inup talk 2011 edited palkar

8/10/2019 INUP Talk 2011 Edited Palkar

1/18

Realization of Multiferroic

anodevices

V. R. Palkar

Centre of Excellence in Nanoelectronics,

Indian Institute of Technology Bombay,Mumbai 400076, India

Acknowledgement: Mrinmoy

Mandal

(Ph.D

Student)Sriparna Chattergy (TIFR)


2/18

Plan of the talk

Introduction to Multiferroics

Fabrication & Characterization

of BDFO nanorods

Conclusions


3/18

Coexistence of ferroelectric & magnetic

ordering

Strain mediated ME coupling

Magnetization M E

Electric Polarization P B

Tremendous application potential

MEMS sensors & actuators, non-volatilememories, multiple memory elements etc.

Ferroelectrics distortion in latticePresence of magnetic element favors

structural symmetry

Scarcity of materials exhibit ing

ferroelectric & ferromagnetic ordering at RT

What are Multiferroics?


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1. V.R. Palkar et.al. J. Appl Phys., 93, 4337 (2003) Bi0.9La0.1Fe1-xMnxO3 (Bulk)

2. V. R. Palkar et al. Physical Review B 69, 212102 (2004) Bi0.9-xTbxLa0.1FeO3 (Bulk)

3. V. R. Palkar et al. Applied Physics Letters 84, 2856 (2004) Bi0.9-xTbxLa0.1FeO3 (TF)4. V. R. Palkar et al. J. Materials Research 22 (8), 2068 (2007) Bi0.9-xDyxLa0.1FeO3 (TF)

5.K. Prashanthi, V. R. Palkar et al. Solid State Commun. 2009 Bi0.7Dy0.3FeO3 (bulk, TF)

Development of novel room temperature

multiferroic

B based (Bi

0.7

Dy

0.3

FeO

3

) system

Bulk Pulse laser deposited Thin films on Si


5/18

Realization of Multiferroic

Devices

(Nanorods and Bulk & micro inductors)Why multiferroic nanorod/wires ?

If multiferroic

properties could be fashioned in nanorods,

implementation in devices could be certainly more

efficient and straight forward

Growth of nano rod or wire like structure

Self organized growth during thermal processing

in rod/wire like structures (ZnO)

Electrolysis through template MOCVD


6/18

Nanoporous

aluminatemplate

(pore diameter

80nm)

Pore diameter and

thickness controllable.

nanowires

grownthrough the template

Diameter same as the

pore size and length

of the nanowire

is

controllable.

nanowires

after

removal of the

template

nanowires

y electrodeposition


7/18

Gold Tip

Deposition

AlloyDroplet

Gold Cluster PrecursorVapours

Annealing WhiskerGrowth

1 2 3 4

Vapour-Liquid-Solid Growth Technique

50000 X

500 nm

Cross sectional view

Top view

Growth of Nanowires

using MOCVD

SEM of NanoWires


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Tilted view 45 angle view

Failure in growing BDFO nanorods

through

porous alumina

template using PLD

Top surface of porous Alumina

template

BDFO deposited using PLD on

Alumina template

Cross sectional view


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Si nanorod (VLS route)

Au

Si

Au-Si

Au-Si

AuSi

Au

SiH4

Si

Liquid phase alloy at eutectic

temp of 400C

Nucleation Nano-rod growth

Termination of growth

SiH4

Au catalyst

ZnO nanorod (Aq. Solution route)

Si

was mounted in up side down position inside anordinary screw-cap pyrex

glass bottle.

Aqueous solution of zinc nitrate (Zn(NO3

)2

.6H2

O)

of strength 0.01M was used as a source of zinc ion.

Hexamethylenetetramine (HMT, (CH2

)6

N4

) of

strength 0.01M was used both as hydrolyzing and

capping agent.

Each sample was kept at 90C for 12 hours andthen cooled down to room temperature

After the reaction was over, samples were

thoroughly washed with de-ionized water until the

pH of the wash became

6.5.

SiH4

200 nm 2 um

J. Vac. Sci. Technol. B 15, 554 (1997) J. Nanoscience Nanotech. 9 (2009) 4792.

Grow th process for

rowth process for

Si

i

ZnO

nO

nanorod

anorod

BDFO S & Z O


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BDFO/Si rodsBDFO/Si rods

BDFO/ Si nano-rod

PLD

Parameters

Optimized

conditions

Laser density attarget

2.6 J/cm2

Target to substrate

distance

4.5 cm

Substrate

temperature

690C

Oxygen pressure 420 mTorr

Repetition rate 10 Hz

SEM image of Si rod

BDFO coated on template Si & Zno rods.

