1 / 22

Funded by US-DOE through grant DEFG02-91ER45439

Funded by US-DOE through grant DEFG02-91ER45439. Frederick Seitz Materials Research Laboratory. Dislocation-Driven Surface Dynamics on Solids Sanjay V. Khare 1 , Suneel Kodambaka, Wacek Swiech, Kenji Ohmori, Ivan Petrov, & Joe Greene Dept. of Materials Science and

nubia
Download Presentation

Funded by US-DOE through grant DEFG02-91ER45439

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Funded by US-DOE through grant DEFG02-91ER45439 Frederick Seitz Materials Research Laboratory Dislocation-Driven Surface Dynamics on Solids Sanjay V. Khare1, Suneel Kodambaka, Wacek Swiech,Kenji Ohmori, Ivan Petrov,& Joe Greene Dept. of Materials Science and Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign 1Department of Physics and Astronomy University of Toledo

  2. 250 Å Spila, Desjardins, D’Arcy-Gall, Twesten, & J.E. Greene, JAP 93, 1918 (2003) Teng, Dove, Orme, & J.J. De Yoreo Science 282, 724 (1998) Brune, Giovannini, Bromann, & K. Kern Nature 394, 451 (1998) Dislocations in solids Bulk dislocation dynamics have been extensively studied. Surface-terminated dislocations affect nanostructural and interfacial stability, crystal growth kinetics, mechanical, chemical, & electronic properties of solids. SiGe/Si Ag/Pt KDP Very little is known concerning the effects of dislocations on surface dynamics.

  3. Objectives • Develop fundamental understanding of the effect of dislocations on surface dynamics • Model system: TiN • Use LEEM to investigate surface morphological evolution kinetics as a function of: annealing time temperature & N2 partial pressure.* *K.F. McCarty & N.C. Bartelt: Phys. Rev. Lett.90, 046104 (2003); Surf. Sci.527, L203 (2003); Surf. Sci.540, 157 (2003); Journal of Crystal Growth270, 691 (2004).

  4. = 5x10-8 Torr 2D TiN(111) island decay: detachment-limited kinetics + highly permeable steps TiN/TiN(111) T = 1550 K 2.8±0.3 eV S. Kodambaka, N. Israeli, J. Bareño, W. Święch, K. Ohmori, I. Petrov, & J.E. Greene, Surf. Sci.560, 53 (2004).

  5. = 5x10-8 Torr TiN/TiN(111) Spirals T = 1688 K ~ 0.5Tm treal = 90 s tmovie = 9 s field of view: 2.5 m Observed during annealing in the absence of deposition/evaporation NOT BCF spirals

  6. TiN(111) spiral step growth T = 1688 K t = 0 s 15 s • near-equilibrium* • shape-preserving • periodic • absence of applied stress & net mass change by deposition/evaporation.  = 47 s 31 s 47 s * S. Kodambaka, V. Petrova, S.V. Khare, D.D. Johnson, I. Petrov, & J.E. Greene, Phys. Rev. Lett. 88, 146101 (2002).

  7. = 5x10-8 Torr TiN/TiN(111) T = 1670 K treal = 650 s tmovie = 13 s T = 1690 K field of view 5.6 m Spirals grow with a constant w& 2D island areas decrease at a constant rate

  8. = 5x10-8 Torr TiN/TiN(111) 2D TiN(111) islands*: Edecay = 3.1±0.2 eV C = 1013.6±0.6 s-1 *S. Kodambaka, N. Israeli, J. Bareño, W. Święch, K. Ohmori, I. Petrov, & J.E. Greene, Surf. Sci.560, 53 (2004). TiN(111) spirals: Egrowth = 4.6±0.2 eV C = 1012.6±0.6 s-1 TiN(111) spiral step kinetics is different from that of 2D islands.

  9. Proposed mechanism: • driving force: bulk dislocation line energy minimization •  surface spiral step formation via bulk point defect transport • dislocation cores emit/absorb point defects at a constant thermally- activated rate. S. Kodambaka, S.V. Khare, W. Święch, K. Ohmori, I. Petrov, & J.E. Greene, Nature429, 49 (2004). Modeling dislocation-driven spiral growth TiN/TiN(111) 2D island decay: Ea= 2.8 eV Spiral step growth: Ed= 4.6 eV Ti or TiN desorption*: Eevaporation~ 8-10 eV Ea << Ed << Eevaporation *D. Gall, S. Kodambaka, M.A. Wall, I. Petrov, & J.E. Greene,J. Appl. Phys.93, 9086 (2003). Spiral nucleation and growth MUST be due to bulk mass transport !!

