Prediction and reconstruction of Scanning Kelvin Probe Microscope
drain semiconductor x. eV n, p, R. Vs. Vd. Vg. âVsd. V(x) p n n' p'. W. R gate dielectric source drain semiconductor .... Dago de Leeuw. Data, discussions, samples.
Potential applications: organic laser if good performances. Important parameters: carrier densities n p, width W. / applied physics department
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n, p, R
p’
R
n’ n n, p, rec
p
1E-3
0
1E-5
-2 n p rec ( = 3 nm)
1E-7
-4
1E-9
-6
V [eV]
Langevin recombination
1E-11 -8
W eV
1E-13 0
Vd Vg Vs
2
4
6
8
10
x [m]
Vsd
1
V(x)
rec (1 nm) rec (3nm) rec (10 nm)
0.01
rec
x semiconductor
source
drain
dielectric gate
1E-4
1E-6
1E-8
Wtheoretical
4.34d 20 200nm
/ applied physics department
8.0
8.5
x [m]
M. Kemerink et al, Appl. Phys. Lett. 93, 033312 (2008)
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lever
Reported experimental results
tip
active layer source
channel dielectric
drain
gate
Optical technique
Electrostatic technique Scanning Kelvin Probe Microscope (SKPM) NiDT Should see a potential drop at x0
Confocal microscope / High fields PPV
J.S. Swensen et al, J. Appl. Phys. 102, 013103 (2007)
E.C.P. Smits et al, Phys. Rev. B 76, 125202 (2007)
/ applied physics department
Wexperimental ~ 2 µm
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SKPM Response for FET Theoretical predictions (drift) from Smits = input of SKPM modeling
Assumption: W = “0” nm
SKPM experiments + 3D modeling
‘real’ W < 0.5 micron One curve = 13 hours !
Note: We checked that the SKPM probe influence only few % the source drain current. / applied physics department
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Simple prediction/reconstruction real signal
measured response
xref
yref h
real signal
measured response
xexp
yexp yref ( x) href ( x) xref ( x ) F ( y ) F ( h) F ( x )
h = Apex(x,y,z) + Cone(x,y,z) + Lever(x,y,z) = electrostatic convolution Hypothesis: one single reference measurement contains all electrostatic interactions / applied physics department
theoretical signal 3D modeling prediction experiment
surface potential (V)
10 8 6 4 2 0 -2
0
2
4
6
8
10
12
position ( m) / applied physics department
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Reconstruction from step edge response Winversed – Wtheoretical = 0.5 – 0.5 = 0 µm real signal
measured response
xexp
yexp Wexperiment ~ 2 µm
Winversed = 0.5 µm
Wtheoretical
4.34d 0.5m 100
6 4
0
5
dV/dx (normalized)
theoretical signal calculated with β = 100 m reconstruction experiment
surface potential (V)
8
dV/dx (normalized)
10
10
2 0 -2
0
2
4
6
2 8
4
6 10
8 12
position ( m) / applied physics department
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Summary • Electrostatic tip-electrodes convolution leads to amplitude loss of measured surface potential with SKPM. Good agreement between experiments and 3D modeling. • Prediction and Reconstruction methods successfully working using the step edge response tool.
surface potential (V)
10 8 6 4 2 0 -2
/ applied physics department
2
6 4
4
6
8
10
12
position ( m)
0
5
dV/dx (normalized)
surface potential (V)
8
• W recombination: • theoretical (Langevin) ~ 200 nm • experimental SKPM response − raw ~ 2 µm − difference with model (β=100) 0 µm
0
10
dV/dx (normalized)
• A higher resolution of SKPM is reached with the step edge response tool.
10
2 0 -2
0
2
4
6
2 8
4
6 10
position ( m)
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8 12
Acknowledgments
Molecular Materials and Nanosystems Group Martijn Kemerink René Janssen Simon Mathijssen
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