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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