Yuav ua li cas electron microscope magnify cov khoom
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 cov tsom iav kho qhov muag kom pom cov qauv zoo ntawm cov khoom ntawm qhov loj heev raws li lub hauv paus ntsiab lus ntawm electron optics.
Lub zog daws teeb meem ntawm lub tshuab ntsuas hluav taws xob yog sawv cev los ntawm qhov tsawg kawg nkaus ntawm qhov sib nrug ntawm ob lub ntsiab lus uas nws tuaj yeem daws tau. Hauv xyoo 1970s, kis tau tus mob electron microscopes muaj kev daws teeb meem ntawm 0.3 nanometers (qhov kev daws teeb meem ntawm tib neeg lub qhov muag yog li 0.1 millimeters). Tam sim no qhov kev nthuav dav tshaj plaws ntawm lub tshuab ntsuas hluav taws xob ntau tshaj 3 lab lub sijhawm, thaum qhov siab tshaj plaws ntawm lub tshuab ntsuas qhov muag yog li 2000 lub sijhawm, yog li cov atoms ntawm qee cov hlau hnyav thiab cov txheej txheem atomic lattices hauv cov siv lead ua tuaj yeem pom ncaj qha los ntawm electron microscope. .
Nyob rau hauv 1931, Knorr-Bremse thiab Ruska ntawm lub teb chaws Yelemees refitted ib tug high-voltage oscilloscope nrog ib tug txias cathode tawm electron qhov chaw thiab peb electron lo ntsiab muag, thiab tau ib tug duab magnified ntau tshaj kaum zaus, uas tau lees tias muaj peev xwm ntawm electron microscope magnified imaging. Xyoo 1932, tom qab Ruska txoj kev txhim kho, kev daws teeb meem ntawm lub tshuab hluav taws xob hluav taws xob tau mus txog 50 nanometers, kwv yees li kaum npaug ntawm lub zog daws teeb meem ntawm lub tshuab ntsuas hluav taws xob nyob rau lub sijhawm ntawd, yog li lub tshuab hluav taws xob hluav taws xob pib tau txais tib neeg lub siab.
Nyob rau xyoo 1940s, Hill hauv Tebchaws Meskas tau siv lub astigmatizer los them nyiaj rau kev sib hloov asymmetry ntawm lub lens electron, uas ua rau muaj kev cuam tshuam tshiab hauv kev daws lub zog ntawm lub tshuab ntsuas hluav taws xob thiab maj mam mus txog qib niaj hnub. Nyob rau hauv Tuam Tshoj, ib tug kis tau tus mob electron microscope tau ntse tsim nyob rau hauv 1958 nrog ib tug daws teeb meem ntawm 3 nanometers, thiab nyob rau hauv 1979 muaj ib tug loj electron microscope nrog ib tug daws teeb meem ntawm 0.3 nanometers.
Txawm hais tias qhov kev daws teeb meem ntawm lub tshuab ntsuas hluav taws xob tau zoo dua li ntawm lub tshuab ntsuas qhov muag, nws tsis yooj yim rau kev soj ntsuam cov kab mob uas muaj sia nyob vim tias lub tshuab ntsuas hluav taws xob yuav tsum ua haujlwm nyob rau hauv lub tshuab nqus tsev, thiab cov irradiation ntawm electron beam kuj yuav ua rau cov qauv lom. raug puas tsuaj los ntawm hluav taws xob. Lwm yam teeb meem, xws li kev txhim kho qhov ci ntawm rab phom electron thiab qhov zoo ntawm lub lens electron, kuj yuav tsum tau kawm ntxiv.
