AVS 50th International Symposium
    Electronic Materials and Devices Wednesday Sessions
       Session EM-WeA

Paper EM-WeA3
Highly Conductive N-type Ultrananocrystalline Diamond: Materials Properties and Devices

Wednesday, November 5, 2003, 2:40 pm, Room 321/322

Session: Diamond/Contacts to SiC
Presenter: J.E. Gerbi, Argonne National Laboratory
Authors: J.E. Gerbi, Argonne National Laboratory
O. Auciello, Argonne National Laboratory
J. Birrell, Argonne National Laboratory
S. Curat, University College London, UK
D.M. Gruen, Argonne National Laboratory
R.B. Jackman, University College London, UK
O.A. Williams, University College London, UK
J.A. Carlisle, Argonne National Laboratory
Correspondent: Click to Email
Ultrananocrystalline diamond (UNCD) is a fine-grained (3-5 nm) diamond material. Synthesized by MPECVD using Ar-rich Ar/CH@sub 4@ plasmas, the electronic, structural, and tribological film properties of UNCD can be tailored by doping with a controlled amount of N@sub 2@. These changes correspond with clear transformations in the film structure, as both the grain size and grain boundary width of the UNCD films increase with nitrogen doping. In addition, we hypothesize that modifications in the bonding of the grain boundaries themselves occur. Together, these changes result in an n-type, highly conductive film that can retain the excellent tribological and structural properties of undoped UNCD. The conduction mechanism of nitrogen-doped UNCD is different than that of single-crystal diamond, with specific nitrogen-carbon and dangling bond complexes in the grain boundaries playing a crucial role. In this work, we discuss this unique conduction mechanism in the context of the UNCD film structure and growth process. We present recent device fabrication results and new Hall measurement results, performed with a field switching setup at variable temperatures, which provide incontrovertible evidence of the n-type conduction and significant mobilities of this material. For example, a film grown with the relatively low nitrogen doping level of ~ 0.2 at.% displays an electron carrier concentration of ~ 5 x10@super 17@ cm@super -3@ and a mobility of greater than 6 cm@super 2@/Vs , while retaining the excellent tribological, chemical, and structural characteristics necessary for conductive MEMS/NEMS and bioelectronics applications. Films with much higher conductivities and doping concentrations can also be produced; doping levels as high as 1.1 at. % N will also be discussed in the context of thin-film diamond electronics. This work was supported by the DOE-Office of Science-Materials Science under Contract No. W-31-109-ENG-38.