Figure 5. Temperature dependent change in the lattice spacing of the (103) planes during heating to 305 °C (closed symbols) and after cooling to 50 °C (open symbols).

(a) The as-grown undosed film shows roughly linear expansion along the (103) plane during heating until the onset of the tetragonal crystal phase transition and with a return to character upon cooling. (b) The 5 × 10¹⁵He/cm² dosed film shows linear expansion without the crystal transition signature and demonstrates a slight decrease in length along the (103) plane after cooling which can be attributed to the loss of He above ~250 °C¹¹.