Evaluation of the space charge trap energy levels in the ferroelectric films

Abstract

A method to evaluate the space charge trap energy levels in ferroelectric (FE) Ba0.3Sr0.7TiO3 film incorporated into a metal/FE/metal parallel plate capacitors structure is presented. It is based on microwave measurements of the capacitance relaxation time after the end of a dc pulse, when the change in measured capacitance is due to internal processes of space charge relaxation [Q(t)] in the FE film. Using the Q(t) dependencies obtained as a function of temperature, the time constants of slow relaxation processes were defined and the trap energy levels were evaluated as Et=0.7, 0.5, and 0.1 eV.

Capacitor structures based on strontium titanate films

“…5 pre sents the high speed performance parameter ΔC/C 0 , which indicates the capacitance of the capacitor within 100 ms after the removal of the control voltage. It can be seen from this figure that the characteristic of the high speed performance has an asymmetric character (which is considered in [14]), and the achievement of the controllability K = 2 at a positive voltage is accom panied by a retardation of the capacitance relaxation by a value of no higher than 1%, which is a promising result for use in devices with fast switching.…”

Ferroelectric BaSrTiO3films structured by an intermediate annealing during the deposition

“…A presence of structure defects in the one-step film provides an origin of charge traps inside FE film and a deterioration of the fast switching factor. An improvement of the BST film microstructure during the annealing in oxygen atmosphere provides decreasing of oxygen vacancies concentration in the BST film and increasing of the barrier heights for electrons injection from Pt into BST [26]. An achievement of tunability n = 74% at E = 40 V/µm (see fig.…”

Injected charge as a cause of the slow dielectric relaxation in thin film Pt/(Ba,Sr)TiO3/Cu structures

“…These estimates correspond to the results obtained previously for the trap energy levels in similar samples by Poole-Frenkel analysis of I-V curves. 39 The thermally released carriers to the left and to the right of the zero-field plane drift in the SC induced electric field to the opposite electrodes. The presence of a "dead" layer keeps the carriers from entering the Pt-electrode.…”