PET Nanocapillaries Research Articles

Charge deposition dependence of electron transmission through PET nanocapillaries and a tapered glass microcapillary

Abstract Charge deposition dependences of electron transmission through insulating PET nanocapillaries and a tapered glass microcapillary are reported and differences with HCI transmission are noted. Investigations were conducted for electrons with incident energies 500–1000 eV, corresponding to energies per charge similar to those used for HCI studies, incident on (1) an array of PET nanocapillaries (density ∼5 × 108/cm2) with diameters 100 nm in a foil of thickness 12 μm, and (2) on a tapered glass microcapillary with inlet/outlet diameters of 800/100 μm and a length of ∼35 mm. The transmission was measured for incident electrons at small sample tilt angles ranging from 0° to 5° with respect to the beam direction. For most angles, including those near zero degrees, there was an initial quiet period during which essentially no transmission was observed, followed by large rises in the transmission during relatively short periods of charge deposition before equilibrium of the transmission was reached. The resulting equilibrium was stable, blocked or had frequent oscillations depending on the incident energy and the capillary used. Observations for both capillaries show that a negative charge patch is needed to guide incident electrons through the capillaries similar to the manner in which HCIs are guided through capillaries.

Sample deterioration in electron guiding through PET nanocapillaries

Follow-up measurements for the transmission of 500 eV electrons through the same PET nanocapillary foil used in earlier work [PRA 76, 042716 (2007)] have been performed. It is found that considerable deterioration of the sample apparently occurred since the earlier work as manifested in substantial reduced transmission intensities and greater fall-off of these intensities with increasing foil tilt angle. It is postulated that surface contamination or an increase in capillary conductivity, or both, causing an inability to maintain charge in the entrance region, led to the observed sample deterioration.

Transmission of fast highly charged ions through Al2O3 and PET nanocapillaries

Transmission of 16 MeV O5+ ions through Al2O3 and PET nanocapillary foils has been investigated. We find that O5+ is transmitted without energy loss for both foils, with little evidence of transmission for other charge states. However, for the PET foil at a detector position slightly displaced from the transmitted O5+ peak, we find large intensities of transmitted ions that have lost considerable energy. It is speculated that these peaks are due to nearly head-on collisions of the incident O5+ ions with carbon and hydrogen atoms in the PET sample.

Density effects on the guided transmission of 3 keV Ne7+ ions through PET nanocapillaries

Experiments for guided transmission of 3keV Ne7+ ions through nanocapillaries in insulating PET polymers are reported. The ion guiding was studied for a two types of PET samples which consist of 200nm capillaries with densities of 1×108cm-2 and 4×106cm-2. The width of the emission profile and the fraction of transmitted ions were measured as a function of the capillary tilt angle. For the high capillary density the profile width of the transmitted ions is independent of the tilt angle in agreement previous studies. However, for the low-density sample the profile width was found to increase by a factor of 2 as the tilt angle increases from 0° to 8°. The results for the fraction of transmitted ions are used to evaluate the guiding angle, which specifies the guiding power of the material. The guiding powers were found to be equal for the two samples. The present results are discussed in terms of scaling laws, which have recently been established.

Guiding of highly charged ions through nanocapillaries in PET: Dependence on the projectile energy and charge

We measured the energy and charge state dependence of the transmission of highly charged ions through nanocapillaries with a diameter of 200nm and a length of 10μm. The nanocapillaries were produced by etching ion tracks originating from 250MeV krypton ions passed through PET polymer foils leading to a significant improvement in the parallelism of the capillaries to former used capillary foils. This improvement allowed us to investigate the guiding effect over a wider range in energy and charge state than done before. In accordance with model calculations, the experimental results show a scaling law describing the dependence of the integrated ion transmission on tilt angle, energy and charge state of the incident ions. The scaling law for capillaries with high parallelism are found to be applicable in a wide range of energies and charge states. New parameters describing the capability of a capillary foil to guide highly charge ions were derived.

Two-dimensional images of transmitted slow neon ions guided by nanocapillaries in polymer foils

We have measured two-dimensional images of 3.5–7keV Ne7+ ions guided by PET nanocapillaries as a function of the deposited charge. The transmitted ion position and shape are found to change with the intensity evolution. After saturation of the guided ion intensity, the transmission profile is nearly isotropic and its angular width amounts to about 1°, which differs from previous measurements.

Guiding of slow neon and molecular hydrogen ions through nanocapillaries in PET

The transmission profiles of atomic 3keV Ne7+ ions and molecular 1keV H2+ and H3+ ions passing through nanocapillaries were studied. Capillaries with a diameter of 100nm and a length of 10μm in insulating PET polymers were used. The high aspect ratio of 100 is achieved by the method of etching ion tracks produced by high-energy xenon impact. The angular distributions of the transmitted projectiles show that the majority of ions are transported in their initial charge state along the capillary axis even when the capillaries are tilted with respect to the incident beam direction. This result indicates ion-guiding, which is produced by charge-up effects influencing the ion trajectories in a self-supporting manner. The guiding effects are found to be different for highly charged neon and singly charged molecular hydrogen. Negligible fragmentation of the molecular ions was observed.

Guided transmission of highly charged ions through nanocapillaries in PET: Study of the energy dependence

We measured the energy dependence of the transmission of Ne 7+-ions through nanocapillaries with 100 nm diameter and 10 μm lengths in an energy range from 1 keV up to 10 keV. The nanocapillaries were produced by etching ion tracks originating from 100 MeV xenon ions passed through PET polymer foils. The foils were tilted at angles up to 20°, so that the incident ions were forced to interact with the capillary surface. Capillary guiding as the result of ion deflection through charges deposited at the inner wall is found for tilt angles up to 20°. The dependence of this effect on the projectile energy is studied in detail. Using a model describing the guiding effect, the attempt is made to determine the energy dependence of the model parameters.

Guiding of slow highly charged ions by nanocapillaries in PET

We measured the transmission of 7 keV Ne 7+ ions through capillaries of 100 nm diameter and 10 μm length produced by etching ion tracks in a polyethylene terephthalate polymer foil. The charge and the angular distribution of the transported ions are investigated. Good agreement with the data, published by Stolterfoht [Phys. Rev. Lett. 88 (2002) 133201] is found. However, we found a measurable dependence of the full width at half maximum (FWHM) of the transported ions as a function of the guiding angle.

Guided transmission of Ne 7+ ions through nanocapillaries in PET: dependence on the tilt angle

We measured the transmission of 3 keV Ne 7+ ions through nanocapillaries of 100 nm diameter and 10 μm length in a PET polymer foil. The capillaries were produced before the transmission experiments by etching tracks of fast xenon ions. The foils were tilted up to 15° for which the incident ions are forced to approach the capillary surface. After a characteristic time the majority of Ne 7+ ions were found to be transmitted in their initial charge state. The angular distributions of the transmitted Ne 7+ projectiles reveals a propagation of the ions parallel to the capillary axis. This indicates that the ions are guided through the capillaries. The capillary guiding is the result of deposit of charges in a self-organizing process. A non-linear model is presented to interpret the experimental observation. The analysis exhibits a significant dependence of the ion transmission on the tilt angle.