Enhancement of Nanoscale Leakage Current Performance of Bismuth Ferrite Thin Films Using Conductive Oxide Electrodes

Abstract

Thin BiFeO 3 ͑BFO͒ films with a thickness of 80 nm were grown on Pt/Ti/SiO 2 /Si͑100͒ substrates at 350-550°C with and without a 100 nm thick LaNiO 3 ͑LNO͒ buffer. The growth of the BFO film with an LNO buffer promotes the appearance of highly ͑100͒-crystallographic features. A high deposition temperature of 550°C yields BFO films with secondary phases. Secondary-ion mass spectrometry depth profiles show no obvious interdiffusion of constituent elements between the BFO and the LNO at growth temperatures of 350-450°C. The buffering of LNO markedly reduces the degree of the surface roughening of BFO films, which is determined by the growth temperature. The spatial distribution of the current image of BFO films grown at 350-450°C on the nanometer scale shows a considerable reduction in the nanostructural leakage current properties of BFO films upon the buffering of LNO because of the effective improvement in the film/electrode interface, chemical homogeneity, crystallinity, and surface roughness of the BFO films. Moreover, impurity phases in the BFO films grown at 550°C act as the dominant conduction path of leakage currents.Enhanced remnant polarization and magnetization compared to a bulk single crystal have been reported in BiFeO 3 ͑BFO͒ thin films. 1,2 Multiferroic BFO thin films are considered among the most promising candidates for ferroelectric random access memories and microelectromechanical systems. The trend toward miniaturization of devices depends on the thinning of films. However, realizing BFO thin films, especially those with a film nanoscale thickness, with the most desired and reproducible electrical properties remains a considerable challenge. 2 Pt is mostly used as an electrode material in ferroelectric capacitors, providing low resistivity and high chemical stability. 3 However, the use of Pt electrodes in the preparation of the ferroelectric layer at a relatively high temperature has some shortcomings. The interface layer caused by atomic interdiffusion and the hillocks are the most important issues. Composite electrodes were recently demonstrated to be effective in enhancing the electrical or crystalline properties of high permittivity oxides from the crystallographic or chemical compatible points. 4,5 Increasing the electrical resistivity of BFO films is very important, and several approaches have been employed to improve their electrical properties, including impurity doping and the use of oxide electrodes. 6,7 Notably, although many efforts have been made to reduce the leakage current in the BFO thin films, understanding leakage phenomena in BFO thin films would benefit greatly from the detection of a leakage current at a spatial resolution that is similar to the length scale of the structural nonuniformities. Such understanding could be exploited in applying BFO thin films in nanodevices. Leakage currents are conventionally measured at microscopic metal-insulator-metal capacitors. 8 Based on this method, the nanoscopic spatial distribution of the leakage current of the insulator layer cann...

Synthesis and Characterization of La and Nd Co‐Doped Bismuth Titanate Ferroelectric Ceramics

“…Due to environmental friendly and other special characteristics, BIT became a potential candidate in the applications of piezoelectric properties (transducers and actuators, ultrasonic devices, medical imaging detectors), memory storage, and optical displays. However, BIT suffers from high leakage of current and domain pinning due to defects such as Bi vacancies accompanied by oxygen vacancies, which prevent it from practical applications. A large number of researches have been carried out dynamically in both thin film and bulk ceramics for the improvement of the performance of BIT.…”

Effect of conductive oxide buffering on structural and nanoscale electrical properties of ultrathin SrTiO3 films on Pt electrodes

“…However, the measured area of the STO/RuO 2 film has a trace of leakage spots at 4 V. As the bias is further increased to 6 V, many leakage spots appear in the measured area. The number and size of the leakage spots increase with applied voltage, because increasing the applied voltage increased the area of tunneling of the electrons, increasing the lateral dimensions of the spots [9]. Comparing the current map and the topography reveals no relationship between the morphology and the local conductivity of the STO/RuO 2 film grown at 500 1C.…”

“…However, a high growth temperature of 700 1C reduces the intensity of Bragg reflections from the STO/Pt film. A high growth temperature of 700 1C may cause extensive atomic interdiffusion between the STO and the metallic electrode, degrading the crystalline quality of the film [9]. The composition modulation for the STO/Pt, STO/RuO 2 , and STO/LNO films grown at 700 1C is shown in Fig.…”

Structural and electric properties of BaSn0.15Ti0.85O3 films on ITO/glass substrate by RF sputtering from powder target

“…The leakage current density of the film devices is closely related to several factors such as cationic/anionic vacancies, structural distortion, grain boundaries, and dielectric-electrode interface [8]. Further, the diffusion between the dielectric-electrode interface is strongly dependent on the preparation process and material properties, especially the preparation temperature and electrode materials of the thin film [9,10].…”