Substantial increase of the superconducting transition temperature in Ti, Zr, and Hf after H(D) implantation

Ti, Zr and Hf are superconductors with rather low transition temperatures, Tsub(c), of 0.4, 0.6 and 0.13K when compared to their neighbours V, Nb and Ta which are good superconductors. In this paper it will be shown that the addition of H and D leads to a substantial increase of Tsub(c) and that this cannot be explained by an electronic density of states argument alone. Various other effects are discussed. The method of low temperature ion implantation was utilized for introducing H and D into Ti, Zr and Hf. Here the H or D atoms are implanted into the target material which is held at temperatures below 5K. Thus, Ti, Zr and Hf remain in their hcp-structure and the transformation into other crystal structures or phase mixtures is hindered. Such a transformation is normally observed with equilibrium H(D) charging methods. (author)