Ultrathin materials made up of only a single layer of atoms are sometimes referred to as two-dimensional (2D) or single layer materials. Applications for 2D materials and their heterostructures in fields such as communications, high speed computing, sensing, and energy harvesting are currently limited by the absence of direct and repeatable synthesis methods for cost effective device fabrication. While conducting (e.g., graphene, TaS2), and semiconducting (e.g., MoS2, WS2) 2D materials are being rapidly advanced for next-generation 2D devices, ultrathin and high strength dielectric materials for transistor gates, capacitors, memory devices, and barrier layers for electrical and ambient environment isolation are far less developed.
This circumstance is primarily a result of the fundamental challenge in synthesis of ultrathin insulating materials at moderate temperatures (generally less than 900° C.) needed for direct growth over large lateral dimensions. In silicon-based electronics, silicon dioxide (SiO2), prepared by plasma enhanced chemical vapor deposition (PECVD), has proven to be a suitable dielectric material due to the large band gap (9 eV), well-matched interfacial properties with silicon, and simple, repeatable processing. However, there is a continuing desire to develop additional ultrathin dielectric materials which unique 2D benefits such as optical transparency and mechanical flexibility, for use in flexible electronic devices and other premium areas of nanotechnology innovation. Attempts to provide suitable ultrathin dielectric alternatives have included Atomic Layer Deposition (ALD) of HfO2 and Al2O3 and thermal activated growth of crystalline hexagonal form boron nitride (h-BN) by chemical vapor deposition (CVD). To date, however, such ultrathin dielectrics have been found to suffer from significant scaling, process tuning, and pinhole-free uniformity challenges.
Thus, there is a continuing need to further develop ultrathin, 2D dielectric materials which do not suffer from the aforementioned difficulties.