Thin film electronic materials such as CrO2, FeSe and La2CuO4 find fascinating
applications in modern spintronic and SQUID devices, besides immense interest from
the fundamental physics point of view. Though the conventional thin film methods such
as the chemical vapor deposition (CVD), pulse vapor deposition (PLD) etc possess
inherent advantages, they also pose several short comings such as complex
instrumentation, high cost, and limitations in stabilizing certain phases.
Yet another very interesting challenge in materials science comes from nanoscopic
inhomogeneities. Limitations to material properties and performance are not imposed
merely by the selection rules. For instance though quantum mechanics poses no
hindrance to room temperature Tc in the cuprate superconductors, nanoscopic
inhomogeneities lead to competing orders and pull down the Tc to liquid nitrogen
temperature (LNT). Thus cuprate superconductors can rightly be called as 'failed room
Solutions to these problems can be sought from electrochemistry. By monitoring two control parameters a) voltage and b) the pH it will be possible to electrochemically form and stabilize a required phase within the conceptual framework of pourbaix diagram (voltage vs pH plot). For instance, from the pourbaix diagram for Chromium in aqueous solutions (Fig. 1) it can be seen that there is a small island where CrO2 is stable. Thus, through a proper control of potential and pH, the electrochemical route promises to offer an easy and cheap yet credible possibilities for forming thin films of oxides such as CrO2 , CuO , and also chalcogenides such as FeS, FeSe etc. on metals, with controlled thickness.
Also, using the same electrochemical control parameters it will be possible to precisely tune the stoichiometry and nanoscopic inhomogeneities under the conceptual framework of defect clustering physics.
In this talk we will discuss about the pourbaix diagrams and the underlying electrochemical principles. We will also briefly outline our ongoing work at IMSc on defect clustering physics.