Arquivo do seminário apresentado pelo professor Fernando Alvarez, pesquisador da seção Unicamp do Instituto Nacional de Engenharia de Superfícies, no dia 20 de agosto de 2013, na seção UCS do Instituto, para um público de 30 estudantes e professores de cursos de graduação e pós-graduação.

1. Surface Engineering Nanostructures
Low energy Ion bombardment nanostructuring Process
Fernando Alvarez
Instituto de Física "Gleb Wataghin", Unicamp, 13083-970, Campinas, SP, Brazil
Collaborators
M. Morales, E. A. Ochoa, S. Cucatti, R. Droppa, R. B. Merlo
Equipamentos e ProcessosEquipamentos e Processos

2. Surface Engineering Nanostructures: An Introduction
• Top Down : photo lithographic, micro-contact printing and catalyst growth, masks,
writing (electron beam), molds
• Bottom Up: Surface Functionalization, Self Organized Nano-Porous Lattice,
supramolecular structures (from atomic to mesosopic scales)
Self Organization by Ion Beam Treated Surfaces
a) Sculpted Substrate By Ion Beam Bombarded
b) Self – Organized Structures Obtained By Ion Sputtering
• Coclusions

3. Flat panels (CNT-FED) Project CANADIS
Top Down Fabrication: Nanostructured Regular Patterns
Nano-Lithography (Project NANOLITH)
Cold cathode for hyper-frequency devices
(> 30 GHz) Propjet CANVADS
Standard Photo-Lithography Electron Beam Patterning Reactive Plasma Etching

4. *
Carbon nanotubes grown by CVD
M. Morales,et al., JPhysD., 2013, IFGW-UNICAMP
Top Down Fabrication: Nanostructured Regular
Patterns
Single Carbon nanotubes between triple-layer catalyst (Al~10 nm/Fe~1 nm!/Mo~0.2
nm) Lacerda et al. APL, 84,269, 2004
Single Carbon nanotubes between two electrodes
Tans, S., et al., Nature 394, 761–764 (1998).

5. EDS
EDS
Bottom Up Fabrication: Mesoporous Patterned Silica
Amphiphilic: from the Greek αµφις, amphis: both and φιλíα, philia: friendships, EDS: Energy Dispersive X-ray Spectroscopy
Pm3n Cubic Symmetry
Cross Section TEM
• Mesoporous (Pm3n) films (dip coating) combining polycondensation of silicate species
and organization of amphiphilic mesophases
• Temperature Evaporation-induced self-assembly of the mesoporous film
• Decorated with iron-based nanoparticles in iron aqueous solution (0.2M FeSO4.7H2O)
M. C. Marchi, C. Figueroa, and F. Alvarez, J. Nanosc. Nanotechn., 8, 448, 2008 , IFGW, UNICAMP
Evaporation-induced self-assembly

6. Bottom Up Fabrication: Mesoporous Patterned Silica
J.J.S. Acuña, M.C. Marchi, C. Figueroa, F. Alvarez , Thin Solid Films 519 (2010) 214–217
• Silica Based Thin Film (Im3m) cubic symmetry
• 7 nm cavities sizes separated by ~1.8 nm walls
• CVD Carbon Nanotubes Growth
TEM-Cross Section SEM-Top View
SEM-Top View

7. Si
Nanotubes growth:Sequential process
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013
IBD-TINxOy
Nickel Particles
CVD-CNTs IBD
Si
Si
+ Annealing
Barrier layer

8. TiNx Buffer Layers Thin Films Preparation
500°C
Sputtering
gun
Turbo
pump
XPS
IBD-TINxOy
H2 Flux 0,1,2,3,4 sccm
Oxygen Containing Control
Si
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013

9. Si
Catalyst Ni Particles: Ion Beam
Deposition
Sputtering
gun
Turbo
pump
XPS
Nickel Particles
750°C
1.5 min
deposition
5 min annealing
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013

10. CNTs analysis
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
20
40
60
80
100
06121824
[H2]/[N2+Ar], %
NumberofCNTs/µµµµm
2
Oxygen Concentration, at.%
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
26
28
30
32
34
36
38
DiameterModeCNTs(nm)
Oxygen Concentration, at.%
06
[H2]/[N2+Ar], %
121824
•Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013

11. CNTs results
O in the film
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013

12. CNTs analysis
12
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
20
40
60
80
100
06121824
[H2]/[N2+Ar], %
NumberofCNTs/µµµµm
2
Oxygen Concentration, at.%
Oxygen
Presence
Inhibit
Ostwald
ripening
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
26
28
30
32
34
36
38
DiameterModeCNTs(nm)
Oxygen Concentration, at.%
06
[H2]/[N2+Ar], %
121824
Original
Number
particles
Smaller
Si
TiNxOy
Ni
Ni
Si
TiNxOy
Ni
Smaller ΦΦΦΦ
CNTs
More
Density CNTs
Ostwald
ripening

