Dr Shantanu Ghose

RTSCTMN-09, Nagpur

IITD

A PRESENTATION on Synthesis and Modification of Nitride, oxide Films at Nanoscale and Magnetic Semiconductor : Role of Energetic Ions

byy SANTANU GHOSH Indian Institute of Technology Delhi New Delhi-16, India

RTSCTMN-09, Nagpur

CONTENTS: A. INTRODUCTION

B. PART-I: Synthesis of Nitride and Oxide Films and Modification at Nanoscale C. PART II: Room Temperature p Ferromagnetism g in Nanoscale ZnO: Ni Films --- A DMS System

FUTURE DIRECTION

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A. INTRODUCTION

What are Nanomaterials? Materials with mophological feature one tenth of a micron or less Why Nanomaterials? Materials engineered to nanoscale for ‘Novel functionalities’

Nano flower Nano dot Nano wire Nano Material World

Nanotube

N Nano cage Nano fibres

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Introduction continued..

How Nanostructured materials look like?

Nanorods

Nanofibers

Hexagonal pattern nanotube

Metal catalyzed nanowires

Nanocombs

Source: www.cnms.ornl.gov/nanosci/lp14.shtm

Nano cage

Introduction continued..

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How Nanostructured materials are synthesized ?

Nanolithography, Atom manipulation, Physical vapor deposition, Chemical vapor deposition, Molecular assembly, Supra molecular chmistry ----- Top down approach ----- Bottom up approach

Au nanoparticle assembly Nanolithography Source: www-rpl.stanford.edu/.../nanolithography/

Introduction continued..

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Where Nanostructured materials are used? Next generation computer chips High density data storage High sensitivity sensors Next generation displays Better insulation materials Long lasting medical implants Automobiles with greater fuel efficiency Better and future weapon platforms

---- A change in Human civilization

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Introduction continued..

Landmarks in technology and human civlization 200,000 BC ---- Stone age 3500 BC ---- Bronze age 1764 ---- Steam power 1946 ---- Computation C i and d iinformation f i 1953 ---- Genetic engineering

1960: ‘The The principles of physics as far as I can see, see do not speak against the possibility of manoeuvring things atom by atom’ ---R. Feynman 1990: ‘Engines Engines of creation creation’ Fourth Estate, Estate London, London 296 ---- E. E Drexler

--- Era of Nanotechnology begins

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B. PART-I Synthesis of Nitride and Oxide Films and Modification at Nanoscale

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Part-I continued..

Deposition of Cu3N (~ 100 nm) films by RF Reactive sputtering system

Deposition Parameters: Film: Copper nitride/Oxide Substrates: Glass, Si RF Power: 100 Watt G Gas: N2 and dA Ar Base Pressure: 1x10-6 torr Process pressure: 5x10-2torr Gas flow: 15 sccm

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Part-I continued.. Evolution of surface morphology of Cu3N film

Atomic force microscope XRD

1-A: Substrate at room temperature 1-B: Substrate at 750C 1-C: Substrate at 1500C

Source: www.nanotech-now.com/.../antoniosiber.htm

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Part-I continued.. Compositional analysis of Cu3N film

Elastic s c recoil eco de detection ec o analysis ys s

1-A

1B 1-B

1-C

S. Ghosh et al. Surf. & Coat. Technol. 142 (2001) 034

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Part-I continued.. Modification at Nanoscale using Swift Heavy Ions (SHI)

Nuclear

Electronic

Sputteredatoms Incident ion

Incident ion

25000 Au(S) (Se)

Sttopping power (keV V/micron)

Sputtered

Vacuum

20000

Bragg's peak Ag(Se)

Solid matrix

Solid Collisioncascade

15000

10000

Ni (Se)

5000

Ag(Sn)

1E-4

Elastic collision process

Ni(Sn)

1E-3

0.01

0.1 1 Energy(MeV)

10

100

1000

S n and S e versus energy for Ni, Ag and Au ion in carbon

Damage Zones

Nano tra

Pictorial representationof collisioncascade andlow energy sputtering

Au(Sn)

0

Atoms

Electronic Excitation and Ionization

Energy Loss Spectra TRIM Simulation by J. P. Bierseck

Part-I continued..

