Condensed Matter Experiments

56
Condensed Matter Experiments Kind of Systems Studied Correlated Electron Systems (superconductors, GMR systems, …) Semiconductors (amorphous, organic, …) Electronic Materials Soft Matter 2D and 1D systems (thin films, Techniques used Low temperature, High Pressure, High Temperature Microscopy, Spectroscopy, Magneto- optics Nature of studies of various types Magnetism, Superconductivity, Transport (elctrical), Phase transitions, Imaging

description

Nature of studies of various types Magnetism, Superconductivity, Transport (elctrical), Phase transitions, Imaging. Condensed Matter Experiments. Kind of Systems Studied Correlated Electron Systems (superconductors, GMR systems, …) Semiconductors (amorphous, organic, …) - PowerPoint PPT Presentation

Transcript of Condensed Matter Experiments

Page 1: Condensed Matter Experiments

Condensed Matter ExperimentsKind of Systems StudiedCorrelated Electron Systems(superconductors, GMR systems, …)

Semiconductors(amorphous, organic, …)

Electronic MaterialsSoft Matter2D and 1D systems(thin films, heterostructures, nanoparticles, graphene, …)

Techniques used

Low temperature, High Pressure, High Temperature

Microscopy, Spectroscopy, Magneto-optics

Nature of studies

of various types Magnetism, Superconductivity,

Transport (elctrical),

Phase transitions, Imaging

Page 2: Condensed Matter Experiments

Amorphous semiconductors Lab

Electronic Structure of disordered semiconductors in thin film form is studied, with a view to understand their behaviour upon exposure to external stimuli, causing metastabilities. Special attention has been paid to the degradation of hydrogenated amorphous silicon (a-Si:H) caused by exposure to light (Steabler-Wronski effect, SWE). Measurements of conductivity, thermopower, sub-gap absorption, Surface photovoltage, ESR, SSPG, etc. have given valuable information about SWE. Some of the important results are: i) SWE affects the surface as well as the bulk of a-Si:H [1], ii) the inhomogeneous samples, having larger potential fluctuations degrade more [2].

SCA 1

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• Nanocrystalline silicon made by the electrochemical

method (Porous Silicon) shows Photoluminescence (PL), but degrades when exposed to ordinary visible light. This is similar to SWE in a-Si:H, but unlike a-Si:H, seems to be mostly a surface effect. We have been able to arrest the PL degradation by coating nc-PSi with a thin layer of a polymer [3]

• Another study involves the understanding of the switching behaviour of chalcogenide glasses and find out why some compositions can produce a more durable switch than the others [4].

Some significant publications1. Shailendra Kumar and S.C. Agarwal, Appl. Phys. Lett. 45,

575-577 (1984). 2. S.C. Agarwal, J. Mater. Sci. – Mater. Electronics, 14, 703-706

(2003).3. N .P. Mandal, A. Sharma, and S.C. Agarwal, Solid State

Comm. 129, 183-186 (2004).4. D.A. Baker, M.A. Paesler, G. Lucovsky, S.C. Agarwal and P.C.

Taylor, Phys. Rev. Lett. 96, 255501 (2006).

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PECVD setupPlasma Enhanced Chemical Vapour Deposition

SCA 2

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Research FacilitiesPulsed Laser Deposition facilityX'Pert Pro MPD X-Ray Diffractometer14 Tesla, 0.3K, Quantum Design Physical Property Measurement SystemResistivity, Hall, magnetoresistance, tunneling measurements down to 4.2 KContact-less measuremnts of the dynamical behavior of vortices in high Tc superconductors in the frequency range of 2 Hz~6 MHz; Penetration depth measurement using a tunnel diode oscillator based resonant circuit 1.6 K Close Cycle Refrigerator with extreme temperature stability of 0.001 KQuantum Design SQUID magnetometer.Time and frequency domain measurements of photo-induced non-equilibrium effects in solids. He-Cd and He-Ne continuous-wave lasers and frequency tripled pulsed (~ 6 nsec) Nd-YAG laser, Low temperature cryostat with fast electronics.Liquid phase pulsed laser ablation using a frequency doubled Nd-YAG laser for preparation of metal nano particle solutionRHK Technology Scanning Probe Microscope with UHV and low temperature facility.

