Swift heavy ion irradiation of GaSb: from ion tracks to nano-porous networks

Ion track formation, amorphisation, and the formation of porosity in crystalline GaSb induced by 185 MeV $^{197}$Au swift heavy ion irradiation is investigated as a function of fluence and irradiation angle relative to the surface normal. RBS/C and SAXS reveal an ion track radius between 3 nm and 5 nm. The observed pore morphology and saturation swelling of GaSb films shows a strong irradiation angle dependence. Raman spectroscopy and scanning electron microscopy show that the ion tracks act as a source of strain in the material leading to macroscopic plastic flow at high fluences and off normal irradiation. The results are consistent with the ion hammering model for glasses. Furthermore, wide angle X-ray scattering reveals the formation of nano crystallites inside otherwise amorphous GaSb after the onset of porosity

Transverse rectification in density-modulated two-dimensional electron gases

We demonstrate tunable transverse rectification in a density-modulated two-dimensional electron gas (2DEG). The density modulation is induced by two surface gates, running in parallel along a narrow stripe of 2DEG. A transverse voltage in the direction of the density modulation is observed, i.e. perpendicular to the applied source-drain voltage. The polarity of the transverse voltage is independent of the polarity of the source-drain voltage, demonstrating rectification in the device. We find that the transverse voltage $U_{y}$ depends quadratically on the applied source-drain voltage and non-monotonically on the density modulation. The experimental results are discussed in the framework of a diffusion thermopower model.Comment: 8 pages, 9 figures, published in PR

Supplementary Material for: Individual Characteristics and Physical Activity in Older Adults: A Systematic Review

<p><b><i>Background:</i></b> People aged 50 years and older are regularly identified as the most sedentary group in the population. However, even within this group, there are considerable interindividual variations in physical activity (PA) levels. They have been the subject of many studies. Based on single studies, no clear picture as to which characteristics are important has emerged. <b><i>Objective:</i></b> The goal of our contribution was to identify which individual characteristics are consistently linked to high PA levels in older adults. <b><i>Methods:</i></b> We conducted a systematic review of the literature considering demographic characteristics (gender, education, marital status, employment), health (subjective, health problems), and psychological factors (motivation, self-efficacy, locus of control). A systematic search of abstracts in the database Web of Science and a thorough screening process according to a priori specified criteria yielded 63 studies for inclusion in this review. <b><i>Results:</i></b> Two psychological factors - motivation and self-efficacy - and the perception of one's health seem to be consistently linked to higher PA levels in older adults. Selected demographic variables - gender and education - may be important for some types of PA. <b><i>Conclusion:</i></b> Our review suggests that differentiation of PA by domains is important for identifying and understanding which individual characteristics are associated with PA levels and how. Pinpointing what reliably distinguishes older adults who are active from those who are not is essential for designing effective interventions to promote PA in later life.</p

Grazing-incidence transmission SAXS investigation of conical etched ion tracks in SiO2

We present results of a systematic study of the morphology of etched ion tracks in amorphous SiO2 using a combination of small angle X-rays cattering (SAXS) and scanning electronmicroscopy. We focus on the analysis of SAXS data obtained in grazing incidence(GISAXS) configuration from conical etched channels with a base radius of less than 50nm. Swift heavy ion irradiation of 2 um thinck thermally grown Si02 layers wer with the 185 MeV Au ions was conducted at the ANU Heavy Ion Accelerator Facility in Canberra, Australia. Low irradiation fluences of 109 ions per cm2 were chosen to minimize overlap of the etched structures. Irradiated samples were etched in aqueous hydrofluoric acid (HF) with concentrations of 5%, for etching times between 30 and 90s. In grazing incidence configuration, we obtain good data quality from the very small cones,since the X-raybeam interacts with a greater proportion of the sample at the very low incidence angle compared with normal transmissionmode.This research was supported by an Australian Government Research Training Program (RTP) Scholarship. The authors also acknowledge financial support from the Australian Research Council (ARC) and the German Research Foundation (DFG

Etched ion tracks in amorphous SiO₂ characterized by small angle x-ray scattering: Influence of ion energy and etching conditions

Small angle x-ray scattering was used to study the morphology of conical structures formed in thin films of amorphous SiO2. Samples were irradiated with 1.1 GeV Au ions at the GSI UNILAC in Darmstadt, Germany, and with 185, 89 and 54 MeV Au ions at the Heavy Ion Accelerator Facility at ANU in Canberra, Australia. The irradiated material was subsequently etched in HF using two different etchant concentrations over a series of etch times to reveal conically shaped etched channels of various sizes. Synchrotron based SAXS measurements were used to characterize both the radial and axial ion track etch rates with unprecedented precision. The results show that the ion energy has a significant effect on the morphology of the etched channels, and that at short etch times resulting in very small cones, the increased etching rate of the damaged region in the radial direction with respect to the ion trajectory is significant