Pab pawg tshawb fawb sib koom ua ke coj los ntawm xibfwb Zhang Peilei ntawm Shanghai University of Engineering Science, Lancaster University, thiab Amplitude Suzhou Laser Co., Ltd. tau luam tawm cov ntaub ntawv tshawb fawb hu ua "Electromagnetic-hydrodynamic coupling thiab morphology tawm tswv yim hauv kev tsim thiab evolution ntawm LIPSS ntawm cov hlau nyob rau hauv femtosecond laserp thoob ntiaj teb ntau yam" hauv {3} Kev ua lej. Pab neeg no tau tsim ib lub qauv multiphysics coupling electromagnetic theory, transient thermophysics, thiab hydrodynamics, thiab siv mem tes-los ntawm-pulse iterative lub tswv yim los kawm txog cov txheej txheem evolution ntawm laser-induced periodic surface structures (LIPSS) on titanium alloy surfaces. Ua ke nrog kev sim tshuaj ntsuam xyuas thiab cov lej simulation, pab pawg tau nthuav tawm lub cev lub cev ntawm kev tsim nanostructure thiab evolution nyob rau hauv lub synergistic nyhuv ntawm Marangoni ntws thiab recoil siab nyob rau hauv lub morphology tawm tswv yim mechanism.
01
Taw qhia
Laser-induced periodic surface structures (LIPSS) yog ib qho tshwm sim ntawm lub cev uas tuaj yeem tsim cov qauv nyob rau ntawm ntau yam ntaub ntawv (hlau, semiconductors, thiab lwm yam) thiab tau kawm ntau yam. LIPSS feem ntau muab faib ua ob hom: LIPSS nrog lub sijhawm ze ntawm lub laser wavelength (LSFL) thiab LIPSS nrog lub sijhawm tsawg dua li lub laser wavelength (HSFL). Rau classical LSFL, cov txheej txheem tsim tau dav lees paub los ntawm kev cuam tshuam ntawm qhov teeb meem laser thiab nto plasmon polaritons (SPPs) zoo siab rau ntawm cov khoom nto (electromagnetic txoj kev xav). Txawm hais tias electromagnetic txoj kev xav piav qhia lub sij hawm thiab kev taw qhia ntawm LSFL, nws tsuas yog piav qhia txog qhov pib lub zog zoo li qub thiab tsis piav qhia txog kev hloov pauv hloov pauv ntawm cov khoom siv hauv laser-induced molten state. Cov txheej txheem tsiv teb tsaws ntawm cov teeb meem nyob rau hauv lub xeev molten resapes lub nto morphology rau hauv ib lub sij hawm ua ke ntawm peaks thiab troughs.
Femtosecond laser processing muaj qhov tshwj xeeb zoo hauv thaj chaw ntawm micro- thiab nano-fabrication vim nws cov kev ua haujlwm siab thiab cov cua sov me me- thaj tsam cuam tshuam. Nws ultrashort mem tes dav concentrates laser zog ntawm cov khoom nto nyob rau hauv ib lub sij hawm luv luv, tsim ib tug tsis yog -thermal equilibrium theem hloov. Electron thermal conductivity thiab electron-phonon coupling lub zog tswj kev sib kis thiab so ntawm electromagnetic zog tso rau hauv cov khoom thaum lub sij hawm ultrafast txheej txheem. Cov xwm txheej no yog cov laj thawj tseem ceeb rau qhov sib txawv ntawm LIPSS morphology pom ntawm ntau yam ntaub ntawv. Txawm li cas los xij, LIPSS tsim yog ib qho kev sib tw ntau-pulse txheej txheem, nrog rau qhov chaw morphology tsim los ntawm txhua tus mem tes ua tus thawj ciam teb rau cov mem tes tom ntej. Tsis tas li ntawd, qhov tsis tu ncua ntawm LIPSS nthuav tawm muaj kev vam meej ntawm cov khoom siv. Cov lej simulations yav dhau los tsis tshua pom muaj qhov cuam tshuam ntawm qhov chaw morphology tsim los ntawm cov pulses yav dhau los ntawm cov pulses tom ntej hauv ntau-pulse, multi{13}}physics ib puag ncig. Kev hloov pauv ntawm cov khoom siv morphology nyob rau hauv ntau-mem tes tej yam kev mob ua rau qhov kub thiab txias inhomogeneity, uas nyob rau hauv lem cuam tshuam rau redistribution ntawm molten kua induced los ntawm kub gradients. Qhov no yuav tsum muaj kev tshuaj xyuas ntau thiab kev sib tham ntawm LIPSS evolution txheej txheem los ntawm lub plawv dhia-los ntawm-pulse foundations.
