Electrical transport properties and modelling of electrostrictive resonance phenomena in Ba2/3Sr1/3TiO3 thin films

Abstract

We present the conduction mechanisms of Ba 2/3 Sr 1/3 TiO 3 thin films integrated in metal-insulator-metal (MIM) capacitors and the modelling of the frequency-dependent electrostrictive resonances (in the 100 MHz-10 GHz domain) induced in the devices upon applying different voltage biases. Au/BST/Ir MIM structures on MgO substrates have been fabricated and, depending on their specific polarization, we highlighted different conduction mechanisms in the devices. Depending on the dc bias polarity, the conduction current across the material shows a space-charge-limited-current behavior under negative polarization, while under positive bias the conduction obeys an electrode-limited Schottky-type law at the Au/ BST interface. The application of an electric field on the device induces the onset of acoustic resonances related to electrostrictive phenomena in the ferroelectric material. We modeled these acoustic 2 resonances over a wide frequency range, by using a modified Lakin model which takes into account the dispersions of acoustic properties near the lower electrode/ thin film interface. I.

VCC-α nullification and leakage reduction in Pt/Ba0.5Sr0.5TiO3/Pt thin-film capacitor by MgO barrier and PDA for energy storage application

“…While depositing titanium, platinum, MgO and Ba 0.5 Sr 0.5 TiO 3 thin-film layers, deposition mode of RF magnetron sputtering equipment was set to be stationary, the flow of sputtering gas (Ar) was kept at 14 sccm and substrate temperature was maintained at room temperature (RT). The substrate was kept at RT during deposition since leakage current performance degradation occurs if insulator deposition is done on annealed substrate [4,23]. During Pt, MgO and Ba 0.5 Sr 0.5 TiO 3 depositions, base pressure of equipment was maintained at 2.5 e-6 mbar and for Ti deposition it was PM5, Agilent Device Analyzer B1500A with pulsed source 5 MHz was made use of capacitance-voltage (C-V ) and current-voltage (I-V ) measurements.…”

“…This makes Richardson constant and electron affinity of Ba 0.5 Sr 0.5 TiO 3 significant in leakage current performance; and both should be low to attain low leakage current density. Since Richardson constant and electron affinity of Ba 0.5 Sr 0.5 TiO 3 are 0.01A cm −2 K −2 [3] and 4.1 eV [4] respectively which are high, high leakage current is expected in Pt/Ba 0.5 Sr 0.5 TiO 3 /Pt thin-film capacitor. A layer of MgO having low Richarson constant (5×10 −5 A cm −2 K −2 ) and low electron affinity (1 eV) [5] is introduced at Pt-Ba 0.5 Sr 0.5 TiO 3 interfaces to reduce leakage current in Pt/Ba 0.5 Sr 0.5 TiO 3 /Pt thin-film capacitor.…”

Characterization and Performance Analysis of BST-Based Ferroelectric Varactors in the Millimeter-Wave Domain

“…The first is based on the metal-insulator-metal (MIM) topology [18,19] in which the ferroelectric layer is integrated between two parallel conductive plates (electrodes), allowing a large field concentration into the active layer, and hence important tuning of the capacitance value. The main drawback of this architecture is the use of overlapped layers, which makes the ferroelectric layer performances dependent on the lower electrode quality, and brings complexity to the fabrication process [20] and which are prone to resonant electrostrictive effects [21]. The second topology is planar, less complex, and consists of an inter-digitated capacitor (IDC) metallic structure [22][23][24] build directly on top of the ferroelectric layer.…”

Suppression of Acoustic Resonances in BST-Based Bulk-Ceramic Varactors by Addition of Magnesium Borate

“…Another disadvantage is the electric-field-induced electrostrictive strain across the ferroelectric layer, which results in acoustic waves that are reflected from adjacent layers, reducing the varactor's Q-factor. In thin-film devices, acoustic resonances are a well-known phenomenon [11,12] and, recently, their presence in thick-film applications has also been observed in the lower MHz range [7]. Going forward, acoustic resonances methodology and a method for their suppression in BST-based bulkceramic varactor will be discussed using the composite ceramic approach.…”