Improvements on the Diamond-V₂O₅ 2DHG Electronic Structure using an Al₂O₃ Passivation Layer

Vanadium pentoxide as well as other high electron affinity transition metal oxides (MoO₃, WO₃ etc) have been used as the electron accepting material for a stable diamond-oxide 2DHG structures. Holes within a few nanometers in the diamond after electron transfer from diamond to vanadium pentoxide. V₂O₅ outperforms other oxides on diamond because of its high electron affinity up to 5.8 eV. This largest potential enables electron transfer to the V2O5 achieving a high sheet carrier concentration at the diamond-V₂O₅ interface. A disadvantage of the charge transfer process is a reduced carrier mobility . We propose to use a thin layer of Al₂O₃ grown by PEALD to serve as a passivation layer and thus increase the carrier mobility between diamond and V₂O₅. After Al₂O₃ growth on H-terminated diamond with a post hydrogen plasma treatment in situ XPS indicates upward band bending confirming that the Al₂O₃ retains the 2DHG structure. In situ XPS indicates the charge transfer process can be tuned by controlling the oxidation state of vanadium in the V_xO_y mixture. The 2DHG structure is established only when vanadium is in its highest oxidation state (+5), while lower oxidation states show a reduction of the 2DHG density.