Post on 30-Dec-2015
Surface Science @ Universidad Autónoma de
Madrid
Roberto OteroRoberto OteroOn behalf of all the members of the Surface
Science Laboratory @ Universidad Autónoma de Madrid
Nanosciences & Surface Science
Optical devices based on organic thin films
Nanomechanical biosensors
Molecular electronic
devices
Functionalized surfaces for
implant applications
Intr
oduct
ion
Organic Optoelectronic Devices
Example: Pentacene thin filmsIn
tens
ity (
a.u.
)
2θ (º)
C. D. Dimitrakopoulos & P. L. Malefant, Advanced Materials 14, 99 (2002)
Intr
oduct
ion
Thin Film GrowthIn
troduct
ion
For organic adsorbates:
-3D molecular structure (degrees of freedom)
-Specificity in intermolecular interactions
Ultra-High Vacuum (UHV)
How long does it take for an atomically clean single-crystal surface to get dirty?
Tmk
P
B2Nº of incident molecules/time × area =
At RT, P = 1 Atm, m = 4 uma, about 7.71 × 1027 molecules per second and square meter hit the surface. For Cu (100) (square lattice with lattice parameter 2.56 Å) this number equals 5 × 109 molecules/second and unit cell
At P = 10-10 Torr, only 6 × 10-4 molecules per second and unit cell hit the surface, i.e. an average of 25 min are necessary to have all the unit cells hit by one molecule
Intr
oduct
ion
Ultra-High Vacuum (UHV)In
troduct
ion
Ultra-High Vacuum (UHV)In
troduct
ion
20 × 20 nm2
O/Cu(110)
PO = 10-8 Torr
tframe = 20 s
Experimental TechniquesIn
troduct
ion
• Structure:– Real Space (STM)– Reciprocal Space (SXRD, TEAS)
• Chemistry (XPS)
• Electronic Structure (UPS, STS)
• Other properties… magnetism? (SP-STM, SMOKE)
Scanning Tunneling Microscopy and Spectroscopy
Scanning Tunneling Microscopy (STM)
STM
Things to do in the lab when you have an STM…
STM
Atomic structure of solid surfaces with vertical pm resolution
Morphology of epitaxial systems
Subnanometer-resolution electronic
spectroscopy
Diffusion of atomic
adsorbates
Atom-by-atom
nanostructure fabrication
TIREMISU (TIme REsolved MIcroscopy of SUrfaces)
STM
José María Gallego
Me
David Écija
Christian Urban
Marta Trelka
SITTA (Sistema Integral de Túnel y Técnicas de Análisis)
STM
Fabián Calleja
Juan José Hinarejos
Amadeo L. Vázquez de Parga
STM/STS: Layer-Dependent Roughening Transition
F. Calleja, M. C. G. Passeggi, Jr., J. J. Hinarejos, A. L. Vázquez de Parga, and R. Miranda, Phys. Rev. Lett. 97, 186104 (2006)
STM
Diffraction and the Reciprocal Space
Elementary Diffraction Theory
n2 k'kR
Reciprocal space vector
Wavelength ≈ Lattice parameter
Diffr
act
ion
X-Rays: SXRDλ ≈ 1 Å, E ≈ 12.3 keV → X Rays
Large penetration depth!!!Large penetration depth!!!
Real Space Reciprocal Space
Diffr
act
ion
Baby Chambers at Synchrotrons
Diffr
act
ion
Jesús ÁlvarezMaría José Capitán
Me
Hamburg
Adenine Self-AssemblyD
iffr
act
ion
Molecule Diffraction from Surfaces
Diffr
act
ion
The Atomic and Molecular Beam Diffraction Apparatus at LASUAM
Diffr
act
ion
Guillaume Laurent
Daniel Farías
Daniel BarredoPablo Nieto
H2 Diffraction
40 50 60 70 80 90 100 1100
1
2
3
4
5
6
7
8
9
10
X2
X2
f = 0º
f = 8.7º
f = 17.7º
Diffr
act
ion
In
ten
sity
[a
.u.]
(1,1)
(0,1)
(1,0)
i+
f [degres]
[101]E
i = 77.5 meV
i = 37.6º
(0,0)
In-plane and out-of-plane H2 diffraction spectra from Pt(111) recorded along the two main azimuths:
P. Nieto, E. Pijper, D. Barredo, G. Laurent, R.A. Olsen, E.J. Baerends, G.J. Kroes and D. Farías, Science 312, 86 (2006)
Diffr
act
ion
Surface PhononsD
iffr
act
ion Phonons on Pd(110):
Chemical and Electronic Characterization
Electrons in SolidSpect
rosc
opy
XRPS
Cristina Navío
Jesús Álvarez
María José Capitán
Spect
rosc
opy
X-Ray and UV Photoelectron Spectroscopy (XPS)
Spect
rosc
opy
3000 Å x 3000 Å
N 1s
Fe 2p
Fe4N stoichiometry
Other Techniques
SMOKE (Surface Magneto-Optical Kerr Effect)
Dr. Julio Camarero
HeNe
laser
polarizer
lens
Wollastonprism
analyser
DSO
Field servo-loop-control
power supplyFREQFREQ
FIELDFIELD
fastphotodiodes
++––
Hall signal
lens
air gap ferrite
/2 plate
1 current sensor
Magneti
sm
Spin-Polarized STM
SampleTip
MsMT
Φ
EF
EF
High current
Amadeo L. Vázquez de Parga
Magneti
sm
Sample: Mn/Fe(001)Mn grown at 370 K (<4x10-
10mbar)
STM image after depositing 7 ML
140 x 150 nm2
Vs= - 0.5 V I=0.5 nA
6
78
9
9
98
8
0.16 nm
0.14 nmFe(001)-whisker
Mn(001)
film
4.5
2.5
0.5-1.0 -0.5 0.0 0.5 1.0 1.5
dI/d
V [n
A/V]
Sample voltage [V]
6789
6
789
99
8
8
dI/dV curves
dI/dV map at +0.2 V
STS measured with clean W tip
Spin-Polarized STMM
agneti
sm
89
10
100 x 100 nm2
Vs= - 0.5V, I=0.5nA
10
11
11
12
Sample voltage [V]-1.0 -0.5 0.0 0.5 1.0
dI/
dV
[n
A/V
]0.5
1.5
2.589
1011
dI/dV map at +0.2 V
89
1011
11
10
9
STM image
With the Fe-coated W tip alternating contrast with a clean W tip there is no contrast
Reversed contrast with different Fe-coated W tips due to different tip magnetization
9
12
dI/dV curves
STS measured at room temperature with Fe-coated W tip
100 x 100 nm2
Spin-Polarized STMM
agneti
sm
80 x 80 nm2
I map at V=0.10 V
6.5 ML of Mn/Fe(001)
Topography
Measured at room temperature
Spin-Polarized STMM
agneti
sm
Conclusion
• A multitechnique approach to address problems related with the growth and characterization of nanostructures