Stanley Joseph Whitehair

Internal stress and elasticity of synthetic diamond films

The internal tensile stress in polycrystalline diamond films deposited on silicon substrates has been measured from 100 to 700 K by a vibrating‐membrane method. The stress increases strongly with temperature, in a manner consistent with the elastic accommodation of the differential thermal strain between diamond and silicon. The results indicate that the films contain a tensile growth stress of about 500 MPa at the deposition temperature of 1123 K. Derived values of the biaxial elastic modulus fall in the range 730–850 GPa.

Enhanced nucleation and growth of diamond on SiC by plasma enhanced chemical vapor deposition using thin metal films

Presented is a method for growing crystalline diamond films by plasma enhanced chemical vapor deposition without the need for seeding with diamond particles. Instead, diamond nucleation and growth is ‘‘catalyzed’’ by a thin metal film which has been either abraded or deposited onto a SiC coated substrate. In the first experiment Fe, Cu, Ti, Nb, Mo, and Ni were abraded onto a SiC surface resulting in varying degrees of diamond nucleation and growth. In the second experiment, Fe films with thickness varying from 5 to 80 A were evaporated onto the SiC. Although the 5 A Fe film did not influence the initial nucleation and growth rate, greater thicknesses did. Preliminary studies of Fe on Si have not shown this effect.Presented is a method for growing crystalline diamond films by plasma enhanced chemical vapor deposition without the need for seeding with diamond particles. Instead, diamond nucleation and growth is ‘‘catalyzed’’ by a thin metal film which has been either abraded or deposited onto a SiC coated substrate. In the first experiment Fe, Cu, Ti, Nb, Mo, and Ni were abraded onto a SiC surface resulting in varying degrees of diamond nucleation and growth. In the second experiment, Fe films with thickness varying from 5 to 80 A were evaporated onto the SiC. Although the 5 A Fe film did not influence the initial nucleation and growth rate, greater thicknesses did. Preliminary studies of Fe on Si have not shown this effect.

Reaction of niobium with diamond films

Abstract The reaction of niobium with diamond films leads to the formation of Nb 2 C at 700°C and to that of a carbon deficient NbC at 900°C. Both processes seem to be dominated by grain boundary diffusion, so that the growths do not proceed in smooth layers parallel to the substrate, but seemingly homogeneously throughout the thickness of the reacting metal (then Nb 2 C) film. The results of backscattering and X-ray diffraction analyses are discussed in terms of what is known about these two compounds with respect to their thermodynamic, kinetic and structural characteristics. The formation of ordered phases with carbon deficiency such as Nb 4 C 3 , or Nb 6 C 5 , and nucleation processes resulting from this are presumed to hinder the formation of near-stoichiometric NbC.

High Density Amorphous Carbon Films and the Preparation of Diamond Membranes for X-Ray Lithography

Abstract Trends in recently reported data on high sp 3 fraction (up to 85%), non-hydrogenated amorphous diamond-like carbon films deposited by ion beam sputtering and laser vaporization are examined. The degree of diamond-like film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity. The data suggest that the combination of incident particle kinetic energy and surface accommodation determine the physical properties of the resultant film. A model is proposed for the condensation of energetic carbon atoms into diamond-like films in which a quench-type surface accommodation mechanism is operative. Diamond Membranes are being developed for x-ray lithographic masks. Typically, these 1-3 micron thick membrane films are deposited onto silicon substrates using microwave driven plasmas. To obtain smooth films with uniform tensile stress, spray and electrophoretic deposition of 0.1 micron diamond seeds were used to control the initial nucleation and growth of the diamond films. The films have a room temperature tensile stress of 25 to 125 MPa. The temperature dependence of the stress is due to the tensile growth stress of the diamond film and the thermal stress of the diamond-silicon layer structure. The films have a biaxial modulus of 800 GPa. X-ray lithography masks have been made and used to print patterns with x-rays from a synchrotron source.

The effects of secondary particle bombardment on ion beam sputtered thin films of Y1Ba2Cu3Ox deposited on MgO (100)

We have investigated the effects of low energy bombardment on the microstructural, compositional, and electrical characteristics of ion beam sputtered thin films of Y1Ba2Cu3Ox. During deposition, secondary bombardment of the growing film was performed using a Kaufman or ECR type ion source with energy ranging up to 125 eV. Microstructural changes have been characterized by TEM and XRD. Ion channeling has been performed to characterize the degree of orientation of the films. The effects of bombardment on the composition of the films were studied by RBS. It has been found that the use of an ECR microwave oxygen ion source trained on the growing films induces as‐deposited superconductivity and also play a role in the texturing of the films. The effects of ion bombardment on the critical current (Jc) and temperature (Tc) are also reported.