A process for selective seeding of conducting substrates (inolybdenun and copper) with submicron diamond particles has been studied. In this process, copper is electroplated through a photoresist mask, and the electroplating is performed in a stirred solution of CuSO4 and H2S04 into which O.l in size diamond particles have been added. This resulted in a continuous layer of diamond particles embedded in the electroplated copper. After the removal of photoresist, this layer has been used to seed further CVD (chemical vapor deposition) diamond growth selectively. Morphology and Raman analysis of both the as-plated copper/diamond matrix and the filir that resulted after further CVD diamond deposition have been reported.

Effect of carbon implantation prior to diamond growth on diamond nucleations has been investigated for various substrates such as Si, Cu, Ti, Ni and Fe. The nucleation density is increased by one order of magnitude for carbonimplanted Si substrate via microwave plasma CVD. The diamond particles grown show well-defined (100) and (111) facets without twins or secondary nucleations. An enhancement of diamond nucleations by two orders of magnitude for carbon-implanted Cu and Ti substrates has been observed via magnet-active plasma CVD. The implanted carbon atoms seem to act as nuclei for diamond growth.

We have developed a technique of depositing a synthetic diamond-like carbon film on glass substrates in atmosphere at ambient temperature. By placing a glass substrate within the plume created by irradiating a carbon target with a Nd-YAG laser, we are able to deposit a diamond-like carbon film on the surface of the substrate. Using a highly purified graphite carbon target insures that only carbon ions are ejected and present in the plume. We will provide an analysis of the films by both vertical and diagonal irradiation (see Figs.1(A) and 1(B)), by Raman spectroscopy and electron probe micro analysis.

The chemistry of diamond chemical vapor deposition has been investigated using carbon- 1 3 labeling of reagents and high gas flow rates which limit potentially complex hydrocarbon chemistry. The sp2 carbon impurity in diamond appears to predominantly originate from methane/methyl radical, as opposed to acetylene. Since methyl radical also appears to be the source of diamond, it is likely that the differentiation between diamond and sp carbon formation occurs on the growth surface, and not in the gas phase. Oxygen species are implicated in hydrogen atom absiraction reactions that increase the concentration of methyl radical and result in higher diamond growth rates. The results are discussed in terms of a mechanism for gas phase chemistry from the combustion literature.

Langmuir probe measurements and optical emission spectroscopy were employed to characterize electron cyclotron resonance plasmas with two different magnetic field configurations. The plasma ternperature was directly measured by a thermocouple immersed inside the plasmas. To deposit diamond at low pressure( lOOmTorr) it is required for the feed sources to contain a large amount of carbon as well as OH radicals. However, the C, H, and 0 ratios still fall into the "diamond domain" of Bachmann's diagram. The oxygen addition to the CHiJH2 plasma leads to the improvement of diamond films prepared at 800mTorr, which is due to the OH radicals formed in the plasma. The addition of oxygen does not increase the plasma temperature. Our results of ECR diamond deposition under various pressures support that neutral-neutral reactions dominate in diamond growth process.

The defect structures of Si surface layer modified by high dose carbon ion implantation have been studied by ESR (electron spin resonance) method. The ESR analysis revealed the presence of three paramagnetic defects, that is, Si-dangling bonds (g=2.0060, Hpp =6.3 Oe) in Si amorphous region caused by the implantation, Si-dangling bonds with C atom neighbors (g=2.0035, LHpp =6.8 Oe) and C-dangling bond with C atoms neighbors. Moreover, it was found that the tight diamond-like C-C bonds are formed in the implanted Si surface layer. The diamond-like C-C bonds have an important role in obtaining high quality synthesized CVD diamonds.

The atomic structure of twin quintuplets in a chemical vapor deposited (CVD) diamond film was investigated by high resolution transmission electron microscopy (HRTEM). We conclude that the twin quintuplets have two main morphologies. The first consists of four =3 twin boundaries and one =81 twin boundary. The =81 twin boundary contains the dislocations needed to accommodate a 7.35° misfit angle between a set of {1 1 1} planes on opposite sides of the boundary. In the second case, the 7.35° misfit angle is accommodated by two or more grain boundaries that are tilted slightly more than the 70.53° tilt of a =3 boundary. These grain boundaries and the conventional diamond lattice twin boundaries are the only types of boundaries that we have observed in CVD diamond.

