Plasma enhanced atomic layer deposition of plasmonic TiN ultrathin films using TDMATi and NH₃

Transition metal nitrides, like titanium nitride (TiN), are promising alternative plasmonic materials. Here we demonstrate a low temperature plasma-enhanced atomic layer deposition (PE-ALD) of non-stoichiometric TiN_0.71 on lattice-matched and -mismatched substrates. The TiN was found to be optically metallic for both thick (42 nm) and thin (11 nm) films on MgO and Si <100> substrates, with visible light plasmon resonances in the range of 550-650 nm. We also demonstrate that a hydrogen plasma post-deposition treatment improves the metallic quality of the ultrathin films on both substrates, increasing the ε₁ slope by 1.3 times on MgO and by 2 times on Si (100), to be similar to that of thicker, more metallic films. In addition, this post-deposition was found to tune the plasmonic properties of the films, resulting in a blue-shift in the plasmon resonance of 44 nm on a silicon substrate and 59 nm on MgO.