Laser & Electron Beam ua
02
Txoj Kev Simulation
Txhawm rau kawm txog kev hloov pauv ntawm LIPSS nyob rau hauv ntau-pulse femtosecond laser irradiation thiab cov tswv yim zoo cuam tshuam txog kev ua haujlwm, simulation workflow decomposes lub laser - teeb meem kev sib cuam tshuam ntawm ib tug mem tes rau hauv peb kauj ruam ua ke: electromagnetic field xam, thermodynamic evolution, thiab cov kua dej rov ua dua. Hauv txoj kev tshawb no, peb tsom mus rau cov txheej txheem evolution pib los ntawm qhov kev txiav txim siab. Lub simulation pib nrog ib tug zoo tagnrho, du dav hlau, qhov twg ablation pits generated los ntawm laser tsis thiab cov khoom teb yog xam raws li "zoo roughness" rau tom ntej electromagnetic coupling. Nyob rau hauv cov qauv no, qhov zoo roughness yog sawv cev los ntawm simulated nto ablation, ib txoj kev uas tshem tawm qhov tsis paub tseeb txuam nrog random thawj nto roughness, cia peb kawm li cas LIPSS cov ntaub ntawv thiab propagates ntawm ablation npoo thiab nyob rau hauv lub nto.
03
Surface Morphology Cov Lus Qhia
Nyob rau hauv multi-pulse femtosecond laser irradiation, qhov tsim ntawm LIPSS tsis yog ib qho yooj yim superposition ntawm ib lub cev teb, tab sis ib tug dynamic evolution txheej txheem nyob rau hauv uas lub nto morphology cuam tshuam ntawm yav dhau los pulses cuam tshuam nrog cov tom ntej pulses. Daim duab 2 qhia txog kev hloov pauv ntawm cov khoom siv saum npoo av morphology thiab qhov sib thooj spatial faib ntawm cov hluav taws xob hauv qab ntau lub pulses. Rau qhov pib pulse (N=1), qhov hluav taws xob xa hluav taws xob rau ntawm cov khoom siv du yog cov tom qab sib xws, feem ntau nthuav tawm cov qauv yoj sawv ntsug tsim los ntawm kev cuam tshuam ntawm qhov xwm txheej thiab pom lub teeb. Raws li tus naj npawb ntawm pulses nce (N=20, N=30), qhov pib du nto evolves mus rau hauv ntiav ablation pits. Qhov tsis yog -planar interface rhuav tshem lub symmetry ntawm lub dav hlau thiab muab cov tawg ri niab nyob rau hauv - dav hlau yoj vector tivthaiv, uas ua rau tsis muaj zog SPP excitation ntawm cov hlau - huab cua interface. Raws li tus naj npawb ntawm cov pulses nce ntxiv (N=40, N=50), lub sij hawm grooves uas tshwm sim ua haujlwm zoo dua li cov diffraction gratings, ua rau muaj zog SPP coupling. Raws li tau pom nyob rau hauv qhov kev pom loj ntawm N=50, kev cuam tshuam ntawm SPP thiab qhov teeb meem tom ntej no ua rau lub zog hluav taws xob hauv cheeb tsam hauv cov grooves, qhov chaw hluav taws xob siv hluav taws xob ntau dua li qhov xwm txheej tshwm sim.
