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In order to calibrate leak-detection instruments, devices based on permeation leaks and physical leaks are used. Unfortunately, permeation leaks are very sensitive to small temperature fluctuations and can be used only with those gases for which permeating materials are available. While, physical-leaks that overcome these restrictions are susceptible to clog, in particular when the gas flow through them is in viscous regime. Furthermore, for many type of leak devices, the conductance is not predictable based on dimensional, gas species and temperature data, for this reason no estimates or only rough estimates of leak rates are possible for conditions under use where they differ from those of the calibration. Here, we present the fabrication and characterization of a new kind of physical-leak devices based on nano-holes, which overcome these problems. Nano-holes, with diameters less than or equal to 200 nm, work in molecular-flow regime up to atmospheric pressure and for this reason they do not clog. The nano-holes are manufactured by milling a silicon nitride membrane by means of Focused Ion Beam (FIB), and their shapes are characterized by both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Because of the capability of the AFM to acquire surface three-dimensional images with very high resolution, it is a very useful tool to perform a topographic characterization of the nano-holes.

We present data concerning the electrical properties of a class of biosensor devices based on bio-functionalized solid state nanopores able to detect different kinds of interactions between probe molecules, chemically attached to the pore surface, and target molecules present in solution and electrophoretically drawn through the nanometric channel. The great potentiality of this approach resides in the fact that the functionalization of a quite large pore (up to 50-60 nm) allows a sufficient diameter reduction for the attainment of a single molecule sensing dimension and selective activation, without the need for further material deposition, such as metal or oxides, or localized surface modification. The results indicate that it will be possible, in the near future, to conceive and design devices for parallel analysis of biological samples made of arrays of nanopores differently functionalized, fabricated by standard lithographic techniques, with important applications in the field of molecular diagnosis.

We study the morphological evolution of surfaces during ion sputtering and we compare their dynamical roughening with aeolian ripple formation in sandy deserts. We show that the two phenomena can be described within the same theoretical framework. This approach explains the different dynamical behaviors experimentally observed in metals or in semiconductors and amorphous systems. In the case of ion erosion, we find exponential growth at constant wavelength up to a critical roughness $W_c$. Whereas, in metals, by introducing the contribution of the Erlich-Schwoebel barrier, we find a transition from an exponential growth to a power law evolution., 7 pages, 4 figures