  10. rloop At steady state: rcore B.C.s: Step velocity: Modeling dislocation-driven spiral growth R(T) - thermally-activated point defect emission/absorption rate C - point defect concentration (1/Å2) Ds - surface diffusivity (Å2/s) ks - attachment/detachment rate (Å/s)  - area/TiN (Å2)  constant growth rate dA/dt S. Kodambaka, S.V. Khare, W. Święch, K. Ohmori, I. Petrov, & J.E. Greene, Nature429, 49 (2004).

  11. Modeling dislocation-driven spiral growth 1 rotation  1 ML in 2/ sec Total surface flux = R/Ao   is a thermally-activated constant Ao : area outside of which R is negligible  : area/TiN (Å2) w : spiral angular velocity (rad/s) R(T) : thermally-activated point defect emission/absorption rate

  12. TiN/TiN(111) wvs. t = 5x10-8 Torr T = 1725 K field of view 5.6 m d/dt ~ 10-5 1/s2 at 1725 K  decreases monotonically with annealing time

  13. 5x10-8 5x10-7 5x10-7 vacuum 1 mm vacuum TiN/TiN(111) wvs. pN2 T = 1670 K 2D TiN(111) island & spiral step kinetics are independent of N2 partial pressure

  14. TiN/TiN(111) 4.5±0.4 eV at 5x10-8 Torr 4.6±0.2 eV in vacuum Espiral is independent of N2 pressure & sample history

  15. Conclusions • Investigated the nucleation & growth kinetics of TiN(111) spiral steps using HT-LEEM. • Spiral growth is qualitatively & quantitatively different from 2D island coarsening/decay. • Spiral growth is localized BCF growth/etch spirals. • Angular velocity: • decreases with time irrespective of N2 pressure. • does not vary significantly with spiral geometry. • thermally-activated with a constant energy barrier (~ 4.5 eV),independent of the sample history & N2 pressure.

  16. LEEM – Modes of Operation Bright Field LEEM Dark Field LEEM Photoemission (PEEM) Mirror microscopy (MEM)

  17. T = 1320 oC T = 1285 oC T = 1350 oC T = 1380 oC 2D TiN(111) island decay ALL islands in the cone decay at nearly same rates  mass is not conserved locally

  18. r1 r2 r3 Modeling decay kinetics of islands in a cone • Solve 2D steady-state diffusion eqn.: • B.C.s: adatom fluxes at island step edges • Derive general relation for dAi/dt • Compare calculated r vs. t with expt.l data Fitting variables: Surface diffusivity Ds Attachment/detachment rate Kd Step permeability p Rate of bulk transport Kbulk Step-step interaction g N. Israeli and D. Kandel, PRB 60, 5946 (1999).

  19. 100 R100 110 R110 2D island coarsening kinetics (Ostwald ripening) 50 Å Island shape fluctuation analysis Surf. Sci. 526, 85 (2003). PRL 88, 146101 (2002). 2D island coalescence kinetics Ta ta Surf. Sci. 540, L611 (2003). Equilibrium island shape Surf. Sci. 513, 468 (2002). 2D TiN island dynamics studies

  20. oLEEM datacalculation TiN/TiN(111) High g, p = 0 & Kbulk = 0 p/Kd = 2000 & Kbulk = 0 Kbulk/Kd = 2.5 & p = 0 T = 1350 oC detachment-limited + highly permeable steps OR bulk diffusion 2D TiN(111) islands decay kinetics

  21. = 5x10-8 Torr TiN/TiN(111) treal = 650 s tmovie = 13 s T = 1670 K field of view 5.6 m Spirals grow with a constant w & 2D island areas decrease at a constant rate

  22. TiN/TiN(111) vs. spiral geometry < 10-9 10-8 5x10-8 10-7 1675 K  (10-2 rad/s) 1650 K field of view 5.6 m Spiral step velocities do not vary significantly with local environment

More Related