Leonid Dubrovinsky and Natalia Dubrovinskaia- Novel Superhard Materials
Nitride Superlattice Thin Films for Superhard Coatings Ramou Akin-Cole MRSEC Program 2004 Advisor:...
-
Upload
eden-cobbins -
Category
Documents
-
view
220 -
download
2
Transcript of Nitride Superlattice Thin Films for Superhard Coatings Ramou Akin-Cole MRSEC Program 2004 Advisor:...
Nitride Superlattice Thin Films Nitride Superlattice Thin Films for Superhard Coatingsfor Superhard Coatings
Ramou Akin-Cole
MRSEC Program 2004
Advisor: Paul Salvador
Graduate Student: Nitin Patel
BackgroundBackground
Hard materials (e.g. TiN, Al2O3) used successfully as coatings to increase tool life by a factor of 4-20.
Diamond and cubic Boron Nitride are the hardest known materials.
Diamond gets oxidized in air at high temperatures.
Cubic Boron Nitride is difficult to produce as thin film.
Cutting tool in operation
How can we design materials that have hardness How can we design materials that have hardness values approaching the hardest known materialsvalues approaching the hardest known materials??
Project ObjectivesProject Objectives Study orientation effects and
hardness with increasing Al content in monolithic Ti1-xAlxN.
Grow Thin Films using Physical Vapor Deposition(PVD) Technique called Pulsed Laser Deposition.
Characterize films using X-Ray Diffraction and Nanoindenter
Grow TiN/Ti1-xAlxN superlattices in both (100) and (111) direction.
Substrate Substrate
TiNTi1-xAlxN
TiNTi1-xAlxN
TiNTi1-xAlx NTiN
ExperimentsExperiments
SrTiO3 (Perovskite) MgO, TiN, AlN(Rocksalt)
TiN AlN MgO STOa(Å) 4.24 4.04 4.21 3.91
Deposition Parameters
PRESSURE : 0.001 - 0.2 Torr
TEMPERATURE: RT - 950 °C
FLUENCE : 2-6 J/cm2
FREQUENCY : 1-10 HzCOOLING: 10-5- 200 Torr
Focusing LensWindow
Deposition Chamber
Target
Plume
Laser Beam
Substrate
Substrate Heater
Target Rotator
Pulsed Laser Deposition
•KrF Excimer Laser:λ = 248 nm
• Energy: ~2 /J cm2
• : 3 Frequency Hz
TiTi1-x1-xAlAlxxN films by alternating N films by alternating depositionsdepositions
Focusing LensWindow
Deposition Chamber
Target
Plume
Laser Beam
Substrate
Substrate Heater
Target Rotator
Pulsed Laser Deposition
•KrF Excimer Laser:λ = 248 nm
• Energy: ~2 /J cm2
• : 3 Frequency Hz
TargetRate
(Å/pulse)# of
pulsesThickness
(Å)
TiN 0.12 9 1.08
AlN 0.29 3/4 1.02
1. Deposit submonolayer of TiN (i.e., 1/4 unit cell thick)
2. Switch target
3. Deposit submonolayer of AlN (i.e., 1/4 unit cell thick)
4. Switch Target
5. Repeat to certain film thickness of Ti1-xAlxN
200 nm Ti0.5Al0.5N : {9Ti / 3Al / 9Ti / 4Al} x 475
10
100
1000
10000
100000
1000000
10000000
100000000
1000000000
10000000000
30 32 34 36 38 40 42 44 46 48 50
SrTiO 3
111
Ti:Al =0:1
Ti:Al =1:3
Ti:Al =1:1
Ti:Al =3:1
10
100
1000
10000
100000
1000000
40 42 44 46 48 50
Monolithic Ti1-xAlxN Films
Inte
nsit
y (
a.u.
)
SrTiO3
100
ST
O (
200)
Ti:Al =1:0
10
100
1000
10000
100000
1000000
10000000
100000000
1000000000
10000000000
30 32 34 36 38 40 42 44 46 48 50
SrTiO 3
111
Ti:Al =0:1
Ti:Al =1:3
Ti:Al =1:1
Ti:Al =3:1
Inte
nsit
y (
a.u.
)
Orientation Intensities and Orientation Intensities and Lattice Parameter versus Lattice Parameter versus
CompositionComposition
1
10
100
1000
10000
0 0.5 1
100 Intensities
111 Intensities
Inte
nsit
y (
a.u.
)
Al:Ti ratio
3.96
4.01
4.06
4.11
4.16
4.21
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Al:Ti ratio
Lat
tice
Par
amet
er (
Å)
111 Substrate
30 35 40 45 50
2-Theta
Intensity
100 Substrate
30 35 40 45 50
2-Theta
TiN/Ti0.25Al0.75N multilayer
MgO
(11
1)
SrTiO3
ST
O (
111)
MgO
Bragg (200) Peak
Bragg (200) Peak
Bragg (111) Peak
MgO
(20
0)Bragg (200) Peak-1
MgO
+1
SrTiO3
Bragg (200) Peak
ST
O (
200)
-1-2
Hardness versus Ti:Al ratioHardness versus Ti:Al ratio
Hardness vs composition
0
5
10
15
20
25
30
35
40
45
50
0 20 40 60 80 100
% Al
Conclusion Al was difficult to grow in crystalline form TiN and Ti1-xAlxN grow epitaxially in 100 direction and not
in 111 direction. Superlattices grow well in 100 direction and not in 111
orientation The hardness values of superlattices show significant
enhancement, over individual component Optimizing processing conditions can enable the growth
of (111) oriented monolithic Ti1-xAlxN films and superlattices