ICMCTF1998 Session DP: D-Posters

Wednesday, April 29, 1998 5:00 PM in Room Atlas Foyer
Wednesday Posters

Time Period WeP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF1998 Schedule

DP-1 Comparison of Mechanical Properties of Mono and Multilayered Ti-C:H Films
J.G. Han, D.J. Kim (Sung Kyun Kwan University, Korea); InS. Choi (LG Cable Co.Ltd., Korea)
Ti-C:H films are synthesized by magnetron sputtering process using Ti target in a gas mixture of C2H2 and Ar. The multilayered Ti-C:H film is deposited in multi couples of TiCx and Ti-C:H by controlling partial pressure of C2H2 up to 2.5 micrometer on D2 steel. The thickness of each couple is limited less than 2000Å. Ti content can be also varied from 10at% to 25at% by controlling C2H2 flow rate. The bonding states of Ti-C:H films are evaluated by Raman spectrum and FT-IR analyses. The mechanical properties of the mono- and multi-layered films were compared in terms of Knoop microhardness, compressive residual stress and adhesion. The compressive residual stress can be reduced by multi-layer deposition up to about 0.9GPa. The multi-layer is also appeared to be highly effective to obtain very low friction coefficient of 0.1. The detail comparisons are discussed on wear resistance and adhesion with respect to Ti contents.
DP-2 Effect of Interlayer on the Adhesion of Diamond Coating on Copper
Q.H. FAN, J.J. Gracio, E. Pereira (University of Aveiro, Portugal)

Diamond coating on copper may find applications in the fields where wear resistance, thermal conduction and electrical insulation, chemical resistance etc. are required. However, due to the fact that copper has no carbon affinity, direct growth of diamond on copper shows no adhesion. A possible solution to this problem is to use an interlayer, which provides sufficient adhesion to both the diamond film and the substrate.

This work demonstrates that, with a Ti or Cr interlayer, adherent diamond coatings on copper can be obtained. A comparative study of the adhesion of the coatings is presented. Pull-off tests showed that, for both of the interlayers, the diamond coating adhesion was better than the strength of adhesive used for the tests, ~13 MPa. However, scratch tests and indentation tests reveal a difference of the coating adhesion, being suggested due to the difference of carbon diffusion in Ti and Cr.

DP-3 Effect of Ion Implantation on Field Emission Characteristic of Diamond Film
H.K. Baik, J.Y. Shim, E.J. Chi (Yonsei University, South Korea)

There has been increasing research on diamond as an emitter material because it has extreme high thermal conductivity, chemical inertness, negative electron affinity and wide band gap. Especially, polycrystalline diamond as a field emitter has extremely low turn-on field. Although several models have been proposed to explain the low field emission from diamond, the origin of low field emission is not well understood. Recently, field emissions from diamond, grown with deposition parameters or post processed, are reported to understand the low field emission.

Post deposition process such as ion implantation and annealing can change electrical and structural characteristics of diamond films. Ion implantation into diamond has been extensively investigated with dopant, dose and energy. With ion dose, the microstructures of diamond films are changed from diamond to amorphous. On the other hand, the resistivities of as-deposited, undoped diamond films are dependent on post deposition processing: annealing ambient. However, the effects of ion implantation and/or post annealing on field emission characteristic of polycrystalline diamond film are not systematically examined.

In this study, we treat diamond films grown by hot filament CVD through ion implantation and/or post annealing. Diamond films are implanted with different dose and/or dopant. Post annealing are performed at various ambient and/or temperatures. Field emission property of post processed diamond are examined. Consequently, the effect of post treatment process on the field emission characteristics will be suggested.

DP-4 Graphite-to-diamond Transition on the CuO-Mg-C System, as a Result of Mechanically Induced Explosive Interaction of Components
A.R. Torossyan, V.G. Martirossyan, T.A. Kostanyan, A.R. Ghandevossyan (National Academy of Sciences, Republic of Armenia)

It is well known 1-4, that as a result of impulsive mechanical alloying (IMA) of some metals with different compounds,in a vibration ball mill,metals are restored from their oxides and sulphides at abnormally high speed and with explosion.As it has been established because of the changes in value of the ignition temperature Ti and the burning speed Vb, inside ball mill container taking place the inflammation and detonation of reaction mixture,that is the super fast liberation of exotermic reaction heat energy and initiation of blast waves 4.The similar machanically induced explosive behaviuor of interaction through components in the [MeO-Me1] mixture are conserved, when a graphite pouders in 7-30% of weight are introduced in system 5.Graphite samples of various structures have been investigated following impulsive mechanical treatment and explosive shock in the ball mill container, during solid-phase explosive interations of components in [CuO-Mg-C] system. X-ray investigations witness the existence of formed diamond phase in the obtained compounds.The machanisms proposed for the formation of diamond under these conditions are pressure-lubrication with disordering graphite atomic lattice during mechanical perturbation and it its reorganisation under the influence of detonation waves, the reaction's fast liberated heat energy and chemical interaction.The astimated pressure (p=10-12 Gpa) and teperature (T≥1333K,the melting temperature of metallic Cu) value are within the region of diamond stability.

