Dynamics of colloids in single solid-state nanopores.

We use solid-state nanopores to study the dynamics of single electrically charged colloids through nanopores as a function of applied voltage. We show that the presence of a single colloid inside of the pore changes the pore resistance, in agreement with theory. The normalized ionic current blockade increases with the applied voltage and remains constant when the electrical force increases even more. We observe short and long events of current blockades. Their durations are associated, respectively, with low and high current variation. The ratio of long events increases with the electrical force. The events frequency increases exponentially as a function of applied voltage and saturates at high voltage. The dwelling time decreases exponentially at low and medium voltages when the electrical force increases. At large voltages, this time decreases inversely proportionally to the applied voltage. The long events are associated with translocation events. We show that the dynamics of colloids through the nanopore is governed mainly by two mechanisms, by the free-energy barrier at relatively low and medium voltages and by the electrophoresis mechanism at high voltage.

Magnetization reversal in Pt/Co(0.5 nm)/Pt nano-platelets patterned by focused ion beam lithography.

Arrays of ultrathin Pt/Co(0.5 nm)/Pt nano-platelets with lateral sizes ranging from 30 nm to 1 µm have been patterned by focused ion beam (FIB) lithography under a weak Ga(+) ion fluence. From polar magneto-optical Kerr microscopy it is demonstrated that nano-platelets are ferromagnetic with perpendicular anisotropy down to a size of 50 nm. The irradiation process creates a magnetically soft ring at the nano-platelet periphery in which domain nucleation is initiated at a low field. The magnetization reversal in nano-platelets can be interpreted using a confined droplet model. All of the results prove that ultimate FIB patterning is suitable for preparing discrete magnetic recording media or small magnetic memory elements and nano-devices.

Epitaxial graphene on cubic SiC(111)Si(111) substrate.

Epitaxial graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of epitaxial graphene films on 3C-SiC(111)Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.

Local tuning of CoPt nanoparticle size and density with a focused ion beam nanowriter.

Ultra-small CoPt nanoparticles (NPs) with a mean diameter of 1.3 nm (around 100 atoms) were deposited on a thin 5 nm self-supported amorphous carbon membrane. The effects of focused irradiation with a newly developed Ga(+) ion source were studied by transmission electron microscopy. While the overall coverage of the NPs remained constant, the mean diameter and the density of the NPs evolve in the dose range from 5 x 10(13) to 1 x 10(15) ions cm(-2). The local tuning of the size and density of CoPt NPs by means of ion irradiation could be used in magnetic data storage applications.

Single-shot diffractive imaging with a table-top femtosecond soft x-ray laser-harmonics source.

Coherent x-ray diffractive imaging is a powerful method for studies on nonperiodic structures on the nanoscale. Access to femtosecond dynamics in major physical, chemical, and biological processes requires single-shot diffraction data. Up to now, this has been limited to intense coherent pulses from a free electron laser. Here we show that laser-driven ultrashort x-ray sources offer a comparatively inexpensive alternative. We present measurements of single-shot diffraction patterns from isolated nano-objects with a single 20 fs pulse from a table-top high-harmonic x-ray laser. Images were reconstructed with a resolution of 119 nm from the single shot and 62 nm from multiple shots.

Exploration of the ultimate patterning potential achievable with focused ion beams.

Decisive advances in the field of nanosciences and nanotechnologies are intimately related to the development of new instruments and of related writing schemes and methodologies. Therefore we have recently proposed the exploitation of the nano-structuring potential of a highly focused ion beam (FIB) as a tool, to overcome intrinsic limitations of current nano-fabrication techniques and to allow innovative patterning schemes that are urgently needed in many nanoscience challenges. In this work, we will first detail a very high-resolution FIB instrument we have developed specifically to meet these nano-fabrication requirements. Then we will introduce and illustrate an advanced FIB processing scheme that is the fabrication of artificial nanopores.

Ion beam nanopatterning in graphite: characterization of single extended defects.

The morphology and the electronic structure of a single focused ion-beam-induced artificial extended defect is probed by several methods including micro-Raman spectroscopy, atomic force and scanning tunneling microscopies and Monte Carlo and/or semi-analytical simulation within standard codes. The efficiency of the artificial defect for deposited metallic cluster pinning is also investigated. We show a correlation between the ion dose, morphology, electronic structure and cluster trapping efficiency. At room temperature, cluster pinning is efficient when the displacement per atom is one or more. Well-ordered patterned cluster networks are considered for potential applications.