High aspect ratio nanostructures: nanotubes, wires, plates, and ribbons. Outline

Transcription

1 High aspect ratio nanostructures: nanotubes, wires, plates, and ribbons Outline 1. Introduction 2. Nanotubes 3. Nanowires 4. Nanoplates 5. Nanoribbons

2 Part One: Introduction Nanostructures Nanostructures 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 versailles/p15.html

3 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, (1998) T.M. Jovin, Quantum Dots finally come of Age, Nature Biotechnology 21, (2003) Part Two: Nanotubes

4 Structure of Carbon Nanotube (CNT) armchair zig-zag chiral Single Wall Carbon Nanotube Structure Multi-walled carbon nanotube Iijima, Nature 1991 Single-walled carbon nanotube Iijima et al; Bethune et al; Nature 1993

5 Single wall Carbon Nanotubes SEM image of carbon ropes with ~10-20 nm diameter and several microns in length More detailed view of cross section of a single walled carbon nanotube bundle, which is comprised of single-walled nanotubes with diameter ~ 1.4 nm. Thess et al., Science, 1996 CNT: Synthesis 1. Arc Discharge 2. Laser Vaporization (ablation) 3. Chemical Vapor Deposition

6 CNT: Properties Mechanical (when defect free): Young s Modulus: 1 TPa Fracture strength: ~100 GPa Thermal (calculated): Electrical: Thermal conductivity: 2000 W/m K CNT can be either metal or semiconductor MWCNTs are typically good conductors: semiconductor with small band gap or metallic CNT: Brittle behavior Brittle behavior is observed in MD simulations at low temperature and high strain (Bernholc and coworkers) Upon increasing strain the tube is cleaved Experimentally tubes are seen to break at around 5% strain, in agreement with (Bernholc, Yakobson) predictions (Smalley APL, 1999; Ruoff PRL, 2000 )

7 Arc-grown MWCNT Arc-grown Multi-wall Carbon Nanotubes (MWCNTs) from MER Corp. AZ. (diameter: 5-15 nm, length: 3-5 um.) 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. CVD-grown Aligned MWCNT Array Aligned MWCNT arrays were synthesized with PE-CVD method on silicon substrate SEM images of aligned MWCNT array Huang et al, Growth of large periodic arrays of carbon nanotubes, App Phys Letter 82(3),2002,

8 Template Synthesized Carbon Tubes (a) Formation of porous alumina layer after first anodization (b) Removal of porous alumina layer (strip-off) (c) Formation of ordered porous alumina layer after second anodization (d) Coating of a protective layer (e) Removal of aluminum layer (f) Removal of bottom layer (i.e., barrier layer) (g) Removal of protecting layer aluminum alumina protective layer Terry T. Xu, Richard D. Piner, Rodney S. Ruoff, An improved method to strip aluminum from porous anodic alumina films, Langmuir, 2003; 19(4); 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);

9 TCNT: Synthesis Strategy TCNT: Result Ordered CNTs (after partially dissolving PAA ) TEM image showing two T-CNTs

10 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), , 2003 BCNT: Cross-section

11 BCNT: TEM Image Part Three: Nanowires

12 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), Boron nanowires and nanotubes Catalysts-assisted growth of boron nanowire-nanotube hybrid structure was discovered. Experiment Method: Chemical Vapor Deposition (CVD) Precusor: diborane (B 2 H 6 ) Substrate: Si with one-micron-thick SiO 2 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.

13 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 catalyst wire tube catalyst tube wire SEM image of nanowire and nanotubes (φ: nm; Au as catalyst) φ: 15-30nm; Pt/Pd as catalyst. Terry Xu, Rod Ruoff, to be submitted. Structure Characterization TEM catalyst shape plays an important role! EELS boron and small amount of oxygen. Detail investigation is underway. Crystalline nanowire Nanowire-catalystnanotube hybrid structure (amorphous) amorphous nanowire Terry Xu, Rod Ruoff, to be submitted.

