Synthesis And Memory Properties Of Novel Two-dimensional SnSe Nanoplates With Resistive Switching Behavior

With the development of the Internet of Things,data throughput increases dramatically.The requirements in memory performance using for the systems are also increasing.Nanodevices based on low dimensional functional materials can greatly reduce the size of the devices and thus augment the storage density.Two-dimensional materials are ideal choice for this vision,because of their atomic thickness and favourable photoelectronic properties.In order to explore the potential application of two-dimensional materials in memory field,this paper starts from two aspects of material growth and device fabrication.The following works have been carried out:1.The controllable growth of IV-VI group,layered two-dimensional Sn Se nanosheets has been realized by physical vapor deposition(PVD)method.It is found that temperature,holding time and carrier gas flow are important parameters affecting the size and thickness of nanosheets.By adjusting these parameters,high quality Sn Se nanosheets with maximum size of 16?m and representative thickness of 5 nm have been obtained.The oxidation process in atmosphere has also been explored:A layer of?2.7 nm thick SnO₂ is formed on the nanosheets thicker than the representative thickness after lefting in atmosphere for 1 day.The existence of the oxide layer lays a good foundation for the realization of resistive random access memory(RRAM)based on conductive filament.2.Using the non-destructive transfer method,the resistive switching devices with cross-bar structure based on two-dimensional Sn Se nanoplates have been fabricated.By comparing key indexes of memory(on/off ratio,operationg voltage,retention time and cycle),it is found that the nanoplates oxided for 1 day possess the best device performance.The set voltage of the nonpolar resistive switching devices was about 1.5?2 V,and reset voltage was about 1?1.5 V.The ratio of high and low resistance state(HRS and LRS)could be up to three orders of magnitude.Retention time was more than 10⁴ s and the cycle was more than 100 times.3.The memory characteristics of Sn Se devices with different oxidation levels were analyzed,and the corresponding resistive switching mechanisms were expounded.The formation/fracture model of the conductive filament for Sn Se devices with best performance were constructed.The increasing of HRS current under high compliance current(I_cc)and the slightly decreasing of LRS current with large device size were well described.Moreover,the temperature stability of the device has been studied,with fitting of the semiconductor property of high resistance.The slope?is consistent with the thermal activation energy of oxygen vacancy in SnO₂,indicating the existence of oxygen vacancies and participation in the conduction process of HRS.