Diamond films have been deposited by hot-filament CVD on silicon using either a gas mixture of pure methane-hydrogen or a mixture of methane-hydrogen and carbon-tetrafluoride, for the study of the influence of the fluorine radicals in the growth process. Raman spectra shows that the fluorine is effective in the etching of non-diamond bonds since the corresponding Raman shift at 1550 cm1 due to sp2 was not observed in the films deposited with the CF1JCH4 gas mixture. Also the FTIR spectra of these films show a better transmittance in the range from 500 cm1 to 4000 cm1, and an apparent increase of the SiC layer thickness. Using the same thermodinamical conditions, with the CF1JCH4 gas mixture diamond films of high quality are deposited at a higher growth rate. AFM measurements of the surface morphology indicates apparently the same vertical roughness in both kinds of films but larger lateral coalescence in the films produced with CF4content.

Diamond-like carbon films with mass density, ranging from 1.7 g/cm³ to 2.4 g/cm³, deposited onto Si in RF glow discharge plasma in benzene were characterized by various techniques in order to obtain a correlation between mechanical, electrical, optical, and thermal properties of the films. Microhardness and optical absorption increase, while electrical resistivity and thermal diffusivity decrease with film density. Etching of DLC films by UV pulses of KrF excimer laser radiation in air was studied. The etch rate was found to decrease with film density. Two etch mechanisms have been identified: (1) carbon oxidation, which provides etch rates V < 5 nm/pulse, and (2) ablation dominating at high fluences (E > 500 mJ/cm²) with V exceeding 100 nm/pulse. Micron-sized patterns in carbon films fabricated by laser etching technique are demonstrated.

Optically smooth diamond films were deposited on Al and Si substrates by the ECR-PACVD method. The films on Al were grown on relatively low temperatures and pressures from CH₃OH/H₂O and were found to have highly defective nanocrystalline structure. The films on c-Si were grown at higher temperatures and pressures from CH₄/H₂/O₂ and were found to consist of highly oriented (100) faceted crystals. The optical constants of the diamond films on c-Si are similar to those of natural diamond.

The potentially wide range of optical constants obtained from differently deposited carbon layers with diverse atomic structure has been the subject of an intensive research in recent years. The optical properties are well known to depend strongly on the level of contamination and the degree of atomic order in the layer material. The purpose of the present paper is to sum up the results of our investigations of optical and electrical properties of numerous differently deposited carbon layers and to relate them to the results of measurements of mass density, the atomic composition of the layers and electron diffraction measurements. In particular, estimation formulas are provided to relate the IR refractive index to the mass density and the hydrogen concentration of the layers. In addition, special attention is paid to the exponential absorption region.

The growth of thin diamond films by chemical vapor deposition currently in a painfully slow process with highly variable results depending on many experimental parameters. By computer modeling of processes at diamond surfaces using a local density functional cluster method, we have found substantial energy barriers (4 - 6 eV) to growth. Overall, the reactions are strongly exothermic though, thus making them irreversible. The results presented here focus on the addition of methyl radicals and acetylene molecules to {100} 2 X 1 reconstructed surfaces. We propose two possible diamond growth mechanisms in which the relatively weak reconstruction bonds have a crucial role.

We have investigated the formation of Schottky barriers on diamond employing metal systems coupled with a shallow Si implant that would form low resistivity, high temperature stable metal silicide contact layer. We find that the barrier height of metals such as Pt, Ti and Mo were reduced when deposited on shallow Si implants and given a heat treatment at 500 degree(s)C. The barrier height of Pt on diamond was reduced from 1.89 eV to 0.97 eV by annealing of a sputtered Pt contact on a Si implanted dose of 10¹⁵ cm^-2 that peaks at approximately 120 angstroms into the diamond surface. Using the same approach, the barrier height of Ti on diamond was reduced from 2.00 eV to 1.29 eV, while the barrier height of Mo remained essentially unchanged. Although we have no direct evidence for silicide formation at this time, the reduction of the barrier height scaled inversely to the temperature of formation of the metal silicide. This is an extremely interesting observation and points to the possibility of achieving very low resistance contacts. We also re-examine the interpretation of barrier height measurements using internal photoemission and attempt to explain the appearance of two barriers and resolve the wide range of reported barrier heights of metals on diamond.

