The APT used in this work is the CAMECA (CAMECA SAS, Gennevilliers Cedex, France) laser-assisted wide-angle tomographic Selleckchem OTX015 atom probe. The experiments were performed with samples cooled down to 80 K, with a vacuum of (2 to 3)×10−10 mbar in the analysis chamber and with ultraviolet (λ=343 nm) femtosecond (350 fs) laser pulses. The laser energy was fixed at 50 nJ/pulse focused onto an approximately 0.01-mm2 spot. To identify the clusters, the algorithm described hereafter was applied. Each

step of this identification comprises the placement of a sphere (sampling volume) over one atom of the volume investigated and the estimation of the local composition of the selected elements by counting atoms within this sphere. If the composition exceeds a given threshold, the atom at the center of the sphere is associated to a cluster. If the composition is lower than the threshold,

the atom at the center of the sphere belongs to the matrix. The sphere Apoptosis Compound Library in vitro is then moved to the next atom, and this procedure is applied again to estimate the composition and to compare it with the threshold value. This approach was used for all the atoms of the volume to identify those belonging either to the clusters or to the matrix. In this paper, a threshold of 75% of Si and 5% of Er was used to identify pure Si nanoclusters and Er-rich regions with a sphere radius of 1 nm. Photoluminescence Selleck Obeticholic Acid study The photoluminescence (PL) properties of the samples were examined using the 476-nm excitation line delivered by an Innova 90C coherent Ar+ laser (Coherent Inc., Santa Clara, CA, USA). The pumping at 476 nm, which is nonresonant for Er3+ ions,

was always used to ensure that Er3+ excitation was mediated by the Si-based sensitizers. The Er3+ PL spectra in the 1.3- to 1.7-μm spectral range were measured at room temperature by means of a Jobin Yvon (HORIBA Jobin Yvon Inc., Edison, NJ, USA) 1-m single-grating monochromator coupled to a North Coast germanium detector (North Coast Scientific Co., Santa Rosa, CA, USA) cooled with liquid nitrogen. The Si-nc PL properties were investigated in the 550- to 1,150-nm spectral range using a Triax 180 Jobin Yvon monochromator with an R5108 Hamamatsu PMT (HAMAMATSU PHOTONICS DEUTSCHLAND GmbH, Herrsching am Ammersee, Germany). The PL signal was recorded in both cases through an SRS lock-in amplifier (SP830 DPS; Stanford Research Systems, Inc., Sunnyvale, CA, USA) referenced to the chopping frequency of light of 9.6 Hz. All PL spectra were corrected on the spectral response of experimental setup. Results and discussion Photoluminescence spectra The PL spectra, recorded on the as-deposited layer and after different annealing treatments, are reported in Figure 1. The highest PL intensity in the 500- to 950-nm spectral range is detected for the sample annealed at 1,100°C for 1 h (Figure 1a).