Condensed Matter-Low Dimensional Systems Laboratory

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Recent Results

NbN-Fe-NbN Josephson Junction array

Vortex-Antivortex Pair Unbinding Driven by the Spin Texture of a Ferromagnet-Superconductor Bilayer

Spin Reorientation in La0.67Ca0.33MnO3 thin film observed by Magnetic Force Microscopy

Field Effect in LTO-STO Heterostructure

Interface Superconductivity

Spintronics : Magnetic Tunnel Junctions

Page 7: Condensed Matter Experiments

(a)[110]

[100]

200 nm

NbN-Fe-NbN Josephson Junction array

Bose et al, APL 2009

0 90 180 270 360

4

5

6

7

8

9

6 K

NbN (30 nm)

R (

a.u.

)

R ()

(Deg)

Fe-NbN (30 nm)

0 90 180 270 360

0

25

50

(Rav, 3.5 kOe)

(RI+, 3.5 kOe)

(RI- , 3.5 kOe)

BθnI

(c)

Fe

NbN~ 50 nm

#2

#1i i

NbN NbN

NbN

(b)

a) SEM micrograph of 40 nm thick Fe nano-plaquettes covered with 30 nm SC NbN.

b) Schematic showing two distinct parallel conduction path for supercurrent.

c) The angular dependence of magnetoresistance of Fe-NbN composite shows maximum super- current dissipation when field (3.5kG) is in the plane of the film (B | n). This is in stark contrast to pure NbN case (max. R when B || n).

Upper inset shows the measurement geometry.

Student working : Saurabh K Bose

Page 8: Condensed Matter Experiments

-300 -150 0 150 3000.00.40.8 0.0

0.40.8

0.00.40.8

0.00.40.8

1.16 mA

1.12 mA

.95 mA

1.1 mA

.81 mA

1.14 mA

1.17 mA

H (Oe)

1.7 K

1.9 K

0.0

0.5

2.1 K

2.4 K

0.00.40.8

R ()

2.7 K

3 K

0.0

0.5

3.5 K

R

()

-2

-1

0

1

2

0.0

0.5

1.0

1.5

M (

emu)

*10-4

-1000 -500 0 500 1000

H (Oe)

R ()

N

O

L

M

(a)

(b)

(a) Temperature dependent R Vs. H Measurements of NbN (10 nm)/ HoNi5 (50 nm) bilayer on (100) MgO substrate.

(b) Comparison of R vs. H and M vs. H at temperature 1.7 K.

NbN TC = 16 K

HoNi5 TCurie = 5.5 K

T Curie < TC

Singh et al. Manuscript submittedStudent working : Gyanendra Singh

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0 G 200 G 300 G

420 G 1000 G

Spin Reorientation in La0.67Ca0.33MnO3 thin film observed by Magnetic Force Microscopy

In Plane Magnetization

Out of Plane Magnetization

Interface

T = 110 KIn Plane Magnetic Field

Singh et al. Manuscript under preparation Student working : Gyanendra Singh

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-20 -10 0 10 200

2

4

-100 -50 0 50 100

-60

-40

-20

0

20

40

60

-20 kV/cm

Cur

rent

(A

)

Vds

(mV)

+20 kV/cm

20K

20 K

Gv(

0) m

S

Eg (kV/cm)

Gv(

0) m

S

0.18

0.20

0.22

0.24 300 K

Vsd

Vg

STOGate Effect of electric field on LaTiO3 thin film

deposited on 0.5mm thick SrTiO3 (100) substrate. Upper inset shows the schematic of the device and lower inset shows the variation in conductance of drain to source channel with gate field.

Rastogi et al. Manuscript submitted

Field Effect in LTO-STO Heterostructure

LTO Mott InsulatorSTO Band Insulator

Student working : Ankur Rastogi

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Temperature dependence of the real and imaginary parts of the pick-up coil voltage of two-coil mutual inductance setup And resistivity measured by four probe method

Interface Superconductivity

La1.48Nd0.4Sr0.12CuO4 (100 nm)

La1.84Sr0.16CuO4 (50 nm)

Substrate SLAO (001)

5 10 15 20 25

0

5

10

15

20

25

30

V (V

)

T (K)

0.0

0.1

0.2

0.3

0.4Im V

(m.

cm)

Re V X 2

Student working : Prasanna Kumar Rout

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Spintronics

Magnetic Tunnel Junctions (MTJs)

-1.0

-0.5

0.0

0.5

1.0

-500 -400 -300 -200 -100 0 100 200 300 400 500

6.4

6.5

6.6

6.7

6.8

6.9(b)

HCo

C

HLSMO

C

(a)

R(k)

Field (Oe)

M(H

)/M

(100

0 O

e)

CoLSMO

20 μm

Junction area 25 μm x 25 μm

Photograph of junctions

SEM image of the junction with one junction zoomed in.

