High frequency printed polymer transistorshome.deib.polimi.it/sampietr/ESO/Caironi2.pdf ·...

1

High frequency

printed polymer transistors

Center for Nano Science and Technology@PoliMi Istituto Italiano di Tecnologia, Milan, Italy

Mario Caironi

“ORGANIC ELECTRONICS - Principles, devices and applications”

Politecnico di Milano, 26 November 2015

Wang et al., TLIST, 2013 Sony

Why improving «speed»

Someya et al.

2

Transconductance

Gate Voltage

Dra

in C

urr

ent

Vgs

Ids

Id

+

+ id

3

If vgs<< VGS ' (saturation regime)

GS GS

Dm OX od

GS v V

di Wg C V

dv L

id = gmvgs

𝐼𝑑 =1

2𝜇𝐶′

𝑂𝑋

𝑊

𝐿(𝑉𝐺𝑆 − 𝑉𝑇)2=

1

2𝜇𝐶′

𝑂𝑋

𝑊

𝐿𝑉𝑜𝑑

2

Transconductance vs. f

Gate Voltage

Dra

in C

urr

ent

Vgs

Ids

Id +

+ id

Frequency AC

Dra

in C

urr

ent

Am

plit

ud

e

id = gmvgs

4

Transit time 5

Carrier velocity

V

Carrier transit time

Frequency AC

Dra

in C

urr

ent

Am

plit

ud

e

id = gmvgs

Cut-off Frequency

fcut-off

L = 10 µm µ = 1 cm2/Vs fcut-off ≈ 400 kHz @10V ≈ 2 MHz @50V

𝑣 = 𝜇𝐸 = 𝜇𝑉

𝐿

102

103

104

105

106

107

10-5

10-4

10-3

10-2

10-1

T/R_T10L05S

T/R_T10L10S

T/R_T10L20S

T/R_T10L40S

T/R_T10L80S

T/R

Frequency

- +

L (μm) Fsat (Hz)

5 2M

10 600k

20 200k

40 40k

80 10k

L (μm) 5 10 20 40 80

Gm 2.7 1.31 0.76 0.36 0.21

Measurement of fcut-off 6

[μA/V]

80 µm

40 µm 20 µm 10 µm

5 µm

Effect of Capacitances

icgd

icgs

Cgs,o Cgd,o

2πfCgdvgs

Measured i’d

id’= id-icgd=gmvgs-j2πfCgdvgs

id

i’d

7

Frequency of Transition fT 8

M. Caironi et al., Semicond. Sci. Technol. 26 (2011) 034006

icgd

icgs

id

i’d icg

2πfCgdvgs

2πfCgvgs

fT

Frequency of Transition fT 9

M. Caironi et al., Semicond. Sci. Technol. 26 (2011) 034006 F. Ante et al., Small 8 (2012) 73

Ideal (no overlap):

Real (overlap):

Lov

fT for all printed OFET

L= 46 µm, W = 1180 µm, dielectric thickness = 700 nm, Vg = Vd = 40 V

Cgs = 2.3 pF - Cgd = 3.8 pF

S. Mandal et al., Organic Electronics 20 (2015) 132-141

Challenges towards printed high-speed circuits

(4) Small Overlap Cap. [Cov]

(2) Short Channel Length [L2]

(1) High Mobility (μ]

N

N

OO

O O

C10H21

C8H17

C10H21

C8H17

*

S

S *

- Organic

- Metal Oxide

- Carbon-based

- Printable Si

Self Aligned Printing

Nano-imprinting

EHD Jet printing

50~200 nm

(3) Small Contact Resistance. [Rc]

SH

FF

F

SH

HH

H

SH

CN

Au

-

+

SH

FF

F

SH

HH

H

SH

CN

SH

FF

F

SH

HH

H

SH

CN

Au

-

+

0 -1 -2 -3 -4 -5

0.0

0.1

0.2

0.3

-2 V

-3 V

-4 V

-ID [A

]

VD [V]

VG=-5 V

SAM

(5) High-Capacitance Dielectrics [Ci]

