Electronic Structures of Clusters of Hydrogen Vacancies on Graphene

Abstract

Hydrogen vacancies in graphane are products of incomplete hydrogenation of graphene. The missing H atoms can alter the electronic structure of graphane and therefore tune the electronic, magnetic, and optical properties of the composite. We systematically studied a variety of well-separated clusters of hydrogen vacancies in graphane, including the geometrical shapes of triangles, parallelograms, hexagons, and rectangles, by first-principles density functional calculation. The results indicate that energy levels caused by the missing H are generated in the broad band gap of pure graphane. All triangular clusters of H vacancies are magnetic, the larger the triangle the higher the magnetic moment. The defect levels introduced by the missing H in triangular and parallelogram clusters are spin-polarized and can find application in optical transition. Parallelograms and open-ended rectangles are antiferromagnetic and can be used for nanoscale registration of digital information.

Dramatic Enhancement of the Nonlinear Optical Response of Hydrogenated Fluorographene: The Effect of Midgap States

“…During hydrogenation, H atoms can be attached to some of the vacancies, forming C–H bonds, whereas some F vacancies may remain. In all cases, different conformations and/or cluster formations can be formed as it has been discussed elsewhere. − The estimation of the effect of each individual situation described above on the band gap value is not known so far to the best of our knowledge.…”

“…Graphane, on the other hand, with all C atoms bonded to H atoms alternately from either side of the graphene plane, is also considered as a wide band gap semiconductor with a reported band gap up to ∼5 eV or even larger. − In addition, its band gap can be tuned effectively with the degree of H coverage. Therefore, for instance, a hydrogenated monolayer graphene with an H atom coverage of ∼12% shows a band gap slightly larger than 1 eV .…”

Effect of Point Defects on Optical Properties of Graphene Fluoride: A First-Principles Study

“…Here we focus on double F-vacancies and eight such double vacancies are considered below, labeled by C1–C8 in Figure . Note that these double F-vacancies are charge neutral and their formation energy is calculated as where E (dGF) is the total energy of the defective graphene fluoride, E (GF) is the total energy of the perfect graphene fluoride, and E (F 2 ) is the total energy of the molecule F 2 . Similarly, we can define the formation energy of substitutional point defects in graphene fluoride as the energy difference between the defective graphene fluoride with respect to the perfect graphene fluoride and diatomic molecules of F 2 , H 2 , N 2 , and O 2 (discussed later).…”

Graphane -- material for hydrogen storage, breathers and kinks

“…Mechanical properties of graphene were studied in [106]. In [107] electronic structures of clusters of hydrogen vacancies on graphene were studied.…”