Recommended
More Related Content
What's hot
What's hot (20)
Similar to Ion beam sputtered nanorippling of binary mxtures
Similar to Ion beam sputtered nanorippling of binary mxtures (20)
More from Dr. Basanta Kumar Parida
More from Dr. Basanta Kumar Parida (20)
Recently uploaded
Recently uploaded (20)
Ion beam sputtered nanorippling of binary mxtures
- 1. Nanoripple formation on binary mixtures – (I-V) characteristic studies and effect of angular swinging Basanta Kumar Parida Department of Physics IIT Ropar IBMEC 2018
- 2. Outline • Ion beam nanopatterning • Mono-elemental system • Binary and compound systems • Motivation • I-V measurement on nanoripples • Effect of swinging on ion beam eroded substrate • Summary
- 3. Ion beam nanopatterning Ion source Sample holder • Single step process for large area nanopatterning (upto few cm2 area) • Faster and cheaper compared to conventional lithographic techniques Before irradiation Ar+ 500 eV, 67o,15 min→Si After irradiation
- 4. • Differential sputtering yield and Differential diffusivity • Results altered topography and composition A B Theoretical background 𝝏𝒉 𝝏𝒕 = −𝒗 𝟎 + 𝜸(𝜽) 𝝏𝒉 𝝏𝒙 + 𝝂 𝒙 𝝏 𝟐 𝒉 𝝏𝒙 𝟐 + 𝝂 𝒚 𝝏 𝟐 𝒉 𝝏𝒚 𝟐 − 𝑲𝜵 𝟒 𝒉 Sputter roughening Diffusion smoothing Bradley-Harper Model Monoelemental system Shenoy et.al., Phys. Rev. Lett., 98, 256101 (2007) • Competition between two processes • Roughening due to sputtering • Smoothening due to diffusion AB compound 𝜕ℎ 𝜕𝑡 = −Ω[ 𝐹𝐴 + 𝛻. 𝐽 𝐴 + (𝐹𝐵 + 𝛻. 𝐽 𝐵)] ∆ 𝜕𝑐 𝑠 𝜕𝑡 = 𝛺 𝑐 𝑏 − 1 𝐹𝐴 + 𝛻. 𝐽 𝐴 + 𝑐 𝑏 𝐹𝐵 + 𝛻. 𝐽 𝐵 Binary compound system Bradley et al. J. Vac. Sci. Technol. A 6, 2390 (1988)
- 5. Nanopatterns on elementary and binary compounds • Nanoripple • Nanodots Binary compound S. Facsko et.al., Science, 285, 1551 (1999) Frost et.al. Phys. Rev. Lett. 85, 4116 (2000) Zhang New. J. Phys 13, 013033 (2011) Ar→Si 500 eV, 30 min, 67o Oblique Incidence Normal Incidence Oblique Incidence with rotation Ar→InP 500eV,2min,10o Monoelemental Without impurity With impurity to elemental surface Ar→GaSb 500eV,30min,0o https://www.hzdr.de/db/Cms?pOid=24344&pNid=2707 Surfactant driven self organization
- 6. Binary mixture Gago et. al. J. Phys. Cond. Mat. 30, 264003 (2018)Parida et al. Curr. Appl. Phys. 18, 993 (2018 ) Morphology transitions with energy variation Silicide formation plays major role for this instability Erosion rate of silicides is larger than for silicon Shielding effect from silicide regions Ar→CoxSi1-x Ar→Si Ar→ MoxSi1-x 𝒙 = 0.27 500eV,Ar+,67o,7.5×1018ions/cm2
- 7. Motivation • Metal-semiconductor system • Transition-metal silicides -used as interconnects or contacts in microelectronics industry • Mixtures containing initially well-mixed species (bulk composition) • Far from strongest coupling (50-50) composition • Sputtering can induce stoichiometric rearrangements in the bulk as well, which affects the surface concentration • Ion induced diffusivity is primarily confined to the surface • Swinging as the new parameter CoxSi1-x is chosen as the binary material
- 8. Ion beam irradiation on Co69Si31 Parameters Ar+ ion 500 eV, 67o, 1.12 − 6.75×1018 ions/cm2 Static substrate Nanoscale ripples become mounds at higher fluence Manuscript submitted… Higher ordering predicts smoother surface than others
- 9. I-V characteristic study Manuscript submitted… Diode like behaviour for patterned surfaces I-V data merge for || and ⟂ directions upto |5| V. Gradual separation after |10| V Resistance is more along parallel direction -20 -15 -10 -5 0 5 10 15 20 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 Current(A) Voltage (V) to the ion beam direction || to the ion beam direction
- 10. I-V characteristic study(contd…) Manuscript submitted… Diode like behaviour for patterned surfaces Macro roughness effect dominates for higher fluence Amplitude of nanoripples play measure role for conductivity 0.00 0.25 0.50 0.75 1.00 -3.8 0.0 3.8 7.6 -1.7 0.0 1.7 3.4 -3.3 0.0 3.3 6.6 -1.5 0.0 1.5 3.0 -9 0 9 18 0.00 0.25 0.50 0.75 1.00 60 min 45 min 30 min 15 min 10 min X (µm) slope Height(nm) Line profiles h 10 20 30 40 50 60 200 400 600 800 1000 1200 1400 1600 1800 10 20 30 40 50 60 Amplitude(nm) Time of irradiation (min) || to the ion beam direction to the ion beam direction Amplitude Resistance(ohm) 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
- 11. Effect of swinging on morphology evolution Kim et al. J. Phys.: Cond Matt 30, 274004 (2018) Asymmetric wall like structure Yoon et al. J. Appl. Phys. 119, 205301 (2016) Transition b/w erosive and diffusive region Square-shaped vacancy islands Ar+ 2 keV 78o, ∆φ=144o Ar+ →HOPG 2 keV Ɵ=78o ∆φ=144o