Student working : Prasanta Kumar Muduli

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0.004 0.006 0.008 0.010 0.012

1E-3

0.01

0.1

1

10

300 200 100

0.0068 0.00700.01

0.1 (

cm)

1/T (K-1)

(

cm)

1/T (K-1)

T (K)

a

b

c

100 150 200

100

1000

10000

R (O

hm)

T (K)

Non-equilibrium features in phase separated state of NdNiO3

Exhibit time dependent effects in phase separated stateThese time dependent effects are attributed to stochastic switching of supercooled metallic regions to stable insulating state.If we decrease the sample size such that it contains few SC regions, then we can observe the effect of switching of individual SC region.

Journal of Physics: Condensed Matter 21 185402 (2009) Journal of Physics: Condensed Matter 21 485402 (2009). KPR 1

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Magnetization Dynamics in Antiferromagnetic Nanoparticles

Aging of ZFC magnetization in NiO nanoparticles at 25 K. Inset shows FC aging.

Memory experiments in ZFC protocol. Difference in magnetization without and with a stop of one hour at 100 K.

0 100 200 300-3

-2

-1

0

M (

10-4

em

u/g)

T (K)

Stop of 1 hour at 100 K

Vijay Bisht and K P Rajeev, J. Phys. : Condens. Matter 22, 016003 (2010).Vijay Bisht, K.P. Rajeev,and Sangam Banerjee. Solid State communications (in press)Earlier related work from the group:S D Tiwari and K P Rajeev , Phys. Rev. B 72 104433 (2005). S D Tiwari and K P Rajeev, Thin Solid Films 505 113 (2006).S D Tiwari and K P Rajeev, Phys. Rev. B 77, 224430 (2008)

KPR 2

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Physics of Novel Magnetic and Superconducting Materials

Zakir Hossain- Department of Physics, IIT Kanpur

Research Interest:(i) Correlated Electron Systems- Quantum Phase Transition and Unconventional Superconductivity

(ii) Search for Novel Superconductors Interplay of superconductivity and magnetism

(iii) Phase transitions: Magnetic order, Quadrupolar order, valence transition

(iv) Properties of Materials under extreme condition of ultra low temperature, high pressure and high magnetic field.

ZH 1

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Magnetism and Superconductivity in Eu0.5K0.5Fe2As2

Parent compound EuFe2As2 exhibits two magnetic transitions at T1 (Eu-moments order) ~ 19K and T2 (Fe-moment order)~ 190 K

Suppression of Fe-moment ordering by potassium doping leads to superconductivity below 32 K.

Featutes in the magnetic susceptibility

are similar to that found in HoNi2B2C which show double reentrance

behavior.

Coexistence of short range ordering of the Eu moments with the superconducting state below 15 K is confirmed by 151Eu Mössbauer and magnetic susceptibility.H. S. Jeevan et.al. PRB 78, 092406 2008 Anupam et.al. J. Phys. Cond. Mat (2009)

0 10 20 30 40

-0.016

-0.012

-0.008

-0.004

0.000

1000 G 500 G 250 G 64 G

(e

mu

/g)

T (K)

ZFC

Eu0.5K0.5Fe2As2

ZH 2

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Co2FeSi Heusler alloy thin filmsMotivation: Promising

candidate for spintronic application

To prepare a good quality film with high crystal and interface perfection and low disorder.

Successful in preparing high quality thin film on SrTiO3(STO) using PLD.

Residual resistivity, ρ10K = 0.65 μΩ cm Residual resistivity ratio (RRR) = 438 Such a high value of RRR and low value of

residual resistivity has not been observed so far for any Heusler alloy thin films.

Higher deposition temperature leads to better crystalline quality as compared to lower deposition temperatures which is in contrast to thin film grown on GaAs semiconductor.

20 30 40 50 60 70 80

10

1000

100000STO (300)

STO (200)

STO (100)

Td = 200oC

2 (Degree)

10

1000

100000STO (300)

STO (200)

STO (100)

Co2FeSi (400)

Td = 400oC

Inte

nsi

ty (

a.

u.)

