Papers

ICMCTF2000 Session DP: D Poster

Tuesday, April 11, 2000 5:00 PM in Room Atlas Foyer

Tuesday Afternoon

Time Period TuP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2000 Schedule

DP-1 Raman Analysis of Diamond-like Carbon Films Using a Filtered Cathodic Arc Method C.F. Chen, Y.J. Tseng, Y.W. Li (National Chiao Tung University, Taiwan,ROC) This work presents a 45-degree angle magnetic filter cathodic arc method to investigate how the substrate bias, hydrogen-doping and nitrogen-doping affect the quality of diamond-like carbon films. Raman analysis results show that without the substrate bias and any reactive gas, the best quality film with lowest Raman I(D)/I(G) ratio is produced, indicating the highest sp³ diamond content in the film. On the other hand, increasing the substrate bias and/or incorporating nitrogen doping into the film during the process degrade the film quality. This film possesses a higher Raman I(D)/I(G) ratio with the G-peak shifting to a higher wave-number and low optical band gap energy, obviously indicating that the film contains more sp² bonded carbon. Moreover, the hydrogen flow affects the film quality to a lesser extent, implying that hydrogen can prevent the nucleation of sp² bonding or graphite and stabilize sp³ bonding. This further confirms that the film contains a more sp³ diamond-like carbon.
DP-2 Optical Properties of Amorphous Carbon Nitride Synthesized by ECR-CVD C.H. Tseng (National Chiao Tung University, Taiwan, ROC); J.H. Lin (National Tsing Hua University, Taiwan, ROC); S.H. Tsai, H.C. Shih, X.W. Liu (National Tsing Hua University, Taiwan, ROC) Amorphous carbon nitride films have been synthesized on silicon by using an electron-cyclotron-resonance chemical vapor deposition (ECR-CVD) system combined with a negative dc bias in a mixture of C₂H₂, N₂ and Ar used as precursors. The N & K analyzer was used to characterize the refractive index and extinction coefficient of the amorphous carbon nitride films. The optical band gap (maximum~2.24 eV) was derived by Tauc's equation. The optical band gap of the amorphous carbon nitride films decayed with the increasing substrate negative dc bias, ECR-Power, flow rate ratio of N₂/C₂H₂, nitrogen to carbon ratio (N/C) determined by X-ray photoelectron spectroscopy (XPS), the increase of graphitic content was examined by Raman spectroscopy and the increase of the N₂⁺ ion density analyzed by the optical emission spectrometer (OES).
DP-3 The Thermostable Thin Film Resistor Based on the Metal-containing Diamond-like Films G.G. Kirpilenko, V.K. Dmitriyev, V.N. Inkin, B.G. Potapov, B.N. Pypkin, E.Y. Shelyukhin (Patinor Coatings Limited, Russia) The metal-containing carbon hydrogenated diamond-like films C:H were deposited and investigated with the purpose of using them as thin film resistors stably working at temperatures up to 800°C. These films were deposited by a CVD method under a pressure of (6-7 Pa) on the substrates, being under high-frequency voltage (1.76 MHz, 500-1000 V), from the plasmatron and magnetron functioning simultaneously. As a plasma-forming substance of the plasmatron, (C₂H@sub 5)₃SiO[CH₃C₆H₅SiO]₃Si(CH₃)₃ was used. As a target of the magnetron, disks of pure chromium, molybdenum or molybdenum disilicide were used. In the process of simultaneous functioning of the plasmatron and magnetron, no interaction of these sources was observed. Moreover, plasma induced by the plasmatron favours burning of magnetron discharge. Research of the C:H:Si:Me-films with the purpose of using them as thermostable thin film resistive elements was conducted on the samples in the form of strips of this film deposited on the substrate of thin dielectric membrane. Changes in conductivity and temperature resistance of the films were investigated under their heat treatment which was conducted both by heating the samples in nitrogen atmosphere up to 900°C and by their self-heating with the flowing current. Element and phase composition of the obtained films was determined by AES and RHEED methods before and after research. It was determined that maximum changes in character and value of conductivity of the films occur in the first few hours of work, and after that no changes are observed within some hundreds hours. Stabilization mechanism of the films parameters in the process of their functioning is being discussed.
