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Electronic transport properties of porous Si nanowires either with embedded Si quantum dots or with a percolative crystalline path are studied as a function of the temperature for the first time. We show that unlike bulk porous Si, the predesigned structure of the wires results in a single distinct conduction mechanism such as tunneling in the former case and variable range hopping in the latter case. We demonstrate that the geometry of the systems with a large internal surface area and high density of the Si quantum dots have a significant conduction enhancement compared to bulk porous silicon. These results can also improve the understanding of the basis of the different electronic transport mechanisms reported in bulk porous silicon.

Magnetic force microscopy (MFM) is a valuable technique to investigate the reversal mechanisms of the magnetization in micrometric and sub-micrometric-patterned thin films that cannot be studied by means of magneto-optical methods because of their limited resolution. However, acquiring tens or hundreds of images consecutively at different applied magnetic fields is often impossible or impractical. Therefore, a field-dependent MFM-derived technique is discussed and applied on square and circular dots of different materials (Ni80Fe20, Co67Fe4Si14.5B14.5, Fe78Si9B13) having sizes ranging from 800?nm to 20??m. Experimental local hysteresis loops are obtained by properly analysing the phase signal of the MFM along a selected profile of the studied patterned structure, as a function of the applied magnetic field. Characteristic features of the magnetization process, such as vortex nucleation and expulsion, transition from C-state to saturated state or domain wall motion in Landau-like domain configuration are identified, and their evolution with the applied field is followed. The necessity to combine experimental and theoretical analyses is addressed by micromagnetic simulations on a model system (a Ni80Fe20 square dot with a lateral size of 800?nm), comparable to one of the studied samples. The agreement between experimental and simulated MFM maps, at different applied fields, and hysteresis loops provides the necessary validation for the technique. Additionally, the simulations have been proven to be necessary to understand the magnetization reversal processes occurring in the studied sub-micrometric structures and to associate them with characteristic features of the hysteresis loops measured with the proposed technique.

The growing interest in the development of nano-superconducting quantum interference devices (nanoSQUIDs) and their applications in nanoscience demands a deep study of these ultra-high-sensitivity nanodevices.In this paper, the main features of niobium planar nanointerferometers as a function of the temperature have been investigated. In particular, two types of nanodevices have been realized and studied: one based on nanobridges and the other on sub-micron Josephson tunnel junctions (JTJs).The nanobridge-based nanointerferometer, fabricated by electron beam lithography (EBL), consists of a sub-micrometric loop (effective area of 0.5 μm2), interrupted by two Dayem nanobridges having a width and length of 50 and 80 nm respectively. The JTJs-based nanointerferometer has two Nb/Al-AlOx/Nb SNIS (superconductor/normal-insulator/superconductor) junctions with an area of 0.09 μm2, connected by a rectangular loop (1 μm × 0.2 μm), and realized by the three-dimensional focused ion beam (3D FIB) sculpting technique. For both nanodevices, measurements of current–voltage characteristics and critical current versus external magnetic flux have been performed at operating temperatures ranging from 4.2 to 1.2 K. The critical current modulation depths, magnetic flux to current transfer factor (current responsivity) and magnetic flux resolution as a function of the temperature have been evaluated for both nanosensors. Furthermore, measurements of the voltage–magnetic flux characteristics and the spectral density of magnetic flux noise have been performed at T = 4.2 K.