Inducement of superconductivity in Fe(Te,S) by sulfuric acid treatment
  Superconductivity of Fe0.95Te0.85S0.15 was induced and enhanced by immersing the as-grown (non-superconducting) sample into sulfuric acid. Dissolved Fe was detected in the sulfuric acid treatment, indicating that excess Fe was removed from the Fe0.95Te0.85S0.15 sample. 
Masanori Nagao, Yoshikazu Mizuguchi, Keita Deguchi, Satoshi Watauchi,   Isao Tanaka, Yoshihiko Takano
cond-mat.supr-con