terahertz spectroscopy · pdf filethursday, 07 january 2010 2 thz spectroscopy has been used...

Terahertz Spectroscopy Applications

(non-biological)

17 December 2009

Thursday, 07 January 2010

2

THz spectroscopy has been used to study:(amongst others, and in no particular order)

• Polymers

• Semiconductors

• Ceramics and glasses

• Organic molecules

• Gas spectroscopy

• Conductive films

• Liquid crystals

• Composites

• Oils

• Nondestructive testing


3

Polymers(non-polar!)

• Observing polymerisation

• Differentiating polymorphs

• Measuring electrical conductivity

• Measuring hygroscopicity

Non-polar, e.g.: Polar, e.g.:

PTFE (Teflon) Polystyrene

Polyethylene PerspexPolypropylene Vinyl


4

Effect of chain length in polyethylene

0.5 1.0 1.5 2.0 2.5

0.0

0.5

1.0

1.5

2.0

2.5

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

PE 300

PE 500

PE 1000

0.5 1.0 1.5 2.0 2.51.510

1.515

1.520

1.525

1.530

1.535

1.540

Re

fractive

in

de

x

Frequency (THz)

PE 300

PE 500

PE 1000

Polyethylene monomer


5

Polymerisation in SU8 SU8 is an epoxy resin used as a UV-curable photoresist

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01.70

1.75

1.80

1.85

1.90

1.95

2.00

2.05

2.10

Refr

active in

dex

THz

0 s

180 s

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00

1

2

3

4

5

6

7

8

9

0 s

180 s

Abso

rptio

n c

oeff

icie

nt

(mm

-1)

THz

0 10 20 30 40 50 60 700.0

0.2

0.4

0.6

0.8

1.0

calculated from absorption coefficient

calculated from refractive index

Poly

mers

isa

tion

dep

th (

mm

)

Time (s)

Propagation of the polymerisation front


6

Differentiating polymorphs

0.5 1.0 1.5 2.0 2.50.0

0.1

0.2

0.3

0.4

0.5

0.6

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

PP homopolymer

PP copolymer

0.5 1.0 1.5 2.0 2.51.497

1.498

1.499

1.500

1.501

1.502

1.503

1.504

PP homopolymer

PP copolymer

Refr

active index

Frequency (THz)

Isotactic

Syndiotactic

Polypropylene


7

Characterization of conducting

poly-3-methylthiophene film

TI Jeon et al, Appl. Phys. Lett. 79/25 (2001) 4142-4144

In this conducting polymer absorption and refractive index are mostly due to the free carriers.

(solid line: Drude model)


8

Observing the metal-insulator transition in PMMA-graphite composite(polymethylmethacrylate)

AM Seo et al, J. Appl. Phys,. 99, 066103 (2006)

By varying the graphite content it is possible to engineer the dielectric constant of the material in order to manufacture absorbers

with a wide range of shielding.


9

Measuring hygroscopicity of polymersJ. Balakrishnan et al, Appl. Opt., 48/12 (2009) 2262-2266

non-polar

polar


10

Semiconductors

• Carrier dynamics

• Electron mobilities

• Quantum dot properties

• Fault inspection

Studied by using optical pump and THz probe


11

Photoinduced metallic state in VO2

using optical pump, THz probe

M. Nakajima et al., Appl. Phys. Lett. 92, 011907 (2008)

Temporal dependence of THz transmittance


12

Electron mobility in GaAs alloys

DG Cooke et al, Appl. Phys. Lett. 89, 122103 (2006)


13

Electron-to-Hole Energy Transferin CdSe Quantum Dots

E Hendry et al, Phys. Rev. Lett. PRL 96, 057408 (2006)


14

Inspection for electrical failuresin semiconductor devices

M. Yamashita et al., Appl. Phys. Lett. 93, 041117 (2008)

Terahertz pulses are generated from nonbiased Si-MOSFETs by exciting p-n junctions with ultrafast

laser pulses. The waveforms of terahertz pulses depend on the interconnection structure near the p-n

junctions.Defects in the circuit wiring give rise to changes in the terahertz emission images.


15

Ceramics and Glasses

• Characterisation

• Relationship with material properties


16

High dielectric constant ceramics

SrTiO3

Ba0.20Sr0.80TiO3

T Fuji et al, Jap. J. Appl. Phys.

