טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShpilman Ze'ev
SubjectElectron Field Emission Measurement and Surface
Characterization of Micron to Nano Grain
Size Diamond Films
DepartmentDepartment of Physics
Supervisors Professor Alon Hoffman
Professor Emeritus Rafael Kalish


Abstract

Here we report on the Electron Field Emission (EFE) properties of nano-crystalline carbon films deposited by the Glow Discharge Direct Current (GDDC) technique. By this method film growth occurs by a subsurface implantation process of energetic carbon species without any pretreatment. Nano-crystalline films of a predominant diamond or oriented graphitic character can be deposited. These Nano-Diamond (ND) films comprise an amorphous layer a few nanometer thick on their surface. The presence of this surface layer inhibits EFE of the as deposited films, which only came to Electrical Discharge (ED). After removal of the amorphous layer by short hydrogen plasma etch (leaving the layer to be H terminated ND), the film emits at a TOF of 15.4±2 and 14±3 (V/mm) for different samples. Thermal treatment of this film at 10300C removes the hydrogen from the surface layer and results in surface reconstruction creating a partially graphitic surface, which leads to degraded EFE properties. Nano-crystalline graphite films whose basal planes display a preferred orientation perpendicular to the surface emit at a TOF of 6±0.31 (V/mm) and 9.4±0.6 (V/mm) (different points on the same sample). The orientation of the films brings local field amplification, which assists the electron emission. A large percent of orientation is liable to screen the local field amplification, thus a correlation was found between the EFE properties and the percentage of orientation. Surface composition, structure and morphology of the films are correlated to the EFE properties by using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photo-electron Spectroscopy (XPS), Electron Energy Loss Spectroscopy (EELS).