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.