Effect of the chemical composition at the memory behavior of Al/BST/SiO2/Si-gate-FET structure

Abstract

The effect of the chemical composition of the ferroelectric barium strontium titanate (BST) on the memory window behavior of Al/BST/SiO2/Si-gate-field effect transistor structure has been investigated. Nanocrystalline BaxSr1−xTiO3 thin films with different x values have been fabricated as metal-ferroelectric-insulator-semiconductor (MFIS) and metal-ferroelectric-metal (MFM) configurations using a sol–gel technique. The variation of the dielectric constant (e) and tan δ with frequency for MFM samples have been studied to ensure the dielectric quality of the material. At low frequencies, e increases as the strontium content decreases, whereas at high frequencies, it shows the opposite variation, which is attributed to the dipole dynamics. The ferroelectricity of the BST within MFM structure has been investigated using C–V characteristics, which show that the ferroelectric hysteresis strength increases as the strontium content decreases. The ferroelectric memory behavior of the MFIS samples has been investigated using C–V characteristics. The results show that the memory window width increases as the strontium content decreases; this is attributed to the grain size and dipole dynamics effect.