Department of Physics

Indian Institute Of Technology Madras , Chennai

Electrochemical Route to Condensed Matter Physics

Speaker : K. Ragavendran, Institute of Mathematical Sciences

2017-03-08

Abstract :

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 temperature superconductors'.
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.

Key Speaker K. Ragavendran, Institute of Mathematical Sciences
Guests None
Place Seminar Room
Start Time 10:00 AM
Finish Time 11:00 AM
External Link None