Modification of thin films and nanoparticles. Johannes Berndt, GREMI,Orléans

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1 Modification of thin films and nanoparticles Johannes Berndt, GREMI,Orléans

2 Low temperature plasmas not fully ionized Ionization degree far away from thermodynamic equlilibrium T electron >> T ion > T neutral Inductively coupled plasma Microwave plasma Capacitively coupled plasma Ne = m -3 Ne = m -3 Ne = m -3

3 Example: discharge in acetylene Electron impact disscociation H 2 + e +2H +e H 2 +e H + H +e Acetylene depletion Mass spectrometer signal / a.u H 2 concentration C2H t / s Creation of radicals and ions H CH H + H - further reactions Counts / s H 2 + Ar + C 4 H 2 + C 6 H 4 + m/e Postive ion Mass spectrum C 8 H 4 + C 10 H 4 +

4 H 2 + e Electon induced reactions H CH H + + CH H C H + C 2 H 2 C 4 H Chemical reactions H C 6 H 5 C 6 H 2 H 4 Positive Ion acceleration Flux of ions and radicals sheath Substrate Positive Ion acceleration Thin films Etching Functionalisation 8 π* σ* 30 incident beam Partial electron yield (au) plasma 30s untreated Photon energy (ev)

5 Classification of species emerging from a plasma «Chemical reactivity» «Kinetic reactivity» «1 +2» Neutral radicals with thermal Energies 20 mev: Positive noble gas ions with high kinetic energies: Positive reactive ions with high kinetic energy H, CH.. N,F,H Ar + Xe +,Ne +.. H +, CH +,..

6 «Separation of chemical reactivity and kinetic reactivity» «Flowing afterglow techniques» Suraftron Gas Glas cylinder pump

7 TIMS Flowing nitrogen afterglow N-->N + N 2 -->N >N + +N plasma N 2 + e - N + + N + 2 e wave launcher plasma Gas flow glass cylinder Counts/sec I Background I Plasma ON I Plasma OFF Suraftron Electron Energy (ev) D Douai, J Berndt and J Winter, Plasma Sources Sci Tech. 11, (2002) 1. Threshold: Ionisation of N-atoms Gas N + e - N + +2 e ev Glas cylinder 2. Threshold: pump Dissociative Ionisation of N 2 N 2 + e - N + + N + 2 e ev

8 Reversible resistivity change of thin silver films target D.Diesing, J.Berndt, D.Douai, J.Winter, Thin Solid Films 409, (2002)

9 H 2 Surfatron 1 Expanding plasma Surfatron 2 Double plasma experiment Wafer Synergistic effects MS = 5 Ar CH 4 H 2 Wafer H-atom source expanding argon Plasma O. Stepanovic, J. Berndt, J. Winter, Thin solid films 516, 6565 (2008) etch rate in nm / min argon plasma + hydrogen plasma argon plasma + H 2 gas position on wafer / cm hydrogen plasma

10 Production of thin Diamond like Carbon films target, S. Hong, D. Douai, J. Berndt, and J. Winter, Plasma Sources Sci. Technol. 14, (2005) C - atoms cm 3 bias C - atoms cm 3

11 «Chemical reactivity» «Kinetic reactivity» «1 +2» Neutral radicals with thermal Energies 20 mev: Positive noble gas ions with high kinetic energies: Positive reactive ions with high kenetic energy N atoms H - atoms Ar + ions H +, CH +,.. etching of DLC films etching of DLC films deposition of DLC films Modification of silver films Synergistic effects

12 Xenon lamp Plasma off

13 Electron and ion flux to the particle levitating dust cloud number of ions and electrons impinging / s electrons ions Some aspects of reactive complex plasmas J. Berndt, E. Kovacevic, I. Stefanovic, J. Winter and L. Boufendi, invited review, Contributions in Plasma Physics 49, (2009) t /µs

14 Production of superhydrophobic surfaces Plasma off Plasma on θ =65 θ =80 θ =130 Particle density

15 Production of superhydrophobic surfaces 160 (a) 140 contact angle cycles of 8 seconds cycles of 4 seconds number of cycles Berndt, J., Acid, H., Kovacevic, E., Boufendi, J. Appl. Phys. θ =65 θ =80 θ =130 Particle density

16 From superhydrophopic to superhydrophilic Plasma treatment

17 From superhydrophilic to superhydrophopic Plasma treatment ν(c-o) δ(ch) ν(c=o) a) untreated material ν(ch) ν(oh) superhydrophob superhydrophil absorbance (au) ν(c-o) ν(c-o) δ(ch) δ(ch) ν(c=o) b) treatment c) EUV-treatment ν(ch) ν(oh) ν(ch) ν(oh) VUV irradiation in vacuum wavelength (cm -1 )

18 Summary Each Plasma surface modification process as e.g. thin film deposition etching functionalisation is governed by a great variety of different species neutral radicals postive ions negative ions nanoparticles which can be calssified according to their «kind of reactivity» chemical reactivity kinetic reactivity chemical reactivity and kinetic reactivity The combined interaction of all these species can lead to synergistic effects