Caratterizzazione di nanotubi di carbonio (CNT) Carlo Mariani Dipartimento di Fisica, Università di Roma “La Sapienza” - brief introduction to CNT - short overview about their synthesis - electronic structure characterization and microscopy INFN, Dipartimento di Fisica, “Pomeriggio su nuovi materiali: nanostrutture”, 30 marzo 2015

NANOTUBI DI CARBONIO diameter = a/  sqrt(n 2 + nm + m 2 ) = 0.78 sqrt(n 2 + nm + m 2 ) [in Å]

NANOTUBI DI CARBONIO: SEMICONDUTTORI O METALLICI? because of the specific symmetry, strong effect on the electronic properties; given (n,m): n=m → metallic n – m= multiple of 3 → semiconducting

C-nanotubes

a few words about CNT growth - metal-catalyzed reactions using chemical vapor deposition (CVD) steps; - initial stage of CNT nucleation with CH3CH2OH molecular precursor, performed by thermal-CVD; - plasma-activated CVDs [hot filament (HF) or microwave (MW)] using CH4 as carbon reservoir example of CNT on patterned Si surface for e-gun cathode application G. Ulisse et alii, IEEE Electron Device Lett. 34, 698 (2013)

a few words about CNT growth - metal-free synthesis by Ge semiconducting nano-particles; - thermal-CVD on nano-indented Si surface; - multi-wall CNTs example of metal-free CNT on patterned Si surface A. Capasso et alii, J. Non-Cryst. Solids 356, 1972 (2010)

aligned CNT - metal-catalyzed high-temperature synthesis; - aligned bundles of CNTs; example of CNT on a flexible electrode Wenwen Yi et alii, J. Nanotechnology 26, (2015) CNT on a Si wafer Scardamaglia et alii, Carbon 83, 118 (2015)

Raman spectroscopy characterization of CNT Camilli et alii, J. Nanotechnology 25, (2014) Angelucci et alii, Physica E 42, 1469 (2010) inelastic light scattering; typical Raman modes associated to the C-network, for different bundles of CNTs

photoelectron spectroscopy, XPS h

Single Particle Scheme of Energy Levels E kin = Final State Kinetic Energy  = Work Function E b F (k) = Binding Energy of the k-th Initial State Photoemission Spectroscopy in the solid state

photoelectron spectroscopy as a tool of C chemical bonding Gupta et alii, Carbon 68, 563 (2014) C-1s at Graphene Grwon on SiC thin-film on Si emerging of the typical Graphene peak as a function of annealing temperature The C 1s core-level as a finger-print of the electronic configuration of the C- network and of the C chemical bonding

photoelectron spectroscopy as a tool of C chemical bonding The C 1s core-level as a finger-print of the electronic configuration of the C- network and of the C chemical bonding C-1s at Graphene flakes, from pristine flakes (center) to annealed Graphene (right) M. Angelucci, PhD Thesis, Sapienza Univ., unpublished (2014)

photoelectron spectroscopy as a tool of C chemical bonding The C 1s core-level as a finger-print of the electronic configuration of the C- network and of the C chemical bonding C-1s at Graphene nano-ribbons C-1s at Graphene under Li exposure Hassoun et alii, Nano Letters 14, 4901 (2014) Massimi et alii, J. Phys. Chem. C 119, 2427 (2015)

XPS and X-ray absorption spectroscopy (XAS) as a tool of C chemical bonding single-wall (SW) CNT clean and after F-exposure C-1s XPS for CNT clean (black) and after F-exposure (pink) Lavskaya et alii, J. Phys. Chem. C 47, 1629 (2009) C-K edge XAS for CNT clean (black) and after F-exposure (gray)

XPS and X-ray absorption spectroscopy (XAS) as a tool of C chemical bonding aligned CNT clean and after N-grafting C-1s XPS as a function of N dose Spatially resolved C 1s spectro- microscopy Scardamaglia et alii, Carbon 83, 118 (2015)

Conclusions and Perspectives: photoelectron spectroscopy as powerful tool for probing C chemical bonding in CNT before and after irradiation