Organic Layer Smooths Dielectric Films

Depositing a few layers of organic molecules on graphene enables subsequently deposited oxide layers to be grown without imperfections, according to a study published in ACS Nano (DOI: 10.1021/nn201414d). The investigation identifies a fabrication step that can improve the quality of insulating layers crucial to the performance of graphene-based electronic devices. To exploit graphene for use as a field-effect transistor electrode, this ultrathin carbon film needs to be selectively coated with smooth, thin, and defect-free layers of insulating materials known as high-k dielectrics. Graphene’s hydrophobicity and inertness, however, prevent dielectrics such as alumina and hafnia from being deposited on graphene smoothly and uniformly. Some surface treatments have been shown to improve the deposition process, but they tend to degrade graphene’s structure and electronic properties. A team of researchers, led by Northwestern University’s Mark C. Hersam, has shown that those problems can be overcome by growing one or two monolayers of a perylene dianhydride compound, PTCDA, on graphene before depositing films of alumina and hafnia. According to the team, surface analysis and electrical measurements show that dielectric films grown that way are highly uniform and conformal, and that the graphene remains undamaged.