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In situ small angle X-ray scattering (SAXS) measurements of ion track etching in polycarbonate foils are used to directly monitor the selective dissolution of ion tracks with high precision, including the early stages of etching. Detailed information about the track etching kinetics and size, shape, and size distribution of an ensemble of nanopores is obtained. Time resolved measurements as a function of temperature and etchant concentration show that the pore radius increases almost linearly with time for all conditions and the etching process can be described by an Arrhenius law. The radial etching shows a power law dependency on the etchant concentration. An increase in the etch rate with increasing temperature or concentration of the etchant reduces the penetration of the etchant into the polymer but does not affect the pore size distribution. The in situ measurements provide an estimate for the track etch rate, which is found to be approximately three orders of magnitude higher than the radial etch rate. The measurement methodology enables new experiments studying membrane fabrication and performance in liquid environments.

We present results of a systematic study of the morphology of etched ion tracks in amorphous SiO2 using a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy. 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 50 nm. Swift heavy ion irradiation of 2 μm thick thermally grown SiO2 layers with 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 90 s. In grazing incidence configuration, we obtain good data quality from the very small cones, since the X-ray beam interacts with a greater proportion of the sample at the very low incidence angle compared with normal transmission mode.

Carbon-fibre reinforced composites are seeing increased deployment, especially in the aerospace industry, and the next-generation of these materials will need to meet demanding performance requirements beyond just specific strength. The incorporation of nanomaterials such as graphene into composites has great potential for enhancing electrical, thermal, and mechanical properties, which could then enable new capabilities such as built-in lightning strike protection and electromagnetic shielding. One major challenge is successful integration of nanomaterials into the composite during the manufacturing process especially for thermoplastic based composites. This work explores the spray deposition of exfoliated graphene in liquid suspensions for the nano-enhancement of electrical properties in carbon-fibre reinforced polyether ether keytone (PEEK) composites. Developed thin films were smooth with RMS roughness of 1.06 μm on Si substrates and RMS roughness of 1.27 μm on CF-PEEK tapes. The addition of 1.3 wt% graphene into the interlayers of CF-PEEK composites resulted in bulk electrical conductivity enhancement both in plane and through thickness of ~ 1100% and 67.5% respectively. This approach allows for pre-consolidation introduction of high-performance nanomaterials directly to thermoplastic prepregs which could open simple pathways for the in-situ manufacturing of carbon-fibre reinforced polymer nanocomposites.

We investigate the effects of direct deposition of different dielectric materials (AlOx, SiOx, SiNx) onto atomically thin TMDC WS2 on its optical response using atomic layer deposition (ALD), electron beam evaporation (EBE), plasma-enhanced chemical vapor deposition (PECVD), and magnetron sputtering. The photoluminescence measurements reveal quenching of the excitonic emission after all deposition processes, which is linked to the increased level of charge doping and associated rise of the trion emission and/or the localized (bound) exciton emission. Furthermore, Raman spectroscopy allows us to clearly correlate the observed changes in excitonic emission with the increased levels of lattice disorder and defects. In particular, we show that the different doping levels in a monolayer WS2 capped by a dielectric material are strongly related to the defects in the WS2 crystal introduced by all capping methods, except for ALD. The strong charge doping in the ALD-capped sample seems to be caused by other factors, such as deviations in the dielectric layer stoichiometry or chemical reactions on the monolayer surface, which makes ALD distinct from all other techniques. Overall, the EBE process results in the lowest level of doping and defect densities and in the largest spectral weight of the exciton emission in the PL. Sputtering is revealed as the most aggressive dielectric capping method for WS2, fully quenching its optical response. Our results demonstrate and quantify the effects of direct deposition of dielectric materials onto monolayer WS2, which can provide valuable guidance for the efforts to integrate monolayer TMDCs into functional optoelectronic devices.

