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

Paper EM-WeA4
Raman Spectroscopy of Ultrananocrystalline Diamond Thin Films

Wednesday, November 5, 2003, 3:00 pm, Room 321/322

Session: Diamond/Contacts to SiC
Presenter: J. Birrell, Argonne National Laboratory
Authors: J. Birrell, Argonne National Laboratory
J.E. Gerbi, Argonne National Laboratory
O. Auciello, Argonne National Laboratory
J. Johnson, Argonne National Laboratory
X. Xiao, Argonne National Laboratory
J.A. Carlisle, Argonne National Laboratory
Correspondent: Click to Email
Raman spectroscopy is often used as an efficient and non-destructive way of determining the bonding structure of diamond thin films. However, interpretation of the Raman spectrum of carbon materials with small grain sizes and a large number of grain boundaries, such as in nanocrystalline, ultrananocrystalline (UNCD), and amorphous diamond, is not straightforward. In order to correctly interpret the Raman spectral features of UNCD thin films, a series of films spanning the range of structures from microcrystalline to UNCD was studied using visible and UV Raman spectroscopy, as well as scanning and transmission electron microscopy. For UNCD, we find that although the sample has been found to be composed of ~95% @super" sp@super 3@-bonded carbon by other techniques including near-edge adsorption fine structure (NEXAFS) and TEM, none of the spectral features observed using visible Raman spectroscopy can be attributed to @super" sp@super 3@-bonded carbon. As the UNCD grains appear purely crystalline in TEM, we identify the disordered carbon at the grain boundaries of UNCD as responsible for all spectral features observed. This enables us to probe the grain boundary structure of UNCD specifically, which is of great utility for understanding the electronic and structural properties of the material. Finally, we interpret the changes in the Raman spectra of UNCD grown under various growth conditions, including low temperature growth; as well as with nitrogen doped UNCD, which results in a large increase in the conductivity of UNCD films. This work was supported by the DOE-Office of Science-Materials Science under Contract No. W-31-109-ENG-38.