title: Mechanism for doping induced p type C60 using thermally evaporated molybdenum trioxide (MoO3) as a dopant.
abstract: Thermally evaporated molybdenum trioxide (MoO3) doped C60 films, which could change n type features of pristine C60 to form a p type mixed C60 layer, are investigated by x-ray and ultraviolet photoelectron spectroscopy. It is found that C60 HOMO progressively shifts closer to the Fermi level after increased MoO3 doping concentration, and final onset of C60 HOMO is pinned at binding energy of 0.20 eV, indicating the formation of p type C60 films. It is proposed that in charge transfer induced p type C60 formation, due to large electron affinity of MoO3 (6.37 eV), electrons from HOMO of C60 could easily transfer to MoO3 to form cations and therefore increase hole concentration, which could gradually push C60 HOMO to the Fermi level and finally form p type C60 films. Moreover, clear different types of C60 species have been confirmed from UPS spectra in highly doped films.
authors.affiliation: College of Physical Science and Technology, Yangzhou University, Jiangsu 225009, China. Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.
authors.forename: Jin-Peng
authors.initials: JP
authors.lastname: Yang
authors.forename: Wen-Qing
authors.initials: WQ
authors.lastname: Wang
authors.forename: Li-Wen
authors.initials: LW
authors.lastname: Cheng
authors.forename: Yan-Qing
authors.initials: YQ
authors.lastname: Li
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Tang
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kera
authors.forename: Nobuo
authors.initials: N
authors.lastname: Ueno
authors.forename: Xiang-hua
authors.initials: XH
authors.lastname: Zeng