Mechanism Analysis Of Triggering Lorenz Chaos Circuit By The Polar Molecules Adsorbed On SiC Surface

The chaotic attractor phase diagram of a chaotic circuit exhibiting the distribution of gas concentration is induced by a week electric current change produced from the adsorption of the polar gas molecules on the SiC film. The gas sensor will have a huge development potential if it was manufactured on the design approach above. At present, there are many different kinds of gas sensors, however various of problems exit in practical application,especially for the poor performance of gas device which relates to people's lives and property are often criticized. The gas sensor with miniaturization, low power consumption, high sensitivity and multi-function are becoming the main tendency. So the high sensitive materials and the signal detection method are expected in the designed sensors. Silicon carbide, the representative of the third generation of semiconductor materials, is beneficial to the sensor manufacture which is characterized with high frequency, high temperature, anti-radiation and high stability for its advantage of wide band gap, high electron mobility, high saturated electron drift velocity, etc. It can significantly improve the resolution and sensitivity of associated sensors based on the feature that high sensitivity to the initial condition and the boundness of chaotic system.Using the density functional theory of first-principles method, CO molecule adsorbed three typical adsorption sites was constructed and analyzed to characterize its electronic properties. The change of system structure, adsorption energy and the charge density difference before and after were comprehensively compared. The results showed that significant charge transfer have taken place in the adsorption process.The linear dependence of the micro-current change by a sensor detection and the chaos attractor track change of chaotic system is main problem in this work. The high sensitive circuit was designed to transform, magnify and digitize week current signal from the processthat polar gas molecules adsorbed on the gas sensing film. The design schemes of analogue and digital chaotic circuit and related control circuit are put forward, which has some practical value.With the improved modular, the Lorenz chaotic circuit is designed by using some nonlinear base unit combined with some discrete components. Two possible methods,sensitivity to circuit component parameters and the sensitivity to the initial values of circuit,are proposed to control the Lorenz system circuit. It shows that the initial values of chaotic circuit meet the requirement of week current signal detection better.Based on the double precision float-point operations specification of the IEEE-754 standard, the continuous signals from Lorenz system are discrete. With the modular program from top to down, The digital chaotic circuit and associated ones are integrated with the floating point multiplication module, a digital signal processing module, a floating point addition/subtraction module and the selection of initial value and iterative value module. The Verilog HDL codes related to these modules above are compiled and synthesized using the software of ISE Design Suits from the company called Xilinx, which meets the needs from our works. These will present a good foundation for circuit miniaturization.