Energy level alignment and molecular conformation at rubreneAg interfaces Impact of contact contaminations on the interfaces.pdfVIP

Applied Surface Science 409 (2017) 22–28 Contents lists available at ScienceDirect Applied Surface Science journal homepage: /locate/apsusc Full Length Article Energy level alignment and molecular conformation at rubrene/Ag interfaces: Impact of contact contaminations on the interfaces Sumona Sinha a,?, C.-H. Wang b, M. Mukherjee a a Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064, India b National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan article info Article history: Received 10 January 2017 Received in revised form 1 March 2017 Accepted 3 March 2017 Keywords: Rubrene/Ag interfaces Impact of contact contamination Clean and unclean Ag substrate surface Energy level alignment Molecular conformation and orientation Surface morphology abstract This paper addresses the impact of electrode contaminations on the interfacial energy level alignment, the molecular conformation, orientation and surface morphology deposited organic ?lm at organic semiconductor/noble metal interfaces by varying of ?lm thickness from sub-monolayer to multilayer, which currently draws signi?cant attention with regard to its application in organic electronics. The UHV clean Ag and unclean Ag were employed as substrate whereas rubrene was used as an organic semiconducting material. The photoelectron spectroscopy (XPS and UPS) was engaged to investigate the evolution of interfacial energetics; polarization dependent near edge x-ray absorption ?ne structure spectroscopy (NEXAFS) was employed to understand the molecular conformation as well as orientation whereas atomic force microscopy (AFM) was used to investigate the surface morphologies of the ?lms. The adventitious contamination layer was acted as a spacer layer between clean Ag substrate surface and rubrene molecular layer. As a consequence, hole injection barrier height, interface dipole as well as molecular-conformation, molecular-orientation and surface morphology of rubrene thin ?lms were found to dep