Condensed Matter and Materials Physics

Biography

Biography: Samit K Ray

Abstract

We shall review our recent work on 2D/3D heterostructures for several electronic and photonic devices. The device using GO/Si on illumination shows a broadband (300 nm-1100 nm) spectral response with a characteristic peak at ~700 nm, in agreement with the photoluminescence emission from GO. Very high photo-to-dark current ratio (˃10⁵) is observed upon illumination of UV light. On the other hand, transition metal dichalcogenides (TMDC), an emerging class of two dimensional materials are interesting due to the presence of a finite and direct energy gap in low dimensions, with a wide range of electronic and optical attributes. We have demonstrated the ability to gradually tailoring the optical properties of MoS₂ nanocrystals in terms of PL response and optical absorption, making them attractive for future photonic devices. Chemical doping and plasmonic enhanced photoresponsivity of two dimensional (2D) n-WS₂/p-Si heterojunctions have also been demonstrated. A sharp band-edge absorption of the hybrid material indicates the presence of spin–orbit coupled direct band gap transitions in WS₂ layers, in addition to a broader plasmonic peak attributed to Ag nanoparticles. Stabilized Ag-nanoparticle (∼4–6 nm) embedded electron rich n-WS₂ has been used to fabricate plasmon enhanced, silicon compatible heterojunction photodetectors. The detectors exhibited superior properties, possessing a photo-to-dark current ratio of ∼10³, a very high responsivity (8.0 A W⁻¹) and an EQE of 2000% under 10 V bias. The results provide a new paradigm for intercalant impurity-free metal nanoparticle assisted exfoliation of n-type few-layer WS_2., with the nanoparticles playing a dual role by inducing chemical doping as well as tunable plasmon enhanced absorption.