Introduction
•Protection of tools – thin films
•Most thin films – hard but brittle
•Combination of hardness and moderate ductility to prevent formation and spreading of cracks
•Nanolaminate Mo2BC
•Prepared by magnetron sputtering

Mo2BC coatings
•Combination of great hardness and moderate ductility
•Stiff Mo-B and Mo-C layers with metallic interlayer bonding
•B – bulk modulus
•G – shear modulus
•B/G > 1,75 ductile materials
•Mo2BC thin films were synthesized using DC magnetron sputtering on Al2O3 at a substrate
temperature of ∼900 °C
Material
B (GPa)
B/G
TiN
295
1,39
Ti0,25Al0,75N
178
1,44
c-BN
376
0,98
Mo2BC
324
1,72

Used characterization methods
•X-ray diffraction
•Scanning electron microscopy
•Electron recoil detection analysis
•

X-ray diffraction (XRD)
•Information about the crystal structure
•Uses the scattering of photons on the atoms of the lattice
•The superposition of the scattered waves from individual atoms leads to classical reflection of
light •The incident rays are reflected from the atomic planes and interfere with each other
•Constructive interference occurs, when the Bragg condition is met

X-ray diffraction (XRD)
•The Bragg equation:
• 2dsinθ = nλ
•λ is the wavelength of the incident light,
d is the distance between atomic planes,
n is an integer and
θ is the angle of incidence.
•

X-ray diffraction (XRD)
•
http://journals.iucr.org/s/issues/2005/04/00/kv5008/kv5008fig1mag.jpg

X-ray diffraction (XRD)
•Three methods of measuring:
•Debye-Scherer – monochromatic light and polycrystaline material
•Laue – polychromatic light and monocrystaline material
•Monochromatic light and monocrystaline material
•
•The combination of polychromatic light and polycrystaline material creates too many diffractions

X-ray diffraction (XRD)
•The sample consists predominantly of Mo2BC •There is a minor contribution detected, stemming from
Mo2C •Good agreement between the measured peak positions and the reference values •The relative
intensities of the diffractogram do not match due to the sample being textured

Scanning electron microscopy (SEM)
•Used for imaging of surfaces
•Focused beam of accelerated electrons
•The beam is focused and directed by electromagnetic lenses and scanns the surface •High vacuum is
necesary to prevent collisions of electrons with gas particles
•Possibility to use with EDX or WDX to determine composition

Scanning electron microscopy (SEM)
•Two basic kinds of signal:
•Backscaterred electrons
•Electrons with high energy reflected from the surface
•Greater penetration depth but worse spatial resolution
•Number of reflected electrons depends on the atomic number of the particle – greater mass – more
reflected electrons – brighter spot
•Secondary electrons
•Electrons emitted from the surface due to inelastic scattering
•Because of their low energy, only electrons created at the surface leave the sample
•Mostly information about topography – electrons are emitted mostly from sharp edges

Scanning electron microscopy (SEM)



Scanning electron microscopy (SEM)
•No formation of pores or cavities
•Surface features with a diameter well below 100 nm
•No crack formation observed around the indent

Energy recoil detection analysis (ERDA)
•Detection of light elements in a heavy matrix
•Analysis of forward scattered ions or atoms
•A single collision
•Particles can by identified by their kinetic energy
•Analysis of particles: TOF, thin foil

Energy recoil detection analysis (ERDA)



Energy recoil detection analysis (ERDA)
•The film consists of 49 at% Mo, 27 at% B and 24 at% C
•The chemical formula Mo2B1.1C1, which is very close to the nominal stoichiometry of Mo2BC.
•O and H were not detected in the film.
•The variation of B from stoichiometric Mo2BC composition is within the expected measurement error.

Conclusion
•Mo2BC thin films were synthesized using DC magnetron sputtering on Al2O3 at a substrate
temperature of ∼900 °C. •XRD measurements and ERDA confirmed that the grown film
is almost phase pure and of near-stoichiometric composition •No formation of cracks was observed
implying moderate ductility •Deformation experiments carried out with nanoindentation confirmed the
high stiffness of Mo2BC
•
•

Thank you for your attention!
•J. Emmerlich, D.Music,M. Braun, P. Fayek, F. Munnik, J.M. Schneider, J. Phys. D: Appl. Phys. 42
(2009) 185406
•Peter E.J. Flewitt, R.K. Wild: Physical Methods for Materials Characterisation, Series in
Materials Science and Engineering
•https://sites.google.com/a/lbl.gov/rbs-lab/ion-beam-analysis/elastic-recoil-detection-analysis-erd
a
•http://journals.iucr.org/s/issues/2005/04/00/kv5008/kv5008fig1.html