DP-4 Effects of Heavy Ion Implantation on the Properties of Tetrahedral Amorphous Carbon Film J.R. Shi, Z. Sun (Nanyang Technological University, Singapore); X. Shi (Nan Yang Technological University, Singapore); B.K. Tay, S.P. Lau (Nanyang Technological University, Singapore); J. Pelzl (Ruhr-Universität Bochum, Germany) The influence of energetic gold beam implantation on tetrahedral amorphous carbon (ta-C) films prepared by filtered cathodic vacuum arc technique is presented. The ta-C films were ion implanted by 2MeV gold ion with varying dose from 10¹² to 3x10¹⁴ cm^-2. The as-deposited and ion implanted films were characterized by using atomic force microscopy (AFM), Raman spectroscopy and Ellipsometer. All films have a smooth surface morphology with RMS roughness less than 0.3 nm over an area of 1microm². The Raman spectra of all the as-deposited and ion implanted films show a G peak around 1565 cm^-1 and a D peak around 1395 cm^-1. The intensity ratio of D peak to G peak, ID/IG remains unchanged (~0.50) for the film implanted with ion dose below 10¹³ cm^-2 and increases to 2.10 for the film implanted with ion dose of 3x10¹⁴ cm^-2. The Tauc optical band gap decreases from 2.05 eV for the as-deposited film to 1.4 eV for the film implanted with ion dose of 10¹³ cm^-2 and becomes very close to zero for the films implanted with ion dose more than 3x10¹³ cm^-2. The results of Raman and Ellipsometer measurements indicate that the carbon atoms become sp²-bonded in the films implanted with large gold ion dose.
DP-5 Pulsed Biased Enhanced HFCVD of Diamond Films on Silicon I.U. Hassan, C.A. Rego (Manchester Metropolitan University, United Kingdom) Diamond films deposited by Hot Filament Chemical Vapour Deposition (HFCVD) usually require some form of surface treatment in order to control the surface roughness and morphology and to improve the adhesion between the diamond films and the substrate. To produce uniform films over large areas bias enhanced nucleation is a promising approach because it gives good control over the films properties. A modified pulsed biased enhanced nucleation method was employed in this investigation to study diamond on silicon substrates. A two step process involving i) repetitive pulsed biasing of the substrate with a bias on time between 0.5-30 minutes with a constant off time of 1 minute and ii) deposition under standard conditions. The total time the bias was left on was 30 minutes. The optimum deposition conditions for our system were found to be substrate temperature of 1100K; methane/hydrogen ratio of 3%; pressure of 20 Torr; filament temperature of 2500K; DC bias of -250V and a duty cycle of 0.5. In general the surface roughness and film morphology of the as grown diamond films critically depended on the duty cycle. Pulsed biasing during the nucleation stage allows uniformity of the amorphous layer to be controlled. Shorter duty cycles of <0.5 gave better control of the surface roughness and morphology without degrading the diamond film quality. With longer duty cycles there was some degradation of the uniformity with greater degree of twinning. Scanning electron microscopy, Raman spectroscopy and atomic force microscopy were employed to characterise the films.
DP-6 Diamond Synthesis Via C-H-Metal using MPCVD and HFCVD M.S. Wong (National Dong Hwa University, ROC); C.A. Lu, H.K. Chang, J.H. Wu, T.S. Yang (National Dong Hwa University, Taiwan, ROC); Y. Liou (Academia Sinica, Taiwan, ROC) Several powder mixtures were used as starting material and processed under the conditions comparable to these for MPCVD and HFCVD methods. The powder mixtures include various combinations of metals (Ag, Cu, Co, Ni and Mn), graphite and diamond. Important experimental variables such as gas flow rate, gas pressure and substrate temperature were varied systematically to search for diamond growth conditions. The results indicate that the metals don't have the significant catalytic effect in diamond growth as expected or reported previously. Of all the samples studied, samples with Ni powders exhibit the highest diamond growth rate, but the rate is only comparable to that for typical CVD. Addition of diamond seeds and usage of 1% CH4 in H2 in the process are necessary to assure diamond growth and nucleation. Solid carbon source instead of gas carbon source can be used for diamond synthesis, but with lower nucleation density and growth rate. The results also suggest that the growth mechanism for diamond synthesis methods explored in this study is similar to that for low pressure CVD.
