This paper reports a systematic study of the plasmonic properties of periodic arrays of gold nanoparticles in contact with a novel transparent conducting oxide (TCO) material - Hafnium-doped zinc oxide (HZO). Resonant coupling of the grating diffraction orders with the propagating surface plasmons along the waveguide film, which can generate large field enhancements, are investigated by FDTD simulations. By tuning the ratio of Hf dopants to ZnO film, the plasmon resonances can be tuned and narrower resonance with FWHM of 2-5 nm are observed. Such plasmonic substrates are shown in this study to have high figure of merit in refractive index sensing applications.