Graphene and graphane functionalization with hydrogen: electronic and optical signatures

Abstract

We proved the possibility of electron gap tuning of graphene‐based materials, using extensive first principles modelling of the structural, electronic and optical properties of partially hydrogenated graphene. Optical tools were proposed to characterize the hydrogenation process. Sub‐monolayer hydrogen passivated graphene and various hydrogen induced superstructures were considered. Electron and optical DFT LDA gaps between 0.2 and 1.8 eV, suitable for microelectronic application, were obtained for low hydrogen coverage structures. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at opposite sides of the graphene sheet) is energetically most favourable and generally produces a larger gap. A more homogeneous H distribution with one‐side bonding to C‐host atoms is, in contrast, less energetically favourable and even structurally unstable. In addition, such H configurations generally produce lower electron band gap. Hydrogen at low coverage not only locally buckles six‐fold carbon rings, it leads to dimerization and subsequent electron localization for neighbouring carbon atoms, which are not H bonded. Such structural and electronic processes are responsible for gap opening and its magnitude. Calculated linear optical response indicates that the optics is not only gap sensitive, but, combined with experimental spectra, can also provide access to microscopic properties of 2D nano‐sheets such as symmetry, hydrogen induced structure, degree of hydrogenation, chemical bonding, and others (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Striving Toward Noble-Metal-Free Photocatalytic Water Splitting: The Hydrogenated-Graphene–TiO2 Prototype

“…35 The C-C bond lengths in graphane and graphone are different from graphene. 34,35,37 Such HG materials exhibit ferromagnetism and more importantly, its band gap is readily tunable, depending on the extent of hydrogenation. When half of the hydrogen in the graphane sheet is removed, the resulting semi-hydrogenated graphene or graphone becomes a ferromagnetic semiconductor with a small indirect gap arising from the formation of strong σ-bonds and the breakage of the delocalized π-bonding network of GR, leaving the electrons in the unhydrogenated carbon atoms localized and unpaired.…”

Functionalized Graphene and Hexagonal Boron Nitride (hBN) Two-Dimensional Heterosystems for Solar Cell Applications

“…Even though we did not carry out more complex and CPU demanding modeling of such random system, we should expect the monotonous increase of the gap with higher H coverage. Indeed, our theoretical finding of the possibility of the gap tailoring in partially hydrogenated graphene [5] has been experimentally proven independently.…”

“…The optical response is important for in-situ spectroscopy of the materials. For more numerical details, see, e.g., [5]. For the most promising systems very accurate calculations of the linear dielectric function, which include many-body corrections, have been carried out.…”

Hybrid functional studies on the optical and electronic properties of graphane and silicane

“…The outstanding optical and electronic properties make it widely used in many areas such as touch screens, ultrafast lasers and transparent coatings [1]. However, the zero band gap restricts its applications in the field of optics and transistor technology [2,3]. Thus, it is crucial to open a band gap for graphene.…”