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200 MeV Au on Cu3N/Si Cu3N on Si (as deposited)

Av. Grain radius: 40 nm

Irradiated with fluence 1 x 1012 ions/cm2

Av. Grain radius: 60 nm

Part-I continued..

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200 MeV Au on Cu3N/Si I di t d with Irradiated ith fl fluence 5 x 1012 ions/cm i / 2

Conductive AFM (CAFM)

Irradiated with fluence 2 x 1013 ions/cm2

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Part-I continued..

200 MeV Au on Cu3N/Si

0

2

4

6

8

0.8

10 10

0

2

4

6

8

5.5

10 10

0.7 8

8 5.0

6

0.5

0.4

4

Cu/Charg ge

N/Charg ge

0.6

6 4.5 4

0.3 2

4.0 2

0.2

0.1 0

2

4

6

8

No. of Bins

Results:

0 10

3.5 0

2

4

6

No of Bins No.

Rapid depletion of N Constant copper counts (±10%)

8

0 10

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Part-I continued..

200 MeV Au on Cu3N/Si 0

2

4

6

8

10

15

10

14 13

8

Current (nA)

12 11

6

10 9

4

8 7

2

6 0

5 0

2

4

6

8

10

F lu e n c e ( x 1 0

12

12

14

) io n s / c m

16

18

20

2

95 % Enhancement Of target current

M t lli it ? Metallicity? S. Ghosh et al , J. NanoSci.&NanoTech. 8,2505–2508(2008)

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PART I CONTINED….

♦ Thermal spike model

∂T C = ∇(K ∇T ) − g(T −T) + B(r, t) ∂t ∂T ρC(T) = ∇(K(T)∇T) + g(T −T) ∂t e

[M Toulemonde et. [M. et al. al J. J Appl. Appl Phys. Phys 46 (1992) 14362]

Thermal spike in electronic subsystem (10-15 sec) Transfer of heat to the lattice. Thermal spike in the lattice (10-11 to 10-13 sec) in cylindrical geometry.

Smaller grain

e

e

e

e

(3) 11

e

Ce = electronic specific heat, C = lattice specific heat, g = electron-phonon coupling, B = energy d it db deposited by iion.

g = f(1/λ )

Materials ejects out through the hot cylinder if temepereture crosses the sublimation temperature. perature

Lowerλ Higher g

Higher T

Higher Sputtering S. Ghosh et.al. REDS 154 (2002) 151.

Part-I continued..

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200 MeV Au on Cu3N/Glass

AFM image of Cu3N/Glass (as deposited)

AFM image: Cu3N/glass (fluence:2 x 1013 ions/cm2)

S. Ghosh et al , J. NanoSci.&NanoTech. 8,2505–2508(2008)

Part-I continued..

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Wh iis the What h next goal? l?

Cu3N To generate patterned nanometallic line in Cu3N matrix ---- an open problem

Part-I continued..

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Deposition of ZnO (~ 100 nm) nanostructured films by Vapor phase transport

Objective: To grow different nanostrutures of ZnO

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Part-I continued.. Provision for Gas Inlet

F U R N A C E

Chemically prepared ZnO powder

Temp: ~ 550 0C Atmospheric pressure Exhaust Without any carrier gas

Quartz Tube Source

Thermocouples

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Part-I continued.. 101

O i i d Parameters: Optimized P •Temp: 550 •Distance: Di 2 4 cm 2-4 •Deposition time: 5 hours 0C

100

002

110 102

103

112

XRD

ZnO Film (~ 100 nm) is formed on Si Columnar growth

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Part-I continued..

TEM

ZnO/Au (30 nm)/Si

50 nm 50 nm

ZnO/Au (15 nm)/Si (2-4 cm)

ZnO/Au (15 nm)/Si (6-8 cm)

S. Ghosh et al , J. NanoSci.&NanoTech. 8 (2008) 2655

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Part-I continued..

