hluav taws xob yog cov khoom siv los ntawm tungsten filament kub cathode, kab sib chaws thiab cathode. Nws tuaj yeem emit thiab tsim cov kab hluav taws xob nrog lub teeb nrawm, yog li kev ruaj ntseg ntawm qhov nrawm nrawm yuav tsum tsis pub tsawg tshaj li kaum txhiab.
Electron microscopes tuaj yeem muab faib ua kis tau tus mob electron microscopes, scanning electron microscopes, reflection electron microscopes thiab emission electron microscopes raws li lawv cov qauv thiab kev siv. Cov kab hluav taws xob xa hluav taws xob feem ntau siv los soj ntsuam cov khoom siv hauv feeb uas tsis tuaj yeem paub qhov txawv ntawm cov tshuab microscopes; scanning electron microscopes feem ntau yog siv los soj ntsuam cov morphology ntawm cov khoom siv, thiab tuaj yeem ua ke nrog X-ray diffractometers lossis electron zog spectrometers los tsim cov khoom siv hluav taws xob Microprobes; emission electron microscopes yog siv rau kev kawm ntawm tus kheej-emitting electron nto.
