The spatial profiles of a VHF H2 plasma (60 MHz) for different discharge gap distances were examined at pressures of 66.7 and 133.3 Pa by two-dimensional simulations using the plasma hybrid code. The electron density had a peak profile, and the maximum density depended on both the discharge gap distance and the pressure. A high-electron-density plasma with a low-electron temperature of approximately 1 eV was predicted by simulation at discharge gap distances of 15 and 20 mm. The plasma potential profile was composed of a plateau at the center and sharp slopes at the two sides. The axial profiles of the H+, H2 +, and H3 + densities were calculated for the discharge gap distances of 10, 15, and 20 mm. It was found that the dominant ion species was H3 + except near the discharge electrode and the H2 + density near the discharge electrode was not negligible compared with the H3 + density at 66.7 Pa.

A two-dimensional simulation on a VHF H2 plasma (60 MHz) was performed using the plasma hybrid code, and plasma parameters were examined as a function of pressure for different discharge gaps. It was found that as the pressure increased, the H3 + and H+ densities as well as the electron density had a maximum at a certain pressure, and the maximum shifted to high pressures as the discharge gap decreased. On the other hand, the H2 + density decreased with the increase in pressure, independent of the discharge gap. The axial profiles of the H+, H2 +, and H3 + densities showed that dominant ions were H3 + in our pressure range.

A capacitively coupled VHF H 2 plasma (60 MHz) was produced by a narrow gap discharge at high pressures, and spatial distributions of the plasma parameters were examined with the Langmuir probe. A bi-Maxwellian electron distribution was observed near the discharge electrode while a Maxwellian one near the center of the inter-electrode gap. The simulation using the PIC code showed that electrons had the Druyvesteyn-like distribution near the discharge electrode.

A VHF H2 plasma was produced by a narrow-gap discharge at high pressures, and the plasma parameters were examined with the Langmuir probe. A bi-Maxwellian electron distribution was observed near the discharge electrode at a discharge gap of 10 mm, while a Maxwellian distribution was seen near the center. When the discharge gap was 15 mm, electrons had a Maxwellian distribution independent of the position. It was found that there must be a threshold in the discharge gap for stochastic heating to occur. The plasma potential near the discharge electrode was higher than that near the center of the interelectrode gap, suggesting the existence of negative ions. The simulation using the plasma hybrid code was carried out. The spatial profiles of the density and temperature of electrons were similar to the experimental results. The plasma potential had a hill-like profile that was quite different from the measured one. The negative ion density was negligible.