Range profiles of low-energy (100 to 1500 eV) implanted³He and⁴He atoms in tungsten I. Experimental results

The range profiles of low-energy (100 to 1500 eV) 3He and 4He atoms implanted in situ, parallel to the [110] direction (±5°) of tungsten, at 60 K have been measured employing an atom-probe field-ion microscope. The absolute depth of each deposited helium atom, from the irradiated surface, was measured directly to within one (110) interplanar spacing (27middot;24 Å). At 60 K both 3He and 4He were found, in other research, to be immobile; thus, the range profiles were determined in the complete absence of any diffusional effects. The mean range (α) of the 3He and 4He range profiles increases monotonically, although non-linearly, as the implantation energy was increased from 100 to 1500 eV; the value of x varies from 33 to 158 Å and from 19 to 195 Å for the 3He and 4He profiles, respectively. The straggling (Δx) of the 3He and 4He range profiles also increases monotonically, although non-linearly, as the implantation energy was increased from 100 to 1500 eV; the value of Δx varies from 23 to 97 Å and from 16 to 124Å for the 3He and 4He profiles, respectively. All of the 3He and 4He range profiles exhibit positive skewness; that is, they are skewed from a normal distribution.