Study On The Characteristics And Applications Of Volatile Memristor Based On V_0.95Ge_0.05O₂

With the development of storage technology,memristor with high memory efficiency and low power consumption has been paid more attention,but there are technical compatibility problems in the integration process of memristor.The memristor based on phase change materials has attracted much attention due to its small unit area and high compatibility with traditional silicon-based complementary metal oxide semiconductor（Si-CMOS）technology.vanadium dioxide（VO₂）,as a typical Mott Insulator which has the first-order phase transformation,achieves the insulator metal transition（IMT）in the condition of near the room temperature.In the process of IMT,the electrical and optical characteristics of the device also change rapidly.It is often used in the study of artificial synapses and artificial neurons.However,in CMOS integrated circuit,the working temperature of plastic encapsulated circuit is close to 80°C,and the working temperature of ceramic metal encapsulated circuit is as high as 125°C.The phase transition temperature of VO₂ is 68°C,which is difficult to meet the practical circuit application and large-scale integration,resulting in the bottleneck of the circuit application of VO₂-based memristor.How to increase the phase transition temperature of VO₂has become a very important research topic.In this paper,the doping method is used to study the preparation of V_0.95Ge_0.05O₂（VGe O）based on germanium doped vanadium dioxide material,to explore the effect of Ge doping on the phase transition temperature,and the application of volatile memristor based on VGe O.The main contents are as follows:1.Ti N/VO₂/n-Si and TiN/VGeO/n-Si memristors are fabricated by magnetron sputtering.The resistive properties of the devices and the effect of germanium doping on VO₂ phase transition temperature are investigated.First,the TiN/VGeO/n-Si device is characterized by X-ray diffraction（XRD）,atomic force microscope（AFM）and transmission electron microscope（TEM）.The VGe O film shows a polycrystalline state with a thickness of about 7nm and an average surface roughness of about 791 pm.The electrical performance test of the device shows typical threshold switching memristor（TSM）characteristics,the switching speed of the device reaches～45 ns,and the switching ratio of the device reaches 2 orders of magnitude,which lays a foundation for the research of the device on the imitation neural network.Finally,the resistive mechanism of the device was analyzed through the fitting of conductive mechanism and correlation test.By fitting the current-voltage（I-V）curve of the device in the high resistance state,it is found that the conduction mechanism conforms to Poole-Frenkel（P-F）.The device produces joule thermal effect under the action of current,and realizes the transformation of high and low resistance value when the IMT temperature is reached.The resistance-temperature（R-T）curves of the two structures were tested,and the TiN/VGeO/n-Si phase transition temperature was increased to 75°C.2.Using the threshold switching characteristics of TiN/VGeO/n-Si memristor device,the LIF artificial neuron model is constructed by connecting with the capacitor resistance to simulate that the accumulated charge of the cell membrane reaches the threshold potential and the neuron activates the output spike pulse.By adjusting the input voltage amplitude and synaptic resistance,the neuronal functions such as threshold discharge,refractory period and intensity response are simulated.Based on the optical response of the device,the frequency response characteristics of neuron circuit under different wavelength and intensity of light regulation are studied,which provides a new way for further simulation of sensitive neurons.3.Using the delay time of threshold memristor with TiN/VGeO/n-Si structure as the source of randomness,a true random number generator was constructed with comparator,counter,and gate circuit,and 5×10⁴ binary random numbers were generated.These random numbers have passed 12 standard randomness statistical test kits（NIST 800-22test kit）developed by the National Institute of Standards and Technology,which provides a reference for memristor in the research of true random number generators.