Work function of graphene multilayers on SiC(0001)

Abstract

The work function and electronic structure of epitaxial graphene as well as of quasi-freestanding graphene multilayer samples were studied by Kelvin probe and angle resolved photoelectron spectroscopy. The work function converges towards the value of graphite as the number of layers is increased. Thereby, n-type doped epitaxial graphene layers have a work function lower than graphite and p-type doped quasi-freestanding graphene layers exhibit a work function higher than graphite. We explain the behaviour by the filling of the p-bands due to substrate interactions.

Role of the Potential Barrier in the Electrical Performance of the Graphene/SiC Interface

“…Since 4H-SiC has a lower value of the work function (by 0.3 eV), compared with 6H-SiC, a higher Schottky barrier of Φ B = 0.6 eV is formed at the interface graphene/4H-SiC, thereby contributing to an increase of the contact resistance. In turn, the work function of graphene varies significantly with the number of layers ( Figure 6) as was reported in a recent paper by Mammadov et al [48]. In particular, it was found that the buffer layer has a reduced work function of 3.89 ± 0.05 eV, and every subsequent layer leads to increasing the work function, reaching a value of 4.43 ± 0.05 eV for the case of trilayer graphene.…”

“…Figure 6. Dependence of the work function of epitaxial graphene (EG) with the buffer layer (red symbols) and buffer-free quasi-free-standing graphene (blue symbols) on the number of layers [48]. Abbreviation of QFG means quasi-free-standing graphene.…”

“…The black symbols correspond to the position of the Dirac point with respect to the Fermi level for epitaxial graphene and quasi-free standing graphene. Reprinted from Mammadov et al [48]. Copyright (2017) with permission from Institute of Physics Publishing Ltd. HOPG, highly-oriented pyrolytic graphite.…”

Large Spin-Orbit Splitting of Deep In-Gap Defect States of Engineered Sulfur Vacancies in Monolayer WS2

“…The different behavior of mono-vs bilayer graphene substrates can be explained by the energetic shift of the V S defect states by 160 meV towards lower energies. A similar shift is observed for the WS 2 VBM, which can be attributed to the smaller screening of monolayer graphene that increases the band gap [35] and a change in work function [36]. Using the charging peak, a 11% voltage drop across the WS 2 layer (at the chosen tunneling condition) was estimated.…”

Модельные Оценки Квантовой Емкости Аморфных И Эпитаксиальных Графеноподобных Соединений

“…Рассмотрим энергетический интервал (0, E g /2). Энергия точки Дирака графена относительно центра запрещенной зоны равна ε D = φ SLG − χ − E g /2, где φ SLG = 4.79 эВ -работа выхода свободного графена [36], χ -электронное сродство полупроводника. Воспользовавшись приведенными в [34] значениями E g (3.23 и 3.00 эВ для политипов 4H и 6H соответственно) и χ (3.17 и 3.45 эВ для политипов 4H и 6H), получим (ξ, ∞).…”