Super-Diffraction Limited Wide FieldImaging and Microfabrication

Based on Plasmonics

Peter T. C. So, Yang-Hyo Kim, Euiheon Chung,Wai Teng Tang, Xihua Wang, ErramilliShyamsunder, Colin J. R. Sheppard

MIT, Boston University, National University of Singapore

2

Overview• Background

– Total internal reflection

• Motivation

• Theory

– Surface Plasmon and Photon coupling

• Experimental Setup

• Experiment & Results

• Future work

3

Total internal reflection (TIR)

(http://qbx6.ltu.edu)

x

z−~ zk z

zE e

[ ]ω= + −0 exp ( )x zE E i k x k z t

4

ω ω− − −= +

= +

2( ) ( )

2

( )

2 [1 cos(2 )]

i kx t i kx tI x Ee Ee

E kx

Uniform excitation Standing wave excitation

ω−= =2( ) 2( ) i kx tI x Ee E

x

z

k

High n

(Chung et al., Opt. Lett., 2006)

ω φ ω

φ

− − − −= +

= + −

2( ) ( )

2

( )

2 [1 cos(2 )]

i kx t i kx tI x Ee Ee

E kx

TIR imaging

5

TIR lithography

π θλ

=2 sinnk

λ θ= /(2 sin )p n

(Ecoffet et al., Adv. Mater., 1998)

= +2( ) 2 [1 cos(2 )]I x E kx

Photosensitive materialx

z

x

z

p: period of the pattern, n: refractive index

p

6

Motivation

Total internal reflection (TIR) of light

Imaging Lithography

Interference of Two Evanescent WavesSurface Plasmon Resonance (SPR)

Strong field enhancement

⇒High S/N ratio

Shorter Wavelength⇒Higher Resolution

7

metal

air

20 ~ 200!!output

input

EE

=

Eoutput

x

z−~ zk z

zE e

---+++ ---+++ ---+++ ---+++ ---+++ ---+++ ---++

glass0θEinput

Field enhancement by SPR

(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

8

0 0( ) sin ( 2 / )sp photon xk k mg g acωε θ π= = + =

spk

( )photon xk 1ε metal

2ε air

glass

k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant

Higher resolution by SPR (I)

0ε

0θa

9

Higher resolution by SPR (II)

1/ 21 2

1 2

0 0

( / 2 )

( ) sin

ω π

ε εωε ε

ωε θ

= ==

⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪

= +⎪⎩

h h

h

surface plasmon

photon x

E hp k

kc

k mgc

TIR +Grating

+TIR gratingkTIRk

ωlight line TIR

xk

k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

0k

532 nm 104 nm !!

10

Experimental setup

11

SPR field enhancement experiment (I)

SiOx (5nm)

Glass (n=1.522)

Fluorescent beads (d = 40nm)SPR angle (~45°)Incident power (7.8 mW)N = 48 samples

SPR sample TIR sample

Bead

Au (40 nm)

12

SPR field enhancement experiment (II)

(a) SPR (P pol) (b) SPR (S pol)

(c) TIR (P pol) (d) TIR (S pol)

12㎛

12㎛

Intensity (A.U.)

13

SPR field enhancement experiment (III)Intensity from 48 beads

SPR(P pol) SPR(S pol) TIR(P pol) TIR(S pol)

Inte

nstiy

(A.U

.)

0

100

200

300

400

500

P-value<0.001

14

TIR Lithography experiment (I)

Spin coating Congo Red solution with deionized waterExposure (800 mW/cm2 S-polarization for 30 min)Exposure (2000 mW/cm2 P-polarization for 10 min)

S-polarization P-polarization

Congo Red (n=1.9)

(Ohdaira, Y., et al., Colloids Surf. A, 2006)

Glass (n=1.522)

150 1.00 2.00㎛

0

1.00

2.00㎛

(Ohdaira, Y., et al.,Colloids Surf. A, 2006)

(a) S-polarization (b) P-polarization

(Kim, Y., et al., In preparation)

TIR Lithography experiment (II)

16

Summary

Interference of two surface plasmon waves for imaging and lithography.

1) Strong field enhancement (high S/N ratio)2) Longer wave vector (higher resolution)

The results:1) SPR strong field enhancement (bead imaging)2) P-polarization Congo Red lithography is possible.

17

Future Work

• Make a corrugated gold coated glass sample• The high resolution (~50 nm) imaging and

lithography with the sample

18

Thank you !

&

Questions ?