Lov

High fT

K.-J. Baeg, M. Caironi, Y.-Y. Noh, Adv. Mater. 2013, DOI: 10.1002/adma201205361

11

Organic Semiconductors Mobility

Mario Caironi

7 October 2013

H. Klauk, Chem. Soc. Rev. 39 (2010) 2643

2013

4 cm2/Vs

10 cm2/Vs

12

Effect of Pre-aggregation 13

200µm

200µm

mesitylene toluene

DCB

CN:CF

THF

Teb: 164.7 °CDielectric constant; 2.4Dipole moment: 0.047 D

Teb: 111 °CDielectric constant: 2.38Dipole moment: 0.31 D

Teb: 181 °Cdielectric constant: 9.93 Dipole moment: 2.14 D

CN: Teb: 259 °CDielectric constant: 5Dipole moment: 1.55 D


CF: Teb: 61.2 °CDielectric constant: 4.8Dipole moment: 1.04 D

bad solvent

good solvent

mesitylene toluene

DCB

CN:CF

THF







bad solvent

good solvent

mesitylene toluene

DCB

CN:CF

THF







bad solvent

good solvent

Deg

ree o

f p

re-a

gg

reg

ati

on

in

so

luti

on

A. Luzio et al. Scientific Reports 3 (2013) 3425

Film formation (spin-coating) 14

1 m

0.1 g/l

2.5 – 3.0 nm


0.5 g/l

1 m

0.0 0.2 0.4 0.6 0.8 1.0

012345 0.5 g/l

X (m)

Y (n

m)

0.0 0.2 0.4 0.6 0.8 1.0

012345 0.8 g/l

X (m)

Y (n

m)


0.8 g/l

1 m

0.0 0.2 0.4 0.6 0.8 1.00123456

Y (n

m)

X (m)

1 g/l


1.0 g/l

1 m

Bucella et al., Nature Communications, 6 (2015) 8394

mesitylene toluene DCB CN:CF

0.01

0.1

1

saturation @Vg=50 V

linear

[cm

2V

-1s

-1]

-10 0 10 20 30 40 5010

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

µ sat

µ lin

[ c

m2V

-1s

-1 ]

Vg [ V ]

toluene

DCB

CN:CF

OFETs characterization 18

A. Luzio et al. Scientific Reports 3 (2013) 3425

200µm

200µm

Macro-aligned nano-fibrils 19

1 m 1 m

Solvent: mesitylene Coating Speed: 3 min/min

0.5 g/l 5 g/l

Sub-monolayer 2.4 - 2.5 nm

Thin film 10 nm

Macro-aligned nano-fibrils 20

1 m

sou

rce

dra

in

sou

rce

dra

in

MHz Fast-coated OFETs 21

Non optimized architecture for

frequency operation!

L = 5 m

Bucella et al., Nature Communications, 6 (2015) 8394

@40V

Printing

Techniques Viscosity [Pas]

Thickness

[µm]

Feature

Size [µm]

Throughput

[m2/s]

Registration

[µm] Features

Flexography 0.05-0.5 0.04-2.5 80 3-30 <200 Inexpensive plate pattern, high throughput,

thick layer / low viscosity ink

Gravure 0.01-0.2 < 0.1–8 75 3-60 >20 Fast printing, high resolution, relatively high

plate cost, low dot gain

Offset 5-100 0.5–2 10–50 3–30 >10 High quality, high throughput,

need for ink additives

Screen 0.5-50 0.015-

100 20–100 2–3 >25

Robust, simple, thick layer, large feature size,

high ink viscosity, slow speed

Inkjet 0.001-0.04 0.01-20 20–50 0.01–0.5 5–20 Non-contact, small ink quantities, digital

printing, low viscosity ink, slow speed

Printing Techniques Patterning Resolution

22

Ink-jet printing of narrow linewidths

Adv. Mater. 20 (2008) 343

40 μm linewidth 5 μm linewidth

Adv. Funct. Mater. 18 (2008) 1031

Nanotechnology 18 (2007) 345202

1-2 μm linewidth

Nat. Mater. 6 (2007) 782

High resolution e-jet

1 μm linewidth

23

PEDOT:PSS PEDOT:PSS

L: critical feature is “self-defined”

Self-Aligned Printing (SAP)

50m50m

1st

2nd

C.W. Sele et al., Adv. Mat. 17 (2005) 997

24

Single-droplet Contacts 25

1st

2

nd

1st Electrode

2nd Electrode

1

2

2nd Electrode

1st Electrode

37 μm

Single droplet

Drying Time of Ink is a Critical Factor

60 s 240 s 300 s

310 s 320 s

340 s

330 s

sintered

(a) (b) (c)

(d) (e) (f)

(g) (h)

50 μm

Extra force exerted by evaporation of the solvent Reliable dewetting, tolerant to surface defects Process window >> 10 μm

