Effects of Annealing under Tellurium Vapor for Fe_1.03Te_0.8Se_0.2Single Crystals

Abstract

In this study, the effects of annealing under tellurium vapor have been investigated for Fe 1.03 Te 0.8 Se 0.2 single crystals. The as-grown crystal is not superconducting. After annealing it at 400 • C for 250 h in tellurium (Te) vapor, it shows metallic resistivity temperature dependence below 150 K and a sharp superconducting transition at 13 K. The sample also shows a full magnetic shielding effect at low temperatures. The improvement in superconductivity has been attributed to the removal of excess Fe, which is inevitably incorporated in the as-grown crystals, by the annealing.

Effects of Iodine Annealing on Fe1+yTe0.6Se0.4

“…The successful removal of the excess iron from the second Fe site [12] by several different methods has been reported. Until now, the optimal conditions of annealing in atmospheres of O 2 [13], S, Se [14], Te [12,15], P, As, and Sb [16,17] have been reported.…”

“…The successful removal of the excess iron from the second Fe site [12] by several different methods has been reported. Until now, the optimal conditions of annealing in atmospheres of O 2 [13], S, Se [14], Te [12,15], P, As, and Sb [16,17] have been reported. However, some elements were only reported to be effective in annealing without carefully studying the optimal condition, such as I (iodine) [13,18] and F [19].…”

Excess iron deintercalation induced superconductivity in Fe(Te, Se) and Fe(Te, S) via sulfur annealing

“…This can be achieved by heating in alcoholic beverages, and in organic acid solutions [13][14][15][16][17][18]. Various other post-annealing methods using I 2 , Te vapor, and acid solution are also reported [19][20][21][22][23].…”

Role of chalcogen vapor annealing in inducing bulk superconductivity inFe1+yTe1−xSex

“…Recently, the recovery of bulk superconductivity in annealed Fe 1+y Te 1−x Se x sample (under Te vapor) has been reported [14,15]. The current lore is that the chalcogen vapor removes excess Fe during annealing.…”

“…3c) prefers a location in the middle of four-chalcogenide atoms on the surface with adsorption energy of 4.12 eV, at a height of ∼0.3 A below the surface Te-atoms. During annealing in Tevapor, Te atoms could be introduced into the material, either forming excess Te or binding with Fe interstitial to form FeTe (or FeTe m with m > 1) complex [14,15]. The adsorption energy of a single Te-atom on the FeTe surface is 1.20 eV, whereas it is more strongly adsorbed by 1.94 eV on the interstitial Fe-atom on the surface to form a FeTe-complex.…”