Determination of Work Function of Graphene under a Metal Electrode and Its Role in Contact Resistance

• Published in: Nano letters 2012-08, Vol.12 (8), p.3887-3892
• Main Authors: Song, Seung Min, Park, Jong Kyung, Sul, One Jae, Cho, Byung Jin
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Contact; Contact resistance; Cross-disciplinary physics: materials science; rheology; Electric potential; Electrodes; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Gold; Graphene; Magnesium oxide; Materials science; Physics; Specific materials; Surface double layers, schottky barriers, and work functions; Voltage; Work functions
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl300266p

Although the work function of graphene under a given metal electrode is critical information for the realization of high-performance graphene-based electronic devices, relatively little relevant research has been carried out to date. In this work, the work function values of graphene under various metals are accurately measured for the first time through a detailed analysis of the capacitance–voltage (C–V) characteristics of a metal–graphene–oxide–semiconductor (MGOS) capacitor structure. In contrast to the high work function of exposed graphene of 4.89–5.16 eV, the work function of graphene under a metal electrode varies depending on the metal species. With a Cr/Au or Ni contact, the work function of graphene is pinned to that of the contacted metal, whereas with a Pd or Au contact the work function assumes a value of ∼4.62 eV regardless of the work function of the contact metal. A study of the gate voltage dependence on the contact resistance shows that the latter case provides lower contact resistance.