Gas sensors are used to determine the concentration of gases, including poisonous and explosive (oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, etc.). They are optical, electrochemical, thermocatalytic, semiconductor. Semiconductor gas sensors have significant advantages, such as miniaturization and low power consumption. However, they also have a number of disadvantages, such as low sensitivity (i.e., they are able to respond only to high gas concentrations) and low selectivity (i.e., the sensor reacts equally to several gases). characteristics of semiconductor gas sensors. There are gas-sensitive thin-film semiconductor structures, which are identical in structure and principle of operation to thin-film transistors (TFTs). To study the gas-sensitive characteristics of these structures, it is necessary to study the change in their current-voltage characteristics (I – V) in the atmosphere of various gases.
The problem or task
To carry out research work was necessary to develop a system for studying the electrical parameters of thin-film structures (TFT transistors) in the atmosphere of various gases.
To solve the problem, an experimental complex was developed for recording the current-voltage characteristics of TFT transistors. The stand performs the following functions: it generates drain-source voltages with the ability to set the range and pitch and output the current value to the screen, generates gate-source voltages with the ability to set the range and pitch and output the current value to the screen, records the current of the conductive channel of the thin-film transistor, measures channel resistance, saves the measurement results to a file for further processing. For measurements in the presence of gas, the sample is placed in a sealed box filled with gas. To build the IVC, at a given voltage at the gate, a sequence of drain-source voltage levels is generated according to the selected range and pitch, and the corresponding current of the transistor channel is measured for each set voltage. After passing the entire range of the specified drain-source voltages, the system changes the gate-source voltage according to the selected range and step, and the process repeats. The software was developed in the NI LabVIEW programming environment using NI DAQmx, NI DCPower and NI DMM drivers. The complex is based on the PXI-1031 chassis with a PXI-8108 controller. The chassis also includes a PXI-6238 multifunction module, a PXI-4132 power supply and a PXI-4071 multimeter. As a result, a complex has been created that allows automating the registration process of the current-voltage characteristics of TFT transistors, reducing the time for conducting one change and conducting a series of scientific experiments in a short time.