Leakage current analysis of hydrothermal BaTiO3 thin films

Abstract

Hydrothermal processing can deposit crystalline ferroelectric films at low temperatures of less than 150°C to achieve permittivities above 100. Such a process, hence, can be attractive in integrating thin film capacitors in organic, silicon or flex substrates. However, their poor insulation strength leading to high leakage current can prevent their wide acceptance. Lattice defects such as hydroxyl groups are attributed to their high leakage currents and lower Breakdown Voltages (BDVs). With appropriate thermal treatments, majority of the OH groups can be removed, leading to improved insulation characteristics. The leakage current behavior of as-synthesized and post-baked hydrothermal thin films are analyzed with various conduction models. The room temperature I-V characteristics are attributed to a combination of ionic and Space-Charge-Limited (SCLC) conduction models for films baked at 160°C while higher baking temperatures of 350°C agree well with Poole-Frenkel type conduction, with an activation energy of 0.57 eV for the defects. The defects, which are presumably OH groups or oxygen vacancies embedded in the barium titanate lattice, act as shallow traps and the trapping and detrapping results in easier conduction. A brief perspective is provided on the suitability of such a hydrothermal thin film capacitor approach for power supply applications.

Epitaxial, electro‐optically active barium titanate thin films on silicon by chemical solution deposition

“…Oxygen site defects are commonplace in perovskite oxides, BTO notwithstanding, and could be a source of diminished ferroelectricity and EO response. In particular, oxygen vacancies or lattice hydroxyls (which occupy oxygen sites and cause Ba vacancies) disrupt local ionic structure in addition to providing free carriers and higher film leakage current . BTO films deposited by vacuum‐based techniques without a sufficiently oxidative environment show high leakages and diminished EO response .…”

“…In particular, oxygen vacancies or lattice hydroxyls (which occupy oxygen sites and cause Ba vacancies) disrupt local ionic structure in addition to providing free carriers and higher film leakage current. 47 BTO films deposited by vacuum-based techniques without a sufficiently oxidative environment show high leakages and diminished EO response. 15 We discount these particular ionic defects as a contributing factor in the EO response of the films in the current study due to relatively low leakages across the tungsten contact gaps as detailed earlier ( Figure S4).…”

Energy Storage and Leakage Current Characteristics of Low-Temperature-Derived Pb0.8La0.1Ca0.1Ti0.975O3 Thin Films Tailored by an Annealing Atmosphere

“…14−16 For example, bulk-limited Ohmic conduction and Pool−Frenkel emission were confirmed as the dominant conduction mechanism in Pb(Zr,Ti)O 3 films under a low electric field and a high electric field, respectively, 17 while a combination of ionic conduction and space-charge-limited current (SCLC), as well as a Pool−Frenkel emission were proposed to clarify the leakage behaviors of a BaTiO 3 thin film with different baking temperatures. 18 Moreover, both bulklimited Ohmic conduction and interface-controlled Fowler− Nordheim tunneling and Schottky emission behaviors were disclosed in orientation-engineered BiFeO 3 thin films in our latest report. 19 Besides this, for the sol−gel-derived ferroelectric thin films, the processing parameters, especially the annealing temperature and atmosphere, are closely related to the production of impure phases and vacancy defects, which will determine the film's level of leakage current and thus the improvement of electrical properties.…”

“…To reveal the conduction mechanisms of these PLCT thin films annealed in different atmospheres, we carried out a detailed study using various charge transport models applying to a metal–ferroelectric–metal (MFM) heterostructure, i.e., bulk-dominated Ohmic conduction, ionic conduction, Poole–Frenkel (P–F) emission, space-charge-limited current (SCLC), as well as interface-controlled Fowler–Nordheim (F–N) tunneling, and Schottky and modified Schottky emissions. ,,, By fitting the J – E curves of PLCT thin films to these models, as shown in Figure b–d, three types of conduction mechanisms were revealed in these films. Specifically, as clearly demonstrated in Figure b, the J – E curve of the PLCT@O 2 thin film can be well characterized by the linear relationship of ln­( J ) vs ln­( E ) with a slope β of almost 1 in both POS and NEG bias, indicating a bulk-limited Ohmic conduction current in the whole electric field.…”

“…Thus, to pave the road for broad technological applications of (La/Ca,Pb)­TiO 3 films, knowledge of the conduction mechanism is a vital step toward solving its leakage current issue. Currently, some charge transport models have been proposed to reveal the underlying leakage behaviors of ferroelectric thin films. − For example, bulk-limited Ohmic conduction and Pool–Frenkel emission were confirmed as the dominant conduction mechanism in Pb­(Zr,Ti)­O 3 films under a low electric field and a high electric field, respectively, while a combination of ionic conduction and space-charge-limited current (SCLC), as well as a Pool–Frenkel emission were proposed to clarify the leakage behaviors of a BaTiO 3 thin film with different baking temperatures . Moreover, both bulk-limited Ohmic conduction and interface-controlled Fowler–Nordheim tunneling and Schottky emission behaviors were disclosed in orientation-engineered BiFeO 3 thin films in our latest report .…”