Graphene Electronics 0609243

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Transcript Graphene Electronics 0609243

Preparation of nGLs
Raman Imaging of nGLs
SiO2: Si
G ~ 1/n
(side view)
(top view)
Graphene Electronics
Micro-Mechanical cleaving process to make nGLs
n-Graphene Layer = nGL ; n is integer
A. Guptaa, X. Honga, P. Joshib,
Y. Tang , H. Romero ,
P. Lammerta, N. Durateb,
G. H. Huanga, C. Cheng-Inga ,
S. Tadigadapab,
J. Zhua,
V. H. Crespi
and P. C. Eklunda,c
Visualization of nGLs
Optical Image
Raman scattering is found to be sensitive
to the number of layers in nGLs.
Splitting of electronic bands is
captured in the shape of 2D band.
1GL shows a single 2D peaks while
nGLs (small n) show 4 peaks which
evolve in 2 peaks for higher n.
Introduce 10% NH3
Contrast in optical image strongly depends on the
thickness of oxide as well as the wavelength of
illuminating light. Graphene shows high contrast in
white light illumination for ~ 100 nm thick SiO2
Transport in FET geometry for nGLs
shows Dirac peak with finite resistance.
Graphene (1GL) FETs patterned into
Hall bar and van der Pauw geometries
show half-integer quantum Hall
sequence 4(n+1/2) at low temperature.
(Rxx) and Hall (Rxy)
measurements of
nGL (n>1) devices at
low temperature.
AFM height measurements for nGLs. Extra thickness
of graphene (0.7 nm) may reflect inherent difference in
attractive AFM tip force between SiO2 and graphene
Theoretical Calculations
1. A. Gupta, Y. Tang, V. H. Crespi and P. C. Eklund, “Raman
Scattering form Incommensurately Stacked Bi-Layer Graphene”
Submitted to Phys. Rev. Lett.)
2. C. Nisoli, P. E. Lammert, E. Mockensturm and V. H. Crespi,
"Carbon Nanostructures as an Electromechanical Bicontinuum,"
Phys. Rev. Lett. 99, 045501 (2007).
5. P. Joshi, A. Gupta, P. C. Eklund and S. A. Tadigadapa,"On the
Possibility of a Graphene Based Chemical Sensor," Solid-State
Sensors, Actuators and Microsystems Conference, 2007.
TRANSDUCERS 2007. International , pp.2325-2328 (2007)
6. P. Joshi, A. Gupta, P. C. Eklund, and S. A. Tadigadapa,
“Electrical Properties of Back-Gated n-Layer Graphene Films”,
Proc. SPIE Int. Soc. Opt. Eng. 6464, 646409 (2007)
7. A. Gupta, G. Chen, P. Joshi, S. Tadigadapa and P. C. Eklund, “
Raman Scattering from High-Frequency phonons in Supported nGraphene Layer Films” Nano Lett. 6 (12), 2667-2673 (2006)
200-400 nm PZT
Non-volatile memory device based on nGL-FET
using ferroelectric film Pb(Zr Ti)O3 (PZT) as gate
oxide. The large remnant polarization field of PZT ( ~
40 µC/cm2) can potentially induce enormous 2D
carrier doping (~3x1014/cm2) and lead to non-volatile
memory effect. Pronounced hysteresis in carrier
density and resistivity as a function of Vg with long
retention time is observed in our nGL-FET.
Nb doped SrTiO3
Incommensurately Stacked Bi-Layer Graphene
2D peak dispersion
and Schematics of
bilayer (IBL)
Graphene phonon dispersion curves calculated from the
bicontinuum theory (solid lines), compared to EELS data.
The bi-continuum theory of graphene provides a unified
treatment of a wide range of electromechanical couplings
well beyond that accessible to a traditional singlecontinuum (i.e. elastic) model.
Chemisorption of hydrogen can
generate well-defined graphenic
bi- ribbons which access a new
regime of electronic coupling
wherein characteristic phonon
energies exceed the characteristic
electronic energy scales for band
The Dirac peak of a graphene device before exposure
to 10% NH3, during exposure to 10% NH3 and after
annealing the NH3-doped device in vacuum (top). The
Dirac peak recovery during vacuum annealing of a
different graphene device exposed to Cl2(bottom)
3. D. Stojkovic, P. E. Lammert and V. H. Crespi, "Electronic
Bisection of a Single-Wall Carbon Nanotube by Controlled
Chemisorption," Phys. Rev. Lett. 99, 026802 (2007)
4. J. Charlier, P. C. Eklund, J. Zhu and A. C. Ferrari,``Electron and
phonon properties of graphene: their relationship with carbon
nanotubes,'' in Carbon nanotubes: Advanced topics in the
synthesis, structure, properties and applications, ed. M. S.
Dresselhaus, G. Dresselhaus and A. Jorio (Springer Verlag,
2007) in press
nGL Sensors
Departments of Physicsa,
Electrical Engineeringb
Material Science and Engineeringc
NSF ECS0609243
Raman spectrum can count n in nGLs
nGL Electronics
The Pennsylvania State University,
University Park, PA, USA
M-K, 2D, 2D’ and 2D+G peaks found to be dispersive with
laser excitation with ~-21, ~100, ~18 and ~100 cm-1/eV
,respectively, for 1GL. Dispersion of different Raman peaks
can be used to map the electronic and phonon band
dispersion in nGLs
Band splitting
for IBL ~ 6 meV
Simulation Package
Incommensurate stacking
of two graphene layers
produces a pair of almost
decoupled graphene layers
2 peaks ~1350 cm-1 and 1384
cm-1 (I1 and I2) are seen in
IBL and compared with
defect induced D band
peaks (1 peak for mono
graphene layer and 4 peaks
for commensurate bi layer)
at the edges of nGLs.
I1 and I2 are activated by a
superimposed potential stemming
from the I stacking. Peak at ~1350
cm-1 found to be dispersive with
excitation energy while 1384 cm-1 is
non dispersive. Peak strength and
dispersive behavior is understood
(right) by perturbing potential from
one layer on another by calculating
the matrix element between suitable
electronic states
Dispersion of 2D
peak for 1GL,
IBL and 2GL.