Kev daws lub zog yog ib qho tseem ceeb qhia ntawm electron microscopy, uas muaj feem xyuam rau qhov xwm txheej ntawm lub khob hliav qab thiab lub wavelength ntawm lub teeb hluav taws xob hla ntawm cov qauv. Lub wavelength ntawm pom lub teeb yog hais txog {{0}}} nanometers, thaum lub wavelength ntawm electron beams muaj feem xyuam rau lub accelerating voltage. Thaum qhov ntsuas hluav taws xob nrawm yog 50-100 kV, lub teeb hluav taws xob hluav taws xob wavelength yog li 0.0053-0.0037 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 feem pua ntawm cov optical microscope, lub zog daws teeb meem ntawm lub electron microscope tseem nyob deb superior rau qhov ntawd. ntawm optical microscope.
Electron microscope muaj peb ntu: lub lens chim, lub tshuab nqus tsev thiab lub hwj huam mov. Lub lens fwj feem ntau suav nrog cov phom hluav taws xob, cov khoom siv hluav taws xob, cov qauv tuav, cov ntxaij fluorescent, thiab lub koob yees duab mechanisms. Cov khoom no feem ntau yog sib sau ua ke rau hauv ib kem ntawm sab saum toj mus rau hauv qab; Lub tshuab nqus tsev yog tsim los ntawm cov tshuab nqus tsev twj, diffusion twj, thiab lub tshuab nqus tsev vacuum. Lub raj xa hluav taws xob txuas nrog lub lens chim; 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 qhov tseem ceeb tshaj plaws ntawm electron microscope lens chim. Nws siv qhov chaw hluav taws xob hauv qhov chaw lossis qhov chaw sib nqus sib nqus mus rau lub axis ntawm lub lens chim kom khoov cov electron khiav mus rau 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 electromagnetic lo ntsiab muag, uas tsom electrons los ntawm ib tug muaj zog magnetic teb generated los ntawm ib tug ruaj khov DC excitation tam sim no dhau los ntawm ib tug coil nrog ncej khau.
Cov phom hluav taws xob yog ib qho khoom siv uas muaj tungsten filament kub cathode, kab sib chaws thiab cathode. Nws tuaj yeem tawm thiab tsim cov kab hluav taws xob nrog lub teeb nrawm, yog li qhov 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. Kev xa hluav taws xob tshuab hluav taws xob feem ntau siv los saib xyuas cov khoom siv zoo uas tsis tuaj yeem daws tau los 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 hluav taws xob Microprobes rau cov khoom siv tshuaj ntsuam xyuas; emission electron microscopy rau kev kawm ntawm tus kheej-emitting electron nto.
Lub tshuab hluav taws xob xa hluav taws xob muaj npe tom qab lub teeb hluav taws xob nkag mus rau cov qauv thiab tom qab ntawd nthuav cov duab nrog lub lens electron. Nws txoj kev kho qhov muag zoo ib yam li lub tshuab kho qhov muag. Hauv hom electron microscope no, qhov sib piv hauv cov duab nthuav dav yog tsim los ntawm kev tawg ntawm cov kab hluav taws xob los ntawm cov atoms ntawm cov qauv. Lub thinner los yog qis-density ib feem ntawm cov qauv muaj tsawg dua electron beam tawg, yog li ntawd cov electrons ntau dhau los ntawm lub hom phiaj diaphragm thiab koom rau hauv cov duab, thiab zoo li brighter hauv daim duab. Conversely, thicker los yog denser qhov chaw ntawm cov qauv tshwm darker nyob rau hauv daim duab. Yog hais tias tus qauv yog tuab heev los yog tuab heev, qhov sib piv ntawm cov duab yuav deteriorate, los yog txawm yuav puas los yog puas los ntawm absorbing lub zog ntawm lub electron beam.
Sab saum toj ntawm kis tau tus mob electron microscope lens chim yog ib rab phom electron. Cov electrons raug tso tawm los ntawm tungsten kub cathode, thiab cov kab hluav taws xob yog tsom los ntawm thawj thiab thib ob condensers. Tom qab dhau los ntawm cov qauv, cov kab hluav taws xob tau teeb tsa rau ntawm daim iav nruab nrab los ntawm lub hom phiaj lens, thiab tom qab ntawd nthuav tawm cov kauj ruam dhau los ntawm daim iav nruab nrab thiab daim iav tsom iav, thiab tom qab ntawd muab duab rau ntawm lub vijtsam fluorescent lossis cov phaj photocoherent.
