Development of instrumentation and automation of a PC based field emission measurement set up

This paper presents the details of instrumentation and automation of a personal computer (PC) based field emission measurement experimental setup. Instrumentation in terms of several other hardware and software were designed to achieve automated field emission measurements in different modes of operation including generation of J${}_e$-E and F-N curves, measurement of hysteresis, short and long term emission stabilities, influence of vacuum,and microarcing. The system uses various in-house developed circuits viz instrumentation configuration, automatic low current measurement, analog signal conditioning chain, analog to digital converter interface, long term field emission stability, vacuum monitoring and PIC16F887 based microcontroller circuits. A two layer software, microcontroller firmware and LabVIEW based virtual instrument, were developed for the field emission measurement and its automation. Performance of this system has been established based on the results of the hardware and software tests on various modules of the system and from the field emission experiments carried out in 30Å thick Ag and MCD samples as discussed in a detailed manner in this manuscript. The field emission experiments carried out on Ag 30Å thick samples showed a turn on voltage and β of 25 V/μm and 2884 respectively. A current density of 1538 μA/cm${}^2$ was measured at 100 V/μm. The emission current stability measurement showed a mean value of $571.5\pm 0.17$ μA over 3 hours.