Yongxian Huang

Implantation dynamics of plasma implantation into insulating strips

Plasma immersion ion implantation (PIII) of insulating materials is quite challenging because of surface charging and capacitance effects. In this paper, we conduct a two-dimensional plasma–sheath simulation of PIII into insulating strips that have practical industrial applications. Our results reveal distortion of the plasma sheath above the parallel strips. Consequently, there exist horizontal components of the ion velocity affecting the implantation results in terms of both the incident ion dose and the penetration depth. The strip dimension is also found to exert a considerable influence on the implantation dynamics. When the strip is wider, the ion dose in the insulating strip is higher but the difference in the vertical velocity is quite small. This illustrates the importance of sample placement in the implantation process.

Ion trajectories in plasma ion implantation of slender cylindrical bores using a small inner end source

Plasma immersion ion implantation (PIII) into slender cylindrical bores with higher efficiency is described in this letter. The use of an inner end plasma source excited by a radio-frequency hollow cathode is investigated theoretically and experimentally. The end source that is covered by a small grounded shielding electrode to ensure steady discharge enables continuous delivery of the required plasmas, and the potential difference in the tube increases the ion impact energy. Particle-in-cell simulation demonstrates that the ion trajectories are complex due to the special electric field configuration that is composed of three regions characterized by ion acceleration, no electric field, and ion deceleration. The end source structure with the open shielding electrode is insufficient to achieve high ion energy, although it is effective in maintaining a steady discharge in the source. Hence, a shielding electrode with a protruding electrode structure is required to conduct high energy PIII; a cylindrical bor...

A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit

A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.

Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid–solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation (LPS) prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.