Pulsed laser deposition synthesis of high entropy carbide (HfNbTaTiZr)C thin films with near-equiatomic composition

The high entropy carbide (HfNbTaTiZr)C is a material predicted to have excellent thermal and mechanical stability and has been reported to possess good anti-wear and frictional
properties. Existing studies on (HfNbTaTiZr)C have focused predominantly on bulk properties. In this thesis pulsed laser deposition was used to grow (HfNbTaTiZr)C thin films on
Si(100) and Al2O3(0001) from a stoichiometric target consisting of HfC, NbC, TaC, TiC and
ZrC. Deposition parameters were optimized for near-equiatomic surface composition of metals
and carbon, measured by X-ray photoelectron spectroscopy. The effects of deposition fluence
(6-8, 7-14 J/cm2
) and process gas pressure (10−2 mbar − 10−1 mbar) on surface composition
were studied. A trend of increasing Nb and Ta concentration at higher deposition fluence was
found. Furthermore a trend of decreasing concentration of lighter metals Ti, Zr, and Nb at
higher deposition pressures was found. The results are explained through ablation threshold
difference, preferential scattering and substrate resputtering. X-ray diffraction on (HfNbTaTiZr)C grown on Si(100) and Al2O3(0001) confirm successful growth of polycrystalline rock salt
(HfNbTaTiZr)C by pulsed laser deposition. A difference in peak broadening of x-ray diffraction spectra from Si- and Al2O3-deposited films indicates a difference in grain size between
deposition substrates. In conclusion, stoichiometric transfer in pulsed laser deposition of a
multi-elemental HfC:NbC:TaC:TiC:ZrC target is discussed and a future outlook is provided on
relevant experiments on (HfNbTaTiZr)C thin films.