1 G.B.Schaffer and P.G. McCormic,Appl.Phys.Lett.55,45(1989) 2 E.G.Avvakumov,Mechanical Methods of Chemical Process Activation (Nauka, 1986),p.305 3 N.G.Danelian,S.K.Janazian and V.V.Melnichenko, Modern Physics Letters B,Vol.5,No 20(1991), 1355-1359 4 N.G.Danelian,S.K.Janazian and V.V.Melnichenko,N.S.Yenikolopian, Modern Physics Letter B, Vol.5, No 19(1991), 1301-1305 5 A.A.Popovich and V.N.Vasilenko Papers at All-Union Sci/Tech conferance on "Mechanochemical Synthesis", Vladivostok,1990,pp. 71-79

DP-5 Wear Properties of DLC Films Deposited Using a Pulsed Carbon Plasma Accelerator
G.G. Kirpilenko, V.N. Inkin, K. Osvold (Patinor Coatings Ltd., Russia); A.Y. Kolpakov, A.I. Maslov (Technology &Tools, Russia); M.V. Pirussky (Metaltest, Russia)

In the study we investigated the wear properties of DLC films deposited in a vacuum chamber using a pulsed carbon plasma accelerator. The DLC films were deposited on polished nickel alloy wafers after cleaning with argon ions followed by the deposition of a titanium layer. The films were about two microns thick.

The DLC films were subjected to abrasion tests fulfilled in a test machine using a rotating cylinder made of WC-6 percent Co. The wear characteristics of the films were obtained measuring the size of the craters made in the film by the cylinder as a function of the number of rotations. There was made a comparative analysis of obtained wear of the diamond-like coatings to wear properties of a number of construction materials.

Auger electron spectroscopy was used for an analyses of the chemical composition of the interface between the carbon film and the substrate. A correlation was seen between the character of the obtained wear and the profile of the element composition of the interface.

Erosion tests using a dry sand-stream unit, were provided for the same DLC films. The thickness of the films were from fifteen to thirty microns and the films were deposited onto tungsten carbide wafers. Finally the coefficient of friction was measured between the DLC film and steel.

The investigations confirm the good wear properties of these films. They have a large potential within wear protection and anti-friction applications.