10

1000

100000STO (300)

STO (200)

STO (100)

Td = 600oC

Co2FeSi (400)

0 80 160 240

0

80

160

240

Td = 600oC

25 50 75 1000

15

30

45

(c

m)

T(K)

cm

T (K) Anupam et al. to be publishedZH 3

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Laboratory for Optical Spectroscopy at Extreme Conditions of high P and low T

Research Interests: Multifunctional Materials: Bulk and thin films. Theoretical and experimental measurements on strongly

correlated electron systems e.g Vanadates, ruthenates and manganites.

Li ion battery materials. Alternate cathode materials. Theory and experiments.

Biomaterials: Structure property correlation in doped Hydroxy-apatite.

Nano-materials such as nc-silicon, nanowires etc. Diamond like carbon films and other nanostructures such as

carbon nanotubes.

Rajeev Gupta

RG 1

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Research Facility

• Sample, pressure calibrant and pressure medium to be loaded in a 200 microns hole!

•MicroRaman system with CCD.• Low T (~ 9 K) cryostat.• High T (~900 K) microscope hot stage.• Miniature high pressure cell.• Simultaneously measurement of transport and optical properties.• Thermal measurements (DSC) upto 900 K.

Location: 107 ACMS Building•Please do visit us sometime! RG 2

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Research Area: Multifunctional Oxides

Background: Phase stability of BiFeO3 and improved properties

New Findings:

Zirconium doping stabilizes the phase of BiFeO3. Single phase films prepared by sol-gel process obtained.

Significant enhancement in electrical and magnetic properties.

Dielectric measurements show that Zr-doping of BiFeO3 films significantly reduces the dielectric loss and leakage currents.

Detailed structural characterization and analysis reveals that the films have a monoclinic structure. Improvement in properties due to “quenching” of defects in doped films. RG 3

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Research Area: Li ion Battery materials

New Findings:

Effect of doping spinel LiMn2O4 with chromium and magnesium has been studied using the first-principles spin density functional theory and compared with experiments.

Suppression of Jahn-Teller distortion on doping supported by experiments and theory.

Theory predicts Insulator-Metal-Insulator transition as a function of doping in case of Cr and in case of Mg the ground state is found to move from insulating to the half metallic state as a function of doping.

Critical issue: Cheaper and environmental friendly substitutes for traditional cathode material in Li ion batteries (LiCoO2)

RG 4

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Research Area: Strongly Correlated Oxides

Motivation: Interplay between spin, orbital and charge degrees of freedom leads to different sequential phase transitions in transition metal oxides

10 20 30 40 50 60 70 80 90 100-0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

45 50 55 60 65

T2 T1

T2

M (

X10

3 emu

/mo

l)

100G

Temperature (K)

ZF FCC FCH

T1

dM

/dT

(a.

u.)

Temperature(K)

10 20 30 40 50 60 70 80 90 100

3

4

5

6

7

30 40 50 60 70

T2 T1

T2

M

x10-1

(em

u/m

ol)

Temperature (K)

ZF FCC FCH

T1

100G

dM

/dT

(a.

u.)

Temperature (K)

MnV2O4 ZnV2O4

Sharp transitions at temperatures T1 ~ 57 K and T2 ~ 55 K.

Transitions at temperatures T1 ~ 57K and T2 ~ 41K.

Closeby magnetic and structural transitions suggesting strong evidence of magneto – elastic coupling.

RG 5

Page 23: Condensed Matter Experiments

New Findings:

Silver doped samples shows presence of TCP.

Ag doped samples show comparable hardness with Parent HAp.

Raman studies show that mode intensity decreases with Ag doping in HAp.

Ag doped samples shows antimicrobial properties.

Ionic conductivity on doped samples shows a cross-over at 450 C.

Research Area: Biocompatible Materials- Hydroxyapatite

Critical issues: To study the structure-property correlation with Ag doping and do antimicrobial studies with S. Epidermidis and E. Coli bacteria.