DP-7 Electron Field Emission from Heat Treated and Nitrogenated Tetrahedral Amorphous Carbon Films J.K. Shin, K.-R. Lee, K.Y. Eun (Korea Institute of Science and Technology, Korea) It was generally reported that thermal annealing of diamond-like carbon films enhances field emission properties. However, the emission mechanism is not clear in carbon-base cathode materials. Therefore, structural investigation is needed to reveal the fundamental features. The effect of thermal annealing on field emission properties of tetrahedral amorphous carbon films deposited by a filtered cathodic arc method were evaluated. The structural changes with thermal annealing were investigated by Raman spectroscopy, AES/EELS, and surface topography measured by AFM. The relations between the emission properties and film structures were investigated in respect of emission uniformity and stability. The emission mechanism will be also discussed.
DP-8 Comparison of Field Emission Behaviors of sp2 Bonded Glassy Carbon Coated by Electrophoresis and Screen Printing S.H. Ahn, K.-R. Lee, K.Y. Eun (Korea Institute of Science and Technology, Korea) Glassy carbon (GC) of amorphous sp2 structure has the advantages for cathode materials such as good electric conductivity, chemical inertness, and sharp surface. To verify possibility of GC as field emitter for FED devices, we deposited GC powder at Mo substrate by electrophoretic method and screen printing method. Luminescence of emission image on phosphor was investigated. The on-set electric field of the emission was in the range of 5 to 10V/µm. Even if the whole area emission occurred at higher voltage, emission response on the electric field is strongly dependent on the deposition method. When using electrophoretic method, there existed a dielectiric MgO layer between GC powder and substrate which acts as a capacitor resulting in delay in the response. However, screen printed GC using Ag paste showed fast response on the electric field. These results implied that the emission from carbon materials is strongly dependent on the conducting behavior of the system and not intimately related with the sp3 content in the materials.
DP-9 Pulsed DC PACVD Process for 4-inch Diamond Wafer Growth W.S. Lee, K.Y. Eun, Y.-J. Baik (Korea Institute of Science and Technology, Korea) Large-area diamond wafer synthesis with single-cathode pulsed direct current PACVD process was suggested. Stabilization of plasma, which was a critical problem in this method, was overcome by controlling cathode temperature and applying pulse dc power. Long-term operation enough to grow diamond wafer as thick as 1mm was possible. Scaling-up over 4-inch area was readily achieved by simple enlargement of electrode diameter to 12cm and power input upto 40 KW. The wafer size can be increased further with simple modification of the electrode. The major parameters determining maximum power input was gas pressure and inter-electrode distance for given deposition area and electrode structure. Hydrogen and methane were used as precursor gases. Methane concentration could be controlled over sufficiently wide range without deteriorating deposition uniformity and without losing stability of plasma. Growth rate greater than 10micrometers per hour was achieved with good uniformity and quality, as shown by Raman spectroscopy and thermal conductivity measurements, at a gas flow rate as small as 100~300 sccm. Thick 4-inch diamond wafers with a wide range of quality, from transparent to opaque, could be grown.
DP-10 Selective Diamond film on the Glass Substrate for Tribologically Enhancement T.G. Kim (Miryang National University, South Korea); W.J. Lee (Pusan-Branch/ Korea Basic Science Institute, South Korea); M.J. Yoon (Kyungil University, South Korea) Selective diamond films on the pretreated substrate were deposited at low temperature (723K), using a microwave plasma-enhanced chemical vapor deposition (MPECVD) system. During the initial deposition, two distinctive processes such as cyclic and non-cyclic gas input of CH4 gas were employed for about 12 min., respectively. Diamond deposition was also carried out as a function of CH4 concentration and exposure time. For the selective deposition, we treated the glass substrate using diamond paste before inserting it into the reactor. The pretreated glass substrate was consisted of stripe-abrasive and no-abrasive regions. We could achieve the low temperature deposition via the remote plasma from the pre-treated substrate, with low microwave power (400 W) and low pressure (13 Torr) during the reaction. On the pre-treated substrate, the enhancement of low temperature selective deposition and crystal quality of the diamond film was observed via the cyclic process during the initial deposition. In addition, short exposure time of CH4 led to the enhanced crystal quality of diamond films during the initial growth.