Daim duab 3 qhia txog kev hloov pauv ntawm cov khoom siv saum npoo av morphology thiab qhov sib thooj ntawm qhov nruab nrab ntawm qhov ntsuas kub ntawm qhov sib txawv ntawm cov pulses (N=1-50). Nyob rau hauv thawj theem (N=1-10), ablation pits rau ntawm lub tiaj tiaj. Nyob rau lub sijhawm no, qhov kub thiab txias ntawm qhov saum npoo yog smoothly faib rau sab nraud, thiab qhov sib txuas ntawm qhov kub thiab txias tau nthuav tawm lub ncov qis thiab dav, qhia txog Gaussian kev faib tawm ntawm lub zog laser. Raws li tus naj npawb ntawm cov pulses nce (N=20-50), siab - qhov sib txawv ntawm qhov sib txawv ntawm qhov sib txawv ntawm qhov kub thiab txias maj mam tshwm sim, raws li qhov tshwm sim ntawm cov txheej txheem ntu ntu. Qhov siab tshaj plaws lattice kub yog concentrated nyob rau hauv lub kwj ntawm cov txheej txheem raws sij hawm, thaum qhov kub ntawm lub ncov tseem qis. Qhov ntsuas kub faib tawm qhia tau hais tias raws li tus naj npawb ntawm cov pulses nce, qhov amplitude ntawm qhov ntsuas kub ntawm qhov ntsuas kub no tau tshaj tawm, thiab lub ncov kub maj mam nce. Los ntawm kev sib txuas qhov no nrog kev hloov pauv ntawm cov hluav taws xob hauv hluav taws xob uas tau qhia hauv daim duab 2, qhov ntsuas kub ntawm cov lattice faib nyob rau hauv ntau lub pulses tuaj yeem piav qhia los ntawm electromagnetic thermal tawm tswv yim mechanism. Electromagnetic hotspots nyob rau hauv cov kwj deg tsim spatial tsis yog -ib puag ncig tshav kub qhov chaw, thaum kawg tsim ib tug periodic lattice kub teb raws li qhov chaw morphology.
04
Dej ntws thaum lub sij hawm melting theem
Femtosecond laser pulse zog yog pauv mus rau lub lattice ntawm electron -phonon coupling. Thaum lub lattice kub ncav cuag lub melting point, ib ntus molten txheej ntaub ntawv rau ntawm cov khoom nto. Cov evolution tom ntej ntawm LIPSS ntawm lub sij hawm picosecond yog tswj tsis tau tsuas yog los ntawm static ablation tab sis kuj los ntawm hydrodynamic thauj nyob rau hauv no molten txheej. Nyob rau hauv cov qauv no, periodicity yog predefined los ntawm electromagnetic zog deposition, thaum Marangoni kev nyuaj siab thiab recoil siab feem ntau tsav lub redistribution thiab tshem tawm cov khoom molten. Daim duab 4, 5, thiab 6 qhia cov kua dej ntws tawm thaum lub sij hawm melting theem ntawm ib tug multi-pulse txheej txheem (N=20-40) raws li lub sij hawm cov qauv evolved ntawm ntiav mus tob. Nyob rau theem no, lub lattice kub tau tshaj qhov melting point tab sis tseem tsis tau mus txog qhov kub ntawm vaporization. Hauv peb daim duab no, a1 thiab a2 sawv cev rau qhov siab tshaj plaws ntawm cov qauv ntu, thaum a3 thiab a4 sawv cev rau cov troughs. Raws li pom nyob rau hauv daim duab 4, nyob rau hauv lub sij hawm thaum ntxov ntawm periodic qauv tsim (N=20), ib tug periodic kub teb tau tsim nyob rau saum npoo, thiab ib tug wavy qauv pib tshwm. Hauv cov cheeb tsam hav uas muaj qhov kub siab tshaj plaws (Daim duab. 4(c)), uas tau tsav los ntawm qhov chaw nro gradient, cov nyhuv Marangoni ua