Using several new techniques, we have made accurate thermal conductivity (K) measurements on CVD diamond films ranging from visually opaque to clear. The optical transparency and thermal conductivity are found to be correlated, which is consistent with the fact that many of the defects that scatter phonons also scatter photons. We find that K is anisotropic, due to phonon scattering by the roughly cone-shaped columnar microstructure of typical films. The local K also shows a gradient with respect to position--near the large-grained top surface of thick films, the local K can be as much as four times higher than near the fine-grained bottom (substrate) surface. Near the top surface of the best films, the local K rivals and may exceed the best gem-quality single crystal diamonds. One might expect the local optical transmissivity likewise to be comparable to high-quality bulk diamond.

The elastic modulus E of diamond is often set equal to 1/s₁₁ equals 1050 GPa, which assumes that is does not vary much with orientation, and many authors use (upsilon) equals 0.2 as an appropriate average value of Poisson's ratio, which is incorrect. In fact, since the elastic constants of diamond are known with great accuracy, it is a straightforward matter to derive exact numbers for E and (upsilon) that take into consideration the stress direction, the intrinsic anisotropy, as well as the crystalline configuration. For CVD diamond deposits, we find that, in a first approximation, the Hershey-Kroner-Eshelby averaging procedures yields acceptable numbers, E equals 1143 GPa and (upsilon) equals 0.0691, which are quite compatible with available experimental evidence. Our measurements of the biaxial modulus, E' equals E(1 - (upsilon) ), made use of the bulge test method to characterize the elastic behavior of both microwave-power and hot-filament assisted CVD diamond films. High- quality deposits yield E' is congruent to 1180 GPa and E' is congruent to 1220 GPa for randomly orientated and (110) textured deposits, respectively: these results confirm that state-of-the-art deposits exhibit elastic properties that are in accord with the measured stiffnesses of natural single- crystal diamond. The residual hydrogen content strongly impacts the elastic behavior and appears to be responsible for the degradation of the modulus observed in this and previous work.

Recent progress in diamond research in HIRAKI-laboratory at Osaka University is briefly introduced, especially on the following topics: low temperature diamond fabrication, ion implantation, hydrogen plasma treatment of ion-implanted diamond to remove ion-induced damage, oxygen diffusion into the bulk assisted by the hydrogen treatment, and hole-burning effect.

We have fabricated CVD diamond windows with transmission of 71.1% at a wavelength of 10 micrometers . Raman spectra of such windows show no evidence of any luminescence or sp² bonding and are quite similar to the spectra to that of type IIa natural diamonds. Hydrogen content of 20 ppm atomic has been determined by quantitative FTIR analysis. The thermal conductivity of this grade of diamond can be as high as 15 W/cm K, as measured by the converging thermal wave technique. We have measured bulk, shear, and Young's modulus and determined Poisson's ratio for optical grade diamond. RF dielectric constant and loss tangent measurements for lower grade diamond yielded 5.6 for the dielectric constant and 6 X 10^-3 for the loss tangent.

The infrared absorption in microwave plasma-deposited, polycrystalline diamond films has been measured for the C-H stretch-mode and the diamond two-phonon mode, giving absorption coefficients of approximately 26 and 7.5 cm^-1 respectively for a 20 micrometers thin film, assuming that the whole thickness of the film is responsible. The C-H absorption band envelope has been deconvoluted into its various components, allowing some estimation of the relative importance of CH, CH₂, and CH₃ grouping in the films. A significant absorption at approximately 3 micrometers due to N-H has been measured in films exposed to atomic nitrogen.

