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Northwestern University Rod Ruoff Nanotechnology
High aspect ratio nanostructures: nanotubes, wires, plates, and ribbons
Northwestern University Rod Ruoff Nanotechnology
Outline
1. Introduction
2. Nanotubes
3. Nanowires
4. Nanoplates
5. Nanoribbons
Northwestern University Rod Ruoff Nanotechnology
Part One:
Introduction
Northwestern University Rod Ruoff Nanotechnology
NanostructuresNanostructures are structures that have at least one dimension between 1 and 100 nanometers.
0D nanostructures
- Quantum dots, nano particles and clusters
1D nanostructures
- Nanotubes, nanowires, nanobelts
2D nanostructures
- thin film, nanoplate
www.bobsievers.com/ versailles/p15.html
Northwestern University Rod Ruoff Nanotechnology
Other methods: Colloidal Quantum Dots
• Dispersed in solution• Coated with hydrophilic
material (usually glass):– Melt/quench method– Sol/gel method
M. Bruchez, et al., “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998)T.M. Jovin, “Quantum Dots finally come of Age,” Nature Biotechnology 21, 32-33 (2003)http://ravel.zoology.wisc.edu/sgaap/Bioinformatics_html/Bioinformatics.htm
Northwestern University Rod Ruoff Nanotechnology
Part Two: Nanotubes
Northwestern University Rod Ruoff Nanotechnology
“armchair”
“zig-zag”
chiral
Structure of Carbon Nanotube (CNT)
Single Wall Carbon Nanotube Structure
Northwestern University Rod Ruoff Nanotechnology
Multi-walled carbon nanotube
Single-walled carbon nanotube
Iijima, Nature 1991
Iijima et al;
Bethune et al;
Nature 1993
Northwestern University Rod Ruoff Nanotechnology
SEM image of carbon ropes with~10-20 nm diameter andseveral microns in length
More detailed view of cross section of a “singlewalled carbon nanotube bundle,which is comprised of single-wallednanotubes with diameter ~ 1.4 nm.
Thess et al., Science, 1996
Single wall Carbon Nanotubes
Northwestern University Rod Ruoff Nanotechnology
CNT: Synthesis
1. Arc Discharge
2. Laser Vaporization (ablation)
3. Chemical Vapor Deposition
Northwestern University Rod Ruoff Nanotechnology
CNT: PropertiesMechanical (when defect free):
Young’s Modulus: 1 TPa
Fracture strength: ~100 GPa
Thermal (calculated):
Thermal conductivity: 2000 W/m •K
Electrical:
CNT can be either metal or semiconductor
MWCNTs are typically good conductors: semiconductor with small band gap or metallic
Northwestern University Rod Ruoff Nanotechnology
Brittle behavior is observed in MD simulations at low temperature and high strain (Bernholc and coworkers)
Upon increasing strain the tubeis cleaved
Experimentally tubes are seen tobreak at around 5% strain, inagreement with (Bernholc, Yakobson) predictions(Smalley APL, 1999; Ruoff PRL, 2000 )
CNT: Brittle behavior
Northwestern University Rod Ruoff Nanotechnology
Arc-grown MWCNT
SEM image of powdered cathode deposit core material with 30-40% MWCNT content from MER Corp.
SEM image of separated MWCNTs on a silicon wafer, after fractionation.
Arc-grown Multi-wall Carbon Nanotubes (MWCNTs) from MER Corp. AZ. (diameter: 5-15 nm, length: 3-5 um.)