Wh iis the What h next goal? l? Optimize the system for other nanostructures (nanorod, nanoneedle, nanowire etc.) Optical and Field emission properties of these nanostructures To grow doped ZnO nanostructures An attempt to grow Ga doped ZnO as transparent conducting oxide (TCO) 100

6

5

80

Ga Doped ZnO : Eg = 3.3 3.32 eV

-2

60

40

Resistivity (x 10 Ohm m-cm)

% Transmitta ance

Pure ZnO : Eg = 3.21 eV

4

3

2

1

20

0 0 .0 0

0 300

400

500

600

Wavelength in nm

700

0 .0 5

0 .1 0

0 .1 5

0 .2 0

G a /Z n O

0 .2 5

0 .3 0

0 .3 5

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C PART C. PART-II II Room T R Temperature F Ferromagnetism i in i Nanoscale ZnO: Ni Films --- A DMS System

Part-I I continued..

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Spin based devices

Challenges: Efficient spin injection

Diluted magnetic semiconductor (DMS)

Ferromagnetic property at room temperature

-- a potential candidate

High ‘spin polarization’

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Part-I I continued..

What is a Diluted magnetic Semiconductor (DMS) System?

Electronics

Optics

Spintronics Magnetism Magnetic impurity Semiconductor host

Promising applications in Spintronic devices

Challenging Issues:(i) Search for a synthesis route (ii) Ferromagnetism at room temperature (iii) Tuning T i the th ferromagnetic f ti properties ti – Role R l off microstructure i t t (iv) Combining RT-FM and optical properties

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Part-I I continued..

Theoretical Predictions Theoretical Tc Values TM Doped

Transition Metal (TM) doped ZnO: Promising DMS

Part-I I continued..

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How ferromagnetism arises in ZnO based DMS? Model 1: Exchange interaction between carriers (mostly generated due to defects)) and localized magnetic g ions ---- Zener [Applicable when electrical conductivity is higher] Model 2: Charge carrier associated with a particular defect may be confined in a hydrogenic orbit. All TM ions within the polaronic radius Interact, shaping bound magnetic polaron (BMP), which may spread ou to overlap l adjacent dj BMPs to realize li magnetic i ordering, d i resulting li ferromagnetism ----- Coey [[Applicable pp when electrical resistivity y is higher] g ] What is the role of nano dimension? ‘Integration Integration of DMS material in future electronics will require very low Dimension in order to make real use of the advantage offered by the spin’ -------- C. Roning

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Part-I I continued..

Brief Review of ZnO Based DMS Systems 1 1.

Ti Tiwari i ett al. l

Source: http://www.ee.ucr.edu/~zyang/Presentations/

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Part-I I continued..

2.

Sharma et al.

Source: http://www.ee.ucr.edu/~zyang/Presentations/

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3. Norton et al.

Source: http://www.ee.ucr.edu/~zyang/Presentations/

250 keV

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Part-I I continued..

4 4. Schwartz et al.

Source: http://www.ee.ucr.edu/~zyang/Presentations/

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Part-I I continued..

Recent Research on ZnO: Ni System ------- Salient Points 1. J. Appl. Phys. 100, 114304 (2006)

Ni 180 keV Implantaion on ZnO Si l crystall Single

2 J. 2. J Appl. A l Ph Phys. 103, 103 093901 (2008)

1,3,5 &7% Ni doped ZnO Film ggrown byy PLD Remarks:Ni substitutes Zn site

Remarks:-

Carrier C i mediated di d FM

Main contribution of FM comes from Ni nanoparticles Ni:ZnO based DMS can’t be ruled out

Influenced byy morphology Low resistivity High carrier density

Part-I I continued..

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Ni (0.02, 0.04, 0.07, 0.11) doped ZnO by Magnetron Sputtering

Ni substitutes Zn FM does not scale with carrier conc.

E l i d on the Explained th b basis i off B Bound dM Magnetic ti P Polaron l (BMP) Model M d l

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Part-I I continued..

