Plasma, photon, and beam synthesis of diamond films and multilayered structures

Three major areas of fundamental research on diamond thin films have been explored during the last period, 1990--1991. A new microwave plasma enhanced laser ablation system has been designed and constructed. This system is currently being used to study the possibility of depositing diamond films on plastic surfaces. A mechanism for nucleating diamond films on single crystal copper surfaces has been proposed and detailed experiments have been carried out. Carbon clusters of C{sub 70} have been successfully used to nucleate diamond on non-diamond surfaces. This invention provides an alternative to using diamond -- grit polish as a nucleating agent

Synthesis and electron field emission of nanocrystalline diamond thin films grown from N2/CH4 microwave plasmas

Nanocrystalline diamond films have been synthesized by microwave plasma enhanced chemical vapor deposition using N2/CH4 as the reactant gas without additional H2. The nanocrystalline diamond phase has been identified by x-ray diffraction and transmission electron microscopy analyses. High resolution secondary ion mass spectroscopy has been employed to measure incorporated nitrogen concentrations up to 8 ×1020 atoms/cm3. Electron field emission measurements give an onset field as low as 3.2 V/μm. The effect of the incorporated nitrogen on the field emission characteristics of the nanocrystalline films is discussed

Plasma, photon, and beam synthesis of diamond films and multilayered structures

In the area of nucleation, it was discovered that C{sub 70} thin films are perfect substitutes for diamond seeds in the growth of diamond films. This research, along with a careful study of diamond growth on carbon ion implanted single crystal copper, have clearly demonstrated that structured carbon is the best precursor for nucleation and growth of diamond films on non-diamond surfaces. In addition, by using fluorine chemistry during diamond growth, it has been shown that diamond films can grow on carbide substrates without the pretreatment of diamond seeding. The growth rates are higher and the film adhesion is much improved

Plasma, photon, and beam synthesis of diamond films and multilayered structures. Final report for the period July 1996 - December 1998

The DOE has been supporting Professor Chang and his students in the area of plasma and photon synthesis of diamond-like and ceramic films with varying complexity during the past three years. We have made substantial contribution to the field during this period of time. Some of the important questions have been addressed, and they include: a. How does the energy (wavelength) of the laser change the composition and energy distribution of the ablated species? b. How do surface mobility and the intensity of the plasma plume affect crystal nucleation and growth? c. How can one manipulate the system parameters during film growth to achieve special properties for unique applications? In the area of photon synthesis, we have shown that amorphous diamond films can have properties very similar to polycrystalline diamond films and yet they may have wider applications in such areas as coating and electronics. For example, we have shown that these films can be used to protect plastics such as polycarbonate surfaces. During the course of our amorphous diamond films research, we have also identified important parameters which alter the film properties. Higher photon energy and laser power density contribute to higher percentage of carbon ion density and energy in the plasma plume. This in turn proves films with higher percentage of diamond-like sp{sup 3} bonds and thus diamond-like properties of the films. Lower photon energies and collision of the plasma plume with background gas will produce films which are rich in graphitic properties. In the area of oxide film growth, we have found, in general, that better crystalline films can be grown by laser ablation at much lower substrate temperatures than by chemical vapor deposition process. This is due to the fact that in laser ablation the depositing species have more kinetic energies and the whole process involves rapid solidification. By using optical emission spectroscopy, we have learned how to adjust the deposition parameters to control film properties such as grain size and crystal orientations. These control capabilities have allowed us to grow oxide films with unique properties, such as high optical nonlinearity. In addition, we have been able to grow films with special crystalline orientations to serve as templates for chemical vapor deposition processes

Parametric excitation of drift waves with the pump near the ion cyclotron frequency in a two-ion-species plasma

Parametric excitation of drift waves in a multi-ion species plasma is observed in a range of pump frequencies, ..omega../sub pi//..cap omega../sub i/ much greater than ..omega../sub o//..cap omega../sub i/ approximately equal to 1.3 to 1.6 and the ion concentration ratio, N(He):N(Ne) = 8:2 to 3:7. The dispersion relation and the excitation mechanism are verified