Thermal helium desorption spectrometry of helium-implanted iron

Post-implantation thermal desorption of helium from poly- and single-crystalline iron

“…First, there exists a sharp peak for each of the spectra, which due to its excessive sharpness is not consistent with a first order dissociation model as generally adopted in classical rate-theory. Such a sharp peak has also been observed for PC iron and ferritic alloys under other implantation conditions [17,20]. In Ref.…”

“…The implantation flux was $7-10 Â 10 10 He/cm 2 s. Grain size of the PC specimens was determined to be on the order of 50 lm through optical microscopy observations. Partial He current was measured in our ultrahigh vacuum thermal desorption system (TDS) [20] as a function of temperature during constant rate (1 K/s) thermal ramping on each of these He-implanted specimens from room temperature up to 1300°C. The He current was then converted to the instantaneous desorption rate by multiplying a proportionality coefficient, determined separately with a calibration procedure.…”

“…In an earlier publication [20], we noted the possibility of spurious background signals interfering with real desorption spectra and causing problems in data analysis. It is thus very critical to have a clean background in order to obtain reliable desorption data.…”

Effect of Fe and C doping on the thermal release of helium from aluminum

“…However, helium started to release when heated to ∼275 • C in the as implanted sample. Therefore, it could be inferred that all the peaks in the THDS spectra of He implanted Al samples correspond to the released helium other than any spurious peaks observed by Xu et al [6] in pure iron. Most of helium atoms induced in Al exist in the form of He n V m (or helium bubbles) [8].…”

“…The parameters used in implantation of Fe, C and He ions are listed in Table 1. According to SRIM calculation [6], Fe, C and He ions are distributed within 110 nm from the surface. Circulating water system was adopted for the cooling of the targets, which rotated slowly at a constant rate during ion implantation, making the implanted ions uniformly implanted in the sample surface.…”