DP-11 Production and Characterization of Fluorinated Amorphous Hydrogenated Nitrogenated Carbon Films M.A.B. de Moraes, J. Wang, S. Durrant (State University of Campinas, Brazil) Fluorinated amorphous hydrogenated nitrogenated carbon films have been produced using plasma enhanced chemical vapor deposition (PECVD). The depositions were carried out in radiofrequency plasmas fed mixtures of ethylene, nitrogen, argon, and carbon tetrafluoride. The flow rate of the latter was systematically varied to produce highly, moderately, and poorly fluorinated material. Transmission infrared spectroscopy (IRS) of the films revealed some structural information, such as the presence of C-H, C-N and C-F bonds, while Rutherford backscattering spectroscopy (RBS) allowed quantification of the nitrogen and fluorine contents. An interesting aspect of this work was the mapping of the declining temporal trends of the spin densities in the films following deposition. The spin densities, which are characteristic of trapped radicals, were determined using electron paramagnetic resonance (EPR) spectroscopy.
DP-12 Hydrogen-containing Carbon Nitride Films Produced by the Combined Hot Filament-PECVD Technique M.A.B. de Moraes, J. Wang, S. Durrant (State University of Campinas, Brazil) Carbon nitride films were prepared by combined hot filament (HF) and plasma enhanced (PE) chemical vapor deposition (CVD) techniques from three mixtures, C₂H₆-N₂-Ar, C₂H₄-N₂-Ar and C₂H₂-N₂-Ar, denominated M₁, M₂ and M₃, respectively. Depositions were carried out in a vacuum chamber fitted with two parallel plate electrodes driven by a 40 MHz generator and a 5 cm long, 0.03 cm diameter Ta filament resistively heated by a dc power supply. Using the same total pressure, Ar partial pressure, and the same rf and filament power, the deposition rate was determined and the films characterized for each of the three gas mixtures as a function of the nitrogen to hydrocarbon (NTH) flow rate ratio. The deposition rate, R, was determined by dividing the film height, obtained by perfilometry, by the deposition time. Transmission and reflection infrared spectrophotometry and Rutherford backscattering spectroscopy (RBS) were used to investigate film molecular structure and elemental composition, respectively. At any NTH ratio: (i) R increased steeply from mixture M₁ to mixture M₃: (ii) the concentration of C=C bonds was higher in the films deposited in the M₃ mixture; (iii) the incorporation of nitrogen, determined by the N/C atomic ratio, decreased from mixture M₁ to M₃. For the mixture M₃, a comparison of the film structure and deposition rate of films produced using the HF-PECVD combination and HFCVD alone was made. For any given NTH ratio, R and the concentration of C-H bonds were higher when the HFCVD technique alone was used. An interpretation of the role of the plasma in the decrease in R is suggested. The influence of the degree of saturation of the hydrocarbon molecules in each mixture on R and on the film structure is highlighted.
DP-13 Effect of Dilution Gas on SiCN Films Growth Using Methylamine J.-J. Wu (Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan); K.H. Chen (Academia Sinica, Taipei, Taiwan); C.Y. Wen (National Taiwan University, Taipei, Taiwan, Taiwan, R. O. C.); L.C. Chen (National Taiwan University, Taipei, Taiwan., Taiwan, R. O. C.); H.C. Lo (National Taiwan University of Science and Technology, Taipei, Taiwan); S.T. Lin (Academia Sinica, Taipei, Taiwan) Methylamine (CH₃NH₂) was employed with SiH₄to deposit amorphous silicon carbon nitride films due to its easy dissociation as well as containing both carbon and nitrogen elements. The effect of dilution gas, such as H₂, N₂, Ar and He, on the film growth was studied in an electron cyclotron resonance plasma CVD reactor. Optical emission spectroscopy (OES) was employed to monitor in-situ the fluorescing species in the gas phase. X-ray photoelectron spectroscope (XPS), Fourier transform infrared (FTIR) spectrometer and transmission electron microscopy (TEM) were employed to characterize the composition, the chemical state, and the structure of the films. At a microwave power of 250W and a substrate temperature of 700°C, silicon carbon nitride film was deposited using He as dilution gas. However, only silicon nitride films were formed using dilution gases of Ar, N₂and H₂but otherwise similar conditions. Spectroscopic study of the gas phase species during growth and discussion on the growth phenomena will be presented in this paper.