We present the shape transformation of a single layer of Au nanoparticles (NPs) when embedded in, and at the interface of, amorphous $\mathrm{Si}{\mathrm{N}}_{\mathrm{x}}$ and $\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$ ($\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{\mathrm{x}}$ and $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$) thin films upon irradiation with 185-MeV Au ions to fluences ranging from 0.3 to $30\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}2}$. Transmission electron microscopy (TEM) and high angular annular dark field microscopy were used to study the ion-shaping process. The former allows us to follow the overall change in geometry, size, and structure, while the latter reveals information about the relative position with respect to the interface. For Au NPs embedded in a single material, a lower elongation rate for $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{\mathrm{x}}$ was found in comparison to $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$. When at the interface of the two materials, TEM reveals a preferential elongation towards $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$. The latter demonstrates the use of $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{\mathrm{x}}$ for confining the ion-shaping process within an intermediate $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$ layer. The simulation of the temperature evolution during a single-ion impact was used to understand the difference in elongation rates between $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{\mathrm{x}}$ and $\mathrm{a}\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$, as well as the asymmetric behavior when located at the interface using the three-dimensional inelastic thermal spike model with bulk thermophysical properties. The calculations show good agreement with the experimental observations and reveal a correlation between the thermal profile and the resulting NP geometry.

Silicon oxynitrides (a-SiO x N y ) are materials whose composition ranges between two binary materials: a-SiO2 and a-Si3N4. In this work, we present a systematic study of the fine structure of the damaged regions produced by swift heavy-ions (SHIs), or ‘ion-tracks’ and quantify the density variation profiles with respect to composition. Thin films were deposited by plasma-enhanced chemical vapor deposition (CVD), where thickness, density, stoichiometry and bond configuration were initially determined. The fine structure and radial size of the ion tracks was determined using small angle x-ray scattering. The tracks exhibit a core–shell cylindrical geometry, with an under-dense core surrounded by an over-dense shell with a smooth transition between the two regions. We observed two trends with composition: a constant increasing ion track radius is observed when the O/Si ratio is below one ( 0 ≤ x ≤ 1 ) . And saturation of the radial dimensions above this value, being similar to a-SiO2. The IR spectra allowed to quantify the bond configuration and its evolution with fluence. After irradiation, the energy deposited by the SHI irradiation leads to a preferential damage of Si–N bonds. IR spectroscopy also showed the formation of new Si–H bonds with increasing fluences and resulting in a rather complex ion-induced structural modification of the a-SiO x N y network.

We present a systematic study of the evolution of chemically etched ion tracks formed in thermally grown a-SiO2 after irradiation with 1.1 GeV and 185 MeV Au ions. The irradiated material was subsequently etched with 2.5% hydrofluoric acid (HF) for different times yielding hollow conical shaped structures of various sizes. The characterisation of these structures was carried out by synchrotron-based small-angle X-ray scattering (SAXS) measurements, enabling the determination of the geometry and dimensions of the etched conical structures with sub-nanometre precision. The results indicate that the track etching behavior is influenced by the ion energy, and that at short etching times the latent track damage in the radial direction becomes significant.

High aspect-ratio nanopores of nearly cylindrical geometry were fabricated by irradiation of 20 μm thick polycarbonate (PC) foils with Pb ions followed by UV sensitization and etching in 5 M NaOH at 60 °C. Synchrotron-based small-angle X-ray scattering (SAXS) was used to study the morphology and size variation of the nanopores as a function of the etching time and ion fluence. The shape of the nanopores was found to be consistent with cylindrical pores with ends tapering off towards the two polymer surfaces in the last ~1.6 μm. The tapered structure of the nanopores in track-etched PC membranes was first observed more than 40 years ago followed by many other studies suggesting that the shape of nanopores in PC membranes deviates from a perfect cylinder and nanopores narrow towards both membrane surfaces. It was also reported that the transport properties of the nanopore membranes are influenced by the tapered structure. However, quantification of the shape of nanopores has remained elusive due to inherent difficulties in imaging the pores using microscopy techniques. The present manuscript reports on the quantitative measurement of the tapered structure of nanopores using SAXS. Determination of this structure was enabled by obtaining high quality SAXS data and the development of appropriate fitting models. The etch rates for both the radius at the polymer surface and the radius of the pore in bulk were calculated. Both etch rates decrease slightly with increasing fluence. This behavior is ascribed to the overlap of track halos which are characterized by cross-linking of the polymer chains. The halo radius was estimated to be approximately 120 nm. The influence of the observed nanopore shape on the pore transport properties was estimated and found to have a significant influence on the water flow rates compared to cylindrical pores. The results enable a better understanding of track-etched membranes and facilitate improved pore design for many applications.

