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M2 sputtering

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basics sputtering, ion beam

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M2 sputtering

  1. 1. Reference Paper: Ghosh, S.; Avasthi, D.K.; Som, T.; Tripathi, A.; Srivastava, S.K.; Gruner, F.; Assmann, W.; Ion velocity, charge state and substrate dependent electronic sputtering of fullerene, Nuclear Instruments and Methods in Physics Research B ,212, 2003, 431–435.
  2. 2. Layout of Presentation Sputtering- Fundamental Effect of Ion Velocity Effect of Charge State Effect of Substrate
  3. 3. What is sputtering? Its Types Basic Principle Its need
  4. 4. The ejection of atoms from the surface of a material (the target) by bombardment with energetic particles is called sputtering. • Used to modify the properties of the materials. • Use of solid targets makes it possible to control the type and composition of the material • Formation of alloy material. • It avoids the use of complicated process chemistry. Sputtering1 Usefulness2
  5. 5. Energetic ion when penetrates solid, it causes – -electronic excitations -nuclear collisions Atoms emission from the surface occurs if the energy transfer in such collisions is enough to overcome surface binding energy. Sputter yield: The average number of atoms ejected from the target per incident ion. Depends on – •ion incident angle •energy of the ion •masses of the ion and target atoms •surface binding energy of atoms in the target Basic Principle3
  6. 6. Electronic Sputtering Nuclear Sputtering Potential Sputtering • Governed by the electronic energy loss process • Governed by nuclear energy loss • Material removal occurs due to atomic collision cascade • Highly charged ion (HCI) has stored potential energy. • HCI can be quite high and produce sputtering in Insulator Types of Sputtering4
  7. 7. Electronic Sputtering study in fullerene Systematic study was done to see the effect of:  Ion Velocity  Charge state  Substrate Dependence
  8. 8. Experimental Section Fullerene films deposited by resistive heating evaporation technique Thickness- 20 nm To study ion velocity dependence: • 130 MeV Ag11+ • 80 MeV Au6+ To study charge state effect: Irradiation by 200 MeV Au 15+ and 32+ charge states. To study substrate dependence: Irradiation by 200 MeV Au15+ ion on substrate- • Si (1 0 0) • Borosilicate glass Similar Se value in C60 1 2 3
  9. 9. ION VELOCITY DEPENDENCE1 Electronic sputtering yields- Au- 1.8 x 104 atoms/ion (more decrease in C content) Ag- 9.8 x103 atoms/ion Au Ag
  10. 10. Explanation low incident ion velocity - higher density of energy deposition (in narrow cylindrical zone around the ion path) Damaged zone more extended in case of Au (low velocity). And electronic sputtering yield is directly proportional to the area of the ion damaged zone
  11. 11. CHARGE STATE DEPENDENCE2 Decrease of NC with fluence in both the cases appears to be of similar kind 200 MeV Au Stopping power is dependent on charge state but due to the possibility of equilibration of the charge state its effect becomes minimal.
  12. 12. SUBSTRATE DEPENDENCE3 Electronic sputtering yields- Si- 2.9 x 104 atoms/ion Glass- 4.5 x104 atoms/ion (more decrease in C content)
  13. 13. Additional heat coming from the substrate will be higher in the case of glass as compared to silicon. Thermal spike generated in films is same Due to ion passage- thermal spike is formed in the substrate (below the C60 film ) This temperature addition results in higher erosion. Reason- •Temperature in Si - smear out more efficiently (higher thermal conductivity, nearly 40 times more) Influencing energy confinement of the film and hence the sputtering yield •Poor crystallinity of glass (electron-phonon coupling strength will be stronger, resulting in high temperature rise). Explanation
  14. 14. Concluding Remarks • Se is 1000 times more than Sn, attributing that the observed loss of C from fullerene films is predominantly due to Se. • On the basis of thermal spike mechanism- Excitation energy of electrons of the material gets coupled to the lattice via electron–phonon coupling mechanism Results in rapid thermal spike (typically more than thousands of Kelvin) is generated in the lattice. It will cause vaporization of materials inside a very narrow zone (nanodimensional) and that get released from the surface.
  15. 15. References-  Avasthi, D.K.; Mehta, G.K.; Swift Heavy Ions for Materials Engineering and Nanostructuring; Springer Series in materials science, 2011, 145.

basics sputtering, ion beam

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