Growth and Characterizations of Indium-Doped Pentacene Thinfilm Prepared by Thermal Co-Evaporation as a Novel Nanomaterial

Abstract

This research is related to growth and characterizations of indium-doped pentacene thin films as a novel hybrid material. Doped films were prepared by thermal co-evaporation under high vacuum. The doping concentration was varied from 0% to 50% by controlling the different deposition rate between these two materials while the total thickness was fixed at 100 nm. The hybrid thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and UV-Visible spectroscopy to reveal the physical and optical properties. Moreover, the electrical properties of ITO/indium-doped-pentacene/Al devices i.e. charge mobility and carrier concentration were determined by considering the relationship between current-voltage and capacitance-voltage. AFM results identify that doping of indium into pentacene has an effect on surface properties of doped films i.e. the increase of surface grain size. XRD results indicate that doping of metal into pentacene has an effect on preferential orientation of pentacene’s crystalline domains. UV-Vis spectroscopy results show evolution of absorbance at photon energy higher than 2.7 eV corresponding to absorption from oxide of indium formed in the films. Electrical measurements exhibit higher conductivity in doped films resulting from increment of both charge carrier mobility and carrier concentration. Furthermore, chemical interactions taken place inside the doped films were investigated by x-ray photoelectron spectroscopy (XPS) in order to complete the remaining questions i.e. how do indium atoms interact with the neighbor molecules?, what is the origin of the absorption at E > 2.7 eV? Further results and discussions will be presented in the publication.