- Diameter :~ 500-800nm

- Height :~ 3-5 m

(including diameter ~300nm of Si or ZnO rod )

BDFO/BDFO/ZnOZnO rodsrods

200 nm

100 nm

BDFO

ZnO

200 nm

ZnO rod BDFO/ZnO rod

Cross sectional view of BDFO/ZnO rod

Table 1.Atomic % of chemical elements present in BDFO/ZnO

rods

grown on Si substrate

O Si Fe Zn Dy Bi

51.65 21.13 7.38 12.51 1.83 5.5

BDFO nanorods

using Si

& ZnO

nanorods

as core


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BDFO/Si rodsBDFO/Si rods BDFO/BDFO/ZnOZnO rodsrods

20 30 40 50 600

Intensity(arb.units)

2 Theta

S

i

Si

BDFO+Go

ld

BDFO+Gold

Si

BDFO

(a)

20 30 40 50 600

150

300

450

BDFO

ZnOZ

nO

BDFO

Intensi

ty

(arb.units)

2 Theta

BDFO

ZnO

XRD of BDFO/Si

BDFO/ZnO

nanorods


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Two point contact

Single point contact

BDFO/Si rodsBDFO/Si rods BDFO/BDFO/ZnOZnO rodsrods

Metallic probe

SiO2

Conductive Si

BDFO/ZnO rod

Metallic probe

Top electrode

W deposition

Lithographically defined electrical

ithographically defined electrical

contact

ontact


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-4 -2 0 2 4

M(

emu)

Magnetic Field (KOe)

BDFO/Si rods

-0.010 -0.005 0.000 0.005 0.010-10.0

-5.0

0.0

5.0

10.0

Polar

ization(C/cm

2)

Applied Voltage (V)

Without Magnetic Field

With magnetic Field (60 Oe)

-0.4 -0.2 0.0 0.2 0.4

-10

0

10

Polarization(uC

/cm

2)

Voltage Applied (V)

BDFO/Si rods

Comparison of multiferroic

properties

BDFO/Si BDFO/ZnO

M(emu)


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Electromagnetic coupling behavior of

lectromagnetic coupling behavior of

BDFO/

DFO/

Si

i

BDFO/

BDFO/

ZnO

nO

nanorods

anorods

using MAFM

sing MAFM

Effect of voltage on magnetic domain

structure

Topography MFM Phase at 0V MFM Phase at 2V

MFM Phase at 6V MFM Phase at 8V MFM Phase at 10V

Topoography 0V Topoography 4V Topoography 8V

MFM Phase 0V MFM Phase 4V MFM Phase 8V

BDFO/Si

nanorods

BDFO/ZnO

nanorods


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Piezoresponse

iezoresponse

behavior of

ehavior of

BDFO/

DFO/

Si

i

BDFO/

BDFO/

ZnO

nO

nanorods

anorods

% contraction in rod dimensions (nm) resulted due to applied voltage is

calculated from AFM images usingWSxM & Olympus analyzing software

0 2 4 6 8 10-2.5

-2.0

-1.5

-1.0

-0.5

0.0

%c

ontraction

Applied Voltage (V)

BDFO/Si rod

M. Mandal

and V. R. Palkar, Materials Research Soc. 2010

M. Mandal, S. Chattarjee and V. R. Palkar, Journal of Appl. Phys. 111, 45313, 2011


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ZnO

Bi0.7Dy0.3FeO3

Si

Bi0.7Dy0.3FeO3

Interfac

iallayer

Cross sectional Study

(a) (b)

TEM images revealing interface of

(a) BDFO/Si

& (b) BDFO/ZnO

nanorods


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Successfully grown multiferroic

BDFO nanorods

using

Si

& ZnO

nanorods

as core material

Ferroelectric properties and coupling coefficient of

BDFO/ZnO

nanorods

are much superior compared toBDFO/Si

nanorods. This could be attributed to formation ofSiO2

like interface in case of BDFO/Si

nanorods

Even piezo

response of BDFO/ZnO

nanorods

is muchbetter. Piezoelectric properties of ZnO

could be acting as

booster

BDFO/ZnO

nanorods

could be directly used as electricity

generators in the electronic circuits more effectively than

ZnO

nanorods

Conclusions


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Thank You

inup talk 2011 edited palkar

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