Creation and erasure of polar bubble domains in PbTiO_(3)films by mechanical stress and light illuminations

The controllable manipulation of polar topological structures(e.g.skyrmion bubble)in ferroelectric materials have been considered as a cornerstone for future programmable nano-electronics.Here,we present the effective creation and erasure of polar bubble states PbTiO_(3)(PTO)multilayers trigged by mechanical stress and light illumination,respectively.It was found that applying atomic force microscope(AFM)tip force can induced formation of nanoscale bubble domains from the initial monodomain state.Moreover,the created bubble domain can be eliminated by exposure to ultraviolet or infrared light illumination.The above results can be understood by modulation of depolarization screening charges and bias fields,as reflected by scanning Kelvin potential microscopic(SKPM)observations,whereby the flexoelectric effect from the tip force tends to remove the screening charges on top surface and modulate the bias field that favors the formation of bubble state while light illumination tends to recover the screen charges and favor the monodomain state.The results provide a good example for multi-field manipulation of polar topologies,which might create a new avenue towards the immerging new concept electronic devices.

Enhanced ferroelectric polarization with less wake-up effect and improved endurance of Hf_(0.5)Zr_(0.5)O_(2)thin films by implementing W electrode

This paper reports the improvement of electrical,ferroelectric and endurance of Hf_(0.5)Zr_(0.5)O_(2)(HZO)thinfilm capacitors by implementing W electrode.The W/HZO/W capacitor shows excellent pristine 2 P_(r)values of 45.1 gC/cm^(2)at±6 V,which are much higher than those of TiN/HZO/W(34.4μC/cm^(2))and W/HZO/TiN(26.9μC/cm^(2))capacitors.Notably,the maximum initial 2 P_(r)value of W/HZO/W capacitor can reach as high as 57.9μC/cm^(2)at±7.5 V.These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode,allowing for enhancement of o-phase formation.Moreover,the W/HZO/W capacitor also exhibits higher endurance,smaller wake-up effect(10.1%)and superior fatigue properties up to 1.5×10^(10)cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors.Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor.These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation,reduces oxygen vacancies,mitigates wake-up effect and improves reliability.

Controlled manipulation of conductive ferroelectric domain walls and nanoscale domains in BiFeO_(3) thin films

Recently,there is a surge of research interest in configurable ferroelectric conductive domain walls which have been considered as possible fundamental building blocks for future electronic devices.In this work,by using piezoresponse force microscopy and conductive atomic force microscopy,we demonstrated the controlled manipulation of various conductive domain walls in epitaxial BiFeO_(3) thin films,e.g.neutral domain walls(NDW)and charged domain walls(CDWs).More interestingly,a specific type of nanoscale domains was also identified,which are surrounded by highly conductive circular CWDs.Similar nano-scale domains can also be controlled created and erasured by applying local field via conductive probe,which allow nondestructive current readout of different domain states with a large on/off resistance ratio up to 102.The results indicate the potential to design and develop high-density non-volatile ferroelectric memories by utilizing these programable conductive nanoscale domain walls.

Domain wall dynamics driven by a circularly polarized magnetic field in ferrimagnet:effect of Dzyaloshinskii-Moriya interaction

In this work,we study the domain wall motion in ferrimagnet driven by a circularly polarized magnetic field using the collective coordinate theory and atomistic micromagnetic simulations,and we pay particular attention to the effect of Dzyaloshinskii-Moriya interaction(DMI).Similar to the case of antiferromagnetic domain wall,ferrimagnetic wall moves at a speed which is linearly dependent on the DMI magnitude.In addition,it is revealed that the DMI plays a role in modulating the domain wall dynamics similar to that of the net spin density,which suggests another internal parameter for controlling domain wall in ferrimagnets.Moreover,the results show that the domain wall dynamics in ferrimagnets is much faster than that in ferromagnets,which confirms again the great potential of ferrimagnets in future spintronic applications.