Qhov zoo ntawm electron microscopy piv rau optical microscopy
Txawm hais tias qhov kev daws teeb meem ntawm electron microscope yog qhov zoo dua li ntawm optical microscope, nws yog ib qho nyuaj rau kev soj ntsuam cov kab mob uas muaj sia nyob vim tias nws yuav tsum tau ua haujlwm nyob rau hauv lub tshuab nqus tsev, thiab irradiation ntawm electron beam yuav ua rau cov qauv lom neeg raug kev puas tsuaj los ntawm irradiation. Lwm yam teeb meem, xws li qhov ci ntsa iab ntawm rab phom electron thiab kev txhim kho qhov zoo ntawm lub lens electron kuj yuav tsum tau mus kawm ntxiv.
Lub zog daws teeb meem yog qhov ntsuas tseem ceeb ntawm lub tshuab hluav taws xob hluav taws xob, uas cuam tshuam nrog lub khob hliav qab ntawm qhov xwm txheej thiab wavelength ntawm lub teeb hluav taws xob 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 hluav taws xob nrawm yog 50 txog 100 kV, lub wavelength ntawm lub teeb hluav taws xob yog li 0.0053 txog 0.0037 nanometers. Raws li lub wavelength ntawm lub electron beam yog ntau me dua lub wavelength ntawm pom lub teeb, yog li txawm yog hais tias lub khob hliav qab ntawm lub electron beam tsuas yog 1% ntawm lub optical microscope, lub peev xwm daws teeb meem ntawm electron microscope tseem nyob deb zoo dua li qhov kho qhov muag. microscope.
Electron microscope muaj peb ntu: daim iav raj, lub tshuab nqus tsev thiab lub txee fais fab. Lub thoob tsuas yog muaj rab phom electron, electron lens, tus qauv tuav, fluorescent screen thiab lub koob yees duab mechanism thiab lwm yam khoom, cov khoom no feem ntau sib sau los ntawm sab saum toj mus rau hauv qab rau hauv ib kem; Lub tshuab nqus tsev muaj lub tshuab nqus tsev twj tso kua mis, diffusion twj thiab lub tshuab nqus tsev vacuum, thiab lwm yam, thiab los ntawm cov raj xa dej txuas nrog lub thoob ntawm daim iav; fais fab mov txee muaj lub tshuab hluav taws xob high-voltage, excitation tam sim no stabilizer thiab ntau yam kev tswj hwm kev tswj hwm.
Electron lens yog ib qho tseem ceeb ntawm electron microscope chim, nws yog symmetrical rau lub axis ntawm lub chim ntawm qhov chaw hluav taws xob teb los yog magnetic teb thiaj li hais tias cov electron khiav mus rau lub axis ntawm lub tsim ntawm lub focusing lub luag hauj lwm ntawm lub iav convex. lens los ua lub luag hauj lwm ntawm lub teeb ntawm lub teeb tsom yog zoo ib yam li lub luag hauj lwm ntawm lub lens, yog li nws yog hu ua electron lens. Niaj hnub nimno electron microscopes feem ntau siv lo ntsiab muag electromagnetic, los ntawm qhov ruaj khov DC excitation tam sim no los ntawm lub kauj nrog ib tug ncej khau uas tsim los ntawm cov hlau nplaum muaj zog los tsom cov electrons.
Cov phom hluav taws xob yog ib qho khoom siv uas muaj tungsten kub cathode, lub rooj vag thiab cathode. Nws emits thiab tsim ib lub teeb hluav taws xob nrog lub teeb nrawm, yog li kev ruaj ntseg ntawm qhov nrawm nrawm yuav tsum tsis pub tsawg dua ib feem ntawm kaum txhiab.
Electron microscopes tuaj yeem categorized rau hauv kis tau tus mob electron microscopes, scanning electron microscopes, reflection electron microscopes thiab emission electron microscopes raws li lawv cov qauv thiab siv. Kev xa hluav taws xob tshuab hluav taws xob feem ntau yog siv los soj ntsuam cov neeg uas muaj lub tshuab microscopes tsis tuaj yeem paub qhov txawv ntawm cov qauv zoo ntawm cov khoom; scanning electron microscope yog tsuas yog siv los soj ntsuam cov morphology ntawm cov khoom siv, tab sis kuj nrog X-ray diffractometer los yog electron spectrometer ua ke los ua ib qho electron microprobe, siv rau kev soj ntsuam ntawm cov khoom muaj pes tsawg leeg; emission electron microscope rau kev kawm ntawm qhov chaw ntawm tus kheej-emission ntawm electrons.
Lub teeb hluav taws xob ntawm lub tshuab hluav taws xob scanning tsis dhau los ntawm cov qauv, tab sis tsuas yog ntsuas qhov saum npoo ntawm cov qauv kom ua rau cov khoom siv hluav taws xob thib ob. Ib lub pob zeb ci ntsa iab tso rau ib sab ntawm cov qauv tau txais cov khoom siv hluav taws xob thib ob, uas tau nthuav dav los hloov qhov kev siv ntawm lub teeb hluav taws xob ntawm CRT, yog li hloov qhov ci ntawm CRT lub fluorescent screen. Lub deflection coil ntawm CRT yog synchronized nrog lub electron beam nyob rau saum npoo ntawm cov qauv, kom lub CRT lub fluorescent screen qhia ib tug topographical duab ntawm tus qauv nto, uas yog zoo ib yam li lub hauv paus ntsiab lus ntawm kev ua hauj lwm ntawm industrial TV teeb.
Qhov kev daws teeb meem ntawm scanning electron microscope yog tsuas 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 lub raj mus rau qhov ntsuas amplitude ntawm tus qauv, uas tuaj yeem sib txawv tsis tu ncua los ntawm kaum rau ntau pua txhiab zaus. Scanning electron microscopes tsis xav tau cov qauv nyias; daim duab muaj lub siab zoo ntawm peb-dimensionality; thiab tuaj yeem txheeb xyuas qhov sib xyaw ntawm cov khoom siv los ntawm kev 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 hluav taws xob nrog cov khoom siv.
Scanning electron microscope electron gun thiab spotting mirror and transmission electron microscope is more or less the same, tab sis thiaj li yuav ua rau lub teeb hluav taws xob zoo dua, hauv qhov tsom iav hauv qab lub hom phiaj lens ntxiv thiab disperser, nyob rau hauv lub hom phiaj lens yog. kuj tau nruab nrog ob txheej ntawm perpendicular rau ib leeg hauv lub scanning kauj. Cov qauv chamber nyob rau hauv lub hom phiaj lens yog nruab nrog cov qauv theem uas tuaj yeem txav tau, tig thiab tilted.
