Do mercury superconducting films grown by vapour phase or by bulk mass transfer?

Synthesis of mercury based superconductors is very complex being influenced by many parameters and thus the formation mechanisms of films are still unclear. This is a challenging situation regarding the potential applications of these very high TC's compounds. The synthesis involves a mercuration step and it is presently unknown whether it occurs by a bulk mass transfer or by a reaction with the mercury vapour. To find out this process we have performed two types of experiments-with and without a contact between the precursor film and the pellet containing the mercury as a source for the reaction. Thin precursor films were grown on CeO2 buffered R-plane sapphire by RF magnetron sputtering and reacted ex situ in a sealed quartz tube to incorporate the mercury. We compare the electrical and structural properties of the films prepared by these two methods to find out the best configuration for the preparation of thin superconducting mercury based films. One of the conclusions is that mercuration without contact is possible; this is an important result to scale up to larger samples.