Nickel doped ZnO (~ 80 nm) films by Fast s atom o be beam spu sputtering e g

ZnO Disc + Ni strips

45 o Substrates

Motor

Fast Atom Beam Source

To Vacuum System

Film: ZnO:Ni Thickness: 80 nm Base Pressure: 10-7 mbar Deposition Pressure: 10-3 mbar Energy of Ar: 1.2 keV

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Part-I I continued..

ZnO: Ni by FAB

TEM & SAD F Frequency (Arb.units) F

X-ray photo electron spectroscopy

1

20 nm 20 nm

XPS

2

3

4

5

6

Particle Diameter (nm)

7

8

9

ZnO (101)

HRTEM 2 nm

Earlier we have seen:seen: i. ii.

Presence of Ni in an O environment in the film Ni2+ partly substitute Zn in the ZnO matrix S. Ghosh et al. App. Phys. A 90 (2008) 765

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Part-I I continued..

ZnO: Ni by FAB 8 6 5K 15K 300K

Magnetissation (emu/g)

4 2 0 -2 -4 -6 6 -8 -6000

-4000

-2000

0

2000

4000

6000

Magnetic Field (Oe)

Films are ferromagnetic upto RT Ch Charge carrier i mediated di t d exchange h iinteraction t ti iis proposed d B. Pandey et al. J. Mag & Mag. Mater 320 (2008) 3347

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Part-I I continued..

200 keV Ni+2 implanted ZnO/Si Film

Implantation p Parameters:

Ion and Energy: Ni22+, 200 keV Projected range: 102. 3 nm and straggling: 43 nm

Ion Implantation Facility IUAC, New Delhi

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Part-I I continued..

Ni Implanted ZnO/Si Surface Morphology G

As deposited p ZnO Av. Grain size: 57 nm

Ni Implanted ZnO Av. Grain size: 98 nm

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Part-I I continued..

Ni Implanted ZnO/Si

Ms = 0.025 emu/cm3 Mr = 0.0030 0 0030 emu/cm3 Mr/Ms ~ 12% Hc = 53.14 Oe

DMS As deposited ZnO Ni Implanted ZnO Av. Grain size: 57 nm

Av. Grain size: 98 nm Resistivity: 1.5 x 10-1 Ohm-cm

S. Ghosh et al. REDS 163 (2008) 215

Charge carrier mediated ferromagnetism

Intrinsic?

Part-I I continued..

Fluence Dependent Study IIon and dE Energy: Ni Ni, 200 k keV V Projected range: 102. 3 nm and straggling: 43 nm Fluences: 6 x 1015 ions/cm2 (A1) 8 x 1015ions/cm i / 2 (A2) 2 x 1016ions/cm2 (A3)

Ni Implanted ZnO/Si

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Ni Implanted ZnO/Si

AFM

XRD

Sample

Av Grain Size (nm) Av.

RMS Roughness (nm)

A1

80

1.4

A2

129

55 5.5

A3

43

3.0

Part-I I continued.. Ni Implanted ZnO/Si

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XPS

Zn O Oa: O2- ion in Zn2+environment Ob: O vacancies within the matrix of ZnO Oc: Loosely bound O on the surface

Chen et al. App. Surf. Sci. 158 (2000) 134

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Part-I I continued.. Ni Implanted ZnO/Si Sample

Resistivity (Ohm-cm)

Carrier Conc. (cm -3 )

A1

1.23 Ohm-cm

9.5 x 1016

A2

1.2 x 10-1 Ohm-cm

1.4 x 1018

A3

1.5 x 10-1 Ohm-cm

1.7 x 1017

Highest O-vacancy L Lowest tR Resistivity i ti it

Remarks:1. Charge carrier mediated FM – primary cause 2. Influence of nanostructure on FM

Highest FM Moment B. Pandey et al. J. App. Phys. 105, 033909 (2009)

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Part-I I continued..

