Background about Carbon Nanotubes CAR Seminar 5 November 2010 Meg Noah

Carbon Nanotubes (CNT) A rolled up graphene sheet Unique physical & chemical properties  flexibility  extremely strong, about 100 times stronger (stress resistant) than steel  light-weight 1/6th the weight of steel  either conductors or semiconductors  intrinsic superconductivity (ballistic electron transport)  ideal thermal conductors  field emitters MAN 10Aug07

SWNT and MWNT Single Wall Nanotube Diameters nm (1.4 nm is typical) Elastic Modulus 1210 GPa Strain 4% Density 1.4 g/cm 3 Multi Wall Nanotube Diameters nm Elastic Modulus 1260 GPa Strain 1.5% Density 1.8 g/cm 3 MAN 10Aug07

Chirality MAN 10Aug07

Chirality and Structural Properties MAN 10Aug07 The hexagonal lattice vectors: For graphite a C-C = Å is the bond distance. For CNT it is about 1.44 Å and depends on radius. SWNT Circumference from Chirality indices (n,m): The Diameter of the SWNT:

Chirality and Electrical Properties Armchair (n=m) All metallic None semiconducting Chiral (n ≠ m) 1/3 are metallic 2/3 are semiconducting metallic when (n-m)=3*integer ZigZag (m=0) 1/3 are metallic 2/3 are semiconducting metallic when n=3*integer Example: (5,5) 200 atoms Diameter = 6.78 Å Length = Å Example: (5,0) 200 atoms Diameter = 3.91 Å Length = Å Example, (5,3) 196 atoms Diameter = 5.48 Å Length = Å MAN 10Aug07

Chirality – Unique ID (n,m) MAN 10Aug07 The Chirality Vector indices (n,m) uniquely define the SWNT:  Diameter  Electronic Properties (metallic, insulating, semiconducting) To know the diameter of a SWNT is to know the chirality indices (n,m), and thus it’s structural, electronic and mechanical properties.

Images are from: = Applications of CNT 1:Tethering cable for he space elevator 2:Low power flexible displays 3:Light weight Bicycle frames 4:Transistors for future central processing unit (CPU)

SEM Images from NEU From the lower magnification (~200X to ~1000X) the CNT length is measured.

SEM Images from NEU Used to visually assess the quality of CNT. Can we develop an automated algorithm for determining quality? Is quality correlated to processing parameters? 13 s 10 mA 200 sccm Cobalt Sputter Time: 13 s Cobalt Sputter Current: 5 mA Ethanol Gas Flow Rate: 200 sccm Bad ResultsGood Results