A Heated Thermocouple Microelectrode And Its Application In Scanning Electrochemical Microscopy

Temperature is one of the most important parameters in electrochemical reaction,As the temperature dependence of thermodynamic and kinetic functions including transport properties such as diffusion are dominant.As the development of nano-material and nano-technology,it is necessary to gain the thermal information in a smaller size.So the submicro resolution temperature measurement is very important.This thesis mainly study the fabrication of a thermocouple microelectrode and its application.The thermocouple microelectrode can be used to detect and image the temperature of micro-zone.Also it can be used for electrochemical experiments and electrochemical imaging.The main contents and result are listed as follows:1.A novel thermocouple microelectrode for applications in SECM and variable temperature electrochemistryThis paper describes a novel strategy for the fabrication of a thermocouple microelectrode by melting Pt and Pt-Rh wires into a measuring junction using a hydroxygen flame.A thermocouple with a tip apex diameter of approximately 20 ?m can be fabricated by sharpening the two wires by electrochemical etching,followed by merging of the two etched ends into a spherical joint to act as the measuring point.The as-fabricated microelectrode can work as a kind of thermocouple to measure the local temperature of the electrode.The microelectrode can be employed to study the electrocatalytic oxidation of methanol.Most importantly,the thermocouple microelectrode can be employed as an SECM tip,for example in the measurement of the reactivity of Cu patterns with bromine on a circuit board over a variable temperature range.2.A new type of synchronous electrochemical imaging and temperature imaging systemA new imaging system consists of a R type thermocouple detection system and an SECM.The R type thermocouple detection system consists of a thermocouple microelectrode,a MODBUS-RTU temperature acquisition card,a RS485 adapter and a 24 V DC power.Through the thermocouple microelectrode,the temperature detection system can combine with the SECM.A ceramic heating apparatus is used to heat a wood substrate with a copper wire in its center.The imaging system can achieve thermal image simultaneously at SECM scanning process.3.A heated thermocouple microelectrode in micromachining of n-GaAs semiconductor and ZnO nanowiresA high frequency heating is used to apply different heating power on the thermocouple microelectrode,then the microelectrode can be warmed up.The effect of different frequency on the K4Fe(CN)6 cyclic voltammetric is dicussed.Under the optimal value,when increasing the power,the temperature of the electrode will increase gradually.The heated thermocouple electrode is applied to the electrochemical micro-maching.The etching effect of heating power to the ZnO nanowires on an indium tin oxide(ITO)substrate is studyed.The effect of different temperature to the n-GaAs semiconductor etching result is also researched.By fitting the experimental result of n-GaAs with the theoretical simulation,the reaction constant at different temperatures can be calculated.