Fig. 2: Optical emission spectrums of the microplasma jet acting on UME tips under different reaction gases and interaction states between the microplasma jet and the DLC-UME under different horizontal spacing.

a Optical emission spectrum of He microplasma jet under the He flow rate of 20 sccm. b Optical emission spectrum of He/O2 microplasma jet under the He flow rate of 20 sccm and the O2 flow rate of 2 sccm. c Optical emission spectrum of Ar microplasma jet under the Ar flow rate of 20 sccm. d Interaction state under maximum horizontal spacing. e Interaction state under medium horizontal spacing. f Interaction state under smaller horizontal spacing