RG 6

Page 24: Condensed Matter Experiments

SB 1

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SB 2

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SB 3

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SB 4

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SB 5

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CDW gap Moire on HOPG, 139nm

Bi2Te3 at 77K

Homemade STM

HOPG

0 100 200 300 4000.0

0.5

1.0

1.5

2.0

Hei

gh

t (n

m)

Length(nm)(b)

Manganite

CDW in 2H-NbSe2 at 8K

Ref: Gupta et.al. Rev. Sci. Instr., 79, 063701 (2008) AKG 1

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Quantum Tunneling and STM

dNeVyxNfeVfVMGyxI tipsam

,,),(),(2

0

Topography : k ~ 1 Å-1

deVfNVdV

dIsam )()()(

Spectroscopy :

~ Nsam (eV) (T ~ 0)

)exp(~ kd

AKG 2

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Our STM Systems

AKG 3

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Hwang et. al., PRL 75, p914 (1995)

LPCMO

Manganites: effect of bandwidth

Singh, et. al., PRB 77, 014404 (08); APL 93, 212503(08); JPCM 21, 355001 (09)

Epitaxial, PLD filmsOn NGO or LSAT

ZBCLCMO

LPCMO PCMO

LSMO

AKG 4

Page 33: Condensed Matter Experiments

STM/S on Graphene FET

Doped Si

SiO2

Vg

A

Vb

-0.4 -0.2 0.0 0.2 0.4 0.6

1

2

3

4

dI/

dV

(a

.u.)

Bias (Vb)

- 60 V

0 V

60 V

nmd

nmeVt

7.0

,2.1,4.0

d

et

K

t

vF exp022

-40 0 40-100

-50

0

50

EF(m

eV)

VG(V)

Slope: 1.21 x 10-3e

gF VE e31037.1

Ref.: RMP 81, 109 (2009 );

0 200 400 600 8000

1

2

Hei

gh

t (n

m)

Distance (nm) 2600 2650 2700 2750 28002000

2500

3000

3500

4000

4500

5000

5500

Inte

ns

ity

(c

ou

nt

W-1s

-1)

Raman Shift (cm-1)

Raman

-60 -40 -20 0 20 40 600.0

0.2

0.4

0.6

Co

nd

uct

ivit

y m-1

V

g (V)

Transport

AKG 5

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Weak Link μ-SQUIDs

AKG 6

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Soft Matter Physics: Inspirational Bio-Organisms for Advanced Materials Applications

1 m

Gecko FootGecko Foot(dry/wet adhesion, self-cleaning)

Lotus LeafLotus Leaf(superhydrophobicity)

MicrofluidicsMicrofluidics(nano/pico-liter liquid control and manipulation)

Hierarchical structures with multi-faceted functions KC 1

Page 36: Condensed Matter Experiments

Wetting: coating something......

liquid beads off substrateclose-up view

Applications: protection, self-cleaning, foul-releasing, anti-fogging, anti-static, non-stick, anti-friction, drag reduction, anti-graffiti, optical

Coating failure (due to dewetting)

KC 2

Page 37: Condensed Matter Experiments

Wetting

Cassie state

Wetting of rough surfaces

Wenzel state

cos = (sg – sl) / lg

Tunable wettability

Electrowetting 200 2

coscos Vd

rV

Wetting of planar surfaces

KC 3

Page 38: Condensed Matter Experiments

Wetting

Thermowetting

Poly(N-isopropylacrylamide) (PNIPAAm)

My approach:

Use to the combination of surface topography and chemistry and control the overall roughness thus the wettability.

Also use responsive polymers to tune the wettability by changing e.g. temperature, electrical signal, light or pH.

Conventional approach:

Vary wettability either by changing the surface chemistry or the physical roughness.

Smooth surface

~ 40o ~ 88o

Topographic surface

~ 158o ~ 80o KC 4

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Microfluidics: liquid transport in microchannels

Patterns of hydrphobic / hydrophilic stripes Patterns of surface grooves

KC 5

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Yashowanta N. Mohapatra Satyendra Kumar

Physics, SCDT, MSP Physics, SCDTIIT Kanpur

Molecular Semiconductors :

Strategies to understand & Optimize Materials for Devices

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Schematic: Device Structure

Single Layer Polymer Light Emitting Diode

PEDOT:PSS

Glass

ITO

Polymer

Ca

Al

Page 42: Condensed Matter Experiments

Diode :A Critical Component

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Goal : Basket of Applications & Products

Source: w4.siemens.de/.../archiv/ pof/heft2_03/artikel18/

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Nano-engineering for Macro-electronics

