Speaker: Mr. Rahul Mahavir Varma

Time Resolved Scanning Tunneling Microscopy for Molecular Science

Date & Time: Thursday 28th September, 2017 at 4.00 PM


Scanning tunneling microscope (STM) is an imaging instrument, which is used in the field of surface science now a day rigorously due to its tremendous capacity to probe the sample in an atomic level. STM can image individual atoms and molecules and thus is able to observe the results of molecular processes such as diffusion, desorption, configuration switching, bond-breaking etc.
However, if the surface changes with time, e.g., because of molecular movement then you have to consider the time-line of the image. In other words, an STM image contains both spatial and temporal information. The STM can therefore be used as a tool to probe time dependent (i.e., dynamic) molecular processes at surfaces. For example, diffusion of molecules [1, 2], rotations of molecules [3] or flipping of molecular structures between stable conformations [4]. The critical factor is the timescale of the dynamic phenomenon. The STM does not have the time resolution to directly measure these dynamic processes since they occur on the femtosecond timescale, but it can observe their result, i.e., a molecule disappeared from one atomic site and found at another in the case of diffusion, or a change in configuration. That is why, we need to study the Time resolved STM (TR-STM) thoroughly so that we can able to resolve all these phenomenon which are occurring at femtosecond timescale.

[1] Wolkow R A and Moffatt D J 1995 J. Chem. Phys. 103 10696

[2] Otero R et al 2004 Nat. Mater. 3 779

[3] Lauhon L J and Ho W 1999 J. Chem. Phys. 111 5633

All are cordially invited to attend