Seminar Series: Friday, March 31, 2017 at 11:00 A.M.
JSNN Seminar Series
Title: “Swift Heavy Ion Induced Surface Nanostructuring of Thin Films.”
Speaker: Madhavi A. Thakurdesai, Ph.D.
Associate Professor at Thin Film Research Laboratory
Department of Physics
Birla College, Kalyan
Date and Time: Friday, 3/31/2017, 11:00 A.M.
Location: JSNN Auditorium
Irradiation by energetic ion beams with energies more than 1 MeV/amu known as Swift Heavy Ions (SHI) is one of the important tool for nanostructuring of surface layers and thin films. The uniqueness of this method lies in the fact that during SHI irradiation, surface nanostructures are created directly without any further chemical or physical treatment. During irradiation the SHI beam loses all its energy to the target mainly via electronic energy loss (Se). This energy transfer may initiate various processes such as (i) sputtering of the material (ii) generation of additional adatoms and surface energy clusters (iii) ion-assisted enhancement of surface diffusion etc. Moreover, If the value of (Se) reaches above a threshold value (Seth) then latent tracks having cylindrical geometry and radius of a few nanometers are formed in the wake of ion beam. Transient melting of the target material may occur if the latent track temperature exceeds melting temperature of the target material. The melted region is cooled quickly to ambient temperature due to rapid transfer of heat to the surrounding region. The resultant solid along the ion track is generally found in a disordered or amorphous state. With increasing ion fluence, number of such modified zones increase and tends to overlap. This track overlapping leads to surface instabilities.
As a result of all the above mentioned ion beam induced phenomenon, various effects such as grain fragmentation and grain growth, ripple formation, formation of nano-sized hillocks , formation of self-affine structures etc. are observed on the surface of thin films after SHI irradiation. The nature of nanostructure formation depends on electrical, thermal and structural properties of the target material, the mass of the projectile ion and irradiation parameters. Thus by controlling irradiation parameters, surface nanostructuring can be achieved in a controlled way. In the present talk, SHI induced surface nanostructures in case TiO2 thin films and CdTe thin films will be discussed. The irradiation is mainly carried out with 100MeV Au, Ag and Ni ion beam. The films are characterized by techniques like; AFM,SEM, XRD,UV-Vis spectroscopy etc. Basic ion-matter interaction behind emergence of surface nanostructures will be discussed. The structural and optical changes induced by SHI irradiation will be discussed. Effect of irradiation parameters such as ion fluence, ion species etc. on nanostructure formation will also be discussed.
Dr. Madhavi Thakurdesai is working as an Associate Professor at Thin Film Research Laboratory, Department of Physics, Birla College, Kalyan. She has developed TiO2 nanostructured thin films using Swift Heavy Ion (SHI) beam irradiation for her doctorate degree. She has also developed rare earth doped TiO2 nanocomposites using the method of chemical co-precipitation followed by hydrolysis (CPH). Visible light photocatalytic activity of these nanocomposites was investigated for the degradation of congo red (CR) dye. It was observed that all the nanocomposites investigated lead to very efficient degradation of the dye. One of her research areas is to develop nano structured chalcogenide thin films for photovoltaic applications. She has also worked on material modification of surfaces using ion beam mixing. Currently she is involved in fabrication of TiO2 based memresistors using Atomic Layer Deposition (ALD) technique. She also completed several research projects. In one of her projects she is aiming at developing white light emitting nano phosphors using rare earth elements in single host lattice. She has authored and co-authored over 20 publications in international journals and conference proceedings. She has also participated in various conferences at national and international level. Recently has visited Clayton State University Georgia, USA under faculty exchange program. She has delivered many talks on Synthesis and Applications of Nanotechnology. She has keen interest in teaching semiconductor device physics and fundamentals of nanomaterials. She has written two books namely Nanoday (Nanotechnology) and Ganiti (History of Mathematics) in her native language – Marathi. In addition she writes articles on recent developments in science and technology.