Field emission applications of graphene-analogous two-dimensional materials: recent developments and future perspectives

Abstract

2D layered materials are widely recognized as the revolutionary class of materials, and hold great promise in the modern device technology industries. The 2D materials family covers almost the entire spectrum of condensed mater physics and devices associated with metal, semi-metal, superconductor, Mott insulator, Bose–Einstein condensates properties. Due to their tunable and suitable electronic, thermal and mechanical properties, different inorganic 2D materials have emerged as possible cathode materials for high performance field emission (FE)-based vacuum micro/nanoelectronic devices. The 2D materials possess more active sites, and strident edges in atomic dimension, vacancies, and defects, which are favourable for high current density cathodes associated with reduced turn-on voltages. Hence, expulsion of electrons from the 2D materials are expected to be noticeably higher due to the reductions in the dimensionality, quantum restraint effect of electrons in 2D fissionable layers, and the occurrence of random and sharp protruding active edges. Furthermore, the enhanced FE characteristics of inorganic 2D materials are achieved by several methodologies, such as phase engineering, defect and vacancy engineering, heterostructure/hybrid materials design, gating, alloying, and photoexcitation. Owing to their exotic mechanical properties, high stretching ability and flexibility nature, the 2D materials-based field emitters have emerged as potential candidates for flexible displays and miniaturized X-ray tubes. For this current review, we proffer an exclusive overview of various emerging 2D materials that are being recognized for efficient and high-performance FE-based applications. Furthermore, the fundamentals of the field emission working principles, recent developments, future perspectives and alternative tunable schemes for enrichment of the field emission functions are herein elaborated comprehensively.