• PACK & Align • BLEND

F8:F38 : E.Moons J Phy C’05

• EMBEDD

Reese et al. Mat. Today 2004

For better: Luminescence, Mobility, Stability, Excitonics

Page 47: Condensed Matter Experiments

0.0 2.0 4.0 6.0 8.0 10.0

0

30

60

90

120

150

180

-2.9eV

-4.8eV

-2.9eV

-4.8eVITO

Ca

AVPV Oligomer

HOMO

LUMO

-2.9eV

-4.8eV

-2.9eV

-4.8eVITO

Ca

AVPV Oligomer

HOMO

LUMO

Polymer

PEDOT/PSS

Electro- luminescence

Glass Substrate

ITO

ITO

EL Enhancement: Blend Dilution

Effect of blend compositions: dramatic and unmistakable

Single layer devices

Low output

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Photoelectronic Process in Polymeric Semiconductor

Schematic showing typical probes and response functions used in characterization of conjugated polymers

The processes to understand – formation and dissociation of excitons & charges and their conversion to one another

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Peak (Energy) : Possible Transitions in AVPV Oligomer

P1 (2.57eV) : Very high states of LUMO Ground States of HOMO

P2 (2.18 eV) : Very high states of LUMO Defect states of HOMO

P3 (2.05 eV) : LUMO HOMO

P4 (1.91 eV) : Ground States of LUMO Ground States of HOMO

P5 (1.82 eV) : LUMO HOMO

P6 (1.78 eV) : LUMO HOMO

P7 (1.66 eV) : Ground States of LUMO Defect states of HOMO

Phenomenological Model: Density of States

Hot Excitons

Relaxed Carriers

PL

EL

-2.2 eV

-5.8 eV

-2.9 eV

-4.8 eV

3.6 eV 1.9 eV

2.6 eV 2.2 eV

-4.4 eV*

1.5 eV

LUMO

HOMO

PVK Polymer

- 2.2eV -2.2eV

- 5.7eV - 5.7eV

-2.9eV

- 4.8eV

PVK PVKAVPV Polymer

HOMO

LUMO

- 2.2eV -2.2eV

- 5.7eV - 5.7eV

-2.9eV

- 4.8eV

PVK PVKAVPV Polymer

HOMO

LUMO

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Molecules Films (Condensed Phase) Interfaces Device Structures Systems

• Inject Carriers• Transport charge carriers (across interfaces)• Carriers form excitons (photophysical species)• Manage excitonic & polaronic processes• Key : Disorder,Delocalization & DOS

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Density of state distribution:

E

DOS

1 2 3 4

12

34

Intrinsic inorganic semiconductor

Inorganic semiconductor with shallow traps

Inorganic semiconductor with deep traps

Organic semiconductor

Where do they show up? ( in which experiments and properties) are still hotly debated

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*

*

n

MeO

MEH-PPV

Al/Ca - electrode

PE DOT : PSSMEH - PPV

Glass substrate

ITO - electrode

Device and Band Diagram of MEH-PPV device

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+

++

+++

Organicsemiconductor

-

----

-

Transient Electroluminescence measurementTransient Electroluminescence measurement

V=0

V>VV>Vthth

Pulse generator

Digital oscilloscope

PMT

Cathode Anode

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Fig 3: Experimental I-V of 75 nm i-layerM-i-p diode at varying temperatures

Fig 4: Exponential slope of I-V of fig 3 verses temperature

9/15/2008 54

0 1 2 3 410-1310-1210-1110-1010-910-810-710-610-510-410-310-210-1

Cu

rre

nt

(A)

Voltage (V)

Exponential RegimeVoltage Range 0.65 to 0.85V

Square Law Regime

Fig 5: Exponential and SCLC voltage range highlighted

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ITO/TPD/Zn(BZT)2/Al device structure.

Zn(BZT)2

ITO

TPD

Al

White light emitting organic hetero-structure:Disorder at the Interface

400 450 500 550 600 650 700 750 8000.0

0.2

0.4

0.6

0.8

1.0

EL

In

ten

sity

(No

rma

lise

d)

Wavelength (nm)

EL spectra of ITO/TPD (50 nm)/Zn (BZT)2(80 nm)/Al device for different magnitude of injection current.

* FWHM ~ 260 nm

* After certain current, EL spectrum is current independent.

* CIE co-ordinate is (0.38,0.40).

“White Light Emitting Zinc based OLED” Inventors: Y. N. Mohapatra, Samarendra P. Singh, S. S. Manoharan, and Q. Mohammad (Patent No.: 1776/DEL/2004)

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Physics Needed for

• Organic Heterosturcture WHITE LIGHT

• Organic Thin Film Transistors for Printable Electronics

• Organic Heterojunction Solar Cells