DP-6 Structural Modifications and Temperature Stability of Silicon Incorporated Diamond-like a-C:H Films
S.S. Camargo, Jr. (Universidade Federal do Rio de Janeiro, Brazil); A.L. Baia Neto (Universidade Federal Rural de Rio de Janeiro, Brazil); R.A. Santos (Universidade Federal do Rio de Janeiro, Brazil); R. Carius, F. Finger (Forschungszentrum Juelich, Germany)
Thermal degradation of diamond-like carbon films and related materials is still one of the major limitations for achieving many technological applications. In this work we present an investigation on the effects of thermal annealing on silicon incorporated hydrogenated amorphous carbon (a-C1-xSix:H; 03 C-H bonds is increased while the olefinic sp2 ones are reduced by annealing. A shift of the Si-H stretching mode to lower wavenumbers and an increased Si-C vibrational mode are also observed, indicating that a more compact material is obtained due to bond reconstruction. On the other hand, the total hydrogen content remains nearly unaffected. In this way, a material with reduced spin density, smaller residual stress, reduced hardness and increased optical gap results, indicating an increased polymeric character. At high annealing temperatures (T=400°C) the material degradation processes start to occur. In case of films with low silicon content, the hydrogen effusion process is an explosive one which is directly related to the graphitization of the material with a significant fraction of the hydrogen content evolving in the form of CH4 molecules. Films with high silicon content presented a better hydrogen stability. For instance, a film with x=0.3 show appreciable hydrogen loss only at annealing temperatures of about 600°C. This fact is related to an inhibited graphitization due to the increased disorder presented by these films.
DP-7 Stabilization of the Cubic Phase of Boron Nitride Thin Films
W. Ota@Td o@-Rivera (Pennsylvania State University); R.F. Messier, L.J. Pilione (The Pennsylvania State University)
Several studies have shown that the cubic phase of boron nitride thin films is stabilized if their deposition occurs under conditions of energetic bombardment during film growth, e.g., a high flux of ions with energies over approximately 50 eV. In sputtering techniques, this energetic bombardment is regulated by deposition parameters like pressure, negative substrate bias, target and plasma gas composition. These parameters control the energy, mass and flux of the ions and energetic neutrals from the plasma. They also control the flux of the boron and nitrogen atoms, therefore, imposing a specified energy and momentum of bombardment, per arriving boron atom, to the growing film. Thin films of boron nitride have been deposited by sputtering in order to study this stabilization process. The films were deposited under different conditions of pressure and negative substrate bias using different noble gases in the plasma. The films were studied by x-ray diffraction, transmission electron microscopy and diffraction, and Fourier transform infrared spectroscopy. The latter one being the primary characterization tool for phase composition. A window of energy and/or momentum per arriving boron atom was defined inside which the cubic phase is stabilized. These results and their implication for the stabilization of the cubic phase will be presented. It will be shown how the negative substrate bias necessary for the stabilization of the cubic phase has to be increased as the pressure increases to compensate for charge exchange collisions in the plasma sheath. A detailed quantification of the factors that define the momentum imparted to the growing film, per arriving boron atom, will be presented and compared with previous studies by ion beam assisted deposition.
DP-8 WC-Co Cutting Tools with Diamond Coatings
S. Silva, V.P. Mammana (University of São Paulo, Brazil); O.R. Monteiro (University of California); M.C. Salvadori (University of São Paulo, Brazil); I.G. Brown (University of California)
WC-Co cutting tools, with different Co contents, were covered with diamond films using microwave plasma assisted Chemical Vapor Deposition. Several treatments, and combinations of them, were done on the surface previously to the diamond film deposition. Some of these treatments were: wet etching to remove excess of Co from the surface, diamond-like carbon (DLC) film deposition to improve the diamond nucleation and TiC coating as interlayer to enhance interface adhesion. Both coatings, DLC and TiC, were deposited using Metal Plasma Immersion Ion Implantation and Deposition (MePIIID). The diamond films morphology and quality were controlled by Scanning Electron Microscopy and Raman Spectroscopy respectively. The diamond films adhesion were estimated with indentation tests.
DP-9 Porous Free-standing Diamond Membranes with Reduced Pores Diameter
V.P. Mammana, S. Silva, R.D. Mansano, P. Verdonck (University of São Paulo, Brazil); A. Pavani Filho (Centro Tecnológico para a Informática, Brazil); M.C. Salvadori (University of São Paulo, Brazil); I.G. Brown (University of California)
As previously reported (Diamond Related Materials, 1997), porous diamond membranes can be fabricated with controlled porosity. The method used consisted on depositing CVD diamond over a silicon wafer patterned with an array of regular distributed protrusions. These protrusions act as molds to the membrane pores. But the silicon etching process used to form the protrusions is limited with respect to its minimal size, meaning that the pores can not be arbitrarily small. In this work we propose a method to reduce the pores sizes using diamond post-deposition over a porous diamond membrane. This post-deposition process reduces significantly the pores sizes, widening the possible applications range of the membranes.
DP-10 Oxygen Plasma Etching of Diamond Coatings Over WC-Co Cutting Tool
S. Silva, R.D. Mansano, A.M.P. Passaro, P. Verdonck, M.C. Salvadori (University of São Paulo, Brazil); I.G. Brown (University of California)
In this work WC-Co cutting tools coated with microwave plasma CVD diamond films were etched with oxygen plasma to reduce its roughness. The diamond film were partially coated with a metallic film, in order to protect the grain boundaries, usually more susceptible to the oxygen plasma. Another feature used was an aluminum frame around the WC-Co insert. This frame made the plasma sheath more uniform along the insert. The etching was performed in a RF parallel plate reactor, fed with oxygen, and the process parameters were optimized. The etched diamond was monitored using Scanning Electron Microscopy, Raman Spectroscopy and the RMS roughness were analyzed using Atomic Force Microscopy.
DP-11 Diamond Deposition from Methanol-Hydrogen-Water Mixed Gas Using a Low Pressure Radio Frequency Inductively Coupled Plasma
M. Hiramatsu, H. Noda, H. Nagai, M. Shimakura, M. Nawata (Meijo University, Japan)
Diamond film formation using radio frequency (rf) inductively coupled plasma (ICP) has been reported by several researchers. Diamond films using ICPs are generally formed at high pressures above 1 Torr and high rf powers. At high pressure, however, it is not easy to deposit the film uniformly over a fairly large substrate. It is necessary to lower the operating pressure for large-area deposition of diamond. In this work, we utilized a low pressure (a few 100s mTorr) rf (13.56 MHz) ICP to deposit diamond film onto scratched silicon (Si). A source mixture of methanol, hydrogen, and water vapor was introduced into a reaction chamber through a quartz tube of 12 mm inner diameter. A 7-turn rf coil, which was made of 1/8 in. copper tubing and cooled with flowing water, was mounted on the quartz tube to produce high-density plasma. The scratched Si substrate was located in a downstream region. Film formation was carried out with varying mixture ratio of source gases at total pressures of 70-140 mTorr, an rf power of 500 W, a substrate temperature of 700 C, and a substrate bias of +30 V. Films were evaluated by scanning electron microscopy and micro-Raman spectroscopy. Diamond was successfully synthesized using a low pressure rf ICP. Diamond crystals exhibiting a well defined 1332 cm-1 diamond Raman peak can be formed using methanol-hydrogen-water mixtures at total pressures below 140 mTorr.
DP-12 Effects of Nitrogen Incorporation on Field Emission Properties of Amorphous Carbon
E.J. Chi, J.Y. Shim, H.K. Baik (Yonsei University, South Korea)

