2006 mrs spring emd v3 a
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Transcript of 2006 mrs spring emd v3 a
Solution coated organic semiconductors towards a-Si performance
MRS Spring 2006San Francisco
Janos Veres, Simon Ogier, Stephen Leeming, Giles Lloyd,
Domenico Cupertino, Richard Williams, Munther Zeidan, Bev Brown
Outline
• Introduction to Merck/EMD
• Organic Semiconductors Development
• Organic Semiconductors for plastic electronics
• Solution coated OSC
• Semiconductor formulations
• Microstructure and uniformity
• Carrier transport
• Stability
• Summary and outlook
One Name - Two Companies
Established by E. Merck in 1891 as U.S. subsidiary; Independent since 1917
Right to use the Merck brand in North America; MSD/Merck Sharp & Dohme outside North America
Established 1668 in Darmstadt, Germany
Right to use the Merck brand outside North America; EMD in North America
Merck & Co., Inc.Whitehouse Station, NJ, USA
Merck KGaADarmstadt, Germany
Introduction to Merck
SalesEUR 5,339 million
Operating resultEUR 755 million
Sales 2004EUR 1,888 million
Operating result 2004EUR 438 million
MerckChemicals
• Large area -increasingly difficult with a-Si• Low cost -printing, ambient processing steps• Flexible devices - plastic substrates, low temperature processing
Organic semiconductors for plastic electronicsDisplays, RFID tags, sensors, memory, photovoltaics
Main driver is processability!
P3HT 0.1 cm2V-1s-1
Sirringhaus et al. Nature 401, 685 (1999)
N
n
X X
YPTAAMerck, 10-2 cm2V-1s-1
Veres et al. Chem. Mater. 16, 4543 (2004)
C8H17 C8H17
S S **n
Si
Si
Rubrene 0.1-0.7 cm2V-1s-1
Stutzmann et al. Nature Mat. 4, 601 (2005)
F8T2Dow, 10-2 cm2V-1s-1
Sirringhaus, Appl.Phys.Lett. 77, 406 (2000)
SS
C12H25
SS
C12H25
* *n
PQT12Xerox, 0.1 cm2V-1s-1
Ong et al. Adv.Mat. 17, 1141 (2005)
S
SS
S ** n
C10H21
C10H21
Merck, 0.15 cm2V-1s-1
Heeney et al. J.Am.Chem.Soc.127, 1078 (2005)
S
S
S
S ** n
C14H21
C14H21
Merck, 0.2-0.6 cm2V-1s-1
McCulloch et al. Nature Mat. 5, 328 (2006)
N
SO
O
CH3C N S O
O
+
1mol% CH3ReO3CCl3, reflux 120-200 C Precursor
pentaceneIBM, 0.1-0.9 cm2V-1s-1
Afzali et al, J. Am. Chem. Soc. 124, 8812 (2002)
Solution coated OSC
Processability +stability + high µ and on/off + large area uniformity
Ambient manufacturing & operation Device performance
SS
C6H13
SS
C6H13
* *n
C6H13 C6H13
TIPSAnthony, >0.4 cm2V-1s-1
Sheraw et alAdv. Mat. 15, 2009, (2003)
Field effect and determining mobility
Drain(D)Source
(S) dielectric+ + + + + + + +
LW
Gate(G)
- - - - - - -
Vg induces opposite charge in the semiconductor.
Conductive channel is established
Linear regime |VDS|<<|VGS |
( )WLVVCLVI tGi
D −= 2µ
1/time mobile chargeDSiG
DS
VWCL
VI
∂∂
=µ
( ) DtGi VVVCL
WI −= µ
Gate dependence of µ without assuming Vt
-60 -40 -20 0 2010-15
10-14
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
VD=-5V
VD=-5V
VD=-60V
Gate Voltage [V]
Dra
in C
urre
nt [A
]
VD=-60V
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Mobility [cm
2V-1s
-1]
PTAA
Si
Si
** n
Blend OSCfilm 50:50
Spin coated
Low-k dielectric (spin coated) Gate (Au) Source, drain
(Au)
Glass or plastic substrate
OSC formulations (A)Example of basic blends
100 µm
Polarised light microscopy (transmission)
Normal light (transmission)
ambient fabrication
• Higher mobility and reduced T activation
• Aliphatic polymers offer good orthogonality
• Reduced hysteresis, absence of trapping groups
• Lower threshold voltages and lower T activation for Vt !
• Reduced moisture take-up & better stability
• Fluoropolymers, ethylene, butylene, propylene
copolymers, hydrogenated styrene, cyclic aliphatics used
J. Veres, S.D. Ogier, S.W. Leeming, D.C. Cupertino, and S. Mohialdin Khaffaf, Adv. Funct. Mat., 13, 199-204, 2003
J. Veres, S.D. Ogier, S.W. Leeming, D.C. Cupertino, S. Mohialdin Khaffaf, G. Lloyd, Proc. SPIE, 2003, San Diego
J. Veres, S. Ogier. G. Lloyd, D. de Leeuw, Chem. Mat. 16. p4543, 2004
Low-k dielectrics
2 3 4 510-6
10-5
10-4
10-3
10-2
10-1
µ [
cm2V
-1s-1
]
(1000/T) [1000/K]
TOFFET (CYTOP)FET (PPCB)FET (PMMA)
-40 -30 -20 -10 0
0
5
10
15
20
25
30
I D [µ
A]
VD [V]
VG=0 to -40V in -5V steps
-40 -20 0 2010-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
VD=-5V
VD=-5V
VD=-60V
Gate Voltage [V]
Dra
in C
urre
nt [A
]
VD=-60V
0.0
0.1
0.2
0.3
0.4
0.5
Mobility [cm
2V-1s
-1]
OSC formulations (A)Early results (2003) µ =0.14 cm2V-1s-1
-40 -30 -20 -10 0 1010-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Gate Voltage [V]
Dra
in C
urre
nt [A
]
Vd -40V
Vd -40V
Vd -5V
Vd -5V
L = 125 µmW = 29.6 mmC = 1.94nFcm-2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
M
obili
ty [c
m2 V-1
s-1]
-40 -35 -30 -25 -20 -15 -10 -5 00
-50
-100
-150
-200
Dra
in c
urre
nt [µ
A]
Drain Voltage [V]
Vg 0 to -40V in 5V steps
Improved OSC formulationsChoice of the right OSC and additives for stabilityµ =0.5-0.6 cm2V-1s-1 on/off>106 ambient operation
All curves include forward and immediately following reverse scans
0.5 mm0.5 mm
100 µm
Film uniformityPolarised light microscopy
Single OSC componentBlend film
-60 -40 -20 0 2010-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Gate Voltage [V]
Dra
in C
urre
nt [A
]
0.0
0.2
0.4
0.6
0.8
1.0
Vd -60V
Vd -60V
Vd -5V
Vd -5V
L = 100 µmW = 1 mmC = 3.2nFcm-2
Mobility [cm
2V-1s
-1]
Uneven filmsHighly random crystal sizeRandom orientationRough topographyPoor device uniformity(occasionally good devices)DefectsGate leakagePoor turn-on
High degree of uniformityGood connectivity, sharp TFT turn-onControlled crystal size, flat topography
Surface topography Tapping mode AFM
0 20 40 60 80
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Nor
mal
ised
cou
nts
[per
s]
depth [nm]
133Cs212C 133Cs28Si16O 133Cs28Si 133Cs219F 133Cs2197Au 133Cs232S
Semiconductor profile by DSIMS Dynamic Secondary Ion Mass Spectroscopy : Composite AExample of film structure
F
1.Cesium ion source2.Duoplasmatron 3.Electrostatic lense 4.Sample
Depth profile by millingaway material from a defined area
Primary ion beamCs+
Secondary ionsto mass spectrometer Si
Au
SC
5.Ion energy analyser 6.Electromagnet - mass analyser 7.Electron multiplier / Faraday cup 8.Fluorescent screen - ion image detector
-40 -30 -20 -10 0 1010-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
Gate Voltage [V]
Dra
in C
urre
nt [A
]
Vd -40V
Vd -40V
Vd -5V
Vd -5V
L = 60 µmW = 1 mmC = 1.5nFcm-2
0.0
0.5
1.0
1.5
2.0
2.5
M
obili
ty [c
m2 V
-1s-1
]
-40 -30 -20 -10 00
-5
-10
-15
-20
-25
-30
Dra
in c
urre
nt [µ
A]
Drain Voltage [V]
Vg 0 to -40V
in 5V steps
Advanced OSC formulations (B)Optimised componentsµ =1.5 cm2V-1s-1 on/off>106
-40 -30 -20 -10 0 1010-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Gate Voltage [V]
Dra
in C
urre
nt [A
]
Vd -40V
Vd -40V
Vd -5V
Vd -5V
L = 20 µmW = 1 mmC = 3.5nFcm-2
0.0
0.5
1.0
1.5
2.0
2.5
M
obili
ty [c
m2 V-1
s-1]
-40 -30 -20 -10 00
-20
-40
-60
-80
-100
-120
-140
-160
Dra
in c
urre
nt [µ
A]
Drain Voltage [V]
Vg 0 to -40V in 5V steps
Advanced OSC formulations (C)Optimised componentsµ =1.2 cm2V-1s-1 on/off>106
1 10 1000.0
0.5
1.0
1.5
2.0
Line
ar M
obili
ty [c
m2 V-1
s-1]
Channel length [µm]
W=1mmC = 3.2nFcm-2
Channel length dependence (C)
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.00.1
1
m
obili
ty [c
m2 V
-1s-1
]
1000/T
EA=56meV
EA=21meV
Temperature activation of mobility
Formulation B
Formulation A
Transport resembles that of single crystal OTFT
-60 -40 -20 0 20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Nor
mal
ised
Mob
ility
Gate Voltage [V]
Temperature decreasing in 20 degreesteps
Temperature activation of mobilityVg dependence
DiG
DSFE VWC
LVI
∂∂
=µ
-60 -40 -20 0 20
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Line
ar M
obili
ty [c
m2 V
-1s-1
]
Voltage [V]
Temp [K] 380 360 340 320 300 280 260 240 220 200 180
VD=-5V
Normaliseddata
Gate dependence of µ is weak µ(Vg) does not change with T
Slight increase of turn-on with T
0 100 200 300 400 50010-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
C
urre
nt [A
]
Time Between Measurements [days]
Original on-current Original off-current Recent on-current Recent off-current
Device lifetime
• Devices remain operational for well over a year
• Typically µ stays within 20%
Each point is a different device!
Bias stress stability
0.1 1 100.01
0.1
1
10
∆VT (V
)
Time (hours)
Stress Conditions,VGS=-30VVDS=-30V
-30 -20 -10 0 1010-9
10-8
10-7
10-6
10-5
10-4
Dra
in C
urre
nt (A
)Gate Voltage (V)
Before Stress After Stress
Stress Conditions,VGS=-30VVDS=-30VTime=7 hours
Threshold voltage variation with time Transfer characteristics before & after bias stress
• Low bias stress
• Fully recovers after resting (accelerated by light)
• Negligible positive bias stress
Summary
Solution (ambient) processable OSC material systems developed at Merck• New OSC and material combinations delivering µ>1 cm2V-1s-1
• Matching dielectrics, contact treatments, interfaces• OSC and their compositions are evolving to address
-deposition processes e.g.printing (multiple components, viscosity, solvent choice)-specific device requirements (substrate, electrodes)
OSC materials are truly a match for a-Si• Reproducible performance, good uniformity • Device operation resembles single crystal OTFT• Hysteresis free and very low bias stress• Promising stability (solution, device) • Real potential to use in ambient manufacturing processes
Implementation of materials and process technology will require more work!• A range of applications can be addressed – first is likely to be displays