Seminar


Department of Chemistry
Indian Institute of Technology Delhi

Probing Interfaces of Heterostructure Quantum Dots and Devices

Dr. Somobrata Acharya
Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India, E-mail: camsa2@iacs.res.in

Date: February 6th 2018 (Tuesday)
Time: 4:00 PM
Venue: Committee Room, Chemistry Department, 6th Floor

Heterostructure nanocrystals (HNCs) consisting of two or more semiconductor components form junction at the interface of the constituent blocks [1]. Unlike the electronic property tuning by band gap modulation of mono-component NCs, HNCs rely on controlling energy states via band-offset engineering at the material interface [2]. I will demonstrate the usefulness of band-offsets by designing component size modulated coupled quantum dots (CQDs-HNCs) composed of a fixed sized ZnSe quantum dot and size-tuned CdS quantum dots. Type-II nature of the interface along with the band-offsets of a single CQDs-HNC is probed by using scanning tunneling microscopy. Selective tuning of band off-sets allows natural separation of photoexcited charge carriers which facilitates photovoltaic features in contrary to the limited photon-to-current conversion efficiencies of mono-component NCs. Furthermore, formation of an electronic component called “differentiator” using a single Cu2S-CdS HNC as active component is demonstrated. The interface plays a key role in converting a square wave signal into pulse signal suggesting that HNC can be used as active circuit components in miniaturized electronics.

    References:
  1. Sengupta, S., Ganguly, N., Dasgupta, I., Sarma, D. D., Acharya S. Long-Range Visible Fluorescence Tunability Using Component-Modulated Coupled Quantum Dots. Adv. Mater. 2011, 23, 1998–2003.
  2. Dalui, A., Chakraborty, A., Thupakula, U., Khan, A. H., Sengupta, S., Satpati, B., Sarma, D. D., Dasgupta, I., Acharya, S. Chemical Tailoring of Band Offsets at the Interface of ZnSe−CdS Heterostructures for Delocalized Photoexcited Charge Carriers. J. Phys. Chem. C. 2016, 120, 10118-10128.


All are cordially invited to attend.
Convener (Seminars)