Luqi Yuan

Low temperature deposition of nanocrystalline TiO2 films: enhancement of nanocrystal formation by energetic particle bombardment

This paper reports the important role of energetic particle bombardment in achieving low temperature deposition of nanocrystalline TiO2 films by reactive DC magnetron sputtering of Ti targets in a mixture of argon and oxygen. In this work, we studied the effect of particle bombardment in the film deposition process by control of external processing parameters, including total pressure Pt and negative substrate bias Vb. The result shows that the variation of energetic particle bombardment has a significant impact on substrate temperature, crystal structure, surface morphology and refractive index n of deposited TiO2 films and we believe the process of non-equilibrium atomic scale heating caused by energetic particle bombardment is the main reason for the nanocrystal formation at low temperature (below 75 °C).

Nanosphere monolayer-templated, ion-assisted nanofeature etching in dielectric materials: a numerical simulation of nanoscale ion flux topography

The results of numerical simulations of nanometer precision distributions of microscopic ion fluxes in ion-assisted etching of nanoscale features on the surfaces of dielectric materials using a self-assembled monolayer of spherical nanoparticles as a mask are presented. It is shown that the ion fluxes to the substrate and nanosphere surfaces can be effectively controlled by the plasma parameters and the external bias applied to the substrate. By proper adjustment of these parameters, the ion flux can be focused onto the areas uncovered by the nanospheres. Under certain conditions, the ion flux distributions feature sophisticated hexagonal patterns, which may lead to very different nanofeature etching profiles. The results presented are generic and suggest viable ways to overcome some of the limitations of the existing plasma-assisted nanolithography.

Ion current distribution during deposition of dielectric material using an insulating porous alumina template

We have presented a numerical simulation of the deposition of dielectric material using an insulating porous template. A Maxwellian distribution has been used to calculate the original ion velocity when the ion leaves the plasma and enters the sheath. The microscopic electrical field over the template is considered to affect the ion motion. It is found that the electron temperature and nanopore structure can change the ion deposition rate effectively. However, the deposition rate decreases only slightly with the rise in plasma density and does not rely on the substrate bias obviously for the reason that the effect of electrical field near the template is limited. The result of our paper indicates that the templated i-PVD of dielectric nanodots is quite different from the templated i-PVD of metallic nanodots, and new ways should be tried for the plasma to fabricate dielectric nanodots using a porous template to make the effect from the electrical field and the substrate bias stronger.