Design Of A Characterization System For Novel Quantum Dot Gas Sensors

For the past few years,many scholars continue to explore the quantum field,and take advantage of the special avtivity of nanomaterials to develop high-performance,low-power gas sensors at home and abroad.The basic principle of semiconductor gas sensor is the change in the resistance of depletion layer caused by the interaction between gas and material surface.The interaction between a gas and a material surface lead to depletion layer resistance changes duing to the fundamentals of semiconductor sensors.The grain radius of quantum dot gas-sensitive material is smaller than the width of depletion layer,at the same time the whole grain is in the state of depletion led to the resistance of the sensor is too high to be measured.As a result,the resistance value of the sensor is too large to be measured.Therefore,in the research and development of sensing materials and devices,the development of performance testing technology is relatively backward.A characterization system based on MPS-010602 data acquisition card was designed for novel semiconductor quantum dot gas sensors,which involved thin films with huge resistance,being difficult to measure.The modules of multiple tunnel voltage acquisition,operating temperature control,temperature and humidity sensors,filters and CA3140 followers with high input 'impedance.MFC visual programming in Visual C++6.0 was used to' develop a human-computer interface,which provided functions of data acquisition,process,real-time display,storage and read.With the cooperation of hardware and software,the stability of voltage signal was guaranteed.In the meanwhile,the high resistors with resistance values ranging from 3-100 were;measured and validated,which measurement error is less than 3%in order to assure the accuracy of the measured data.The characterization system can realize the functions,which relationships between response of the quantum dot gas sensor and gas concentration,response and recovery characteristics measurement of the quantum dot gas sensor,electivity measurement of the quantum dot gas sensor,multichannel measurement,response measurement of the quantum dot sensor at the multiple operating temperatures,and the resolution measurement of the characterization system for the quantum dot gas sensor.With the purpose of verifying the functions of characterization system,this article uses the quantum dot that average grain size of was 1.9 nm,afterwards make the quantum dot into gas film sensor and completing the test of related functions.Through the test and verification of the characterization system function,the results showed that the advantages of wide range,high precision and anti-interference ability,which could meet the requirements of characterization of semiconductor quantum dot gas sensors.This characterization system incorporates an "electronic nose",a sensor system that combines the pattern recognition function of a neural network with a sensor array as the front-end probe.Using BP neural network pattern recognition technology of nonlinear mapping and parallel processing and high self-learning,this process establishes neural network model through MATLAB,processing signals from the sensor array,achieving.the qualitative and quantitative analyses of concentrations of the mixed gas in the test chamber,thus realizing the purpose of identification test chamber gas environment.