1、Pulsed Laser Deposition(PLD)Huang Yan Wang JianlinGe Wen Zhao Yuan Yun YuUNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINAI.Thin Film DepositionII.Pulsed Laser Deposition a)Compared to other growth techniques b)Experimental Setup c)Advantages and DisadvantagesIII.Basic Theory of PLDIV.OpportunitiesThin
2、Film Thin Film DepositionDepositionTransfer atoms from a target to a vapor(or plasma)to a substrateThin Film Thin Film DepositionDepositionTransfer atoms from a target to a vapor(or plasma)to a substrateAfter an atom is on surface,it diffuses according to:D=Doexp(-eD/kT)eD is the activation energy f
3、or diffusion 2-3 eVkT is energy of atomic species.Want sufficient diffusion for atoms to find best sites.Either use energetic atoms,or heat the substrate.targetsubstrateEvaporation(Molecular beam epitaxy-MBE)targetsubstrateChemical vapor deposition-CVDAr+substrategasSputteringLow energy deposition(M
4、BE):0.1 eV may get islanding unlessyou pick right substrate orheat substrate to hightemperatures High energy deposition(Sputtering 1 eV)smoother films at lower substrate temperatures,but may get intermixingLow energy deposition(MBE):0.1 eV may get islanding unlessyou pick right substrate orheat subs
5、trate to hightemperatures High energy deposition(Sputtering 1 eV)smoother films at lower substrate temperatures,but may get intermixingTarget:metals,semiconductorsLaser:UV,10 ns pulsesVacuum:Atmospheres to ultrahigh vacuumFilm thickness:typically 100-200 nm.Deposition rate:0.1 nm/pulseSlot 6DEPOSITI
6、ON CHAMBERVIDEO CAMERATOP WINDOWROTATIONMOTOREXCIMER LASERl=248 nmHEATER WITHTHERMOCOUPLEBEAM CONDITIONING&FOCUSING YBCO TARGET PRESSURETRANSDUCERVALVESTO VACUUM&O2WINDOWSSERVO-CONTROLLEDMIRRORSUBSTRATEPLUMEINSERTABLEBEAM ATTENUATORWINDOW晑晑 晑晑MANUAL EM SENSORAUTOMATED EM SENSORRAMANSENSORSlot 6Slot
7、13Exact transfer of complicated materials Flexible,variety,easy to implement Easy to prepare targetEpitaxy at low temperatureFast growth rate Uneven coverageHigh defect or particulate concentration Not well suited for large-scale film growthMechanisms and dependence on parameters not well understood
8、Subsurface BoilingLaser superheats subsurface layer before surface reaches evaporation pointSurface breaks apart into large(micron-sized)globule particles when the subsurface expands.Expansion of plume causes sudden drop in pressure just above surfaceShock wave pulls droplets of liquid off of surfac
9、eThermal shock causes irregularities in surface to break off Surface morphology Previous ablationParticulates are randomly shaped substrate temperature the target-substrate distance ambient oxygen pressure and annealing temperature target consistency pulse laser energy laser frequencySi（110）substrat
10、e600 The only variable:Ambient gas speciesAr/O2/N2Constant:248nm KrF Pulse frequency 8HzPulses number 4000Laser fluence(1.60.2)J/cm2Y2SiO5:Ce standard phosphor powdersDifferent nanostructure:substrate temperature of 600 and an oxygen background pressure of 100 Pa.SEM images of ArF-deposited films SE
11、M images of KrF-deposited films pencil-like structuresa columnar structureZinc oxide nanostructures grown by pulsed laser depositionD.Valerini et al,Appl Phys A,2007The good crystalline qualityonly the(002)and(004)diffraction peaks of the ZnO wurtzite crystal structure are visible.deposited in 1 Pa
12、of oxygen at a Si substrate temperature of 600 by using the two ablation wavelengths.Ultrahigh quality films Circuit writing Isotope Enrichment New Materials Nanoparticle production Ultrahigh quality films Circuit writing Isotope Enrichment New Materials Nanoparticle productionMBEPLDHigher quality f
13、ilmsbetter magnetic propertiesMagnetic Moment of fcc Fe(111)Ultrathin Films by Ultrafast Deposition on Cu(111)J.Shen et al.,Phys.Rev.Lett.,80,pp.1980-1983 Ultrahigh quality films Circuit writing Isotope Enrichment New Materials Nanoparticle production Direct writing of electronic components-in air!R
14、apid process refinement No masks,preforms,or long cycle times True 3-D structure fabrication possible Single laser does surface pretreatment,spatially selective material deposition,surface annealing,component trimming,ablative micromachining,dicing and via-drilling Ultrahigh quality films Circuit wr
15、iting Isotope Enrichment New Materials Nanoparticle productionOver twice the natural enrichment of B10/B11,Ga69/Ga71 in BN and GaN filmsPlasma centrifuge by toroidal and axial magnetic fields of 0.6MG!Isotope Enrichment in Laser-Ablation Plumes and Commensurately Deposited Thin Films P.P.Pronko,et a
16、l.Phys Rev.Lett.,83,pp.2596-2599 Ultrahigh quality films Circuit writing Isotope Enrichment New Materials Nanoparticle productionTransient States of Matter during Short Pulse Laser AblationK.Sokolowski-Tinten et al.,Phys.Rev.Lett.,81,pp.224-227 Fluid material state of high index of refraction,optically flat surface Ultrahigh quality films Circuit writing Isotope Enrichment New Materials Nanoparticle productionNew Materials and NanoparticlesD.B.Geohegan-ORNLCarbon/carbon collisons-buckyballsFast carbon ions-diamond filmsStudy of plasma plume and deposition of carbon materials
