In this paper, a one-dimensional (1-D) implicit particle-in-cell Monte Carlo Collision (IPIC-MCC) method is introduced to study the plasma kinetic features of thermo-field emission at a direct-current argon atmospheric micro-scale discharges under different operation conditions, such as field enhance coefficient β (1~10), cathode temperature (2000~3300K) and gap size (1~10µm) at an invariant applied voltage (20V).

In the 1-D IPIC-MCC simulation, Hantzsche-fit formula is employed as emission model, and tungsten as the most refractory metal is set for the cathode material. First, the conditions of temperature and electrical field where thermo-field emission is available are determined by comparing the emission current densities of a typical Hantzsche-fit formula to a general Murphy-Good expression. Then, kinetic simulation results under different conditions are analyzed, demonstrating the importance of the gap size and temperature on thermo-field emission in micro-scale discharges. It is observed that all conditions considered exhibit a self-sustainable and steady discharge mode at an external applied voltage of 20V. Simulation results show the collision between particles become more intense with the increasing cathode temperatures and the increasing electrode gap sizes.