Lou Feng-Jun

Guided transmission of oxygen ions through Al2O3 nanocapillaries

The transmissions of oxygen ions through Al2O3 nanocapillaries each 50 nm in diameter and 10 μm in length at a series of different tilt angles are measured, where the ions with energies ranging from 10 to 60 keV and charge states from 1 up to 6 are involved. The angular distribution and the transmission yields of transported ions are investigated. Our results indicate both the existence of a guiding effect when ions pass through the capillary and a significant dependence of the ion transmission on the energy and the charge state of the ions. The guiding effects are observed to be enhanced at lower projectile energies and higher charge states. Meanwhile, the results also exhibit that the transmission yields increase as the tilt angle decreases at a given energy and charge state.

Guiding of 150 keV O6+ ions through nanocapillaries in an uncoated Al2O3 membrane: special time dependence of the transmission profile width

This paper reports that the transmission of O6+ ions with energy of 150keV through capillaries in an uncoated Al2O3 membrane was measured, and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed. Due to using an uncoated capillary membrane, our c is larger than that using a gold-coated one with a smaller value of E-p/q, which suggests a larger equilibrium charge Q(infinity) in our experiment. The observed special width variation with time and a larger width than that using a smaller E-p/q were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation.

Interaction of 18-keV O{sup -} ions with Al{sub 2}O{sub 3} nanocapillaries

The transmission of 18-keV O- ions through Al2O3 nanocapillaries with 50 nm in diameter and 12 mu m in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV O-) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (O-, O-0, and O+) decreased when the tilt angle increased. In transmitted particles, the fraction of O- declined but that of O-0 and O+ ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.The transmission of 18-keV O{sup -} ions through Al{sub 2}O{sub 3} nanocapillaries with 50 nm in diameter and 12 {mu}m in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV O{sup -}) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (O{sup -}, O{sup 0}, and O{sup +}) decreased when the tilt angle increased. In transmitted particles, the fraction of O{sup -} declined but that of O{sup 0} and O{sup +} ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.

Guiding of 60 keV O6+ Ions through Nanocapillaries in an Uncoated Al2O3 Membrane

We measure the transmission of O6+ ions with a higher energy of 60keV (in turn a higher value of Ep/q) through capillaries in an uncoated Al2O3 membrane, and obtain agreements with previously reported results in general angular distribution of the transmitted ions and the transmission profile width variation with capillary tilt angle. The transmission fractions as a function of the tilt angle can be fitted to the semi-empirical Gaussian-like function well. Due to using uncoated capillary membrane, our Ψc is larger than that using gold-coated one, in spite of our larger value of Ep/q, which suggests a larger equilibrium charge Q∞ in our experiment.