Frequency-driven dielectric analysis of ultrathin HfOx-TiOx composite films

• TiO x –HfO x ultra-thin films deposited by pulsed-DC sputtering in layer-by-layer configuration. • Amorphous, smooth films show increased band gap with TiO x insertion. • Cole–Cole analysis shows non-Debye and broader relaxation time with TiO x insertion. • Dielectric loss and leakage current decrease with TiO x insertion. This study investigates the frequency-dependent dielectric properties of ultrathin HfO x -TiO x composite films (HTO) in a metal–oxide–semiconductor (MOS) configuration over a frequency range of 1 kHz to 3 MHz. The films were deposited using a pulsed-DC magnetron sputtering technique in an atomic layer deposition-like manner, incorporating very thin TiO x layers within the bulk of HfO x . Structural analysis revealed that the films are amorphous and exhibit uniform and smooth surfaces. The dielectric constant ( ε ′) and dielectric loss ( ε ′′) exhibit a decreasing trend with increasing frequency, demonstrating typical dielectric behavior. Furthermore, the characteristic dielectric relaxation frequency shifts toward lower frequency values with the insertion of TiO x . The Cole-Cole plot confirms the non-Debye relaxation behavior across all samples. Optical spectroscopy analysis reveals a systematic increase in the optical band gap upon more TiO x insertion. Analysis of current–voltage (I-V) characteristics demonstrates low leakage currents across the composite films. Understanding the dielectric parameters and the electrical characteristics is crucial for the potential application of these films in advanced electronic applications.