rau cov kua dej ntws los ntawm kev kub ceev los ntawm qhov chaw nruab nrab ntawm lub hav mus rau cov peaks uas nyob ib sab. Hloov pauv, nyob rau thaj tsam crest nrog qhov kub qis tshaj plaws (Daim duab. 4(b)), cov kua dej los ntawm cov kwj deg uas nyob ib sab tau pom los sib sau ua ke thiab nce siab. Kev sib piv ntawm cov cheeb tsam no qhia tau hais tias siab -ceev sib txawv khiav hauv cov troughs thiab qis - ceev converging ntws nyob rau hauv crests. Raws li tau pom nyob rau hauv cov dej ntws ntawm Fig. 4(b) thiab (c), qhov ntws ntawm cov kua dej ntws mus rau cov crests ua rau cov dej ntws rov qab tob dua hauv lub pas dej molten, rov qab los hauv qab lub ncov mus rau lub hav. Qhov kev sib xyaw ua ke ntawm cov dej ntws tawm sab nraud thiab sab hauv hauv qab ntws ntawm tus kheej- koom ua ke rau hauv ib khub ntawm Marangoni vortices nyob rau hauv txhua lub crest thiab trough ntawm lub caij nyoog qauv. Los ntawm kev sib piv cov duab, nws tuaj yeem pom los ntawm Figs . 4, 5, thiab 6 tias raws li cov hav tob zuj zus, cov kua dej saum npoo tau maj mam nyob hauv lawv (Figs. 4(c), 5(c), thiab 6(c)). Cov kwj ha sib sib zog nqus hauv cheeb tsam hluav taws xob muaj zog, yog li inhibiting lateral thermal diffusion los ntawm lub hav mus rau cov peaks uas nyob ib sab. Qhov no ua rau muaj qhov ntsuas kub siab tshaj plaws tau khaws cia hauv cov hav. Yog li ntawd, txij li thaum lub zog tsav cov dej txav nyob ntawm qhov kub thiab txias, cov rog no tau nce zuj zus nyob hauv cov hav. Los ntawm qhov kev xav ntawm kev nce tus naj npawb ntawm pulses, qhov no txhais tau hais tias lub zog ntawm cov pulses tom ntej yog siv los ua kom cov grooves uas twb muaj lawm, es tsis yog ablate twb tsim peaks los yog tsim cov qauv tshiab. Yog li ntawd, qhov siab qhov sib txawv ntawm cov ncov thiab hav tsis tu ncua nce, ua rau kom maj mam sib sib zog nqus ntawm cov qauv ntu ntu.
05
Simulation Verification
Txhawm rau qhia txog cov txheej txheem tsim ntawm cov txheej txheem ntu ntu uas tau tsav los ntawm kev sib koom ua ke ntawm cov teebmeem electromagnetic thiab cov kua dej ntws hauv ntau-pulse irradiation, qhov morphology evolution saum npoo tau pom nyob rau hauv txoj kab scanning sim tau muab piv nrog cov txiaj ntsig ntawm cov qauv multiphysics, raws li pom nyob rau hauv daim duab 7. Nyob rau hauv lub ntsiab theem ntawm pulse. npog los ntawm random nanoparticles tsim los ntawm ablation -redeposition thiab molten kua thauj. Hauv kev simulation, peb siv lub cev sib npaug ntawm qhov pib ntawm LIPSS evolution, uas yog laser-induced ablation pits. Ob qho tib si nanoparticles random thiab ablation pits tuaj yeem ua raws li cov ciam teb rau cov pulses tom ntej, yog li zoo siab SPP. Tom qab pulses tsim kom muaj qhov kub thiab txias ntawm qhov tsis yog -planar nto los ntawm SPP cuam tshuam, tsav tsheb rov faib cov khoom molten nyob rau lub sijhawm no. Tom qab ntawd, Marangoni quab yuam thiab recoil siab pib tsav lub redistribution ntawm molten kua, yog li txhawb kev tsim ntawm LIPSS.
