Trushin Fundamentals

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Fundamentals of thin filmFundamentals of thin filmgrowthgrowth

O. TrushinO. Trushin

Institute of Physics and Technology of RAS,Institute of Physics and Technology of RAS,

Yaroslavl Yaroslavl branch,branch, Yaroslavl Yaroslavl, Russia, Russia



OutlinesOutlines

•• Introduction ( Applications of thin films)Introduction ( Applications of thin films)

•• Methods of thin film growthMethods of thin film growth

•• Methods for monitoring the growthMethods for monitoring the growth

•• Mechanisms of growthMechanisms of growth

•• Epitaxial growthEpitaxial growth

•• Thermodynamics versus kineticsThermodynamics versus kinetics•• Surface diffusionSurface diffusion

•• Strain relaxationStrain relaxation



Introduction:Introduction:

Applications of thin films Applications of thin filmsThin Film – thickness < 1 μm



Methods of thin film growthMethods of thin film growth

•• Liquid phaseLiquid phase epitaxyepitaxy•• ElectroElectro--chemical deposition (galvanic)chemical deposition (galvanic)

•• Physical vapor deposition (PVD)Physical vapor deposition (PVD)

•• Chemical vapor deposition (CVD)Chemical vapor deposition (CVD)

•• Plasma sprayPlasma spray



Physical Vapor DepositionPhysical Vapor Deposition

•• Thermal vacuum evaporationThermal vacuum evaporation•• Electron beam evaporationElectron beam evaporation

•• IonIon

--plasma sputteringplasma sputtering

•• Magnetron sputteringMagnetron sputtering

•• Laser ablationLaser ablation

•• Molecular beamMolecular beam epitaxyepitaxy



Thermal vacuum evaporationThermal vacuum evaporation



Electron beam evaporationElectron beam evaporation



Magnetron sputteringMagnetron sputtering



Laser ablationLaser ablation



Chemical vapor deposition (CVD)Chemical vapor deposition (CVD)



Molecular beamMolecular beam epitaxyepitaxy



Experimental methods forExperimental methods for

monitoring of thin film growthmonitoring of thin film growth

•• RHEEDRHEED – – Reflection High Energy ElectronReflection High Energy Electron

DiffractionDiffraction

•• LEEDLEED – – Low Energy Electron DiffractionLow Energy Electron Diffraction

•• HASHAS – – Helium Atom ScatteringHelium Atom Scattering•• XX--ray diffractionray diffraction

•• TEMTEM – – Transmission Electron MicroscopyTransmission Electron Microscopy•• AFM AFM – – Atomic Force Microscopy Atomic Force Microscopy

•• STMSTM – – Scanning Tunneling MicroscopyScanning Tunneling Microscopy



Reflective High Energy ElectronReflective High Energy Electron

Diffraction (RHEED)Diffraction (RHEED)

STM, diffraction pattern and RHEEDof Fe/Fe(001) growth



Low Energy Electron DiffractionLow Energy Electron Diffraction

(LEED)(LEED)Low-energy electron diffraction (LEED) is a technique for the determination of the surface structureof crystalline materials by bombardment with a collimated beam of low energy electrons (20-200eV)

and observation of diffracted electrons as spots on a fluorescent screen.



Helium Atom Scattering (HAS)Helium Atom Scattering (HAS)HAS is unique in that it does not penetrate the surfaceof the sample at all!



Transmission Electron MicroscopyTransmission Electron Microscopy

a) Vapor – Crystal , b) Vapor – Liquid - Crystal



Scanning Tunneling MicroscopyScanning Tunneling Microscopy



Basic mechanisms of growthBasic mechanisms of growth

• Adsorption of atoms from gas

•Cluster formation•Critical size islands growth•Coalescence of neighboring islands•Percolation of island network

•Continuous film growth h>300 A



Epitaxial growthEpitaxial growthThe oriented growth of one crystalline material on the single crystal surfaceof a different material is called EPITAXY



Regimes of epitaxial growthRegimes of epitaxial growth

a) 3D island growth (Volmer-Weber)b) Layer-by-Layer growth followed by 3D island growth (Stranski-Krastanov)

c) Layer – by – Layer (Frank-van der Merwe)



Wulff Wulff constructionconstruction∫ = mindAγ

Shape = envelope (inner)of planes

Pb crystal: a) 300 C, b) 320 C, c) 327 C



Thermodynamics of thin filmThermodynamics of thin film

growthgrowthThin film growth is unequilibrium phenomena

Kinetic factors compete with thermodynamics

Local equilibrium approximation

a) Layer growth : θ = 0, γS> γF+ γS/F

b) Island growth: θ > 0, γS< γF+ γS/F

γF

γS γS/F

θWetting conditions:



CappilaryCappilary Model of NucleationModel of Nucleation),(),( 00 T pT p vapor solid μ μ =

( )0/ln p pkT =Δμ

At equilibrium

At pressure p change in chemicalpotential per particle

Enthalpy change due to creation

of 3D island containing n particles X nnG D

3/2

3 +Δ−=Δ μ

)( //

)(

S F S F S

l

F l

l C C X γ γ γ −+=∑ E n t a l p y

Critical size

n



Kinetics of thin film growthKinetics of thin film growth

Some kinetic effects that may play a role in the incorporationof deposited adatoms.

(a) Downhill funneling: the deposited particle slides down a slope untila local minimum of the surface height is reached.(b) Knockout process: the momentum of the arriving particle sufficesto push out a surface adatom at a terrace edge.

(c) Steering effect: attractive forces can influence the trajectory of thearriving particle significantly.



Morphology of thin filmsMorphology of thin films

Roughening transition



Surface diffusionSurface diffusion

The Ehrlich-Schwoebel barrier ES



Interlayer diffusion and surfaceInterlayer diffusion and surface

alloyingalloying

(a) vapor deposition of Pt onto Ru(0001)

(b) annealing to 1350 K

Driving force:a) segregationb) energetic deposition



PostPost--deposition evolutiondeposition evolution



Misfit strain relaxationMisfit strain relaxation



Thin film texture formationThin film texture formation



ReferencesReferences

•• I. Markov Crystal growth for beginners,I. Markov Crystal growth for beginners,

World Scientific 2003World Scientific 2003

•• J. A.J. A. Venables Venables Introduction to Surface andIntroduction to Surface and

Thin Film Processes , Cambridge Univ.Thin Film Processes , Cambridge Univ.Press, 2001.Press, 2001.

•• H.H. LuthLuth Surfaces and Interfaces of SolidSurfaces and Interfaces of SolidMaterials , Springer 1998.Materials , Springer 1998.

Trushin Fundamentals

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