19

Future Work (II)

~80 nm~200 nm

(Maier, Plasmonics: Fundamentals and Applications. 2007, Springer)

20

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

kx (108/m)

W (1

015H

z)

SP dispersion relation of glass-Au-air

Surface plasmonlight lineTIRTIR+grating

Future Work (II)

508 nm 105 nm473 nm excitation

Air

Au

Glass

138 nm

21

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

kx (108/m)

W (1

015H

z)

SP dispersion relation of glass-Au-Congo Red

Surface plasmonlight lineTIRTIR+grating

Future Work (II)

Congo Red

Au

Glass

130 nm

513 nm 104 nm532 nm excitation

22

Resolution I

x

( ) ( )NA61.0

NA4.0 λλ

<=∆r

( ) ( )⎟⎟⎠⎞

⎜⎜⎝

⎛−′+⎟⎟

⎠

⎞⎜⎜⎝

⎛+′

NA2.0~

NA2.0~ λλ xhxh

(MIT 2.710 Optics lecture note)

23

Resolution II

• Rayleigh resolution criterion (imaging)

• Optical Projection Lithography resolution

λ λθ

=0.61 0.61sinNA n

λ λκ κθ

=1 1 sinNA n

θ

Numerical ApertureNA= n sin θ

Objective lens

Κ1: constant for a specific lithographic process

(Chiu at al., IBM Journal of Research and Development, 1997. 41)

Polarization

S-polarization P-polarization

Ei

kiBi

Interface

Er kr

Br

Et

ktBt

Ei

kiBi

Interface

Erkr

Br

Et

ktBt

http://www.monos.leidenuniv.nl/smo

25

Linear polarizer

(Collett, Edward. Field Guide to Polarization, SPIE Field Guides vol. FG05, SPIE (2005))

26

Surface Plasmon-Coupled Emission

(E. Chung, thesis, MIT, 2007)

27

AFM

• Deflection of the cantilever is measured.

• Feedback mechanism prevent the collision of the tip and the surface.

Humphris at al., A mechanical microscope: High-speed atomic force microscopy,

Applied Physics Letters 86, 034106 (2005).

28

Piezoelectric effect

-

+

-

+

+

-

+

-

(+)

(-)A pushing force:

(aka: compression)A pulling force:(aka: tension)

(+)(-)

(http://www.ndt-ed.org/)

The unit cell of crystal silicon dioxide deformation

+

-

+

-

29

Fluorescence

(http://www.probes.com/)

30

Congo Red

(Ohdaira, Y., et al., Colloids Surf. A, 2006)(http://en.wikipedia.org/wiki/Azobenzene)

31

Spin coating

Centrifugal force spread a fluid resin.

32

CCD & CMOS

Uniform image quality

High fill factor

Low noise

Simple

Cost less

Consume less power

Many function

Integration on one chip

33

t-testPopulation

µσ

Mean: Standard deviation:

Mean: Standard deviation: Number of samples:

XSn

Sample

µ−=

/XTS n

µ≠P value : the provability that when random sampling

X

µsmall P value : we can trust as with higher probability.

X

34

Original experimental setup

35

Fringe spacing

( )2 TBx = f / sinM n θ

11

2 1

1p(x )=2 M

TBf ff x

λ⎛ ⎞⎛ ⎞⎜ ⎟⎜ ⎟

⎝ ⎠⎝ ⎠

p= sin2nλ θ

(E. Chung, thesis, MIT, 2007)

36

SPR field enhancement experiment (IV)

(E. Chung, thesis, MIT, 2007)

37

Surface plasmon and photon coupling (I)

1/ 21

0 0

2

1 2

( ) sin

ε εε

ωε θ

ωε

⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪

=⎪⎩

surface plasmon

photon x

kc

kc

k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

TIRk

ωlight line

TIR

'xk

0k

Grating

gratingk

ωlight line

'xk

0k1/ 2

1 2

1 2

0 0( ) sin

ε εωε ε

ωε θ

⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪

= +⎪⎩

surface plasmon

photon x mk g

kc

c

38

Surface plasmon and photon coupling (II)

11/

2

0 0

1

2

2

( ) sin

ε εε

ωε θ

εω⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨

⎪=⎪⎩

surface plasmon

photon x

kc

kc

k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

TIRk

ωlight line

TIR

'xk

0k

39

Wave vector change by grating

0

(sin sin )2 2( ) ( ) (sin sin )

m i

out x in x m i

AB CD a mmk k k m mga a

θ θ λ

π λ πθ θλ

− = − =

⎛ ⎞− = − = = =⎜ ⎟⎝ ⎠

(Hecht, OPTICS, 2001, Addison Wesley)

A D

B Cθi θm

a

40

Wavelength dependence of various materials

(Hecht, Optics. 2002, Addison-Wesley)

41

Dispersion in atom

(Hecht, Optics. 2002, Addison-Wesley)

42

Dispersion relation of SP (I)

(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

43

Dispersion relation of SP (II)

(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

44

Dispersion relation of SP (III)

(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

45

Dielectric function of gold

(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)

Source of Noise in Optical Detectors

(1) Optical shot noise (Ns) –inherent noise in counting a finite number of photons per unit time

(2) Dark current noise (Nd) –thermally induced “firing” of the detector

(3) Johnson noise (NJ) –thermally induced current fluctuation in the load resistor

Since the noises are uncorrelated, the different sources of noise add in quadrature

2222JdS NNNN ++∝

(MIT 2.710 Optics lecture note)