Amorphous carbon(a-C) films have attracted much attention as a field emitter due to their unique diamond-like properties. However, the properties of the films are found to depend strongly on their microstructure, i.e., sp3/sp2 carbon bonding ratio and hydrogen content. From the recent studies, it has been shown that nitrogen incorporation can cause the reduction of the electrical resistivity and optical bandgap width. Therefore, nitrogen-incorporated amorphous carbon (a-C:N) has been proposed as a superior electronic material to amorphous carbon.like a-C, the properties of a-C:N films also depend on the microstructure which can be varied by deposition conditions such as reactant gas ratio (methane, nitrogen, and argon), plasma power, deposition pressure, etc. In this study, the effects of deposition conditions on the film composition and properties will be systematically studied. Also, thermal properties of the grown films will be examined in order to test thermal stability and to study the modification of the properties induced by heat treatment. Finally, the correlation between the film properties and field emission characteristics will be investigated.

a-C:N films are grown by helical resonator PECVD on the silicon wafer or silicon tips. In this process, methane gas flows downstream and disperses above the substrate. Plasma generating gases, nitrogen-argon mixture, pass through the discharge zone and flow the reactor. In order to find the effect of nitrogen incorporation, the ratio of nitrogen to argon was changed. After deposition, heat treatments up to 900K are carried out.The films are analyzed by the methods such as Raman, Fourier transformation infra-red, and x-ray photoelectron spectroscopy. Field emission tests are performed with a diode structure at a pressure lower than 5xE-9Torr. Based on these analyses, the influence of the nitrogen incorporation on the film properties and the field emission property are studied.