200 keV Ni+2 implanted ZnO/Sapphire -4

2.5x10

200 K KeV V Ni on Z ZnO/sapphire O/ hi (b (by PLD)

2.0x10 2 0 10-4 -4

1.5x10

-4

1.0x10

(002)

Momen t (emu)

(00 04)

(00 06)S

5 % Ni implanted ZnO (0 006)S

(002)

400k 300k 200k 100k 0

7 % Ni implanted ZnO

5K

-5

5.0x10

0.0 -5.0x10-5 -4

-1.0x10

-1.5x10-4 -4

-2.0x10

(00 04)

800.0k 600.0k 400.0k 200.0k 0.0

2% Ni implanted ZnO 3% Ni implanted ZnO 5% Ni implanted ZnO 7% Ni implanted ZnO

-4 4

-2.5x10

(002)

600.0k

200.0k

(0 004)

((006)S

400.0k

-4

-4

2.0x10

-4

(002)

M emu

0.0 300k

2% Ni implanted 3% Ni implanted 5% Ni implanted 7% Ni implanted

300K

-5

5.0x10

0.0 -5.0x10-5 -4

-1.0x10

(004)

100k 0 20

Pure ZnO (006)S

200k

-4

1.0x10

Moment (O Oe)

((004)

200.0k

1.5x10

2 % Ni implanted ZnO (006)S

400.0k

2000 4000 6000 8000 10000

2.5x10

0.0 600.0k

0

Magnetic Field (Oe)

3 % Ni implanted ZnO

(002)

In ntensity

-10000 -8000 -6000 -4000 -2000

-4

-1.5x10

-4

30

40

50

2θ

60

70

80

-2.0x10

-4

-2.5x10

-10000 -8000 -6000 -4000 -2000

0

2000 4000 6000 8000 10000

Applied Field (Oe)

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Part-I I continued.. 2.1x10

-5

2.0x10

-5

1.9x10

-5

1.8x10

-5

1.7x10

-5

1 6x10 1.6x10

-5

1.5x10

-5

1.4x10

-5

1.3x10

-5

As-d ep osited Z nO/Sa pph ire

% Transmission T i i

80

ZFC-FC at 100 Oe 2 % Ni implanted ZnO Sapphire

Trans smittance (%)

M (emu)

1 00

60

i.2%Ni: ZnO-> 85% ii. 7%Ni: ZnO->68%

40 20 0 200

0

50

100

150

200

250

300

T

300

40 0

500

600

70 0

8 00

W a ve len g th (n m )

4.0x10-6

3.5x10-6

M (emu)

FC 3.0x10

-6

2.5x10

-6

2 0x10 2.0x10

-6

Field 100 Oe 7% Ni implanted ZnO/Sapphire

ZFC 1.5x10

-6

1.0x10

-6

0

50

100

150

200

250

Sample

Resistivity (Ohm-cm)

Pure ZnO

14.85

2 % Ni implanted ZnO

4.33

3 % Ni implanted ZnO

11.56

5 % Ni implanted ZnO

2.87

7 % Ni implanted ZnO

5.73

300

T

Transparent Magnetic Semiconductor at Room Temperature

Part-I I continued..

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Remarks:i. Resistivity of the films are relatively high ii. FM strength does not scale with resistivity iii. Defect mediated Bound magnetic polaron is proposed for explanation ------ Needs further investigation

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Part-I I continued..

What is the next goal? RT-FM is not enough g Check for ‘spin polarization’ Grow a spin ‘tunneling magnetoresistance (TMR)’ device FM

I FM

A current project under MIT, Govt. of India

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Scientific Group: p S. Ghosh, B. Pandey and P Srivastava, P. Srivastava (IIT Delhi, India)

D. K D K. A Avasthi, thi D D. K Kabiraj bi j P. Kumar and D. Kanjilal (IUAC, New Delhi)

J.C.Pivin (CSNSM, France) S Zhou S. Zh and dH H. S Schmidt h id (FZD, Germany)

Ackno ledgement: Acknowledgement: • Dept. of Physics, IITDelhi • Accelerator Group, IUAC, New Delhi • UGC UGC-DAE-CSR, DAE CSR, Indore • DSI, Singapore • DST, New Delhi • CSIR, CSIR New Delhi • CSNSM, France • FZD, Germany

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‘India cannot afford to miss the revolution in Nanotechnology. We should not be at the receiving end when the world is driven by Nanotechnology’ ------- Prof. C. N. R. Rao