25 MeV. In the aligned spectrum, there are two additional peaks due to the scattering from Al and O in the amorphous Al2O3 surface oxide (typically approximately find more 4 nm thick), which formed upon exposure of the sample to air. The low value of χ min = 7.3% indicates a high crystalline quality of the Al film. A simulation of the random spectrum (Figure 1) by the RUMP code [14] reveals that the thickness of the Al film is 150 nm. Figure 1 RBS/channeling for Al/Si heterostructure. Random (■), aligned (○), and simulated (—) spectra of 2.023 MeV He+ backscattered from the Al film on Si (111). The symmetric XRD θ-2θ scans of the Al/Si(111) heterostructure in the 2θ range 20° to 70° are shown in Figure 2. The only Al peak that can be

detected is the Al(111) diffraction peak at 2θ ≈ 38.5°, Selleckchem NVP-BEZ235 illustrating that the crystalline Al film is highly oriented with respect to the Si substrate as Al(111)//Si(111).

Figure 2 XRD θ -2 θ scans of the Al/Si heterostructure. Determination of the implanted Pb content and depth distribution Immediately after implantation, the implanted Pb content and Pb depth profile in Al were obtained from the experimental RBS spectra. Figure 3 shows the random RBS spectra of the samples with the same implantation current density at 2.0 μAcm-2 but different implantation fluences (<4.0 × 1016 cm-2). The detector geometry is shown in the inset. At low fluences, Pb is deposited inside the Al layer and only Al can be sputtered. This leads to a recession of the surface and a shifting of the Pb peak to the Ribose-5-phosphate isomerase sample surface. After careful analysis of the RBS spectra, an average experimental sputtering yield is estimated to be approximately 3.2, which is smaller than the result of Stopping and Ranges of Ions in Matter (SRIM) simulation (7.0 ± 0.2) for random implantation in pure Al [15]. The reduced sputtering yield is probably due to the lower deposited energy density at the surface for the channeled ions compared to the random implanted ions [16]. Our results show that the sputtering

yield of channeled Pb implantation is reduced by a factor 2.2 compared to the one of non-channeling implantation (obtained from SRIM simulation). This reduction is consistent with a reduction by a factor of 2 to 5, which is generally found for bombardment close to the major crystal axes with respect to other directions in single-crystalline targets [17]. In addition, with increasing fluence, the increased stopping power (both elastic and inelastic) in the Pb-enriched zone results in a reduced projected range of implanted Pb ions. The fluence-dependent projected range not only causes the Pb depth profile to move towards the surface but also leads to an enhancement of Pb concentration in the Pb-enriched zone. When the Pb depth profile reaches the surface, Pb starts to get self-sputtered. In this case, if the sputtering yield of Pb is larger than 1, a decrease of the Pb content with increasing implantation fluence can be observed.