- 12. Pristine -200o+200o Z=50nm -50o+50o -75o+75o -150o+150o -125o+125o -180o+180o -100o+100o (a) (b) (c) (d) (e) (f) (g) (h) Z=21nm Z=50nm Z=30nmZ=50nm(c) -75o+75o Z=45nmZ=35nmZ=24nm Z=40nm Constant parameters Ar+ ion 500 eV, 67o, 1.12×1018 ions/cm2 7 rpm speed during Swinging Effect of swinging on CoxSi1-x -7 0 7 0 1000 2000 3000 -6 0 6 -18 -9 0 9 -5 0 5 -12 -6 0 6 -8 0 8 16 -7 0 7 14 0 1000 2000 3000 -8 0 8 16 A Height(nm) As-grown d -50 o +50 o -75 o +75 o -100 o +100 o cauli flower like -125 o +125 o cauli flower like -150 o +150 o -180 o +180 o X (nm) -200 o +200 o Cauliflower like structures appear 80 120 160 200 240 280 320 360 400 3.5 4.0 4.5 5.0 5.5 6.0 80 120 160 200 240 280 320 360 400 3.5 4.0 4.5 5.0 5.5 6.0Linear fit Roughness(nm) Angle of total swing (degree) Manuscript under preparation
- 13. Swinging (-100o +100o) Constant parameters Ar+ 500 eV, 67o,1.12×1018 ions/cm2 Surface gets rougher at an optimum speed of rocking Swinging speed variation 1 rpm 7 rpm Z=25 nm Z=30 nm 15 rpm Z=35 nm Z Bi-periodic ion incidence on the swinging surface But single period for the rotating surface Anisotropic surface modification and the reduced symmetry in the pattern Lateral mass transport caused by the swinging substrate Manuscript under preparation As-grown roughness ~6.5 nm 0 3 6 9 12 15 4.4 4.8 Roughness(nm) Speed (rpm)
- 14. Summary • I-V measurement may help in electrical assistance in future • Higher resistance for better ordered structures • Cauliflower like structures appear due to swinging • Linear increment in roughness for different angles • Surface smoothen for swinging surfaces compared to as-grown surfaces Supervisor - Dr. Subhendu Sarkar Dr. Mukesh Ranjan, FCIPT, IPR, Gandhinagar Dr. K. S. Hazra INST, Mohali CRF, IIT Ropar MHRD, India Acknowledgement
Editor's Notes
- Ion beam sputtering, i.e. the removal of atoms from a solid substrate due to the impingement of energetic charged particles Due to the interaction of the ions with the substrate, the surface topography is modified and under certain conditions regular nanostructures can evolve by self-organization processes
- Only one step in a wide variety of materials an attractive alternative route for the production of nanopatterned surfaces
- As energetic ion enters into the substance there forms a disturbed region inside the substance called Collison cascade. Few atoms get sufficient energy to come out of the surface due to these which can be explained by an instability theory of Bradley and Harper. The irregularities over the surface(like crests or trough) lead to instability due to which trough erodes faster than the crest. Hence the instability creates roughening of the surface which competes with the thermal surface diffusion where matters flow to the crests to the tough leads to the smoothening. Hence Formation of nanopattern are due to the competition between two processes. One is the roughening due to the surface curvature and other smoothening due to thermal diffusion. Both effect combinely result nanoripples. Our group basically works on binary compound which is….
- Typical patterns formed as I have explained earlier are nanoripples and dots. For monoelemental surfaces like Si, Ge and metals etc, IBS at oblique incidence create nanoripples, where as for binary compound cases like III-V semiconductors (GaSb, GaAs, InP etc) there is the formation of hexagonally ordered nanodots which are mostly crystalline nature for few minutes of sputtering. As referred in the fig. The two cases are normal incidence or oblique incidence ion beam with rotating substrate can create these nanodots. (1)Ar→Si 500 eV, 67o (2)Ar→GaSb 500 eV, 67o both for 30 min (3)Ar→InP 500 eV, 2 min, 10o Representative patterns for different cases
- Dominant diffusing species is silicon The stability of amorphous interlayer depends on the composition
- Presented the correlation between morphology and local electrical conductivity for ripple structures formed
- Presented the correlation between morphology and local electrical conductivity for ripple structures formed
- Quasi 2 dimensional mass transport make various sputter effects from different incident angles Both transport and sputtering effect produce salient patterns orientational change with angle Asymmetrical wall like structures
- Nanoscale surface ripples generated by oblique-incidence ion bombardment of a solid are generally full of defects, and this has prevented the widespread adoption of ion bombardment as a nanofabrication tool. We advance a theory that predicts that remarkably defect-free ripples can be produced by ion bombardment of a binary material if the ion species, energy and angle of incidence are appropriately chosen. This high degree of order results from the coupling between the surface height and composition, and cannot be achieved by bombarding an elemental material. surface ripples with an exceptionally low density of defects have already been generated by OIIB of silicon (ziberi jpcm 09)