Prof. B. R. Mehta, Indian Institute of Technology Delhi, will be visiting the School of Engineering. As part of his visit he will deliver a seminar entitled, "Studying Nanoscale Interfaces in 2D-3D Heterojunctions". Abstract and biography are given below.

Date & Time: 11:30, Thursday, 23rd March
Venue: Room 514, Rankine Building

Abstract

Studying the nature of interface between two dissimilar semiconductors has ever been a complex experimental and theoretical issue. Due to the extremely small thickness of 2D materials, studying the junction involving a 2D layered materials is even more challenging.  In this presentation, our recent CAFM and KPFM based experiments on understanding the nature of nanoscale interface formed between Graphene-Si, MoS2-ZnS and CdS-CZTS junctions will be presented. Surface potential changes at the graphene-Si junctions under light conditions have been examined using Kelvin probe force microscopy investigations in surface and junctions configurations. Voc nanoscale maps derived from these measurements show that topographical impurities and wrinkled boundaries on the graphene surface affect junction performance. In a separate study, patterned MoS2 2D layers having feature size varying from 10 um to 1 um have been grown by a combination of stencil lithography and magnetron sputtering technique. Structural, optical and junction properties of composite layers having wide band gap ZnS films and 2D MoS2 layers have been investigated. 2D heterojunction having mono and few layers MoS2 thickness result in high interface photovoltage in comparison to bulk MoS2 layer. KPFM based difference method has been used to observe the nanoscale changes in the junction behaviour at the grain boundaries with respect to crystalline grain in ZnO/CdS/CZTS/Mo device. A direct measurement and nanoscale mapping of an atomically thin junction in the final finished device without any adverse influence of contact layers, adsorbates and surface impurities are some of the important highlights of the present methodology.

Biography

Prof. B. R. Mehta is currently Schlumberger Chair Professor of Semiconductor Physics at Indian Institute of Technology Delhi, New Delhi, India. He is also Institute level Dean of Research and Development. He did his M.Sc. in Physics from Punjabi University Patiala, M. Tech in Solid State Materials and Ph. D in Physics from IIT Delhi. He has worked as post-doctoral fellow at University of British Columbia, Canada; guest scientist at University of Saarbrucken, Germany; and guest professor at University of Duisburg, Germany. His major research interests are; Science and Technology of Thin     Films and Nanostructured Materials for Solar Cell, Resistive Memory, Thermoelectric and Gas Sensor Devices. He is the recipient of MRSI Medal (Material Research Society of India, 2002), DAAD Fellowship (Deutscher Akademischer Austausch Dienst, 2000) and Marie Curie International Fellowship (European Commission, 2006) and Material Science Prize of MRS India 2017. He is on the Editorial Board of Journal of Nanoscience and Nanotechnology and has about 200 journal publications. One of his projects-NanoSwitch- has been selected by European Commission as a Success Story project.

First published: 20 March 2017

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