14 CaB 6 : Properties of CaB 6 Crystal structure CsCl type B 6 octahedra and Ca atoms Physical properties T m = 2235 C ρ = 2.43g/cm3 E = 451GPa ρ e = 222µΩ-cm Vicker hardness = 27GPa Applications Surface protection, wear resistant materials High neutron absorbability, nuclear industry, etc. Crystal structure of CaB 6 CaB 6 : Experimental Conditions Low pressure chemical vapor deposition (LPCVD) growth of CaB 6 nanowires Reactant: B 2 H 6 gas precursor, CaO powder Catalyst: Ni, PtPd alloy Temperature: C Pressure: ~150mtorr Substrate: Si with 1µm thick SiO 2, sapphire, fused quartz SEM image of CaB 6 nanowires Terry T. Xu, Jian-Guo Zheng, Alan W. Nicholls, Sasha Stankovich, Richard D. Piner, Rodney S. Ruoff, Calcium Boride Nanowires: Synthesis and Characterization, Nano Letters, 4(10), (2004)

15 CaB 6 : Experimental Results Nanowires with catalyst on tip C Nanowires without catalyst on tip C Ni catalyst [001] [001] CaB 6 nanowire TEM images TEM images 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), (2004). SiC nanowire grown from SiC fibril (supplied by Dick Nixdorf) Hairy fibers for composites?

16 Part Four: Nanoplates Thin Graphite Film Thin graphite films at the edge of Highly Ordered Pyrolytic Graphite (HOPG).

17 Thin Graphite Film Graphite Platelet 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, (1999).

18 Tin Oxide Disk SnO diskettes were synthesized by evaporating either SnO or SnO 2 powders at elevated temperature ( o C). Type I SnO 2 disk SEM image of SnO disk Type II disk with growth feature of terrace and spiral steps Dai ZR, Pan ZW, Wang ZL, Growth and Structure Evolution of Novel Tin Oxide Diskettes, J. Am. Chem,. Soc., 2002, 124, Part Five: Nanoribbon

19 Typical width: nm ZnO Nanoribbon Width to thickness ratio: 5-10 (a) SEM and (b) TEM images of ZnO nanobelt Pan, ZW, Dai, ZR, Wang ZL, Nanobelts of semiconducting Oxides, Science, 291(2001), SnO 2 Nanobelt TEM image of SnO 2 nanoribbon Structure model of SnO2 nanoribbon Dai, ZR., Pan, ZW., Wang, ZL, Ultra-long single crystalline nanoribbons of tin oxide, Solid State Communication, 118 (2001)

20 Ga 2 O 3 Nanoribbon/Nanosheets Nanoribbons and flat nanosheets of Ga 2 O 3 were synthesized by evaporating GaN at high temperature with the presence of oxygen. SEM and TEM image of Ga2O3 nanoribbons and nanosheets Dai ZR, Pan ZW, Wang ZL, Gallium Oxide Nanoribbons and Nanosheets, J. Phys. Chem.B, 2002, 106, Boron Nanoribbons Catalyst-free growth of single crystal α tetragonal boron nanostructures at relatively low temperature and pressure. Experiment Results Method: Chemical Vapor Deposition (CVD) Precusor: diborane (B 2 H 6 ) Substrate: Si with one-micron-thick SiO 2 Pressure: ~200 mtorr Temperature (center position of the tube furnace): 900 C Puffy ball deposition were observed in the C temperature zone region. Puffy balls were made of nanostructures having different morphology. The nanostructures are single crystal α tetragonal boron. Terry Xu

21 Boron Nanoribbon: morphology Overall view of the puffy ball Nano-scrolls (w: nm; t: ~20nm) Grass-like nanoribbons twisted, zigzag edges w: nm; t: ~20nm Ends of the nanoribbons split into nanowires (w:20-100nm; t: ~20nm) Boron Nanoribbon: Structure Characterization TEM image of twisted nanoribbons HRTEM image and diffraction pattern 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. 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);