Density of States Calculations for Carbon Allotropes and
Carbon structures were simulated in order to deepen understanding of the properties of nanodiamond films. These properties were compared with the experimental results of different techniques, such as Near Edge X-ray Absorption Fine Structure (NEXAFS). The simulation was done by tight-binding methods for samples of hundreds of atoms.It is experimentally observed that Chemical Vapor Deposition (CVD) nanodiamond films grow by deposition of hydrocarbon rich plasma presenting a structure of nanodiamond cores embedded in amorphous carbon. Consistent computational simulations of these structures, where it is possible to calculate physical processes in them, are required in order to deepen understanding of the processes leading to the growth of nano-diamond films. Specifically, Density Of States (DOS) calculations when compared with the experimental results from NEXAFS measurements enable us to interpret the NEXAFS characteristics. Our DOS calculations were in good agreement with experimental NEXAFS results.
New computational techniques, making possible larger and more accurate simulations were developed during this thesis. A new characterization method for carbon hybridization states was developed, leading to improved visualization of the samples, in order to give new insights into the comprehension of the sample geometry. A technique to simulate a geometrical structure of nanodiamond cores embedded in amorphous carbon was developed in order to simulate nanodiamond film growth in CVD conditions as observed experimentally at the Techni on. Initial studies of hydrogenated samples were made and some studies of their stability and DOS were carried out.