Mohd Alim Khan

Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

This article reports the influence of substrate bias during growth and of hydrogen and nitrogen incorporation on density of states [N (EF)] and field-emission threshold (Eturn-on) in tetrahedral amorphous carbon (ta-C) films, deposited using an S-bend filtered cathodic vacuum arc process. The variation in negative substrate bias from −20 to −200 V was found to initially lead to a small decrease in N (EF) and Eturn-on, and a small increase in the emission current density (J) at 12.5 V/μm in the case of as-grown ta-C films; beyond −200 V substrate bias there is a reversal in the trend. The values of N (EF)=1.3×1017 cm−3 eV−1, Eturn-on=8.3 V/μm, and J=6.19 mA/cm2 were observed at −200 V substrate bias. However at −300 V the properties were not very different from those at −200 V substrate bias and so with a view to use the higher energy, hydrogen and nitrogen incorporation studies were carried out in this condition. It was observed that there was further enhancement in properties with hydrogen and nitrogen i...

Characterization of Boron- and Phosphorous-Incorporated Tetrahedral Amorphous Carbon Films Deposited by the Filtered Cathodic Vacuum Arc Process

This paper reports the X-ray photoelectron spectroscopy (XPS), X-ray-induced Auger electron spectroscopy (XAES), and Raman studies of boron- and phosphorous-incorporated tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc process. A systematic study of the influence of varying boron (B) and phosphorous (P) content on the properties of the as-grown ta-C films deposited at high negative substrate bias (-300 V) is reported by analyzing the C 1s, B 1s, and P 1s core levels using photoelectron spectroscopy. The sp3 and sp2 contents in the films were determined by measuring the width of the X-ray-induced Auger peaks. B incorporation in ta-C films up to 2.0 at. % increases the sp2 content and decreases the sp3 content by 3.6%, whereas P incorporation up to 2.0 at. % results in an increase of sp2 content and decrease of sp3 content by ~ 30%. The valence band spectra show changes in the Fermi level as B and P are incorporated into the ta-C films. The characteristic Raman spectra confirm the high sp3 content in the deposited films. Thus, the study demonstrates, in the case of high negative substrate bias films, that a pronounced decrease in sp3 fraction or the diamond-like nature of the ta-C films occurs upon P incorporation in comparison to that upon B incorporation.