Influence of frequency and bias voltage on dielectric properties and electrical conductivity of Al/TiO₂/p-Si/p⁺(MOS) structures

In this study, the frequency and voltage dependence of the dielectric constant (e'), dielectric loss (e''), loss tangent (tan δ), electric modulus (M' and M'') and ac electrical conductivity (σac) of Al/TiO2/p-Si (MOS) structures has been investigated using the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics. A TiO2 thin film was deposited on the p-type Si substrate by using the sol–gel dip coating method. These C–V and G/ω–V characteristics were measured by applying a small ac signal of 50 mV amplitude in the frequency range 5 kHz–1 MHz, while the dc bias voltage was swept from (−4 V) to (4 V) at room temperature. Experimental results show that e', e'', tan δ and σac are strongly frequency and voltage dependent. Accordingly, it has been found that as the frequency increases, e' and e'' values decrease while an increase is observed in σac and the electric modulus. The results can be concluded to imply that the interfacial polarization can more easily occur at low frequencies consequently contributing to the deviation of dielectric properties and ac electrical conductivity of Al/TiO2/p-Si/p+ (MOS) structures.

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