43/9B (2004) 6765–6768

PH Bolivar, IEEE Trans. MTT

51/4 (2003), 1062-1066


17

Different grades of Boron Nitride

0 1 2 32.00

2.05

2.10

2.15

2.20

2.25

0 1 2 30

2

4

6

8

Refr

active I

ndex

Frequency (THz)

RIpa

RIpe0

RIpe90

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

smAbpa

smAbpe0

smAbpe90

HBC

0 1 2 32.00

2.05

2.10

2.15

2.20

2.25

0 1 2 30

2

4

6

Refr

active I

ndex

Frequency (THz)

RIpa

RIpe0

RIpe90

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

smAbpa

smAbpe0

smAbpe90

HBN

0 1 21.95

2.00

2.05

2.10

2.15

2.20

0 1 20

2

4

6

8

10

12

14

16

Refr

active I

ndex

Frequency (THz)

RIpa

RIpe0

RIpe90

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

smAbpa

smAbpe0

smAbpe90

HBR

0 1 21.95

2.00

2.05

2.10

2.15

2.20

2.25

0 1 20

2

4

6

8

10

12

14

16

18

Refr

active I

ndex

Frequency (THz)

RIpa

RIpe0

RIpe90

Absorp

tion c

oeff

icie

nt

(cm

-1)

Frequency (THz)

smAbpa

smAbpe0

smAbpe90

HBT


18

Relationship with Boron Nitride properties

1.7 1.8 1.9 2.0 2.1 2.2 2.30

5

10

15

20

HBT

HBR

HBC

HBN

Po

rosity %

Density (g/cm3)

single

crystal

0 2 4 6 8 10 12 14 16 18 20 22 24

2.00

2.05

2.10

2.15

2.20

HBTHBCHBR

parallel

perpendicular 0°

perpendicular 90°

Refr

active in

dex @

1T

Hz

Porosity %

HBN

6 8 10 12 14 16 18 20 22 240

2

4

6

8

10

12

14

PA

PE 0°

PE 90°

Absorp

tion @

2 T

Hz (

cm

-1)

Porosity %

HBN

HBR

HBC

HBT

Boron Nitride (BN)

is birefrigent

and dichroic

Crystals are

oriented

along the

pressing axis

no decreases with porosity

ne remains constant

O-ray absorption

increases faster

than E-ray

Conclusion: porosity between

platelets is anisotropic,

oriented along the O-axis


19

Magnetoelectric contributions to the permittivity of Eu1-xYxMnO3

A. Pimenov et al., Phys. Rev. B 77, 014438 2008

Magnetoelectric effect Antiferromagnetic resonance


20

Silicate glasses (Schott)

0.0 0.5 1.0 1.5 2.00

20

40

60

80

Ab

sorp

tio

n c

oeff

icie

nt

(cm

-1)

Frequency (THz)

silica

Pyrex

BK7

SF15

SF10

SF6

NZK7

B270

SK10

0.0 0.5 1.0 1.5 2.0

2.0

2.5

3.0

3.5 silica

Pyrex

BK7

SF15

SF10

SF6

NZK7

B270

SK10

Refr

active

index

Frequency (THz)


21

Silicate glassesrelationship with material properties

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.50.2

0.3

0.4

0.5

0.6

0.7

0.8

0.50 + 0.06ρ

(ε

− 1

) /

(ε

+ 2

)

Density (g/cm3)

silica

Pyrex

0.17 + 0.05ρ

THz

visible

0 1 2 3 4 5 6 7 8 9 10

1.5

2.0

2.5

3.0

3.5 @ 0.5 THz

@ 589 nm

Re

fractive

in

de

x

Thermal expansion coefficient @ 20/300 °C (10-6

/K)

silicaPyrex

2 3

10

100

1000

Kh

2 x

10

-24 (

cm

-1s

2)

Refractive index @ 0.5 THz

silica

Pyrex

800 1000 1200 1400 1600 1800 2000

10

100

1000

Kh

2 x

10

-24 (c

m-1

s2)

Glass melting point T m

(K)

silica

Pyrex


22

Liquid Crystals

• Dielectric properties

• Conductivity

• Mixtures and colloids


23

Liquid crystal colloid with SiO240-n-pentyl-4-cyanobiphenyl (5CB)

M Ohe et al, Mol. Cryst. Liq. Cryst., 480, 21–28 (2008)


24

Temperature-dependent optical properties40-n-pentyl-4-cyanobiphenyl (5CB)

RP Pan et al, J. Appl. Phys. 103, 093523 (2008)


25

Differentiating polymorphs

of organic molecules


26

Polymorphs of acids

P. Fromentin et al, 978-1-4244-2120-6/08/$25.00 ©IEEE.


27

Temperature-Induced Phase

Transitionsin Polymorphic

Forms of Sulfathiazole

JA Zeitler et al, J. Pharm.Sci.

