Modeling studies of an impinging jet reactor design for hybrid physical-chemical vapor deposition of superconducting MgB₂ films

An impinging jet reactor was developed for the deposition of superconducting MgB₂ thin films by hybrid physical-chemical vapor deposition, a technique that combines Mg evaporation with the thermal decomposition of B₂H₆ gas. A transport and chemistry model for boron film deposition from B₂H₆ was initially used to investigate the effect of carrier gas, Mg crucible temperature and gas flow rates on boron film growth rate and uniformity. The modeling studies, which were validated experimentally, demonstrated a reduction in B₂H₆ gas-phase depletion and an increased boron film growth rate using an argon carrier gas compared to hydrogen. The results were used to identify a suitable set of process conditions for MgB₂ deposition in the impinging jet reactor. The deposition of polycrystalline MgB₂ thin films that exhibited a transition temperature of 39.5 K was demonstrated at growth rates up to ∼50 μm/h.