26

27

● 100% yield possible ● Very low leakage, < 2 pA at 10 V ● Breakdown voltage > 2 MVcm-1

Caironi et al., ACS Nano 4 (2010) 1452

leakage

High Yield Electrodes Array

Fully Solution Processed SAP-FET

Au source

Au drain

Ag gate

500μm

Caironi et al., A

CS

Nano 4

(2010)

1452

28

100X objective

Power = 2 mW

λ = 515nm

250 fs, 500 kHz

Direct-writing of submicron channels 29

Ag

Ag-inks

1

2

745 nm

S. Bucella et al., Organic Electronics, 14 (2013) 2249

Effect of Contact Resistance 30

Rule of Thumb for µapp

Natali, Caironi, Adv. Mater. 24 (2012) 1357

31

𝐼𝑟𝑒𝑎𝑙 = 𝐼0

𝑅𝐶ℎ

𝑅𝐶ℎ + 𝑅𝐶

𝐿𝑀𝐼𝑁 → 𝑅𝐶 = 𝑅𝐶ℎ

Laser-ablated Semi-transparent electrodes 32

λ = 1030 nm 50X, 20 mW

1.5 µm

PEDOT:PSS

Gate

Source Drain

0 5 10 15 200

1

2

3

4

5

6

7V

G ( V )

0

5

10

15

20

I DS (

µA

)

VDS

( V ) 0 5 10 15 20

0.0

0.1

0.2

0.3

0.4

0.5 VG ( V )

0

5

10

15

20

I DS (

µA

)

VDS

( V )

PEI μsat ~ 10-2 cm2/Vs μsat ~ 0.1-0.2 cm2/Vs

Geometry • W = 60 μm

• L = 1.5 μm Y. Zhou et al, Science 336 (2012) 327

Doping as a way to control injection and

uni-/ambi-polar transport

CsF F4TCNQ

33

Effect of Doping 34

High Supply Voltage 35

~ 500 nm

Low-k polymer dielectrics εr = 2 - 3

𝐶′𝑂𝑋 =

𝜀

𝑑≈ 5

𝑛𝐹

𝑐𝑚2

Forcing the use of gate voltages ≥ 40 V

Low Voltage OFETs with Hybrid Nanodielectrics 36

30 nm

10 nm

D

G

S

Al2O3

substrate

PMMAsemiconductor

A. Luzio, et al. Adv. Funct. Mater. 24 (2014) 1790

Printable dielectrics

Issue with downscaling 38

' (saturation regime)

GS GS

Dm OX od

GS v V

di Wg C V

dv L

𝑔𝑚 ∝ 𝐶′𝑂𝑋

𝑉𝑜𝑑 = 𝑐𝑜𝑛𝑠𝑡

𝐶𝑂𝑉 = 𝐶′𝑂𝑋

𝑥𝑂𝑉𝑊 ∝ 𝐶′𝑂𝑋

2πfCgvgs

fT

How to reduce Overlap Capacitance:

1. Split Gate

Jun Takeya et al., Adv. Mater. 2014 DOI: 10.1002/adma.201304976

RC !!

39

Split gate via lithograpyhy

Jun Takeya et al., Adv. Mater. 2014 DOI: 10.1002/adma.201304976

40

How to reduce Overlap Capacitance:

2. Self-Aligned Gate

Y.Y.Noh et al, Nat. Nanotechnol. 2 (2007) 784-789

41

fT of solution processed OFETs 42

Y.Y.Noh et al, Nat. Nanotechnol. 2 (2007) 784

Self-Aligned Printed 100 - 500 nm gaps

OFET fT: record values

SCALABLE PRINTING and DIRECT-WRITING

Our work

43

f T [MHz]

L [m] x OV [m] 1 cm2/Vs 5 cm2/Vs 10 cm2/Vs

2 2 9.58 47.9 95.8

1 2 22.8 114 228

1 1 38.3 192 383

0.5 1 91.3 457 913

0.5 0.5 153 767 1533

Perspective? Polymers

1985 1990 1995 2000 2005 2010 201510

-6

10-5

10-4

10-3

10-2

10-1

100

101

102

Best

Rep

ort

ed

Mo

bil

ity [

cm

2/V

s]

Year

Polymer Semiconductors

P-type (holes)

N-type (electrons)6 cm2/Vs

25 cm2/Vs

44

March 2015

Thank you for

your kind

attention

45

High frequency printed polymer transistorshome.deib.polimi.it/sampietr/ESO/Caironi2.pdf ·...

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