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The critical parameters determining the generation of the pulse-modulated argon atmospheric-pressure inductively coupled plasma (AP-ICP) microjet were studied by varying the power, P, pulse-modulation frequency, f, and duty ratio, DR. The temporal changes in the net output power, Pnet, monitored between the very high frequency power supply and matching network by an rf sampler, and ArI 4s′[1/2]1O–4p′[1/2]0 emission from the antenna were measured to elucidate the behavior of this plasma. The AP-ICP microjet, which produces high-density (0.9–1.1×1015 cm−3) nonequilibrium plasma, consists of an alumina discharge tube with the inner diameter of 0.8 mm. The generation diagram of the pulse-modulated plasma was created by having f as the horizontal axis and DR as the vertical axis while varying P up to 50 W. At f≤10 kHz, the plasma was generated at above the linear lines of f and DR, which indicated the existence of the critical power-off period of approximately 80 μs. At f>10 kHz, the pulse-modulated plasma was produced above constant DR and almost independent of f. The time-averaged power, P¯, which is the product of P and DR, had to be more than 8–10 W to sustain the pulse-modulated plasma. From the measurement of the temporal changes in the net power and ArI emission, the dynamic behavior of the pulse-modulated plasma was revealed as follows. The prebreakdown period was present for ∼5 μs after the power was turned on. Once the plasma was generated, the impedance was changed and the reflected power gradually decreased. A strong emission peak was observed immediately after the breakdown, followed by the gradual increase up to the steady state. Finally, the intense afterpeak was observed at 0.8 μs after the power was turned off.

Local reduction of the copper oxide film was performed by an atmospheric-pressure inductively coupled plasma (AP-ICP) microjet and the fundamental characteristics of the removal process were studied. CuO and Cu 2 O films were formed on the sputtered Cu surface by thermal annealing. The sample was then exposed to the Ar-H 2 AP-ICP microjet. The chemical composition, morphology, and the film thickness before and after the plasma treatment were analyzed by XPS, optical microscopy, and SEM/EDX. CuO and Cu 2 O were reduced to form porous Cu at the speed of 380 nm/min. Heterogeneous reduction patterns inside the Cu 2 O layer were observed due to the fast diffusion of H atoms through the narrow gap between the columnar structures.

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