Electron beam induced deposition (EBID) is a process used for the fabrication of three-dimensional nanostructures of a variety of materials, but direct deposition of pure metallic structures has rarely been achieved. Typically, MeCpPtMe3 as a precursor for Pt leads to a carbon rich deposit with ~15 at.% Pt, which negatively affects its application as an electrical contact. We report a new process for Pt purification: in situ annealing with electron beam post-irradiation under oxygen flux, which can completely purify a thin (<100 nm) Pt EBID structure at substrate temperatures as low as 120 °C. We have developed a sequential method in which a thin Pt EBID structure is deposited on a previously purified structure and subsequently purified. The resistivity of the contact grown by this sequential procedure is observed to be ~70 ± 8 μΩ cm-only six times higher than that of pure bulk Pt. Thus, sequential deposition and purification proves to be an effective method for fabricating pure Pt structures of desired dimensions.

No abstract

A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with Monte Carlo simulations of the new pCT system are reported. The digital tracking calorimeter is a multilayer structure with a lateral aperture of 27 cm × 16.6 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and two additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker's structure only differs from the calorimeter layers for the carrier made of ∼200 μm carbon fleece and carbon paper (carbon-epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALICE pixel detector (ALPIDE) chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50-220 MeV/u) proton and ion beams at the

Using scanning tunneling microscopy and a diffraction experiment, we have discovered a new ordered surface alloy made out of two bulk-immiscible components, Fe and Au, deposited on a Ru(0001) substrate. In such a system, substrate-mediated strain interactions are believed to provide the main driving force for mixing. However, spin-polarized ab initio calculations show that the most stable structures are always the ones with the highest magnetic moment per Fe atom and not the ones minimizing the surface stress, in remarkable agreement with the observations. This opens up novel possibilities for creating materials with unique properties of relevance to device applications.