气敏薄膜器件吸附极性气体分子产生微弱的电流变化可用来诱导混沌电路，进而产生不同混沌吸引子相图可表征气体浓度空间分布，由此制作的气敏传感器具有很大发展前景。目前虽然气敏传感器种类繁多，但在实际应用中存在各种各样的问题，尤其对于那些与人们生命与财产息息相关的瓦斯传感器在性能方面饱受诟病。传感器的微型化、低功耗、高灵敏度和多功能化成为目前瓦斯器件的发展趋向。这就要求人们不仅要生产出优良的气敏材料，还要在已有的信号检测方法基础上改善和发展更好的信号检测技术。作为第三代半导体材料的典范，碳化硅因其宽禁带、高电子迁移率、高饱和电子漂移速率等优点，有利于高频率、耐高温、抗辐射、高稳定性的传感器件制作。基于混沌系统对初始条件高度敏感性和有界性的特点而发展而来的信号检测方法，能显著地提高相关传感器的分辨率和灵敏度。 为获得SiC(011)表面吸附电导特性，本文基于第一性原理的密度泛函理论的计算，建立了CO分子在SiC(011)薄膜表面三个典型吸附位的化学吸附模型，对比分析了系统吸附前后的表面结构变化、吸附能以及差分电荷密度差图。计算结果表明，在吸附过程中三个不同位置均能观察到电荷的转移过程。 为了很好的将传感器检测到的微电流变化与混沌系统的吸引子轨迹变化联系起来，本文以Lorenz混沌系统为研究对象，设计出相应的微电流信号处理电路来对极性气体分子吸附在气敏薄膜产生的微弱电流进行转换、放大和数字化处理，最终满足控制混沌电路的数据要求。并提出了模拟型混沌电路和数字型混沌电路以及相关的控制电路设计方案，为进一步应用开发提供研究基础。 采用改进型模块化的设计流程，利用分立元器件组成的非线性基本单元设计出相应的模拟型Lorenz电路。从Lorenz混沌电路的初始条件敏感性出发，设计了两种可行的混沌控制方案，一是电路元件参数敏感控制；二是电路初始值敏感控制。通过相关的电路分析和仿真结果对比，我们发现控制混沌电路的初始值，能更好地满足微弱电流信号检测的要求。 基于IEEE-754标准的双精度浮点数运算规范，对连续Lorenz系统进行离散化处理后，采纳自顶而下的模块化设计方案，由浮点数乘法运算模块、数字信号处理模块、浮点数加/减法运算模块以及初始值和迭代值选择模块整合而成数字型混沌电路及相关控制电路。通过Xilinx公司开发的ISE Design Suits软件对相关模块的Verilog HDL代码进行仿真和综合，很好地满足了课题设计的要求,为电路设计微型化奠定了基础。

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 process that 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.