Dielectric model of point charge defects in insulating paraelectric perovskites

Abstract

Some point defects (i.e., oxygen vacancies) create deep trapping levels in the bandgap of the paraelectric phase ferroelectric crystals. Under applied DC field the traps release electrons via the Poole-Frenkel mechanism and become charged. The electric field of a point charge polarizes the crystal locally reducing its permittivity. In this paper a simple theory is proposed for calculating the DC field dependent apparent (measureable) permittivity of a paraelectric crystal with point charge defects. It is shown that the apparent permittivity of a paraelectric crystal may be sufficiently lower as compared with the defectless crystal. This reduction is in addition to the possible reduction of the apparent permittivity associated with the interfacial "dead" layers and strain.

Quantification of flexoelectricity in PbTiO3/SrTiO3 superlattice polar vortices using machine learning and phase-field modeling

“…space charge term of Eq. ( 5 ) was replaced by a point source with a Gaussian distribution 43 : where ρ ( r ) is the charge density in C m −3 , Q is the total charge carried by defects, and σ is the standard deviation. The attendant volumetric strain effect of defects was not yet considered.…”

Effect of Titanium Content on the Sensing and Impedance Characteristics of High-κ TbTixOyElectrolyte–Insulator–Semiconductor pH Sensors

“…The conductance circuit comprises the depletion capacitance ( C sc ), oxide capacitance ( C ox ), interface trap capacitance ( C it ), and resistance ( R it ), as shown in Figure a. The capacitance of the space charge layer (depletion layer) in oxide/semiconductor is given by C sc = C normald 1 C normald 2 C normald 1 + C normald 2 = ε normalo ε normals ε normalo italicL normalD + ε normals italicL normalr = q N eff N ε normalo ε normals k normalB T ( N eff ε o + N ε s ) where C d1 and C d2 are the capacitance of the oxide and semiconductor depletion layer per unit area, ε o and ε s are the permittivities of the oxide and semiconductor, respectively, L r is the length of the space charge region in the oxide, L D is the Debye length in the semiconductor, N eff is the effective concentration of the fictitious polarization charge in the oxide, and N is the doping concentration in the semiconductor. The interface-trapped charge exists within the forbidden gap due to the interruption of the periodic lattice structure at the surface of a crystal.…”

Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

“…The fast reversible variation of C p is explained by the trapping of carriers in the charged defects with a dielectric model of point charge defects in paraelectric perovskites, where the electric field from a charged point defect locally polarizes the surroundings to reduce its permittivity [45]. We apply this model to the charged defects of the Ag-GeTe for the following two reasons.…”