Manipulation of Electric Field Effect by Orbital Switch

Abstract

753wileyonlinelibrary.com is a combination of ferroelectric/ferromagnetic model materials. More importantly, the connection and breakdown of interfacial covalent bond could be tuned by the ferroelectric displacement of Ti orbital under electric fi eld. [ 9 ] When this covalent bond is introduced into the interface between ionic liquid (IL) and LSMO, where gate voltage could generate an in-depth and enduring modulation of carrier density in the LSMO, it produces a chance for controlling the bulk electric-fi eld effect. Such a switchable covalent bond determined by the orbital reconstruction might also make the orbital degree of freedom straight forward to the application in microelectronic device, which has been dominated only by charge and spin by far. Results and DiscussionLSMO/BTO heterostructures were grown on STO substrates by pulsed laser deposition (PLD). The ferroelectric switching could be observed in the heterostructure with an ultrathin BTO of 3.2 nm as shown in the out-of-plane piezoresponse force microscopy (PFM) image. A series of alternative d.c. bias of +3 V → −3 V → +3 V → −3 V → +3 V are applied to the BTO and a 1000 mV a.c. voltage is utilized to read the phase reversal subsequently as presented in Figure 1 a. The apparent 180° phase contrast implies the existence of the ferroelectric switching in the fi lm: a positive voltage triggers the ferroelectric polarization toward the LSMO bottom layer, whereas a negative voltage polarizes the BTO upward. It is noteworthy that the phase contrast remains after repetitive measurements for many times. The ferroelectricity of BTO mainly originates from compressive strain produced by STO substrate and LSMO underneath as the X-ray diffraction (XRD) of LSMO (20 nm)/BTO (80 nm) on STO substrate in Figure 1 b shown. The 2 θ angle for BTO (002) peak is around 44.17° and corresponding c -axis lattice constant is 4.10 Å (4.04 Å for tetragonal ferroelectric phase), suggesting that the BTO fi lm under in-plane compressive strain is tetragonal ferroelectric phase. [ 10,11 ] Here the thick BTO 80 nm is used to give a clearer diffraction peak and the c -axis lattice constant for thinner BTO fi lm should be larger due to its less strain relaxation.To directly illustrate the ferroelectric movement of Ti ions under electric fi eld, the atomic resolution aberration-corrected high-angle annular dark fi eld scanning transmission electron microscope (HAADF-STEM) image with its analysis is presented in Figure 2 . Coherent growth of 3.2 nm BTO on 20 nm Manipulation of Electric Field Effect by Orbital SwitchBin Cui , Cheng Song , * Haijun Mao , Yinuo Yan , Fan Li , Shuang Gao , Jingjing Peng , Fei Zeng , and Feng

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“…Because d à 33 consists two parts 24,25 : one is the intrinsic contribution, which is related to structural lattice of the crystal; the other is the extrinsic contribution to the piezoelectric effect, which is associated with the domain contributions. [26][27][28] d à 33 firstly increases and then decreases, reaching a maximum with Sn content of 0.006. The enhanced piezoelectric properties of air and reduced fired Sn6 samples can be explained as the domains near the PPT region are more mobile under the applied electric field.…”

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