Determination of the thermodynamic temperature between 236 K and 430 K from speed of sound measurements in helium

We report speed of sound measurements in helium at 273.16 K and at eight temperatures in the range between 236 K and 430 K. These results determine the difference (T  −  T 90) between the thermodynamic temperature T and its approximation T 90 by the International Temperature Scale of 1990 (ITS-90). The uncertainty of our measurements of (T  −  T 90) spans between a minimum of 0.25 mK near 247 K and a maximum of 0.89 mK at the freezing point of indium (429.75 K) with comparable contributions from the uncertainty of our acoustic determination of T and from the uncertainty of our laboratory realization of ITS-90. On the overlapping temperature ranges these results are consistent with other recent acoustic determinations of (T  −  T 90). We also present evidence that (T  −  T 90) can be determined with comparably small uncertainties by the alternative, time-saving procedure of measuring the speed-of-sound in helium using only a single, judiciously-chosen, pressure on each isotherm

influence of block copolymer feature size on reactive ion etching pattern transfer into silicon

A successful realisation of sub-20 nm features on silicon (Si) is becoming the focus of many technological studies, strongly influencing the future performance of modern integrated circuits. Although reactive ion etching (RIE), at both micrometric and nanometric scale has already been the target of many studies, a better understanding of the different mechanisms involved at sub-20 nm size etching is still required. In this work, we investigated the influence of the feature size on the etch rate of Si, performed by a cryogenic RIE process through cylinder-forming polystyrene-block-polymethylmethacrylate (PS-b-PMMA) diblock copolymer (DBC) masks with diameter ranging between 19–13 nm. A sensible decrease of the etch depth and etch rate was observed in the mask with the smallest feature size. For all the DBCs under investigation, we determined the process window useful for the correct transfer of the nanometric cylindrical pattern into a Si substrate. A structural and physicochemical investigation of the resulting nanostructured Si is reported in order to delineate the influence of various RIE pattern effects. Feature-size-dependent etch, or RIE-lag, is proved to significantly affect the obtained results

Nanometrology

In the present paper an overview of metrology at the nanometric scale is given. After an introductory part on terminology and definitions concerning generic objects at the nanoscale, nanoparticles are taken as example to describe the overall features of these systems and typical characterization issues occurring from a metrological point of view. The case of nanoparticles is then further examined in depth with reference to gold nanoparticles, whose peculiar properties deriving from nano-scaled effects, like surface plasmon resonance, are discussed in detail, along with the state of the art on the main fabrication methods and applications in different sectors. Finally, a case study on the detection, by gold nanoparticles, of a contaminant used for food adulteration, namely melamine, is presented and analyzed

Submicron machining and biomolecule immobilization on porous silicon by electron beam

Three-dimensional submicrometric structures and biomolecular patterns have been fabricated on a porous silicon film by an electron beam-based functionalization method. The immobilized proteins act as a passivation layer against material corrosion in aqueous solutions. The effects' dependence on the main parameters of the process (i.e., the electron beam dose, the biomolecule concentration, and the incubation time) has been demonstrated

Refractive index gas thermometry between 13.8 K and 161.4 K

We have measured the refractive index of helium using a quasi-spherical copper microwave resonator at five different temperatures in the interval between the triple point of hydrogen at 13.8 K and the triple point of xenon at 161.4 K for pressures up to 380 kPa. From these results and additional measurements of the refractive index of neon near 54.4 K, 83.8 K and 161.4 K we determine the differences (T - T90) between the thermodynamic temperature T and its approximation T90 by the International Temperature Scale of 1990 (ITS-90). We have estimated the isothermal compressibility of copper and the effective compressibility of our microwave resonator by different methods including resonant ultrasound spectroscopy (RUS) and microwave measurements with helium at 273.16 K. We compare the results of these compressibility estimates and discuss the associated uncertainty. From the refractive index measurements, we estimate the second density virial coefficient of helium and neon which are found in good agreement with the ab initio calculations of the same properties