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Small angle x-ray scattering was used to study the morphology of conical structures formed in thin films of amorphous SiO

Ion track formation, amorphization, and the formation of porosity in crystalline GaSb induced by 185 MeV $^{197}\mathrm{Au}$ swift heavy ion irradiation is investigated as a function of fluence and irradiation angle relative to the surface normal. Rutherford backscattering spectrometry in channeling configuration and small-angle x-ray scattering reveal an ion track radius between 3 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 nanocrystallites inside otherwise amorphous GaSb after the onset of porosity.

In(1–x)Al(x)Sb films with four Al relative concentrations (0, 20, 30 and 40%) were deposited using magnetron sputtering onto a SiO2/Si substrate and subsequently irradiated with 14 MeV Au6+ ions with fluences in the range of 1 × 1012–3 × 1014 cm−2. Grazing incidence X-ray diffraction analysis showed the formation of a polycrystalline compound structure with a zinc blende phase for all of the In(1–x)Al(x)Sb films. When irradiated, it is easier to amorphize ternary compound (In(1-x)Al(x)Sb) than its binary counterparts (InSb and AlSb), and there was no indication of the amorphous phase of AlSb or any other kind of irradiation-induced damage observed. In(1–x)Al(x)Sb films become porous after irradiation with sufficient fluence for all the Al concentrations studied (except AlSb) and for a given irradiation fluence, the higher the Al concentration in the film, the less porous it became after irradiation. In regard the chemical components on the surface of the films, X-ray photoelectron spectroscopy showed that there was no Al–Sb bonding on the surface and that there was a small increase in the relative amount of oxygen (except for Al 20%) in the irradiated samples when compared to non-irradiated ones.

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.

Electromagnetic levitation for containerless undercooling of bulk melts was combined with diffraction of synchrotron radiation to study in situ the crystallization of metastable phases in metals undercooled below their melting temperature prior to solidification. Energy dispersive X-ray diffraction was applied to identify the crystallographic phases formed during crystallization of the undercooled melt. The binary Ni–V alloy was chosen as a model system, because it shows phase competition of three different crystallographic phases, bcc, fcc and an intermetallic phase of tetragonal structure. In addition, the crystallization of undercooled melts of the easy glass-forming alloy Zr–Al–Ni–Cu was investigated.

Liquid samples of Co80Pd20 were cooled below their liquidus temperature Tl and supercooled towards the paramagnetic-ferromagnetic transition temperature TC(l) by means of the Electromagnetic Levitation (EML) technique. Muon-Spin Rotation (μSR) measurements were used to determine the spin precession frequency f and the transverse muon-spin relaxation rate Γ in the liquid supercooled sample at temperatures T > TC(l). Γ increases by a factor of 5 when T approaches TC(l), indicating large spin fluctuations caused by the onset of spontaneous magnetization. The temperature dependence of the inverse frequency shift Δf−1 reflects a Curie-Weiss behaviour of the paramagnetic susceptibility. The experiments strongly suggest the existence of ferromagnetic ordering in a liquid metal.

Physical review letters 86(6), 1038 - 1041 (2001). doi:10.1103/PhysRevLett.86.1038, Published by APS, College Park, Md.

The metastable state of an undercooled melt can provide access to the formation of metastable phases whose crystallographic structures differ from their stable counterparts. The electromagnetic levitation technique is used here to undercool bulk melts without containers. This technique, combined with energy dispersive x-ray diffraction of synchrotron radiation, allows in situ study of the rapid crystallization of undercooled Ni–V alloys. The binary Ni–V alloy was chosen as a model system, because it shows phase competition of three different crystallographic phases, bcc, fcc, and an intermetallic phase of tetragonal structure at intermediate concentrations. The diffraction experiments provide for direct identification of the various crystalline phases formed from the nonequilibrium state of the undercooled melt. The phase selection is investigated as a function of undercooling temperature for Ni–V alloys of different concentrations.

Electromagnetic levitation has been used to undercool an alloy of Co80Pd20 below the Curie temperature of the solid α phase. If the temperature of the undercooled liquid decreases below the Curie temperature an attractive force between the sample and an external permanent magnet was observed. This may indicate the existence of a metallic liquid showing magnetic ordering.