| AVS 55th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF-WeA |
| Session: | Computational and Experimental Studies of Thin Films |
| Presenter: | V.E. Strel'nitskij, NSC "Kharkov Institute of Physics and Technology", Ukraine |
| Authors: | V.E. Strel'nitskij, NSC "Kharkov Institute of Physics and Technology", Ukraine A.I. Kalinichenko, NSC "Kharkov Institute of Physics and Technology", Ukraine S.S. Perepelkin, NSC "Kharkov Institute of Physics and Technology", Ukraine |
| Correspondent: | Click to Email |
The known approach to formation of compressive stress in thin films by ion bombardment1 uses the formalism of the point-like thermal spike (PTS) to describe acceleration of kinetic processes responsible for stress relaxation. But the PTS model does not reflect adequately real thermodynamic conditions in vicinity of the ion path in the target material. It does not take into account the finitness of the initial volume of the energy release which depends on energy E of the ion and thermal properties of material. As a result the known formula for residual stress σ (E) in thin film under ion bombardment1 matches with experimental data only by too high values of the activation energy of migration of defects U > 3 eV. Also σ(E) does not depend on the substrate temperature T0. In this paper the rate of kinetic processes in carbon films at low-energy ion deposition in the model of the nonlocal thermoelastic peak (TEP)2 of the ion is analyzed. The approximate expressions for temperature T, pressure P and the number of sp2 to sp3 transitions in the TEP depending on energy of the ion and substrate temperature T0 were derived and applied for modification of the expression of σ(E).1 Unlike the previous expression σ(E) the modified one depends on E in accordance with experimental data when U is closed to 0.3 eV (the typical value for the activation energy of interstitials). Also σ decreases substantially with T0 in temperature range 300 to 600 K. Calculation of σ and T permitted determining “the initial locations” and “P,T- trajectories” of the ion TEPs on phase P,T- diagram of carbon2 and investigating possibility of DLC formation depending on E and T0. As the steady residual stress σ decreases with the substrate temperature increase from 300 to 600 K the initial locations and P,T- trajectories of TEPs shift preferably from the region of diamond stability to that of graphite stability. Such behavior which is pronounced for TEPs with energies E > 100 eV suggests that sp2 –bound carbon forms preferably in TEPs of low-energy ions C+ at temperature of deposition T0 > 600 K. This conclusion agrees qualitatively with experimental data.
1C.A. Davis: Thin Solid Films 226 (1993) 30.
2A.I. Kalinichenko, S.S. Perepelkin, V.E. Strel’nitskij, Diam. Relat. Mater. 15 (2006) 365.