Northwestern University Rod Ruoff Nanotechnology
CVD-grown Aligned MWCNT Array
Aligned MWCNT arrays were synthesized with PE-CVD method on silicon substrate
Huang et al, Growth of large periodic arrays of carbon nanotubes, App Phys Letter 82(3),2002, 460-462
SEM images of aligned MWCNT array
Northwestern University Rod Ruoff Nanotechnology
Template Synthesized Carbon Tubes
(c) Formation of ordered porous alumina layer after second anodization
(d) Coating of a protective layer
(a) Formation of porous alumina layer after first anodization
(b) Removal of porous alumina layer (strip-off)
(e) Removal of aluminum layer
(f) Removal of bottom layer (i.e., barrier layer)
(g) Removal of protecting layer
aluminum alumina protective layerTerry T. Xu, Richard D. Piner, Rodney S. Ruoff, An improved method to strip aluminum from porous anodic alumina films, Langmuir, 2003; 19(4); 1443-1445
Northwestern University Rod Ruoff Nanotechnology
TCNT: Porous Anodic Alumina (PAA) Films
Top Surface Bottom Surface Cross section
Terry T. Xu, Richard D. Piner, Rodney S. Ruoff, An improved method to strip aluminum from porous anodic alumina films, Langmuir, 2003; 19(4); 1443-1445
Northwestern University Rod Ruoff Nanotechnology
TCNT: Synthesis Strategy
Northwestern University Rod Ruoff Nanotechnology
TCNT: Result
Ordered CNTs (after partially dissolving PAA )
TEM image showing two T-CNTs
Northwestern University Rod Ruoff Nanotechnology
Bone-shape Carbon Nanotube
Terry T. Xu, Frank T. Fisher, L. Cate Brinson, and Rodney S. Ruoff, Bone-shaped Nanomaterials for Nanocomposite Applications, Nano Letters, 3(8), 1135 -1139, 2003
Northwestern University Rod Ruoff Nanotechnology
BCNT: Cross-section
Northwestern University Rod Ruoff Nanotechnology
BCNT: TEM Image
Northwestern University Rod Ruoff Nanotechnology
Part Three: Nanowires
Northwestern University Rod Ruoff Nanotechnology
Crystalline Boron Nanowire
SEM image of boron nanowires on alumina substrate TEM image of a boron nanowire
Otten, Carolyn Jones; Lourie, Oleg R.; Yu, Min-Feng; Cowley, John M.; Dyer, Mark J.; Ruoff, Rodney S.; Buhro, William E., Crystalline Boron Nanowires, Journal of the American Chemical Society, (2002),124(17),4564-4565.
Northwestern University Rod Ruoff Nanotechnology
Boron nanowires and nanotubes
Catalysts-assisted growth of boron nanowire-nanotube hybrid structure was discovered.
• Experiment– Method: Chemical Vapor Deposition (CVD)– Precusor: diborane (B2H6)– Substrate: Si with one-micron-thick SiO2– Catalyst: gold (Au), Pt/Pd alloy (nominal 80:20, Pt:Pd)– Pressure: ~200 mtorr– Temperature (center position of the tube furnace): 900°°°°C
• Results– Interesting boron nanowire-catalyst-nanotube hybrid structure was
discovered. Smallest nanostructure was ~ 8-10 nm.– Catalyst geometry in the B nanostructure plays an important role.– Detailed investigation is underway.
Northwestern University Rod Ruoff Nanotechnology
morphology• Catalyst-assisted growth of nanowires and nanotubes.• Interesting nanowire-catalyst-nanotube hybrid nanostructures were commonly
observed. • Smaller catalyst smaller nanowires/nanotubes. So far, the smallest one we
can synthesize was about 8-10 nm in diameter.
tube catalystwire
tube
SEM image of nanowire and nanotubes (φφφφ: 30-150nm; Au as catalyst)
tubecatalyst
wire
φφφφ: 15-30nm; Pt/Pd as catalyst.
Terry Xu, Rod Ruoff, to be submitted.
Northwestern University Rod Ruoff Nanotechnology
Structure Characterization
Crystalline nanowire Nanowire-catalyst-nanotube hybrid structure (amorphous)
amorphous nanowire
• TEM catalyst shape plays an important role!• EELS boron and small amount of oxygen.• Detail investigation is underway.
Terry Xu, Rod Ruoff, to be submitted.
Northwestern University Rod Ruoff Nanotechnology
CaB6: Properties of CaB6
Crystal structure of CaB6
•Crystal structure –CsCl type–B6 octahedra and Ca atoms
•Physical properties–Tm = 2235°C– ρ = 2.43g/cm3–E = 451GPa–ρe = 222µΩ-cm–Vicker hardness = 27GPa
•Applications–Surface protection, wear resistant materials–High neutron absorbability, nuclear industry, etc.
Northwestern University Rod Ruoff Nanotechnology
CaB6: Experimental ConditionsLow pressure chemical vapor deposition (LPCVD) growth of CaB6 nanowires
SEM image of CaB6 nanowires
Terry T. Xu, Jian-Guo Zheng, Alan W. Nicholls, Sasha Stankovich, Richard D. Piner, Rodney S. Ruoff, Calcium Boride Nanowires: Synthesis and Characterization, NanoLetters, 4(10), 2051-2055 (2004)
•Reactant: B2H6 gas precursor,CaO powder•Catalyst: Ni, PtPd alloy•Temperature: 850-900°C•Pressure: ~150mtorr•Substrate: Si with 1µm thick SiO2, sapphire, fused quartz
Northwestern University Rod Ruoff Nanotechnology
CaB6 : Experimental Results
Nanowires without catalyst on tip880-890°C
TEM images
[001]
Nanowires with catalyst on tip890-900°C
TEM images
Ni catalyst
CaB6 nanowire
[001]
Calcium Boride Nanowires: Synthesis and Characterization Terry T. Xu, Jian-Guo Zheng, Alan W. Nicholls, Sasha Stankovich, Richard D. Piner, Rodney S. Ruoff*, Nano Letters, 4(10), 2051-2055 (2004).
