An Experimental Study of the Influence of An Experimental Study of the Influence of Imperfections on the Buckling Imperfections on the Buckling

of Diamond-like Carbon Thin Filmof 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 LeeFuture Technology Research Division

Korea Institute of Science and Technology, KOREA

R. Wang, A. G. EvansPrinceton Materials Institute, Princeton University, USA

Purpose– The observation on the sources of interface imperfection

Defect, Free edge, Substrate Curvature

– Optimization of imperfection instability

Purpose and overviewsPurpose and overviews

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 delaminationObservation for the condition of defect-induced delamination

The Source of ImperfectionThe Source of Imperfection

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

Imperfection deriven Delamination Buckle deriven Delamination

Introduction of Interface delaminationIntroduction of Interface delamination

Interface delamination on Diamond-Like Carbon film

The reflection of Small defects on the film surface after deposition

Large defects

Imperfection I – Interface defectsImperfection I – Interface defects

4 m 10 m 10 m

10 m 10 m 10 m 20 m

t=1 sect=5 sec

Free edge effect on delamination

Delamination sequence from free edge ( t = Real time)

Imperfection II - Free edgeImperfection II - Free edge

5 m 50 m

200 m 10 m

Thickness of film h= 0.13 m h= 0.80 m

Free edge

“Substrate curvature plays a role of imperfection”J. W. Hutchinson, JMPS, 49, 2001

b2 / Rh

Imperfection III – Substrate Curvature effectImperfection III – Substrate Curvature effect

> 1 The condition of Preferred

Propagation direction

Concave : axial Convex : circumferential

Observation on defect siteObservation on defect site

 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 ~ 0.46m 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  

Experiments on defect effectsExperiments on defect effects

Cross sections of defect sites - AFMCross sections of defect sites - AFM

Surface topology

Profile of Cross section

Cross sectioning : small defect - FIBCross sectioning : small defect - FIB

Defect Geometry

Thickness of film h ~ 0.46m

Wavelength : 10 mAmplitude : ~0.9 h

Before cut

After cut

Cross sectioning : Large defect - FIBCross sectioning : Large defect - FIB

Defect Geometry

Thickness of film h ~ 0.46m

Wavelength : 40 m Amplitude : ~ 1.6 h

Before cut

After cut

Moon et al, Acta Mater., 2002

- Auger electron spectroscopy-

Film surface(Refection of defect)

Chemical analysis underneath defect sites -AESChemical analysis underneath defect sites -AES

Underneath film(Defect on substrate)

5 m 10 m

Discussion and SummaryDiscussion and Summary

Energy release rate with imperfection sizeEnergy release rate with imperfection size

Hutchinson, He, Evans, 2000, JMPS

iG min

The condition ofDelamination propagation

Lc

h11

int

R h

E R

3/2

Sub-critical No delamination

Stationary Delamination only

Super-critical Propagation of delamination

Summary of Observation on defect sitesSummary of Observation on defect sites

2/8* mJGlass

* Weiderhorn, S. M., J. Am. Ceram. Soc., 1967, 50, 407.

E=90~100GPa

R =1.9GPa

h 0.46m

.

•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

Lc

h11

int

R h

E R

3/2

SummarySummary