The Si wafers were first cleaned ex situ in a 2% hydrofluoric acid solution

and subsequently in situ using a two-step silicon-flux method (silicon beam clean) Volasertib in vitro [10]. This procedure results in a Si(111) surface which is free of contaminants and which exhibits the Si(111) 7 × 7 reconstruction, as confirmed by in situ reflection high energy electron diffraction and scanning tunneling microscopy. A 150-nm-thick Al layer was then evaporated at room temperature in a molecular-beam epitaxy setup with a base pressure of 5 × 10-11 Torr. The deposition rate (approximately 0.2 Å/s) was monitored in situ with a quartz crystal microbalance which is calibrated using X-ray reflectivity. After deposition, the sample was annealed in situ at 350°C for 2 h in order to improve the crystalline quality of Al films. Ion implantation

Ion implantation was performed at room temperature using Pb+ ions at 90 keV with implantation fluences ranging from 0.4 × 1016 to 1.2 × 1017 cm-2. In order to reduce the lattice damage, a channeling geometry was used [11]. The implanted sample was fixed by a clamp pressing the wafer on the sample holder, which is made of stainless steel. By tuning the anode current, the beam current extracted from ion source was controlled. The current densities were C646 cell line maintained at 0.5, 1.0, and 2.0 μAcm-2, respectively, for each sample set with a current fluctuation < 5% during implantation. Structural characterization Rutherford backscattering spectrometry (RBS) with a 2.023 MeV He+ beam was used to determine the Pb content and Pb depth distribution in the samples, whereas the crystallinity of the Al films is assessed by ion

channeling, i.e., RBS with the ion beam directed along a high-symmetry crystal direction. The minimum yield χ min, which is the ratio of backscattering yield with aligned versus random beam incidence, is a direct measure of the crystalline quality of a film [12]. The backscattered He+ particles were detected by two Au-Si surface barrier detectors with an energy resolution of about 15 keV, which were placed nearly at backscattering angles of 10° and 72°, respectively. Conventional room temperature X-ray diffraction (XRD) was performed on a Bruker D8 diffractometer using Cu Kα1 radiation with a wavelength of 0.1542 nm. We used θ-2θ scans to identify the orientation of the epitaxial Al film and the PKC412 embedded Pb NPs and to estimate the average size of the embedded Pb particles from the width of diffraction peak using the Scherrer equation [13]. Results Virgin Al film on Si(111) Before ion implantation, the structure of the epitaxial Al layers, which served as the matrix for embedded Pb NPs, was characterized by RBS/channeling and XRD. Figure 1 shows the random and aligned RBS spectra of the virgin Al film grown on Si(111). The detector geometry used in this backscattering measurement is shown in the inset.