Variation of Band Gap in Graphene Grown by Plasma Enhanced Chemical Vapor Deposition

Abstract

Graphene is a two-dimensional monolayer with linear dispersion relation near the Dirac point and has attracted much interest owing to its superb material properties, such as very high mobility of 10,000 cm2/Vs at room temperature and quantum hall effect to promise for the potential in nanoelectronics [1-4]. However, graphene is a semimetal without an energy band gap which is required to be used as an electronic transistor. Recent studies have shown that band gap is formed at various situation, in nanoribbons, [5] bias-applied, and [6] strained or molecule-doped graphene [7,8]. Though the band gaps were generated in various structures, the control of the electrical properties is still a challenge. On the other hand, defects and impurities in graphene are important in electrical transport, because scattering is a hurdle in carrier transport in graphene, making the modulation of graphene transport quite important for physical and device application. In particular, defects in graphene have been intensely studied because quasi-localized states near the Fermi energy can be induced due to vacancy [9,10]. Here, we report that band gap engineering has been achieved by PECVD growth and plasma treatment can induce modulation of the defective properties of graphene. The graphene films were synthesized by plasma-enhanced chemical vapor deposition (PECVD) at 950 °C on sapphire substrate without catalyst, and the radio frequency plasma power was fixed at 150W. Carrier gas was argon (300sccm) and hydrogen (30sccm). The hydrocarbon, CH4 (1sccm) was used as a source precursor during the growth. Growth time was adjusted from 5min to 60min. Pristine graphene was identified as a bilayer using an optical microscope and Raman signal. Raman spectra of the graphene films were measured at an excitation of 514.5nm at room temperature using a spectrometer (Horiba Jobin-Yvon, HR800UV). The electrical transport was characterized as a function of temperature using low temperature measurement system (Sungwoo Instrument & Sumitomo). Crimson Publishers Wings to the Research Mini Review