The following are my notes based on the seminar by Prof. Jiwoong park from Cornell at the UT Austin on April 14, 2011.
Functionality
New material new devices, achieving potential applications need manipulation
Challenges:
Single CNT devices, not many publications, challenging part is you need to locate CNT and use lithography to define electrodes,
CdSe/ZnS quantum nanocrystal, Small change make big difference
Synthesis—characterization—assembly/purification
Synthesis: down to atomic details
Characterization: structural and functional identification of individual nanostructureure
Functionality: properties leading to new science and applications
CNT hererogeinity: chirality, length, bundling, defects
Graphene: Poly graphene: grain size, angle, defects, grain boudaory
Lijima 1991, smalley 1985, Geim 2005?
Sp2 bonded carbon allotropes: growing family
Structure sensitive electronic structure
Density of states of semiconducting nanotubes
2d fluorescence imaging
On-chip rayleign imaging
Weissman, smalley 2002
Reyleigh : spatial and spectrally resovled nanotube imaging
Pros: Brightness, visible detection and both active for semi and metal
Cons: reject exciation laser (dark field geometry), clean surface really well-refractive index matching
Cons: background scattering
Roger at UIUC, fully aligned CNT
Resonance freq for different CNT in Rayleigh spectroscopy on aligned CNTs
Nanoletter. 2011 Jan, by Joh
Excitonic (quantum mechanical) CNTs as optical wire – optical conductivity of CNT for light?
Long range intertube coupling: energy transfer
–Electronic and energy conversion
Avouris group, pohotcurrent band gap and more
Tsen 2009 Nature
McEuen group science 2009—multiple exciation generation in CNT pn junctions—ultra-efficient solar cell and IR photodetectors
– CNT 0.75-0.4 band gap for semi-CNT
CNT photophysics minimize spectral loss, long range energy transfer
-going beyond Shockley-Queisser limit
Graphene:
Levendo — transfer free CVD grpahene device
Graphene aas a chemical inner diffusion barrier
Graphen as etching mask
Grain boundary/step edges in CVD and epi grapheme
Mechanical properties, can we image single crystal?
– Free standing CVD graphene, Huang Nature, 20011 Jan. Calsination process. 300 C in air
– Pentagon and heptagon pairs from dislocation in a clean high angle grain boundary bu STM
– TEM dark field
– Temperature dependent grain size
– How to increase grain size??
– McEuen group, controlled nucleation
Graphene for new applications
– Electrical, mechanical –rubber band-
– COF thin film synthesis with Ditchtel Science 2011 April
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