The (220) lattice spacing of a silicon crystal was measured by combined x-ray and optical interferometry to about 3×${10}^{\mathrm{-}8}$ relative accuracy. The value obtained is ${\mathit{d}}_{220}$=192015.551±0.005) fm. After correcting for the impurity-induced lattice contraction, ${\mathit{d}}_{220}$=192015.569±0.006 fm is obtained

We analyzed the physical properties of hydrogenated amorphous silicon (a-Si:H) samples grown by plasma-enhanced chemical vapor deposition, by means of infrared spectroscopy, mass-density, and optical measurements. We applied the usual infrared spectroscopic techniques to evaluate the amount of incorporated hydrogen and to investigate the influence of the Si-H bonding configurations on the optical and electronic properties of a-Si:H obtained by this widely used deposition process, and with parameters so chosen as to obtain films having state of the art characteristics. We carried out an exhaustive study of the different infrared absorption peaks, generally ascribed to different bonding configurations of H in Si, with a view to distinguishing the different contributions of SiH, ${\mathrm{SiH}}_2$ (${\mathrm{SiH}}_2$ ${)}_{\mathit{n}}$ to the spectral response of the material and to relating them to deposition temperature. The correlation of this infrared spectral analysis with mass-density measurements has evidenced that, for hydrogen content below 10 at. %, isolated SiH and ${\mathrm{SiH}}_2$ bonds occur, whereas, with higher hydrogen concentrations, the formation of (${\mathrm{SiH}}_2$ ${)}_{\mathit{n}}$ chains gives rise to empty cavities where hydrogen is preferentially incorporated. In addition, optical measurements show that samples deposited at temperatures below 170 °C exhibit energy gaps and defect densities, which are quite different to those expected if only the effects of SiH groups are considered.

We report on the systematic characterization of photoluminescence (PL) lifetimes in NV${}^{$-${}}$ and NV${}^{0}$ centers in 2-MeV H${}^{+}$-implanted type Ib diamond samples by means of a time-correlated single-photon counting (TCSPC) microscopy technique. A dipole-dipole resonant energy transfer model was applied to interpret the experimental results, allowing a quantitative correlation of the concentration of both native (single substitutional nitrogen atoms) and ion-induced (isolated vacancies) PL-quenching defects with the measured PL lifetimes. The TCSPC measurements were carried out in both frontal (i.e., laser beam probing the main sample surface along the same normal direction of the previously implanted ions) and lateral (i.e., laser beam probing the lateral sample surface orthogonally with respect to the same ion implantation direction) geometries. In particular, the latter geometry allowed a direct probing of the centers lifetime along the strongly nonuniform damage profiles of MeV ions in the crystal. The extrapolation of empirical quasiexponential decay parameters allowed the systematic estimation of the mean quantum efficiency of the centers as a function of intrinsic and ion-induced defect concentration, which is of direct relevance for the current studies on the use of diamond color centers for photonic applications.