Physics of 2D Materials for Developing Smart Devices

Abstract

Rapid industrialization advancements have grabbed worldwide attention to integrate a very large number of electronic components into a smaller space for performing multifunctional operations. To fulfill the growing computing demand state-of-the-art materials are required for substituting traditional silicon and metal oxide semiconductors frameworks. Two-dimensional (2D) materials have shown their tremendous potential surpassing the limitations of conventional materials for developing smart devices. Despite their ground-breaking progress over the last two decades, systematic studies providing in-depth insights into the exciting physics of 2D materials are still lacking. Therefore, in this review, we discuss the importance of 2D materials in bridging the gap between conventional and advanced technologies due to their distinct statistical and quantum physics. Moreover, the inherent properties of these materials could easily be tailored to meet the specific requirements of smart devices. Hence, we discuss the physics of various 2D materials enabling them to fabricate smart devices. We also shed light on promising opportunities in developing smart devices and identified the formidable challenges that need to be addressed.

1. Introduction

In 1965, Gordon Moore stated that the number of transistors on a chip doubles every two years. Over the last 5 decades, Moore’s law has worked fairly well, driving significant improvement in performance and a sharp decrease in the prices of electronic circuits. However, it starts saturating particularly due to the introduction of multifunctional devices as a very large number of components are required to be embedded into the same system leading to excessive heat generated within the chip [1]. Thus, the scientific community has to look beyond conventional materials to revive Moore’s law for making high-performance and low-dimension smart devices. The atomically thinned layered materials popularly known as two-dimensional (2D) materials showed a high probability of bringing back Moore’s law to life. The properties of these 2D materials are completely distinct from their bulk counterpart. The band gap, electron mobility, and contact resistance change very rapidly as the bulk semiconductors thinned down to few-layer to monolayer thickness [2, 3]. Since the isolation of graphene (the mother of all 2D material) in 2004 by Prof. Geim and Novoselov, numerous other 2D materials have been explored for their wide range of applications in nano-electronic and photonic smart devices.

Similar to graphene, several other 2D materials have extensively been studied and grabbed huge attention with their unique electronic, optical, mechanical, and chemical properties [4–6]. These 2D materials outperform conventional materials primarily due to the availability of easily tunable properties in the former, which is an essential ingredient for modern smart devices. The intrinsic characteristics of these materials could easily be tailored by strain engineering, phase engineering, defect engineering, forming heterostructures, changing the number of layers, or modifying the surface morphology. The 2D materials possess negligibly small dimensions in one direction. For example, mechanically exfoliated single layers of graphene and MoS2 have a thickness of 3.4 and 6.5 Å, respectively. The practical applications of traditional devices are limited by the inherent properties of conventional materials. For instance, conventional devices are rigid and lose their mechanical and electronic attributes upon bending. The natural flexible and excellent transparent nature of atomically thin materials overcome these limitations and make them promising candidates for foldable and wearable flexible devices [7, 8]. In recent years, stretchable smart devices have also been developed using 2D materials as these materials can withstand high deformation without losing their inherent characteristics. Smart wearable fabrics with tuneable properties could be designed for environmental monitoring, complex computing, and flexible Internet of Things (IoT) applications.