Two-Dimensional Van der Waals Materials for Thin Film Transistor Applications.

摘要

Research on two-dimensional nanomaterials has become a topic of considerable interest since the pioneering work experimentally introducing the two-dimensional carbon allotrope of graphene in 2004. The atomically thin hexagonally arranged carbon crystal structure has offered the opportunity for numerous studies in condensed matter physics and materials science, revealing new phenomenon and remarkable properties. Graphene has excellent chemical and mechanical stability, allowing researchers to probe the properties of graphene in a wide variety of applications and in contact with a wide variety of materials. Ballistic transport of graphene at room temperature suggests that graphene would be poised to enter in to a wide variety of microelectronic application; vii however, synthesis methods and surface effects have so far limited the widespread use of graphene. Additionally, the absence of electronic band gap in graphene, classifying it as a "semi-metal", limits the use of graphene to areas other than logic applications.;In this work, fabrication methods for the improved synthesis graphene and selected two-dimensional transition metal dichalcogenides, molybdenum disulfide and tungsten disulfide, are presented for thin film transistor applications. First, the introduction of thin film zwitterionic polymer interlayers in graphene devices is outlined as a means to reduce the contact resistance between metal contacts and the underlying graphene layer. Second, a self-assembly nanoscale lithography process utilizing diblock copolymer templates as an etching mask directly on the surface of graphene is shown as a method to introduce a band gap in graphene due to quantum confinement effects. The third chapter applies to another class of two-dimensional materials, transition metal dichalcogenides, which, unlike graphene, can exhibit suitable electronic band structures for logic applications. When the thickness of these transition metal dichalcogenides is reduced to a single atomic layer, electronic band states transition from an indirect band gap to a direct band gap. A wafer-scale method for the synthesis of atomically thin transition metal dichalcogenides by the thermolysis of spin coated precursors is introduced which holds promise for next-generation low-power consumption applications.