Refractive index N, extinction coefficient k, and surface roughness (alpha) of synthetic diamond thin films are strongly dependent on the growth process. The current presentation describes a multiparameter optical transmittance curve fitting method to determine refractive index n, extinction coefficient k, thickness t, and surface roughness (alpha) of synthetic CVD diamond thin films taking account optical scattering of the light by the coating surface. All the data in this method, instead of extreme values in the conventional enveloped method, of IR transmittance curve are used to fit the above properties of diamond films in a short time by specially developed computer software. The accuracy of determination can be improved.

Results accumulated in our laboratory and elsewhere suggest that a common reaction mechanism is operative in all of the diamond CVD techniques using a hydrocarbon diluted in hydrogen as the reactor gas feed composition. Detailed investigations into the chemistry involved in diamond CVD have been conducted using microwave plasma assisted CVD and DC arc jet plasma CVD reactors. Results from optical spectroscopic, mass spectrometric, electrostatic probe and kinetic model calculations support a applicability of a mechanism originally developed to describe the oxidation of methane in flames to diamond CVD. The evidence supporting this applicability along with relevant implications for future directions in diamond research will be discussed.

Among the strong carbide forming elements, ten of them have melting points above 1400 degrees Centigrade. The observed transition layers between CVD diamond films and the substrates of Mo, Si, W, Ta, Nb, and Ti have been reported previously. In this paper, further research results on transition layers for the substrate elements of V, Cr, Zr, and Hf are presented. The specimens are prepared in an arc discharge plasma CVD system with the substrate temperature of 900 - 1000 degrees Centigrade and characterized by a high resolution X-ray diffusion diffraction instrument. the experimental results show that the transition layers are polycrystalline VC and V₂C, Cr₇C₃ and HfC for the substrates of V, Cr, and Hf respectively. For the transition layers between CVD diamond films and Zr substrates, the composition of polycrystalline ZrH, ZrC, and their complex compound are verified and the content of hydride is comparable to the content of carbide in this case.

Substantial thinning/polishing of diamond films (by as much as approximately 100 micrometers ) through simple diffusional reaction at 900 degree(s)C with Mn or Fe is reported. The observed thinning effect is attributed to the diffusional transfer of carbon atoms from diamond to manganese or iron in contact, as these metals exhibit large solid solubility for carbon at the reaction temperature. Mn appears to react with diamond much faster than Fe. Patterning of diamond films by selective area deposition of Mn films followed by reaction heat treatment and chemical etching is also described. These thinning techniques using metal powders, foils, or deposited films may conveniently be used for removal of undesirable parts of the films such as rough growth facets on the top surface or the fine grained bottom layer with inferior physical properties. These techniques also allow simultaneous thinning of a large number of diamond films.

Boron doped and undoped diamond films were prepared by a hot filament method of chemical vapor deposition (CVD). Up to 10²⁰ cm^-3 boron concentration was obtained in doped specimens. Infrared (IR) absorption and luminescent emission of diamond films were measured and discussed. Absorption peaks of 1971.3 cm^-1, 2020.0 cm^-1, and 2161.4 cm^-1 were observed in undoped diamond films, which are assigned to two-phonon lattice vibration absorption of diamond. Two absorption peaks at 2850 cm^-1 and 2910 cm^-1 were usually observed in CVD diamond films, which is very similar to that of C-H vibration absorptions in CH₂-radicals. In the range of 300 nm - 800 nm, four typical luminescent emissions were observed, which are 2.76 eV broad emission, 2.34 eV broad emission, 2.16 eV sharp emission with a low- energy shoulder and a sharp emission at 1.675 eV. The 2.34 eV emission is originated from the donor-acceptor (D-A) pairs, the others are originated from defect related centers.

An exploratory study was conducted to determine the feasibility of polishing CVD diamond films with abrasive-liquidjets. A nozzle system that produces a high-velocity radial flow (between nozzle and workpiece) with zero or near-zero impact angles was used for polishing tests. The abrasive particles are acted upon by hydrodynamic forces to effect polishing. The relatively high particle flow rates (10 g/s) and velocities (over 150 m/s) result in relatively high polishing rates. The inertial effect of the abrasive particles appears to contribute significantly to the material removal. A diamond film was polished from 3 to 1.3 microns at a rate of 2.7 micron/s/mm² using 600-mesh SiC abrasives.