13. 1W. K. Burton, N. Cabrera and F. C. Frank, Royal Soc., 243, 1950; D. Walton in Nucleation, Edited by A. Z. Zettlemoyer, Marcel Dekker, INC. NY, 1969; W. K. Burton , N.
Cabrera. And F. C, Frank, Phil. Trans. Roy Soc., London, A243, 302, 1951
Surface Structuring: a brief introduction
• Atoms deposited from the vapor phase
• Self-Organizing: Mean Way between kinetic and thermodynamic phenomenon (non-equilibrium)
• Surface diffusion on a flat surface (terrace): primary mechanism (activated process)
• Mean displacement adatom λλλλ: distance before remains immobilized or detaching to the vapor1
λλλλ=λλλλ0exp [ (εεεεs-us)/2kT]
εεεεs : evaporation energies (from the surface to the vapor phase)
us : jumping activation energy between two neighboring equilibrium positions distant λλλλ0 each other
λλλλ
Jumping
Detaching
F
• D/F>>1 Process Governed by Thermodynamic
(Near Equilibrium)
• D/F<<1 Process Governed by Kinetic
D= Diffusion Coefficient

14. Lagally and Zhang, nature, 417, p907, 2002
Thin Films Growth: Surface Phenomenon
Potential Barriers
•Along a Terrace
Crossing
• 3D-Barrier
• 2D-Barrier
• 1D-Barrier
Ehrlich & Schwoebel
Barrier

15. Surface Structuring: Continuation
• Interlayer mass transport: control vertical uniformity
• Controlled by energetic barriers at the step
Ehrlich & Schwoebel Barrier (E-S) : Scale with local coordination
Ehrlich &Schwoebel Barrier

16. S. J. Liu et al. Appl. Phys. Lett., Vol. 80, No. 18, 6 May 2002
{111}
{111}
Top View
Diffusing along the terrace
Eb~ 0.45 eV

17. S. J. Liu et al. Appl. Phys. Lett., Vol. 80, No. 18, 6 May 2002
{111}
{111}
Top View
Instability: Piling up along the terrace
Eb~ 0.45 eV

18. Low energy Ion bombardment nanostructuring Process
Fine control Deposition Parameters
• Ion Species and Ion Energy
• Impinging Angle
• Flux (Dose)
• Beam Size
• Substrate Temperature

19. Campinas Sky, SP, Brazil
Snow Ripples
Las Leñas, Argentina
Atacama Desert, Chile
Ion Beam Sputtering
Si (110) Xe, 1keV, Perpendicular
Morales, Merlo, Droppa, and Alvarez, 2013. DFA, IFGW, UNICAMP

20. Topography Accident: Sand and Snow
Sand(Snow) Dunes: At the hill or depression, Different Velocities
Clouds: ripples between the dry, cool air above and the moist, warm air
below
Less Velocity
Αννννεµος: Wind God

21. Nano-Structures on Gallium Antimonide: Ar+ Ion Sputtering
Facsko et al., Science 285,1999, p1551
Hexagonal Symmetry
4x1017 cm-2, 40 s 2x1018 cm-2, 200 s 4x1018 cm-2, 200 s
500nm 500nm 500nm
GaSb
Fluences:5.2x1031/nm2;Tempo: 90 min and λλλλ=37–43 nm
Au
ΘΘΘΘ~730
Dual Ion Beam Sputtering, 2keV

22. Xe+ Patterning: Experiment
Cucatti & Alvarez, PSE 2012
22
•Substrate
•Ion gun
•Turbo
•pump
Material: SS 316, Policrystal (austenite)
XPS

23. Xe+ Patterning
Fixed parameters:
• Room temperature (~25ºC)
• Time: 30 min
• Energy: 1 KeV
• Current density: 0.37 mA/cm²
• Power: 0.4W/cm²
• Dosis: 2.2 x 1018
• Working pressure: 1.4 x 10-3 mbar
•23 •PSE 2012 S. Cucatti Sep 12
Different impinging angles
β = 0º, 15º, 30º, 45º, 60º
Austenitic Stainless Steel 316L
Mirror-polished samples (roughness < 1.5 nm)

24. Xe+ Bombardment (SS 316L)
β =15º β = 45º β = 60º
Patterns depend on crystalline orientation
Diffusion regime: time to reach equilibrium
Cucatti , Morale,Alvarez, DFA, IFGW, UNICAMP, 2013
SEM-FEG

25. SEM-FEG images from AISI 316L using (Xe+, 1 keV)
•25 •PSE 2012 S. Cucatti Sep 12
Crystalline
grains evidenced
Patterns within
the crystalline
grains
15º
Pattern

