Diamond samples with varying defect densities have been synthesized by chemical vapor deposition, and their field emission characteristics have been investigated. Vacuum electron field emission measurements indicate that the threshold electric field required to generate sufficient emission current densities for flat panel display applications (>lO mA/cm") can be significantly reduced when the diamond is grown so as to contain a substantial number of structural defects. The . defective diamond has a Raman spectrum with a broadened peak at 1332 cm-*' with a full width at half maximum (FWHM) of 7-11 cm-'. We establish a strong correlation between the field required for emission and the FWHM of the diamond peak. The threshold fields are typically less than 50 Vl,um and can reach as low as 30 Vl,um for diamond with a FWHM greater than 8.5 cm-'. It is believed that the defects create additional energy bands within the band gap of diamond and thus contribute electrons for emission at low electric fields. Cp I995 American Institute of Physics.

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Diamond films and islands grown by chemical vapor deposition were implanted with boron, sodium, and carbon ions at doses of 10 14-10 15 /cm 2. This structural modification at the subsurface resulted in a significant reduction of the electric field required for electron emission. The threshold field for producing a current density of 10 mA/cm 2 can be as low as 42 V/m for the as-implanted diamond compared to 164 V/m for the high quality p-type diamond. When the ion-implanted samples were annealed at high temperatures in order to anneal out the implantation-induced defects, the low-field electron emission capability of diamond disappeared. These results further confirm our earlier findings about the role of defects in the electron emission from undoped or p-type doped diamond and indicate that the improved emission characteristics of as-implanted diamond is due to the defects created by the ion implantation process.

The thermal conductivity of thick-film diamond prepared by chemical vapor deposition (CVD) has been measured with heat flowing in a direction perpendicular to the plane of the film. A laser flash technique with fast infrared detection has been devised for measurement of thin samples with high conductivity. The conductivity perpendicular to the plane is observed to be at least 50% greater than with heat flowing parallel to the plane. This anisotropy is attributed to low-quality grain boundaries in the columnar microstructure. The observed dependence of the thermal conductivity on microstructure has important implications for thermal management of microelectronic devices with CVD diamond.

The thermal conductivity of chemical-vapor-deposited diamond films on silicon is measured for the case of heat flow parallel to the plane of the film. A new technique uses thin-film heaters and thermometers on a portion of the film which is made to be free standing by etching away the substrate. Effects of thermal radiation are carefully avoided by choosing the length scale properly. Data for several films yield thermal conductivities in the range 2–6 W/cm °C. This is comparable to copper (4 W/cm °C) and is in a range that would be useful as a thin-film dielectric material, provided that the interface thermal resistance can be minimized. The conductivity varies inversely with the growth rate and the Raman linewidth.