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Deposition and Characterisation of Protective
DLC Coatings on Viscoelastic Substrates
V. Buríková1, Z.Bochnícek1, D. Franta1, P.
Stahel1, L. Kelar1, J. Burík2, P. Klapetek3, O.
Bláhová4, V. Perina5, J.Zemek6, L .Zajícková1 1
Masaryk University Brno, CR 2 IPM ASCR, Brno, CR
3 Czech Metrology Institute Brno, CR 4West
Bohemian University Pilzen, CR, 5Institute of
Nuclear Physics ASCR, Rez at Prague,
CR 6Institute of Physics ASCR, Prague, CR
vilmab_at_physics.muni.cz
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Outline

• Introduction
• DLC films
• Experimental conditions
• Film characterisation
• Thermomechanical stability
• DLC films on plastic substrates
• Conclusion

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Diamond-like carbon films

• High hardness
• High wear resistance
• Low friction coefficient
• Chemical inertness
• Transparency in visible and IR spectral
  region
• Biocompatibility
• High electrical resistance

Ternary diagram of bonding in Amorphous
carbon-hydrogen alloys J.Robertson/Mater. Sci.
Eng. 8 37 (2002)
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Experimental conditions
The parallel electrodes consist of graphite and
the bottom electrode was capacitively coupled to
the RF generator working at frequency 13.56 MHz.
The supplied power P in the range from 50 to
250 W. The negative self bias voltage Ub ranged
from -270 to -540 V. The flow rate of methane
QCH4 was in the range from 1.4 to 3 sccm. The
flow rate of HMDSO (C6H18Si2O) QHMDSO and the
flow rate of HMDSZ (C6H19Si2N) QHMDSZ - 0 - 0.8
sccm. The flow rate of hydrogen or
nitrogen was 0.35 sccm.

• CH4 / H2
• CH4 / HMDSO / H2
• CH4 / HMDSO / N2
• CH4 / HMDSZ / H2

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Film characterisation techniques

• Combined RBS/ERD analysis, X-ray photoelectron
  spectroscopy
• Laser desorption ionisation time of ligth mass
  spectrometry (LDI TOF MS)
• variable angle spectroscopic elipsometry,
  refractometry
• depth sensing indentation technique Fischercope,
  Nanoindenter XP,
• continuous stiffness measurements
• CSM pin-on-disc tester, friction and wear
  resistance
• atomic force microscopy, MFM, LFM
• surface energy measurement SEE system Advex
  Instruments
• Thermal desorption spectroscopy
• measurements of the internal stress,
  (interferometry, X-ray diffraction technique)

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I. group - Diamond-like carbon films

• high compressive intrinsic stress spontaneous
  delamination and
• chipping of the film

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Diamond-like carbon films

• low thermal stability
• hydrogen loss, graphitisation

Thermal desorption spectroscopy
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Optimalizace vrstev z hlediska mechanických
vlastností
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Films prepared from mixtures of CH4 / HMDSO / H2,
CH4 / HMDSO / N2 or CH4 / HMDSZ / H2

• CH4 / HMDSO / H2 - decrease in compressive
  intrinsic stress constant hardness (22 GPa) and
  elastic modulus (120 GPa) up to 0,4 sccm HMDSO,
  followed by substantial decrease . The
  interfacial fracture toughness had a maximum
  around 0,4 sccm of HMDSO, substantial increase in
  thermal stability
• CH4 / HMDSO / N2 - decrease in compressive
  stress, maximum hardness 18 GPa, elastic modulus
  105 GPa, at 0,4 sccm of HMDSO and 0.35 sccm of N2
  - with increasing N2 flow rate the hardness and
  elastic modulus decreased, increase in thermal
  stability
• CH4 / HMDSZ / H2 , maximum hardness 20 GPa,
  elastic modulus 116 GPa, at 0,4 sccm of HMDSZ and
  0.35 sccm of H2 - with increasing HMDSZ flow
  rate the compressive stress increased, increase
  in thermal stability

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Effect of HMDSO, N2 or HMDSZ on the temperature
dependence of the compressive stress
CH4 / HMDSZ / H2
CH4 / H2
CH4 / HMDSO / N2
CH4 / HMDSO / H2
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Thermal desorption spectroscopy - example
CH4 / HMDSO / H2 65.1 / 18.6 / 16.3 P 50 W Ub
-375V The as-deposited film consisted of 48 at
of carbon, 43 at of hydrogen, 7 at of silicon
and 2 at of oxygen. After annealing the film
composition changed to 70 at of carbon, 4at of
hydrogen, 18 at of silicon and 8 at of oxygen.

The films on silicon substrates were annealed in
the laboratory furnace Classic Clare 4.0. The
furnace chamber was evacuated by turbomolecular
pump down to minimum pressure of about 10-5 Pa.
The studied samples were subjected to heating
with constant heating rate of 10K/min. The mass
spectrometer Pfeiffer Vacuum Prisma 80 was set in
order to follow the evolution in time of 8
specific masses.
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Dependence of mechanical properties on annealing
temperature
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Mechanical properties of polycarbonate substrate
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HMDSZ/CH4/H2 mixture
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HMDSO/CH4/H2 mixture
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Conclusion
Nanostructured diamond-like coatings were
prepared with low compressive stress, high
fracture toughness, low roughness, low friction
coefficient and good adhesion to different
substrates. The coatings were stable up to 400oC.
The hydrogen and hydrocarbon desorption did not
cause deterioration of the films. The hardness
and elastic modulus of films increased. The films
could withstand temperatures up to 1000oC
without delamination. Doping of DLC with Si, O
and N enabled us to modify the properties of the
coatings in relatively wide range. Films prepared
at optimum conditions are suitable as protective
coatings on plastics
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Acknowledgement The present work was supported
by the Scientific Foundation of the Czech
Republic under projects GACR 106/05/0274,
202/05/0607, 202/07/1669 and by Academy of
Science of the Czech Republic KAN311610701.
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