Growth, characterization and electron field emission measurements from thin film cold cathode materials fabricated by a modified microwave plasma assisted chemical vapor deposition diamond process.

摘要

This thesis presents the results of electron field emission measurements on thin film cold cathode fabricated by a modified microwave plasma assisted chemical vapor deposition diamond process. Specifically, the modification is due to the addition of nitrogen and oxygen, in varying ratios, to the growth plasma. The thin films were grown on polished molybdenum substrates. The growth conditions were for a constant methane (10%CH₄/H₂) and hydrogen (H₂) concentration of 60:40 at T = 900–950°C. The nitrogen oxygen ratios, N₂/O₂, ranged from 1:1 to 50:1. In addition films were grown with just nitrogen and just oxygen.; Characterization of the thin film materials has been carried out by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The results indicate that the material is a disordered tetrahedrally bonded carbon with crystal size of $\approx$10–100nm. The disorder of the material results in a departure from the cubic symmetry of the diamond lattice. This symmetry breaking is a result of stacking faults and nano-twinning.; The field emission results indicate that certain N₂/O ₂ ratios and film thicknesses show low turn on fields and current densities desirable for cold cathode devices. Specifically, N₂/O₂ = 33–50 and film thickness = 1–2 microns (μm) are shown to be the most desirable. Turn on fields as low as 1–2 V/ μm and current densities of >1mA/cm2 have been measured. Comparisons of films grown in this study with polycrystalline diamond films grown by a multiple laser process have been made.; Testing of simple cold cathode devices have been carried out. The device is based on a simple triode configuration. The proposed application is as a cold cathode ionization gauge for high and ultra high vacuum pressure measurements. Problems with total emitted current and current stability have been addressed through the testing of different insulating and metal gate materials as well as several triode configurations. Current measurements of greater than 10 milliamps have been realized.