DP-13 Linear Arc Assisted CVD Reactor for Diamond and Related Coatings
V.I. Gorokhovsky (Arcomac Plasma Processing Lab., Canada)
The Linear Arc Assisted CVD reactor 1 overcomes the disadvantages of conventional Arc Torch CVD reactors by creating a homogeneous, concentrated plasma column in a cylindrical reaction tube. Substrate holders are configured to act as a reaction tube liner confining the arc in a channel containing the substrates. Longitudinal and transverse magnetic fields are used to manipulate the plasma column into contact with the substrates. The voltage- current characteristics of Ar-H2-C H4 linear cascade arc relative to process parameters is studied. The temperature of substrates is affected by the balance between energy flow from the plasma column and heat removal through water cooling of the reactor wall. Properties of Diamond coatings deposited on a variety of 3D substrates like shank-shaped dental burs and carbide inserts processed in a CVD reactor with a 1 m reaction zone will be presented. 1V.Gorokhovsky, U.S.Patent No. 5,587,207
DP-14 Ion Hardened a-C:H Thin Films
S.N. Dub (Institute for Superhard Materials, Ukraine); N.I. Klyui (Institute of Semiconductor Physics, Ukraine)
Amorphous hydrogenated carbon (a-C:H) films were prepared by glow- discharge decomposition of butane onto polymeric substrates in the pressure range from 0.6 to 10 Torr. For a set of samples produced at different pressures, nanohardness and wear resistance were investigated. At low-energy growth conditions (high pressure in the reactor, low substrate temperature) the deposition of polymer-like a-C:H films takes place. Such films exhibit a low hardness (of 0.2 to 0.6 GPa) and wear resistance and a load-displacememt curve typical for polymers (viscoelastic behavior). On reducing the pressure in the reactor, an increase in nanohardness and wear resistance of polymer-like a-C:H films was observed. At the pressure below 5 Torr, the deposition of a-C:H films with nanohardness up to 5 GPa and extremely high elastic recovery of the indent depth (> 90 %) occurs. The wear resistance of such films is much higher than should be expected from their hardness. An enhancement in mechanical properties of polymer-like a-C:H films is caused probably by an ion bombardment of the growing film surface. Ion bombardment of the polymer (PET) surface with 150-keV C+ ions has confirmed this assumption. Tests of polymer samples with different thickness of a hardened layer have shown that the high elastic recovery is not connected with the influence of the soft underlying unaltered substrate material but it is the property of a modified surface layer. Ion bombardment is a well-known method to improve mechanical properties of a polymer surface. But the thickness of a modified layer is usualy less than 1 micron. Ion bombardment during film deposition allows us to obtain ion-hardened polymer-like a-C:H films with a much higher thickness (> 4 micron). Due to the high wear resistance and adhesion to polymeric substrate, as well as to the possibility of being deposited onto large substrates at temperatures below 80 °C, ion-hardened polymer-like a-C:H films are promising protective coatings for polymeric materials.
DP-15 Wear Resistance of Cubic BN Films in Various Environments
S. Watanabe, S. Miyake, M. Murakawa (Nippon Institute of Technology, Japan); K. Miyoshi (NASA, Lewis Research Center)
Because of the high hardness of c-BN, many researchers believe that these films offer great opportunities for wear parts, cutting tool inserts, rotary tools and dies. C-BN will be valuable for protective coatings on surfaces that come into contact with iron-based materials, where diamond cannot be used because of its high chemical wear due to its aggressive reaction with iron. Therefore, it is important from tribological points of view that the friction and wear properties of c-BN film in contact with steel be investigated in detail. This paper deals with the wear properties of c-BN films that were synthesized by magnetically enhanced plasma ion plating (MEP-IP). The investigation was conducted to examine the friction and wear of the c-BN films. Sliding friction experiments were conducted with c-BN films formed on Si wafer substrates in contact with 440C stainless-steel balls in three environments: vacuum, ambient air and water. Two sets of comparative sliding friction experiments were conducted: (1) with amorphous boron nitride (a-BN), titanium nitride (TiN) and titanium carbide (TiC) films sliding against 440C stainless balls in air, and (2) with c-BN films sliding against A1050 aluminum balls in vacuum, air and water.
DP-16 Gas Desorption and Absorption Properties of Carbon Based Materials Used for Cathode Ray Tube
M. Hashiba, Y. Hirohata, T. Hino (Hokkaido University, Japan); H. Shinbori, S. Deyama, H. Chiyoda (Hitachi Powdered Metals Co., Ltd., Japan)
For numerous carbon based materials used as coating of cathode ray tube, the gas desorption properties were examined by using a technique of thermal desorption spectroscopy. The major outgassing species were H2O and CO2. The major peak temperature of such the desorption was 100-200 °C. The desorption amount was very large for the material with rich graphite content, and small for that with rich TiO2 or water glass content. Baking temperature required for gas reduction becomes approximately 400 °C. Gas absorption experiments were also conducted. The absorption amount of H2O or CO2 increased with the content of graphite, and the addition of TiO2 powder very much enhanced the absorption amount.
DP-17 Fabrication and Characterization of the Sub-micron Cone-shaped Diamond Field Emitter Arrays
C.-F. Chen (National Chiao Tung University, Rep. Of China); D.-R. Wang (National Chiao Tung University, China)
Non-doped and phosphorous-doped miniature-size cone-shaped diamond and conic diamond field emitter arrays have been successfully fabricated using bias assisted microwave plasma chemical vapor deposition (BAMPCVD). The fabricated array was placed in a high vacuum pumping system with the pressure of ~10-5 Torr and the emission current as a function of the anode voltage was measured. The distance between the ITO glass anode and the device surface was held constance at 50 μm throughout the measurement. As a result, a curent larger than 0.3mA was obtained for an anode voltage of 600V. A linear relationship in the Fowler-Nordheim plot indicated the existence of electron field emission from the fabricated diamond field emitter array.
Time Period WeP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF1998 Schedule