Ш.results and discussion Ш. results and discussion a) w composition b) stress and mechanical...
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ШШ .. Results and discussionResults and discussiona) W Composition
b) Stress and Mechanical Properties
c) TEM-microstructures
0 2 4 6 8 10 12 141.2
1.5
1.8
2.1
2.4
2.7
3.0
3.3
Re
sid
ua
l s
tre
ss
(G
Pa
)
W/(W+C) (at.%)
ШІІІ
C
Si substrate
Ar
W
W incorporated carbon nanocomposite films
prepared by hybrid ion beam deposition
Ai-Ying WangAi-Ying Wanga a ,,**([email protected])([email protected]), Hyo-Shin Ahn, Hyo-Shin Ahnaa, Kwang-Ryeol Lee, Kwang-Ryeol Leeaa, Jae-Pyoung Ahn, Jae-Pyoung Ahnbb
aaFuture Technology Research Division, Korea Institute of Science and Technology, Seoul, 130-650, South KoreaFuture Technology Research Division, Korea Institute of Science and Technology, Seoul, 130-650, South KoreabbNano-Materials Research Center, KIST, South KoreaNano-Materials Research Center, KIST, South Korea
ІІ . Introduction. IntroductionSignificant progress in understanding the growth behavior and atomic bond structure of diamonSignificant progress in understanding the growth behavior and atomic bond structure of diamon
d-like carbon (DLC) film has been achieved in the last three decades. Nevertheless, high residud-like carbon (DLC) film has been achieved in the last three decades. Nevertheless, high residu
al stress and poor adhesion are still the main barriers to its applications. In the present work, we al stress and poor adhesion are still the main barriers to its applications. In the present work, we
employed a hybrid deposition method to prepare W incorporated DLC films in a wide range of employed a hybrid deposition method to prepare W incorporated DLC films in a wide range of
W concentration from 2.4 to 12.5 at.%. W concentration from 2.4 to 12.5 at.%. We observed a stress jumping behavior as the W conceWe observed a stress jumping behavior as the W conce
ntration increased from 2.4 to 5.0 at.%. Beyond 5.0 at.%, gradual decrease in the residual stress ntration increased from 2.4 to 5.0 at.%. Beyond 5.0 at.%, gradual decrease in the residual stress
was observed as in the previous work.was observed as in the previous work. High resolution TEM analysis showed that the stress ju High resolution TEM analysis showed that the stress ju
mping was closely related to the change in the W incorporation behavior from atomic scale incmping was closely related to the change in the W incorporation behavior from atomic scale inc
orporation into the amorphous carbon matrix at low W concentration to formation of a nanosizeorporation into the amorphous carbon matrix at low W concentration to formation of a nanosize
d d -W-W22C phase at higher W concentration. Ab initio calculation of the excess energy by atomic C phase at higher W concentration. Ab initio calculation of the excess energy by atomic
bond distortion suggested that the stress reduction with atomic scale W incorporation was due tbond distortion suggested that the stress reduction with atomic scale W incorporation was due t
o the reduction of the directionality of W-C bonds.o the reduction of the directionality of W-C bonds.
ПП . Experimental. Experimental
Working gas: Ar + C6H6 (total: 12sccm)
Base pressure : 2.0 10-6 Torr
Substrate bias : - 200 V
Power density of target: 4.2~7.3 W/cm2
Deposition Pressure : 0.6 ~ 1 10-4 Torr
Thickness: 350±50nm
Substrate: P-type Si(100), 500m, 100m
Wn+
H+, Cm+
0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.950
2
4
6
8
10
12
14
16
W c
on
cen
trat
ion
(at
. %)
Ar fraction in the gas mixture
bias -200V
0 2 4 6 8 10 12 1415
20
25
30
35
40
120
130
140
150
160
170
180
190
200
Ha
rdn
es
s (
GP
a)
W/(W+C) at.%
Ela
sti
c m
od
ulu
s (
GP
a)
21±3 GPa
170±15 GPa
!! Stress jumping occurred with increasing W concentration. The mechanical properties also showed the same dependence, although the variation is not as significant as that of the stress.
(e)
4 nm
-W2C (102)
-W2C (101)
4 nm
(c)
-W2C (101)
4 nm
(b)(a)
4 nm 4 nm
(d)
-W2C (102)
-W2C (101)
І П Ш
Region І : nanosized W embedded in carbon matrix.
Region П : Segregation of tungsten started.
Region Ш : crystalline carbides phase presented
(a) 3.0, (b) 4.2, (c) 5.1, (d) 8.7, (e) 12.5 at.%
d) GIXRD-phase identification.
e) Raman and EELS- atomic bond structure
f) Ab Initio Calculation – energy increase due to bond distortion
g) Stress Jumping and Atomic Bond Structure
І
П
Characteristic of amorphous structure.
Weak crystallinity of carbides.
Ш High crysallinity and fraction of carbides.
20 30 40 50 60 70 80 90
-WC1-x
-W2C
-W2C
(311)
(220)
(200)
(111)
(112)
(103)
(002)
(002)
3.0
4.2
W 12.5 at. %
2degree)
Inte
ns
ity
(a
.u.)
8.5
5.1
(100)
(002)
(102)
(110)
(103)
(200)
(112)
(112)
(103)
(21
0)
(222)
(400)
(206)
(117)
(506)
(530)
(444)
WCx
400 600 800 1000 1200 1400 1600 1800 2000
2 4 6 8 10 12 141540
1545
1550
1555
1560
1565
1570
G-p
eak
posi
tion
(cm
-1)
W/(W+C) at.%
5.1
4.2
W 3.0 at.%
8.5
6.7
Inte
nsi
ty (
a.u
.)
Wave number (cm-1)
12.5
No change was observed in the carbon network with the W incorporation.The less significant change in the mechanical properties can be understood in terms of the unvaried amorphous carbon network.
90 100 110 120 130
0.00
0.08
0.16
0.24
0.32
0.40
0.48
0.56
0.64
To
tal
en
erg
y v
ari
ati
on
s,
(eV
)
Bond angle (degree)
C-C bond W-C bond
0 2 4 6 8 10 12 141.2
1.5
1.8
2.1
2.4
2.7
3.0
3.3
Re
sid
ua
l s
tre
ss
(G
Pa
)
W/(W+C) (at.%)
ШІІІ
Region І : W essentially acts as a relaxation site of nearby carbon network, resulting in a significant stress reduction as W is incorporated.
Region Π: Segregation of W as a preliminary form of carbide seems to enhance the distortion of nearby carbon network.
Region Ш : Formation of the large crystalline W2C phase relieves the distortion of the bonds.
C-W bonds has more flexibility to accommodate the distortion of the surrounding carbon network comparing with the rigid C-C bonds.
ⅣⅣ.. ConclusionsConclusions
W-C:H nanocomposite films prepared by hybrid ion beam deposition.
The significant stress reduction by W incorporation.
The stress is reduced by 50% at 4.2 at.% W, while hardness is only reduced by 20%.
W essentially acts as a relaxation site of surrounding carbon network via forming more flexible C-W bond, which proposed a generic origin of the stress reduction with W incorporation.
Evolution of crystalline carbides plays a subsidiary role on the stress reduction in case of higher W concentration.
W concentration is varied by the Ar fraction in gas mixture.
Defined by stress jumping
250 300 350 400 450 500
0.0
0.2
0.4
0.6
0.8
1.0
No
rma
lize
d I
nte
ns
ity
Energy (eV)
W 3.0 at.% 4.2 5.1 12.5
*
*