Research On Nano-Crack Switching Device Driven By Ferroelectric Domain Switching

With the booming development of the Internet of Things technology and the widespread popularity of mobile electronic devices,high-speed,high-density,and low-power consumption have become the main goals pursued by future electronic devices.In order to overcome the fundamental energy-efficiency limitation of conventional CMOS technology,a series of novel energy-efficient electronic devices have been proposed,including nanoelectromechanical(NEM)switch and ferroelectric devices.Among them,NEM switch has the characteristics of abrupt current switching behavior,quasi-zero leakage current and ultra-high ON/OFF ratio,and can realize ultra-low standby power consumption.On the other hand,ferroelectric devices exploit ferroelectric polarization switching to work,and usually have the advantages of non-volatility,high-speed and low control voltage.In this thesis,we proposed a novel nano-crack switching device driven by ferroelectric domain switching,which not noly has a simple structure,but also conbines the advantages both of NEM switches and ferroelectric devices.In addition,such nano-crack switches can not only realize the non-destructive readout operation of the ferroelectric olarization states in a simple manner,but also provide a new feasible way for developing of low-power,high-density memory and logic applications.This thesis mainly conducets the research work from the following several aspects:Firstly,the study found that although the cracks could be induced and then propogated through the top Mn Pt film under an out-of-plane electric field based on a PMN-PT/Mn Pt heterostructure,the distribution of the cracks was random,especially their location,shape,direction and number were uncontrollable,which greatly limited the practical application of such cracks.By processing the Mn Pt film into a“bridge-like”structure,the generation and switching of crack can be precisely controlled,that is,only one crack can be induced at the edge of the middle active area of the"bridge-like"structure,and then the crack will expand along the width direction.The controlled ferroelectric nanocrack switch has quasi-zero leakage current,ultra-high ON/OFF ratio and non-volatile current-switching behavior,which can be used to implemented the non-volatile and low-power information storage in the future.Secondly,by applying a small in-plane voltage between two separated Mn Pt electrodes on PMN-PT substrate,which can not only achieve the purpose of effectively controlling the generation and switching of cracks,but also significantly reduce the required control voltage.By optimizing the electrode layout,three modes of crack switching are constructed respectively:including non-volatile switching of single-crack,complementary switching of two-cracks,and complementary switching of single-crack.In addition,the complementary switching behavior of cracks are related to the complementary E_Z distributions.And the control voltage will be scaled down significantly as shrinking the gap width of electrodes.AFM and PFM measurements show that the nonvolatile switching of cracks is accompanied with the ferroelectric domain switching.The phase-field simulation demonstrates from the microscopic view of strain and energy that the dynamic reversible opening and closing process of the crack is caused by the non-uniform ferroelectric domain switching.Finally,the prospect and potential of such ferroelectric domain switching-induced nanocrack switching devices in low-power memory and logic applications were discussed.On the one hand,the mechanical opening and closing behavior of crack driven by ferroelectric domain switching has the feature of nonvolatility and quasi-zero leakage current,thus such device can be used to implement non-volatile and low-power memory.On the other hand,the spontaneous complementary switching characteristics of cracks under the in-plane electric field also provide a new approach for developing high-speed,low-power and high-density reconfigurable logic applications.For example,the complementary and controllrable single-crack based device can be used to implement non-volatile inverter.And also,the complementary and controllable double-crack device can be used to construct high-speed,low-power and high-density reconfigurable computing systems.