95/11 (2006) 2486-2498


28

Gas Spectroscopy


29

Gas absorption spectra

0.0 0.5 1.0 1.5 2.0 2.5 3.00

2

4

6

8

10

12

Absorp

tion (

a.u

.)

Frequency (THz)0.5 1.0 1.5 2.0 2.5

0.00

0.05

0.10

0.15

0.20

7

21

19

17

1513

11

Absorp

tion (

cm

-1)

Frequency (THz)

J' = 5

9

Water vapour Carbon monoxide

THz TDS is not suitable for high-resolution gas spectroscopy,due to its low resolution compared with other techniques.


30

Linestrengths and self-broadening parameters of carbon monoxide

0 1 2 3 4 50.00

0.05

0.10

0.15

0.20

J' =9

linear fit

Absorp

tio

n p

eak a

mp

litu

de (

TH

z/m

)

Pressure (bar)

0 1 2 3 4 50.0

2.5

5.0

7.5

10.0J' =9

linear fit

Lin

ew

idth

(G

Hz)

Pressure (bar)

5 10 15 200

2

4

6

8

10

12

14

16

HITRAN

measured

Lin

e in

ten

sity (

cm

-1/m

ole

cu

le.c

m-2

) x 1

0-2

2

J'

5 10 15 201.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

HITRAN

measured

Self-b

roadenin

g p

ara

mete

r (G

Hz/a

tm)

J'

linestrengths

self-broadening

parameters


31

THz absorption of para and ortho vapours at different humidities

212→303: 79.496 cm-1

312 →321: 173.365 cm-1

303 →312: 136.76 cm-1

111 →202: 37.137 cm-1

202 →211: 70.091 cm-1

211 →220: 95.176 cm-1

X. Xin et al, J. Appl. Phys. 100, 094905 (2006)


32

Oils

• Characterising oils

• Relationship with oil properties

• Identifying oil additives

• Observing oil degradation/contamination


33

Shell Oils

0.0 0.5 1.0 1.5 2.00.0

0.2

0.4

0.6

0.8

1.0

Absorp

tion c

oeffic

ient (c

m-1

)

Frequency (THz)

MVI 40 mineral oil, few parrafins

HVI 160 mineral oil, paraffinic

Tellus R5 mineral oil with additives

Risella MH mineral oil, purified

0.85 0.86 0.87 0.88 0.89 0.90 0.91

0.15

0.20

0.25

oils with additives

oils without additives

purified oil

Ab

so

rption

@ 0

.5 T

Hz (

cm

-1)

Density (g/cm3)

0.0 0.2 0.4 0.6 0.8 1.0 1.22

4

6

8

10

12

Absorp

tion c

oeffic

ient (c

m-1

)

Frequency (THz)

new

used

overused

Degradation of engine oil


34

Oil properties

D Mittleman et al, Am. Chem. Soc. Petroleum Research 48172-AC6


35

Composites


36

Carbon nanotubes embedded in deformable rubber

R. Rungsawang et al., J Appl. Phys. 103, 123503 (2008)

Strain causes alignment of CNTs


37

Nondestructive testingof fibreglass aircraft composites

CD Stoik et al, Opt. Express, 16/21 (2008) 17039


38

Moisture content of materials


39

Oil-water complexes of lubricating oilsmeasuring the water content

S. Gorenflo et al, Chem. Phys. Lett. 421 (2006) 494–498


40

Moisture content of paper

D. Banerjee et al, Opt. Express, 16/12 (2008) 9060


41

Measuring the thicknessand moisture content of paper

P. Mousavi et al, Appl. Opt. 48/33 (2009) 6541-6546


42

Observing aqueous foam drainage

sodium dodecyl sulfate (SDS)

- anionic surfactant

(CTAB) cetyl

trimethylammoniumbromide

– cationic surfactant

Triton X-114

- nonionic surfactant

Ultra Dawn dish soap

- mixed surfactants

Guinness beer

- protein surfactant solution

J. Heuser et al, Langmuir 2008, 24, 11414-11421


43

Conclusion

THz spectroscopy can be applied

in many and varied

areas of research

Think what it can do for you

For more information:

http://www.npl.co.uk/electromagnetics/terahertz/

☺

terahertz spectroscopy · pdf filethursday, 07 january 2010 2 thz spectroscopy has been used...

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