M.F. Rose

Growth of Polycrystalline Diamond over Glassy Carbon and Graphite Electrode Materials

Boron-doped polycrystalline diamond thin films were grown over glassy carbon electrode material and POCO graphite by a microwave plasma-assisted chemical vapor deposition (CVD) using a gas mixture of methane and hydrogen. As-deposited films were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy for their morphology and chemical nature, respectively the diamond films grown over glassy carbon and graphite electrode material may have some use in electroanalysis since the doped diamond films are electrically conductive, erosion resistant, and chemically inert.

Polishing of polycrystalline diamond by hot nickel surface

A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851°C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848°C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by hot nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.

Growth of diamond thin films on nickel-base alloys

Abstract Microwave plasma-assisted chemical vapor deposition has been employed to grow diamond films (thickness up to 50 μm) using a gas mixture of hydrogen (H 2 ), methane (CH 4 ), and oxygen (O 2 ) on various substrates such as Ni 200, MONEL 400, INCONEL 600, INVAR, single crystal nickel with orientations of (100), (111), etc. Nucleation of diamond on the substrates has been achieved by seeding with diamond particles, manual scratching, and ultrasonic agitation in methanol (CH 3 OH) containing diamond particles. The substrate underwent H 2 microwave plasma treatment for 5–60 min to remove any oxide film present prior to diamond growth. Growth of diamond over MONEL 400 was achieved at various CH 4 concentrations in H 2 . As-deposited films were analyzed by scanning electron microscopy (SEM), Raman spectroscopy, secondary ion mass spectroscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy. According to SEM the morphology of the grown films was (100) texture over the entire surface ( 2 ) of Ni 200 substrate. Raman analysis of the top side of deposited film confirms for diamond and on the back side of the free-standing film shows the characteristic peaks for diamond and graphite. As-deposited films were diamond and other forms of non-diamond carbon on INCONEL 600 and INVAR.

Plasma etching and patterning of CVD diamond at <100°C for microelectronics applications

Abstract Oxidation resistance of diamond is an important characteristic to be considered in high-temperature microelectronics and other applications. We have tested the stability of CVD diamond by exposing it to Ground State Atomic Oxygen (GSAO, O) at a temperature of 74°C. Polycrystalline diamond is quite stable at this temperature using O. We have also tested the stability of diamond using Excited State Atomic Oxygen (ESAO, O*). Initially, CVD diamond was exposed to O* for 15 min at 63°C, and diamond etching was observed. We have also carried out the experiments at different time intervals such as 30 and 45 min. The etching rate of the polycrystalline diamond using O* is ≈ 0.2–0.25 m/min at 63°C. We have successfully patterned the diamond (polycrystalline and single crystal) using a Ni mask by exposing the sample to O* for a longer time. O* etched the diamond uniformly in all the directions of the diamond crystal as opposed to the molecular oxygen. Stability of the single crystal diamond has been tested using O* by using Ni mask material. We were able to etch the single crystal diamond (type IIa, 100 orientation) quite uniformly. The etching rate of single crystal diamond using O* was observed to be 0.3 m/min.

Kinetic studies of hydroquinone_quinone at the boron-doped diamond electrode by cyclic voltammetry

Abstracts are not published in this journal

Optical spectroscopy studies of surface breakdown of polycrystalline diamond thin films in vacuum

Diamond is known to be an excellent electrical insulator and thermal conductor. These properties of diamond make it an attractive candidate as the insulating material for high voltage systems to be used in low earth orbit (LEO) and interplanetary space environment. However, to the knowledge of the authors, the surface flashover and surface breakdown characteristics of polycrystalline diamond thin films have not been investigated to date. In this work we will present experimental results of surface flashover characteristics of polycrystalline diamond and other synthetic thin films in vacuum. Electrical characteristics of surface breakdown and optical emission spectra of the surface flashover plasma are investigated. Optical spectroscopic studies of the luminosity of the discharge reveals information about the excited and ionized species in the vicinity of the surface. An optical multi channel analyzer was used to identify the emission lines of the optical spectrum.

High voltage transmission line operation in simulated lunar environment

Possible design alternatives of a high voltage transmission line system for use with the proposed lunar base have been studied. Because of substantial environmental differences between the Moon and the Earth, the techniques used in the Earths atmosphere may not be applicable in the lunar environment. Therefore, the thermal and electrical characteristics of transmission lines in the lunar environment need to be investigated. The information about the thermal and electrical conductivities of the lunar soil is not sufficient to predict the initiation and the characterization of electrical breakdown on or beneath the soil surface in the presence of high power systems. In addition, the induced electric field and thermal effects may cause failure of high voltage transmission lines operating within the soil. The soil characteristics may be permanently altered due to induced effects and thereby prevent operation of high power systems. We present the results of experiments where a small transmission line segment is placed into simulated lunar soil and operated in a high vacuum environment. The effects of the simulated lunar soil, the applied field strength, geometry and material of the transmission lines, and the ambient temperature on the operation of the high voltage transmission lines were investigated.