In this research we analyse different plasma wave propagation mechanism of microcavity discharge in pure Argon at two different pressures. Experimental results of a pulsed micro-DBD with 2 and 50 kPa Argon, 180 um gap, at room temperature, show that two distinct pressure-dependent propagation modes exist. In the low pressure regime, the discharge propagates perpendicular to the applied electric field forming distinct channels, but many vertically-oriented filaments distributed throughout the domain at high pressure discharge. And the discharge duration time in high pressure is around 5 times shorter than that in low pressure. A 2D Particle-In-Cell (PIC-MCC) model with chemical reactions, photoemission, and secondary electron generation, is established to investigate the formation mechanism of the two propagation modes. Models of the initial ionization processes show that there are two different breakdown mechanisms for these two pressures, where secondary emission of electrons from the dielectric is dominated either by ion impact or by photon impact. The investigation is of great significance for further reveal of the principle of microplasmas discharge.

Since the physical and electrical properties of plasmas are similar to the semiconductor
device, the plasma devices are proposed to be good candidates for switching controlled
devices while applied in harsh environments. In the proposed paper, a microplasma device
with dielectric barrier structure constructed with three electrodes (two driven electrodes and
one trigger electrode) is fabricated, and the electrical characteristics of the proposed device
are investigated in 2 kPa of argon. From the experimental results, a stable conducting current
is obtained through two driven electrodes in the device due to gas discharge, since the
hysteresis characteristic of discharge plasmas (discharge is still maintained when driven
voltage is below the breakdown voltage of the gas because of the existence of residual charge
particles), the device can be switched from OFF to ON state through pre-discharge by a pulse
applied on the trigger electrode. While in the device ON, this trigger voltage attracts channel
charged particles to the surface of the dielectric layer, quenching the discharge plasma current
and the device can be switched from ON to OFF state. The trigger pulse that makes the
device switch successfully is from single to continuous up to 80 kHz. The influence of pulse
parameters on the switching process is also investigated, pulse amplitude and pulse width are
found to be important to whether the device can be switched ON or OFF, peak current after
switched, and the response speed of switching ON current, however, these switching
parameters are barely affected by the rising and falling time of the pulse. The results are
significant for the application of microplasma switching devices.

Silicon nanowires (SiNWs) are introduced into microdischarge to improve microplasma properties due to its field emission electrons and field enhancement effect. The geometrical arrangement and dimensional features of SiNWs have desicive influence on field emission properties, thus the dependence of microplasma emission performances on the SiNWs morphologies is investigated in this paper. The different morphologies of SiNWs can be prepared by electrocatalytic metal-assisted chemical etching with varied etching currents. With the increase of etching current from 3 mA to 30 mA (AgNO3:HF:H2O2 = 0.02:4.6:0.1 mol l−1, deposition time 1 min and etching time 10 min), the field emission current density J of the SiNWs prepared at 20 mA etching current is the largest ∼0.28 mA cm−2 at a field 4.5 V μm−1, and turn-on field is the lowest of 3.52 V μm−1. Accordingly, the microplasma in the device fabricated on the SiNWs-decorated substrate (etching current at 20 mA) has the strongest average emission intensity of ∼11 565 a.u., the minimal relative standard deviation of emission intensity 4.9% and the fastest propagation velocity of 471 km s−1. The field emission electrons of SiNWs could inject more seed electrons into microcavity which causes higher electron collision probability, and the field enhancement effect at tips of SiNWs can provide more energy for the charged particles, which are helpful to the microdischarge. The most difficulty is to balance the distance of emitters and the percentage of SiNWs in entire emission region because the shielding effect will reduce while the surface emitter numbers will decrease when the distance of emitters increases. Here, a ‘proper percentage of SiNWs’ of 19.3% is obtained what indicates that if SiNWs percentage is greater than the threshold, field enhancement factor β eff is weakened by the decrease of aspect ratio and the increase of percentage. When SiNWs percentage is less than 19.3%, β eff will increase and be dominated by the percentage of SiNWs. The results are significant for the application of SiNWs in microdischarge devices.