Two aspects of Bi2se3 quasi 2d nanoflakes: flexible, wearable pressure sensor and sspm based all-optical switching and photonic logic gate

Abstract

In the past few decades, there has been great emphasis on developing nanomaterials for their practical applications. Extensive effort has been made to design and accurately control the material’s composition, morphology, and heterostructures showing exciting properties. Among several properties of the nanostructures, dimensionality is one of the most important parameters. This thesis work aims to address some of the crucial problems. With modern, flexible electronics development, pressure sensors have drawn much attention. Flexible pressure sensors can be used in many applications such as health care monitoring, human-machine interfacing, robot prosthetics and IOT application. In recent years, flexible electronics have been a topic of massive interest due to their application in various fields, and they are widely employed as pressure sensors. A novel pressure sensor should have high sensitivity, mechanical flexibility, fast response time, low fabrication cost, simple processing, etc. Among different types, the piezo-resistive pressure sensor is thought to be the most energy-efficient and cost-effective as it does not require a complex fabrication method. The signal acquisition methods are also accessible. Recent research contributions mainly focus on the device's cost-effectiveness and efficiency. For these reasons, Bi2Se3 Nanoflakes (NFs) have been considered the primary material for this study. The Bi2Se3 NFs were synthesized using a simple solvothermal technique. This first work, entitled "Wearable, Ultrawide-Range, and Bending-Insensitive Pressure Sensor Based on 2D Bi2Se3 NFs coated tissue for Human-machine Interface and Healthcare Devices" aimed to investigate the pressure sensing capabilities of Bi2Se3 NFs coated pressure sensor and the application in healthcare device. Layer variation, concentration variation and electrode metal variation are done to find the best sensitive device. The best operating piezo-resistive pressure sensor's sensitivity is 25.1 kPa-1 (in the range 0-2 kPa). In addition, the sensor can detect mobile vibration, weak airflow from the mouth, voice recognition, bending, differentiating between different amounts of pressure etc. All these characteristics are attributed to the high sensitivity of the pressure sensor. Also, the optimized sensor is used to fabricate an array of matrices resembling electronic skin. This e-skin array can be used to detect spatial pressure distribution and pressure magnitude. It is believed that such a low-cost, easy-to-fabricate pressure sensor can open up new opportunities and applications in e-skin and intelligent wearable electronics. The second work, titled "Kerr Non-Linearity in 2D Bi2Se3 for all Optical Switching and Photonic Logic Gate Application, " is an optical study of Bi2Se3 nanoflakes done to calculate non-linear optical parameters such as non-linear refractive index, third order susceptibility. This study is done using by SSPM technique. Here 2D Bi2Se3 nanoflakes were synthesized using a low-cost, simple chemical route. Basic characterizations like FESEM, EDS, XPS, and Raman Spectroscopy were done for deep understanding regarding this nanoflakes sample. The Bi2Se3 NFs are a promising material for non-linear optical applications in this study. The calculated non-linear refractive indexes and third order non-linear susceptibility were 7.74 X 10-6 esu and 1.9 X 10-8 esu for NMP solvents, respectively, at 671nm laser excitation. The large values indicate strong coherent non-linear interaction between light and suspended Bi2Se3 nanoflakes. Based on the SSPM method, Bi2Se3-SnS2 based diode has been investigated to demonstrate non-reciprocal light propagation. Also, an all-optical "OR" gate application has been performed using the cross-phase modulation method involving two laser beams of a different wavelength. It is believed that such a non-linear optical phenomenon can open up a new pathway for Bi2Se3-based all-optical device application.