Zhenhua Tang

Temperature dependence of magnetoelectric effect in Bi3.15Nd0.85Ti3O12–La0.7Ca0.3MnO3 multiferroic composite films buffered by a LaNiO3 layer

Multiferroic composite thin films were fabricated based on ferroelectric (FE) Bi3.15Nd0.85Ti3O12 (BNT) and ferromagnetic (FM) La0.7Ca0.3MnO3 (LCMO) parents with different growth sequences of BNT–LCMO/LNO/STO (BL) and LCMO–BNT/LNO/STO (LB). Ferroelectric behaviour along with remnant polarization (2Pr) of 50 μC cm2 and 40 μC cm2 at room temperature, saturated magnetization values around 206 emu cm−3 and 192 emu cm−3 at 100 K were measured for BL and LB composite films, respectively. The temperature dependence of the magnetoelectric (ME) coupling effect was investigated and the ME voltage coefficients of 63 mV cm−1 Oe−1 and 60 mV cm−1 Oe−1 at 100 K were respectively obtained for the BL and LB films. The results show that the composite films exhibit both good ferroelectric and ferromagnetic properties, as well as a substantial ME effect. Moreover, it is demonstrated that the layer sequences and temperature have significant impacts on the magnetoelectric coupling behaviour of these double-layered thin films, which is very likely caused by the magnetic–mechanical–electric interaction, substrate clamping and interface coupling.

Large memory window and good retention characteristics of ferroelectric-gate field-effect transistor with Pt/Bi3.4Ce0.6Ti3O12/CeO2/Si structure

Bi4?xCexTi3 O12(x?=?0.0, 0.4, 0.6 and 1.0) ferroelectric-thin films were fabricated by chemical solution deposition. Among these thin film samples, Bi3.4Ce0.6Ti3O12 (BCT) exhibits the best ferroelectric property. An n-channel metal?ferroelectric?insulator?silicon (MFIS) ferroelectric-gate field-effect transistor (FeFET) with Pt/BCT/CeO2/Si structure was fabricated and characterized. Due to the relatively good interface properties between the insulator layer (CeO2) and ferroelectric-gate layer (BCT), the device shows a nearly unchanged memory window of about 3.2?V after a 24?h retention test and a field-effect mobility of approximately 24.6?cm2?V?1?s?1. These results suggest that the Pt/BCT/CeO2/Si FeFET is suitable for high-performance ferroelectric memory application.

Influence of substrates on resistive switching behaviors of V-doped SrTiO3 thin films

V-doped SrTiO3 (V:STO) thin films on Si and Pt/Ti/SiO2/Si substrates are synthesized by sol–gel method to form metal–insulator–metal (MIM) structures. Bipolar resistive switching (RS) characteristics were investigated in Pt/V:STO/Si and Pt/V:STO/Pt structures respectively. The enhancement of resistive switching behavior in Pt/V:STO/Pt/Ti/SiO2/Si structures were demonstrated in terms of the maximum operation voltage reduced from 20 to 2 V and the improved ROFF/RON ratio increased from 102 to 103. The electrochemical migration of oxygen vacancies resulted from the metal–oxide interfaces was applied to explain the resistive switching behaviors. On the basis of current–voltage characteristics, the switching mechanisms for the low resistance state (LRS) and high resistance state (HRS) currents of V:STO films are considered as Ohmic and trap-controlled space charge-limited current (SCLC) behavior, respectively.

Magnetoelectric Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 composite thin films derived by SOL–GEL method

Magnetoelectric (ME) Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 (BNT–LCMO) composite thin films were deposited on Pt/Ti/SiO2/Si(100) substrates by a simple SOL–GEL method and spin-coating process with two different deposition sequences: BNT/LCMO/Pt/Ti/SiO2/Si(BLP) and LCMO/BNT/Pt/Ti/SiO2/Si(LBP). Our results show the composite thin films exhibit both good ferroelectric and magnetic properties, as well as a ME effect. BLP thin films have larger maximum ME voltage coefficient values than LBP structured thin films. The deposition sequence has a notable effect on the ferroelectric and magnetic properties and ME coupling behavior of the bi-layer thin films.