▎ 摘　　要

We developed a polymer-free (PF) transfer method and examined the optimum annealing temperature and time for the polymer-free graphene to improve the graphene-metal contact. To further tune the work function of graphene to reduce contact resistance, we report solution doping combined with the PF method, and by using P-doped graphene, the contact resistance is markedly reduced to 24 Omega mu m, which is an extremely low value in recent research. Photoemission spectroscopy was used to investigate the graphene/Au interface to explain the results of our contact resistance measurements, and the highest FET mobility of these low-contact devices was 14400 cm(2)V(-1)s(-1) for intrinsic graphene in this study. (C) 2018 The Japan Society of Applied Physics.