1. of Diamond-like Carbon Thin Film
An Experimental Study of the Influence of Imperfections on the Buckling
of Diamond-like Carbon Thin Film
Myoung-Woon Moon, Kyu-Hwan Oh
School of Materials Science and Engineering, Seoul National University, KOREA
Princeton Materials Institute, Princeton University, USA
Jin-Won Chung, Kwang-Ryeol Lee
Future Technology Research Division
Korea Institute of Science and Technology, KOREA
R. Wang, A. G. Evans

2. Purpose and overviews Purpose Overview
The observation on the sources of interface imperfection
Defect, Free edge, Substrate Curvature
Optimization of imperfection instability
Overview
(Characterization of defect on the interface)
- Surface profile on defect site : Atomic Force Microscopy
- Cross sectioning of defect site : Focus Ion Beam
- Chemical analysis for defect : Auger Electron Spectroscopy
Observation for the condition of defect-induced delamination

3. The Source of Imperfection

4. Introduction of Interface delamination
General systems with Delamination or Buckle
-Highly compressed film
DLC or Diamond film on glass / Si
Gold on copper film on sapphire
Amorphous (hydrogenated ) Si film on glass/Si
Stainless steel on polycarbonate
Thermal Barrier Coatings system
Interface delamination on Diamond-Like Carbon film
Imperfection deriven Delamination Buckle deriven Delamination

5. Imperfection I – Interface defects
The reflection of Small defects on the film surface after deposition
4 mm
10 mm
10 mm
Large defects
10 mm
10 mm
10 mm
20 mm

6. Imperfection II - Free edge
Free edge effect on delamination
Free edge
5 mm
50 mm
Delamination sequence from free edge ( t = Real time)
t=5 sec
t=1 sec
10 mm
200 mm
Thickness of film h= 0.13 mm
h= 0.80 mm

7. Imperfection III – Substrate Curvature effect
“Substrate curvature plays a role of imperfection”
J. W. Hutchinson, JMPS, 49, 2001
L > 1
The condition of Preferred Propagation direction
Concave : axial
Convex : circumferential

8. Observation on defect site

9. Experiments on defect effects
 Deposition with CVD
Diamond-like carbon films on glass substrates by PECVD with CH4 and C6H6 plus N2,
Negative self bias voltage : -100 to -700V
The film thickness : 0.13 ~ 0.46mm
Residual compression : 1GPa and 3GPa  resulting in telephone cord buckles.
AFM
In tapping mode (Digital Instrument company).
 Images of representative buckles and cross sectional profiles
FIB
Dual-Beam FIB (FEI Company, DB235).
 Direct cut along the buckle (damage free)
 To create the straight-sided buckle from telephone cord buckle.
AES
Auger Electron Spectroscopy
 Chemical analysis on several defect sites

10. Cross sections of defect sites - AFM
Surface topology
Profile of Cross section

11. Cross sectioning : small defect - FIB
Defect Geometry
Thickness of film
h ~ 0.46mm
Wavelength : 10 mm
Amplitude : ~0.9 h
Before cut
After cut

12. Cross sectioning : Large defect - FIB
Before
cut
After
Defect Geometry
Thickness of film
h ~ 0.46mm
Wavelength : 40 mm
Amplitude : ~ 1.6 h
Moon et al, Acta Mater., 2002

13. Chemical analysis underneath defect sites -AES
Film surface
(Refection of defect)
Underneath film
(Defect on substrate)
10 mm
5 mm
- Auger electron spectroscopy-

14. Discussion and Summary

15. Energy release rate with imperfection size
The condition of
Delamination propagation
Hutchinson, He, Evans, 2000, JMPS

16. Summary of Observation on defect sites
=1.9GPa
E=90~100GPa
Sub-critical
No delamination
Stationary
Delamination only
Super-critical
Propagation of delamination .
* Weiderhorn, S. M., J. Am. Ceram. Soc., 1967, 50, 407.

17. Summary The source of imperfection on the interface
Defect, Free edge, and substrate curvature effect
The characterization of Defect
AFM :Measurement of Profile of defect on the film surface
FIB : Cross sectional analysis with fine
AES : Chemical analysis on foreign defect on the interface
The condition of Defect-induced delamination