Dielectric relaxation and leakage current properties of oxygen vacancy engineered titanium oxide-based thin-film devices

Abstract The oxygen vacancy engineered TiO x films, deposited by reactive rf sputtering at different Ar:O 2 ratios are studied by grazing incidence x-ray reflectively (GIXRR) and x-ray photo electron spectroscopy (XPS). Afterwards metal–oxide–semiconductor (MOS) devices were fabricated with the TiO x as gate dielectric and patterned aluminium metal as top electrodes. As evident from the GIXRR data, both surface and interface roughness decrease with increase in oxygen partial pressure ( P O 2 ) in the plasma. XPS studies indicate reduction of oxygen vacancy and Ti 3+ concentration with the increase in P O 2 . Frequency dependent dielectric studies show highest capacitance at lower frequency range that tend to saturate above ∼10 4 Hz due to a reduced ability of the dipoles to follow the electric field. The loss factor tan( δ ), the distinct loss peaks corresponding to the characteristic relaxation frequencies shifts towards higher frequencies with increase in oxygen vacancy concentration due to reduced relaxation time with decreasing vacancy. Cole–Cole studies indicate reduction in dielectric permittivity with the increase in P O 2 in the plasma. The peak value of imaginary part of dielectric constant ( ϵ ′ ′ ) corresponding to dielectric relaxation also decreases with P O 2 in the plasma proving more stable dielectric properties. Real part of ac conductivity ( σ ac ′ ) found to be independent of frequency proves long range charge transport and the hopping process does not depend on frequency. I − V studies show decreasing memory windows with increasing p O 2 in the plasma. In nutshell, changes in surface and interface roughness, dielectric relaxation time, dielectric permittivity and memory windows are observed with the reduction of oxygen vacancy in the TiO x films.