The electronic structure of fullerene (C60) deposited on calcium (Ca) was investigated using in-situ ultraviolet photoelectron spectroscopy. The energy level alignment at the C60/Ca interface was estimated by combining both shifts of the highest occupied molecular orbital (HOMO) level and of the vacuum level during the step-by-step deposition of C60 on Ca. The HOMO level of C60 shows shifts relating to band-bending, resulting in an electron injection barrier of 0.2 eV with accumulation contact with the Ca substrate. The vacuum level reveals an interface dipole of 1.11 eV with negative poles on the C60 side. Noticeably, gap states are formed at the interface region, which might pin the Fermi level and be responsible for the formation of the interface dipole. The complete interfacial energy level diagram of C60/Ca is presented.
Bibliographical noteFunding Information:
This work was supported by a research project of the Korea Research Foundation (Grant No. 2010-0015727 and 2010-0003009 ) and Korea Research Council of Fundamental Science and Technology (KRCF) through the KRISS project of “Development of Advanced Industrial Metrology”. Also Greonggi province supported this project through the GRRC program [GRRC Kyung Hee 2010-B07].
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry