| PhD Seminar

Name of the Speaker: Mr. Sudarsan Majumder (EE17D409)
Guide: Dr. Soumya Dutta
Online meeting link: http://meet.google.com/dzc-uunx-aba
Date/Time: 12th June 2025 (Thursday), 4:00 PM
Title: Monolithically Integrated Low-Dimensional Nanoelectromechanical Resonators

Abstract :

Low-dimensional material-based nanoelectromechanical systems (NEMS) devices are the platform with the potential to disrupt the next generation of sensing technologies. The field of low-dimensional NEMS (LDNEMS) took off nearly two decades ago with the integration of carbon nanotubes and graphene in NEMS. However, due to the long-standing challenges in fabricating these devices on a large area, a scalable path towards integrating these devices with CMOS-BEOL compatibility has yet to be paved. It can be reasoned that this yield-related bottleneck has hindered comprehensive studies of such devices, thereby limiting critical insights into the intricate coupling between mechanics and electrodynamics. Therefore, this presentation shall broadly encompass the aforesaid aspects of LDNEMS resonators.

The first part of the presentation will briefly reflect on the work presented in seminar 1. The development of various nanofabrication processes, including advanced photolithography techniques, developed to achieve high yield in fabricating reduced graphene oxide (rGO)-based NEMS, will be summarized. This precis will lead to describing a process integration scheme that successfully achieves cost-effective, truly monolithic, transfer-free, chip-scale integration of thousands of rGO NEMS resonators within a 1 cm × 1 cm area at temperatures compatible with CMOS-BEOL integration.

The talk shall then depart from the technology-emphasized tone and deep dive into discussing the physics of nanoscale vibrations and their coupling to charge transport through these devices, studied using Lock-in-based detection techniques. A successful outcome of this exercise is the realization of a novel NEMS transduction technique called the direct piezoresistive method, which will be discussed in detail. This will be followed by a comprehensive analysis of modal vibrations and their implications on resonance transduction using heterodyne frequency mixing techniques. Inference from this discourse will be shown to reveal key deviations from conventional models and forge a unified framework that systematically restructures the existing interpretations of mixing currents and their implications on high-sensitivity measurements and response characterization. Last but not least, as an application of this novel framework, a contactless method to extract strain-induced electronic behavior and band-gap modulation in low-dimensional materials will be proposed.