Study of Graphite Nanofibers by the Scanning Atom Probe

In this study, graphite nanofibers (GNF) were analyzed by using the scanning atom probe (SAP) [ 1]. Graphite nanofibers (GNF) were grown on a SUS304 needle by the thermal CVD method. The SUS needle was mounted in the SAP and mass analyzed by applying DC and pulsed voltages to the specimen at room temperature. The field emission characteristics were also examined by operating the SAP as a field emission microscope. At the beginning of the mass analysis of GNF, small mass ions (< 100 amu) which could be ascribed to not fully decomposed precursor gas were detected. No significant mass peaks were detected in the mass range m/n = 100-200. After the removal of the surface layer, the detection rate of the clusters with the mass larger than 200 amu increased. The evaporation voltage of GNF is found to be significantly lower than the voltage expected from its field emission characteristics. The largest mass peak was C23H2+ in the range of m/n = 200-300. The C23H2+ mass peak had a tail due to the weak C-H bond of the clusters. Other noticeable peaks were C18H7+, C22H2+, C-22(+), and C-20(+).