Al-based memristor applied to habituation sensory nervous system

Abstract

Sensory nervous system (SNS) can build the connections between organism and outside environment. Both of synapse and neuron are cornerstones of human biological system, which can transmit information to human brain and receive the feedback from central nervous system. Finally, the corresponding responses to the external information are performed. However, the information from outside environment should be received by SNS all the time. It is important for organism to distinguish between the stimuli that required attention and those that are irrelevant and no need to response. Habituation is one of fundamental properties of SNS to form such discrimination. It plays an important role for organism to adapt the environment and filter out irrelevantly repetitive information. In this study, an nc-Al/AlN structured based memristor with a thickness of 40 nm is produced by the sputtering method. The top and bottom electrode are of Ag and Al respectively, forming a sandwiched structure device. Habituation is found in the nc-Al/AlN thin film based memristor which has been rarely reported before. Both of current-voltage (<i>I</i>-<i>V</i> ) and pulse voltage measurement are executed on this device at room temperature. In the <i>I</i>-<i>V</i> measurement, the memristor shows unipolar switching properties which may be caused by conductive filament connecting or breaking. In the voltage pulse measurement, pulse interval is an important factor to affect memristor conduction. If the pulse interval is quite large, that is, the pulse frequency is low, the memristor will get maximized conduction very slow or in infinity time. If choosing an appropriate pulse voltage and interval value, the habituation will be observed after several stimulus pulses. The larger pulse interval needs more pulse numbers to cause memristor to be habituated, but which results in higher device conduction finally. A habituation memristor can act as synapse and connect with neuron to build the whole leaky integrate-and-fire (LIF) model which is quite often used in circuit design to mimic a real organism neuron behavior. In this model, neuron could be fired only when it gets enough stimuli from previous neuron. If the stimulus pulse frequency is low, there is observed no firing phenomenon in this case. In this study, the input signal of LIF model is a continuous voltage pulse with an amplitude of 1.2 V and interval of 5 ms. Such an input signal will be transmitted by habituation memristor to a neuron electronic element. The output signal is the pulse generated by neuron when it is fired. According to the results, the frequency of output signal is smaller than input information which complies with the basic characteristics of habituation. It is supposed that organisms should not response to this repetitive pulse any more and it will make neuron have more capabilities to handle following information.