Qhov kev nthuav dav ntawm daim iav nruab nrab tuaj yeem hloov pauv tsis tu ncua los ntawm kaum tawm lub sijhawm mus rau ntau pua txhiab lub sijhawm feem ntau los ntawm kev hloov pauv ntawm qhov excitation tam sim no; los ntawm kev hloov lub focal ntev ntawm daim iav nruab nrab, cov duab electron microscopic thiab electron diffraction dluab tuaj yeem tau txais ntawm qhov me me ntawm tib cov qauv. Txhawm rau kawm cov qauv hlau tuab dua, Fab Kis Dulos Electron Optics Laboratory tau tsim lub tshuab hluav taws xob ultra-high voltage electron microscope nrog rau qhov nrawm ntawm 3500 kV. Schematic daim duab ntawm scanning electron microscope qauv
Lub teeb hluav taws xob ntawm lub tshuab hluav taws xob scanning tsis dhau los ntawm cov qauv, tab sis tsuas yog scans thiab ua rau cov khoom siv hluav taws xob thib ob nyob rau saum npoo ntawm cov qauv. Cov siv lead ua ci ntsa iab tso rau ib sab ntawm cov qauv tau txais cov khoom siv hluav taws xob thib ob, ua kom nrov nrov thiab hloov kho cov kab hluav taws xob siv hluav taws xob ntawm cov duab raj, yog li hloov qhov ci ntawm qhov screen ntawm lub raj duab. Lub deflection coil ntawm daim duab tube khaws synchronous scanning nrog lub electron beam nyob rau saum npoo ntawm cov qauv, yog li ntawd lub fluorescent screen ntawm daim duab raj tso saib cov duab topographic ntawm tus qauv nto, uas yog zoo ib yam li lub hauv paus ntsiab lus ua hauj lwm ntawm ib tug industrial TV. .
Qhov kev daws teeb meem ntawm lub tshuab ntsuas hluav taws xob ntsuas hluav taws xob feem ntau yog txiav txim siab los ntawm txoj kab uas hla ntawm lub teeb hluav taws xob ntawm cov qauv saum npoo. Qhov kev nthuav dav yog qhov piv ntawm qhov ntsuas amplitude ntawm daim duab raj mus rau qhov ntsuas amplitude ntawm tus qauv, uas tuaj yeem hloov pauv tsis tu ncua los ntawm kaum tawm mus rau ntau pua txhiab zaus. Scanning electron microscopy tsis xav tau cov qauv nyias nyias; daim duab muaj zog peb-dimensional nyhuv; nws tuaj yeem siv cov ntaub ntawv xws li cov khoom siv hluav taws xob thib ob, cov khoom siv hluav taws xob nqus, thiab X-rays tsim los ntawm kev sib cuam tshuam ntawm cov kab hluav taws xob thiab cov khoom siv los txheeb xyuas cov khoom muaj pes tsawg leeg.
Cov phom electron thiab condenser lens ntawm scanning electron microscope yog roughly tib yam li cov kis tau tus mob electron microscope, tab sis nyob rau hauv thiaj li yuav ua kom lub electron beam thinner, lub hom phiaj lens thiab ib tug astigmatizer yog ntxiv nyob rau hauv lub condenser lens, thiab ob pawg. Kev sib nrig sib txuas ntawm cov kab hluav taws xob tau teeb tsa hauv lub hom phiaj lens. coil. Cov qauv chamber hauv qab lub hom phiaj lens yog nruab nrog cov qauv theem uas tuaj yeem txav, tig thiab qaij.