Northwestern University Rod Ruoff Nanotechnology
SiC nanowire grown from SiCfibril (supplied by Dick Nixdorf)
“Hairy fibers for composites?
Northwestern University Rod Ruoff Nanotechnology
Part Four: Nanoplates
Northwestern University Rod Ruoff Nanotechnology
Thin Graphite FilmThin graphite films at the edge of Highly Ordered Pyrolytic Graphite (HOPG).
Northwestern University Rod Ruoff Nanotechnology
Thin Graphite Film
Northwestern University Rod Ruoff Nanotechnology
X. K. Lu, H. Huang, N. Nemchuk and R. S. Ruoff, Patterning of highly oriented pyrolytic graphite by oxygen plasma etching, Appl. Phys. Lett., 75, 193-195 (1999).
Graphite Platelet
Northwestern University Rod Ruoff Nanotechnology
Tin Oxide Disk
Dai ZR, Pan ZW, Wang ZL, Growth and Structure Evolution of Novel Tin Oxide Diskettes, J. Am. Chem,. Soc., 2002, 124, 8673-8680
Type I SnO2 disk
Type II disk with growth feature of terrace and spiral stepsSEM image of SnO disk
SnO diskettes were synthesized by evaporating either SnO or SnO2 powders at elevated temperature (200-400oC).
Northwestern University Rod Ruoff Nanotechnology
Part Five: Nanoribbon
Northwestern University Rod Ruoff Nanotechnology
ZnO Nanoribbon
Pan, ZW, Dai, ZR, Wang ZL, Nanobelts of semiconducting Oxides, Science, 291(2001), 1947-1949
(a) SEM and (b) TEM images of ZnO nanobelt
Typical width: 30-300 nmWidth to thickness ratio: 5-10
Northwestern University Rod Ruoff Nanotechnology
SnO2Nanobelt
Dai, ZR., Pan, ZW., Wang, ZL, Ultra-long single crystalline nanoribbons of tin oxide, Solid State Communication, 118 (2001) 351-354
TEM image of SnO2 nanoribbon Structure model of SnO2 nanoribbon
Northwestern University Rod Ruoff Nanotechnology
Ga2O3 Nanoribbon/Nanosheets
Dai ZR, Pan ZW, Wang ZL, Gallium Oxide Nanoribbons and Nanosheets, J. Phys. Chem.B, 2002, 106,902-904
SEM and TEM image of Ga2O3 nanoribbons and nanosheets
Nanoribbons and flat nanosheets of Ga2O3 were synthesized by evaporating GaN at high temperature with the presence of oxygen.
Northwestern University Rod Ruoff Nanotechnology
Boron Nanoribbons
Terry Xu
Catalyst-free growth of single crystal αααα–tetragonal boron
nanostructures at relatively low temperature and pressure. Experiment
–Method: Chemical Vapor Deposition (CVD)
–Precusor: diborane (B2H6)
–Substrate: Si with one-micron-thick SiO2
–Pressure: ~200 mtorr
–Temperature (center position of the tube furnace): 900°C
•Results–Puffy ball deposition were observed in the 600-750°C temperature zone region.
–Puffy balls were made of nanostructures having different morphology.
–The nanostructures are single crystal α–tetragonal boron.
Northwestern University Rod Ruoff Nanotechnology
Boron Nanoribbon: morphology
Overall view of the puffy ball
“Nano-scrolls” (w: 800-3200nm; t: ~20nm)
Grass-like nanoribbons • twisted, zigzag edges• w: 200-450nm; t: ~20nm Ends of the nanoribbons split into
nanowires (w:20-100nm; t: ~20nm)
Northwestern University Rod Ruoff Nanotechnology
Boron Nanoribbon: Structure Characterization
• Diffraction pattern single crystal α–tetragonal boron
• HRTEM crystallized structure covered by a 1 to 2 nm thick amorphous layer
• EELS boron and small amount of oxygen• The amorphous oxide layer was apparently formed
after the sample was exposed to ambient.
TEM image of twisted nanoribbonsHRTEM image and diffraction pattern
EELS spectrum
Terry T. Xu, Jian-Guo Zheng, Nianqiang Wu, Alan W. Nicholls, John R. Roth, Dmitriy A. Dikin, and Rodney S. Ruoff, Crystalline Boron nanoribbons:Synthesis and Characterization, Nano Letters, 2004; 4(5); 963-968.