Txhawm rau kom muaj txiaj ntsig zoo dua ntawm cov txiaj ntsig simulation, LIPSS nyob rau hauv ib zaug -femtosecond laser illumination tau muab piv nrog cov lej simulation. Raws li pom nyob rau hauv daim duab 8, ob qho tib si qhia tau hais tias muaj kev sib raug zoo nyob rau hauv spatial periodicity. Txhawm rau txheeb xyuas lub sijhawm no, lub cheeb tsam greyscale contours ntawm SEM duab tau muab rho tawm raws li cov kev taw qhia perpendicular rau LIPSS, yielding lub sij hawm nruab nrab ntawm kwv yees li 980 nm rau cov qauv kev sim. Daim duab 8(b) qhia txog tus ntoo khaub lig simulated-sectional contour ntawm tib lub spatial scale. Los ntawm daim ntawv qhia qhov chaw simulated contour mus rau SEM duab ntawm tib lub koom haum thiab teev, nws tau pom tias qhov chaw nyob ntawm qhov simulated ncov thiab hav zoo sib xws rau cov kab txaij ci thiab tsaus nti hauv SEM duab. Lub sijhawm simulated yog kwv yees li 960 nm, uas yog qhov pom zoo zoo nrog cov txiaj ntsig kev sim ntsuas siv txoj kev contour.
06
Xaus
Txoj kev tshawb no tau tsim cov qauv multiphysics raws li kev tshawb xav electromagnetic, kua dej dynamics txoj kev xav, thiab cov khoom siv thermophysical ntawm cov ntaub ntawv los ntawm cov lej simulation. Nws tau piav qhia los ntawm qhov pib ua kom tiav qhov tsim ntawm cov qauv ntu ntawm cov hlau qhov chaw uas tau tsav los ntawm kev sib koom ua ke ntawm cov teebmeem electromagnetic thiab cov kua dej tsis ruaj khov nyob rau hauv multi-mem tes femtosecond laser kho. Los ntawm kev ua tiav cov mem tes rov ua tiav ntawm kev simulation ntawm cov khoom siv saum npoo thiab kev sib piv ntawm cov txiaj ntsig simulation nrog cov txiaj ntsig kev sim, peb txiav txim siab tias qhov tsim ntawm LIPSS yog qhov tshwm sim ntawm kev sib koom ua ke ntawm electromagnetic thiab kua dej dynamics.
Kev sib cuam tshuam ntawm qhov teeb meem femtosecond laser thiab cov khoom nto, nyob rau hauv lub xub ntiag ntawm nto roughness, excites SPPs uas cuam tshuam nrog qhov teeb meem teeb. Cov txheej txheem no ua rau lub sijhawm ua ntu zus thiab tsis yog -ib puag ncig lub zog tso rau ntawm cov khoom siv. Peb tau lees paub tias qhov tsim nyog ntawm qhov roughness no tuaj yeem yog ablation pits tshwm sim los ntawm laser nws tus kheej, uas tuaj yeem ua tus ciam teb rau SPPs zoo siab. Qhov saum npoo morphology tsim los ntawm yav dhau los pulses ua raws li ib tug diffraction grating rau tom ntej pulses, txhim kho SPP coupling efficiency. Thaum lub sij hawm no lub zog yog absorbed los ntawm cov khoom, nws sai transforms mus rau hauv ib tug sib raug zoo lattice kub gradient teb, tsim ib ntus molten txheej rau ntawm qhov chaw. Qhov no nyias nyias molten txheej, cuam tshuam los ntawm lub sij hawm kub gradient, yog lub cev tsis ruaj tsis khov, yog li ua kom muaj dej thauj khoom uas tswj cov khoom tsiv teb tsaws. Thaum lub sij hawm melting theem, lub Marangoni quab yuam, uas tau tsav los ntawm nto nro, migrate cov molten kua los ntawm siab - kub troughs mus rau qis - kub crests, ua ib tug siab - ceev divergent ntws nyob rau hauv lub troughs thiab ib tug tsawg - ceev converging ntws nyob rau hauv lub crests. Raws li tus naj npawb ntawm cov pulses nce, cov troughs maj mam sib sib zog nqus, thiab cov kua saum npoo yog maj mam cia rau hauv cov troughs. Thaum lub sij hawm vaporization theem, qhov ntxiv nce hauv lattice kub yog nrog los ntawm kev nce ntxiv hauv recoil siab. Nyob rau lub sijhawm no, lub siab rov qab ua haujlwm raws li qhov tseem ceeb ntawm kev tsav cov kua dej, siv lub zog muaj zog los tsav cov kua dej los ntawm qhov chaw ntawm cov troughs downwards mus rau subsurface, thaum tseem tom qab tso cov kua rau cov crests.
