Partially Hydrogenated Graphene: Semiconductor Material with a Tunable Gap and Its Non-Destructive Optical Characterizat
- PDF / 7,952,152 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 98 Downloads / 157 Views
Partially Hydrogenated Graphene: Semiconductor Material with a Tunable Gap and Its Non-Destructive Optical Characterization F. Gaspari 1, A.I. Shkrebtii 1, P. McNelles 1, J.L. Cabellos 2, and B.S. Mendoza 2 1 University of Ontario Institute of Technology, Oshawa, ON, L1H 7K4, Canada 2 Centro de Investigaciones en Optica, Leon, Guanajuato, 37150, Mexico ABSTRACT We report first principles modeling of partially hydrogenated graphene, with a variety of hydrogen induced superstructures. The dependence of the optical gap on hydrogen content and coverage is examined, to assess the best configurations suitable for optoelectronic applications. Electron and optical DFT LDA gaps in the range between 0.2 and 1.5 eV were obtained for low hydrogen coverage. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at the opposite sides of the graphene sheet) is energetically most favourable and generally produces larger gap. More homogeneous H distribution one-side bonded to C-host atoms is, in contrast, less energetically favourable or even structurally unstable and generally produces smaller gap. In addition, ordering of hydrogen was observed at 50% of H, that offers a possibility of transforming 2D graphene to an array of 1D nanowires Calculated linear optical anisotropy and nonlinear second harmonic generation (this will be discussed in a forthcoming paper) indicate these are not only gap sensitive, but can provide an access to microscopic details of the 2D nano-sheets such as symmetry, hydrogen induced structure, degree of hydrogenation, chemical bonding and many others, all promising for device application. The approach developed can be used for graphene/ graphane single layer or bilayer, formed on top of various substrates, where experimental geometries may not provide conditions for complete hydrogenation of the 2D nano-sheet(s). INTRODUCTION Since 2004 we have witnessed a spectacular growth of a research on graphene, a new class of 2D nanomaterials [1]. Although graphene demonstrates a lot of exciting properties, its zero-gap band structure limits graphene application in 2D microelectronics. As was demonstrated recently [2], hydrogenation of graphene produces a stable free standing film, graphane. However, its 5 eV gap is indicative of insulator-like rather than semiconductor properties. Recently we proposed controlled hydrogenation of graphene in order to tailor the films’ gap, graphene-like silicon and germanium [3], while the independent experimental confirmation of hydrogenation processes has been published very recently [4]. It has been shown that chemical functionalization of graphene introduces an energy gap [5], and several modelling studies aimed at assessing the potential applications of functionalized graphene have been reported. For instance, Fiori et al. [6] use GW approximation to calculate the energy bands of hydrogenated graphene, and to analyze the theoretical performance as basic component for Field Effect Transistors. The authors indicate that both graphane and semihydrogenate
Data Loading...
