Wouter Jolie

Structure and Growth of Hexagonal Boron Nitride on Ir(111)

Using the X-ray standing wave method, scanning tunneling microscopy, low energy electron diffraction, and density functional theory, we precisely determine the lateral and vertical structure of hexagonal boron nitride on Ir(111). The moiré superstructure leads to a periodic arrangement of strongly chemisorbed valleys in an otherwise rather flat, weakly physisorbed plane. The best commensurate approximation of the moiré unit cell is (12 × 12) boron nitride cells resting on (11 × 11) substrate cells, which is at variance with several earlier studies. We uncover the existence of two fundamentally different mechanisms of layer formation for hexagonal boron nitride, namely, nucleation and growth as opposed to network formation without nucleation. The different pathways are linked to different distributions of rotational domains, and the latter enables selection of a single orientation only.

Interfacial Carbon Nanoplatelet Formation by Ion Irradiation of Graphene on Iridium(111)

We expose epitaxial graphene (Gr) on Ir(111) to low-energy noble gas ion irradiation and investigate by scanning tunneling microscopy and atomistic simulations the behavior of C atoms detached from Gr due to ion impacts. Consistent with our density functional theory calculations, upon annealing Gr nanoplatelets nucleate at the Gr/Ir(111) interface from trapped C atoms initially displaced with momentum toward the substrate. Making use of the nanoplatelet formation phenomenon, we measure the trapping yield as a function of ion energy and species and compare the values to those obtained using molecular dynamics simulations. Thereby, complementary to the sputtering yield, the trapping yield is established as a quantity characterizing the response of supported 2D materials to ion exposure. Our findings shed light on the microscopic mechanisms of defect production in supported 2D materials under ion irradiation and pave the way toward precise control of such systems by ion beam engineering.

Charge puddles in the bulk and on the surface of the topological insulator BiSbTeSe2 studied by scanning tunneling microscopy and optical spectroscopy

The topological insulator BiSbTeSe

Energy-Dependent Chirality Effects in Quasifree- Standing Graphene

_2

Comment on "interfacial carbon nanoplatelet formation by ion irradiation of graphene on iridium(111)".

corresponds to a compensated semiconductor in which strong Coulomb disorder gives rise to the formation of charge puddles, i.e., local accumulations of charge carriers, both in the bulk and on the surface. Bulk puddles are formed if the fluctuations of the Coulomb potential are as large as half of the band gap. The gapless surface, in contrast, is sensitive to small fluctuations but the potential is strongly suppressed due to the additional screening channel provided by metallic surface carriers. To study the quantitative relationship between the properties of bulk puddles and surface puddles, we performed infrared transmittance measurements as well as scanning tunneling microscopy measurements on the same sample of BiSbTeSe

Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference

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Confinement of Dirac electrons in graphene quantum dots

, which is close to perfect compensation. At 5.5 K, we find surface potential fluctuations occurring on a length scale

Graphene on weakly interacting metals: Dirac states versus surface states

r_s = 40-50

Oxygen orders differently under graphene: new superstructures on Ir(111)

nm with amplitude

Step-induced faceting and related electronic effects for graphene on Ir(332)

\Gamma = 8-14