26. Xe+ Bombardment SS 316L- Roughness
PSE 2012 S. Cucatti Sep 12
• Competition between the diffusion and
erosive regime ³
• Lower angle increasing sputtering
• Pattern: direction of the beam
Increase of impinging angle
0 15 30 45 60
0
5
10
15
20
25
RMSRoughness(nm)
Impinging angle ββββ (degrees)
Only polished (<1.5 nm)
•[3U.Valbusa, C. Boragno, F. Buatier de Mongeot, J. Phys.: Condens. Matter 14 (2002) 8153-8175

27. Patterning effect on nitrogen diffusion
New Nitrided Phase
Small Precipitated
Needle Precipitated
Cucatti et al, DFA,IFGW,UNICAMP, 2013

28. Bombardment Effect

29. Experimental: Ion Beam
Energy
(nominal): 20 – 1200 eV
PO2 <10-8 mb
Current
(nominal): ~1mA/cm2
TARGET
ION GUN 1
UHV
XPS
SUBSTRATE
T Controlled
ION GUN 2
TURBO
PUMP
NG+
Ion gun
(Kaufman)
Noble gases Bombardment (NG +): Ar +, Kr, + Xe +Noble gases Bombardment (NG +): Ar +, Kr, + Xe +
Ar, Xe+

30. Ion-driven patterning: Bradley & Harper Model
ConvexConcave
M. Bradley and J. M. E. Harper, J. Vac. Sci. Technol. A, 6,4, 1988
Closer: More Energy in ΘΘΘΘ´ Faster Erosion
ΘΘΘΘ´
ΘΘΘΘ

31. Ripples Wavelength: Diffusive Regimen
λλλλ=2ππππ (2K/||||vi||||)1/2
i=x,y directions and vi, the largest velocity
Erosion Regimen
• Strong Sputtering preventing accommodation by diffusion
• The surface nanostructure is forced to following the direction of the ions
• Increasing roughness with impinging sputtering angles.
• The erosion is mild and diffusion “fast”
• The Ripples align along the crystalline direction (thermodynamically
equilibrium)

32. Self-organized 2-D Ni particles deposited on titanium nitride
(a) Near normal substrate ion bombardment
(b) Pattern formed after bombardment
(c) Thin film of TiNxOy on the patterned substrate
(d) Self-organized nickel particles deposited on the template
M. Morales, R. B. Merlo, R. Droppa Jr, and F. Alvarez, submitted, 2013 , IFGW, UNICAMP
Sequential steps in the growing process of the nickel particles self-assembling

33. Near normal substrate ion bombardment

34. TiN Deposition: Ion Beam Deposition
Sputtering
gun
Turbo
pump
XPS
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013
N2

35. The original pattern is conserved
Sculpted Si Perpendicularly Xe+ beam TiNxOy coated on sculpted Si
Patterned Si Substrate + Coating

36. TiN + Ni Particles Ion Beam Deposition
Sputtering
gun
Turbo
pump
XPS
Carbon nanotubes grown by CVD, M. Morales,et al., JPhysD., Submitted, 2013
Si
Nickel Particles
750°C
1.5 min deposition
5 min annealing

37. •Self-organized 2-D Ni arrange
•Lattice constant of a x b
2-Fold Symmetry
ππππ
ππππ
+

38. AFM Image
• Lattice constants: |a|≈171 nm, |b|≈184 nm, 690
• Defects: missing row (“edge dislocations”)

39. Adatoms: diffusion and coalescence
•The Ni particles diffuse on the surface until incorporated at a nucleation
center.
•Adatoms diffuse a mean displacement λλλλ constrained to move on the
crest due to the Ehrlich-Shhwoebel barrier,
λλλλ= λλλλ0 exp [ (εεεεs-us)/2kT]
εεεεs Evaporation energies from the surface to the vapor phase
us Jumping energy between two equilibrium positions distant λλλλ0 each other
•The adatom diffuses along the top of the hill until meeting a second
atom
• A particle sink and depleted surrounding neighborhood start.

40. S. J. Liu et al. Appl. Phys. Lett., Vol. 80, No. 18, 6 May 2002
{111}
{111}
Top View
Instability: Piling up along the terrace
Eb~ 0.45 eV

41. Ehrlich-Shhwoebel (E-S) barrier
λλλλ
Self - Organization

42. Conclusions
• Process generating organized nanostructures: top down, bottom up and
ion driven
• Different possibilities generating nanostructures by bombarding
• Ion driven patterning can generate regular patterns
• Self-organized metallic nano-particles on coated patterned silicon
• Self-organization: Irregularities still important (Improving process
necessary)
• Lack of general theoretical understanding of the general process
of self-organization