DP-14 Field Emission from SiCN Films with Two-layer Structured F.-G. Tarntair (National Chiao Tung University, Hsinchu, Taiwan); J.-J. Wu (Academia Sinica, Taipei, Taiwan); C.Y. Wen (National Taiwan University, Taipei, Taiwan, Taiwan, R. O. C.); L.C. Chen (National Taiwan University, Taipei, Taiwan., Taiwan, R. O. C.); K.H. Chen (Academia Sinica, Taipei, Taiwan); H.C. Cheng (National Chiao Tung University, Hsinchu, Taiwan) Two-layer structured SiCN films were deposited in an electron cyclotron resonance plasma CVD reactor. The wide-band gap nano-crystalline film was grown on top of the amorphous interlayer of several hundreds nm thick. For most cases, the composition of SiCN films can be expressed as (Si, C)₃N₄ with various Si/C ratios. Furthermore, strong sp² C-N bonding structure was observed in the a-SiCN interlayer. The SiCN films with two-layer structures showed promising field emission properties. For instance, a sample with Si/C~1 exhibited emission current density that was 3 times higher than that of doped diamond film. The turn-on field, required to draw field-emission current density of 0.01 mA /cm², of the same film was 13 V/µmm, which was lower than that of doped diamond film at 30 V/µmm. We believed that an optimized field emission property of the SiCN films could be obtained by adequate two constituent layers. Comparative studies for the field emission properties of the two-layer structured SiCN with various composition and volume ratios will be discussed.
DP-15 The Effect of Si Addition on the Properties of DLC Films Deposited with Negative Carbon Ion Beam I.K. Kim, Y.H. Kim, D.Y. Lee, H.K. Baik (Yonsei University, Republic of Korea) Diamond-like carbon (DLC) films have been studied extensively for various industrial applications due to its superior properties such as high electrical resistivity, optical band gap, wear rate, and low friction coefficient. Such a excellent properties depend on the sp³/sp² ratios in the films. DLC films with sp³/sp² ratios above 80% are called tetrahedral amorphous carbon (ta-C), but its synthesis is not easy and it have wide ranges of energy window. In order to synthesize ta-C film more easily, silicon have been added to the DLC films by many researchers. But, each group reported silicon addition effect differently. In this study, we used Cs+ ion gun sputtering deposition system to deposit silicon-incorporated DLC films and controlled silicon concentration in the films by using Si-C mixed sputtering target with different Si/C ratios. The structural changes of the DLC films by silicon addition were investigated usine AES, Raman, EELS and XPS (X-ray Photoelectron Spectroscopy) bulk plasmon energy loss spectra. It was observed that silicon atoms in the DLC films bond mainly carbon atoms by XPS. Back-scattering electron energy loss and XPS bulk plasmon energy loss spectra showed that silicon addition reduced the atomic density of direct negative ion beam deposited DLC films. Sp@super 3)/sp² ratios of the DLC films was also proved to decrease as silicon concentration increases by raman spectra. The reduction of atomic density and sp³/sp² ratios of silicon-incorporated DLC films were discussed by the decrease of compressive stress in the direct negative ion beam deposited DLC films.
DP-16 Synthesis of the Diamond Polycrystal Films from Oxygen-acetylene Flame on the Metal Substrate at Low Temperature Thermal Measuring A.S. Zolkin, D.V. Sheglov (Novosibirsk State university, Russia); V.N. Savenko (Novosibirsk State university, Rusia); A.V. Matveev, E.V. Grigoryev (Novosibirsk State university, Russia); V.I. Semenov (Institute of Thermophysics, Russia) Diamond films and particles that were synthesized by deposition from oxyacetylene flame on the molybdenum substrates under atmospheric conditions. The study deals with morphological evolution of diamond films in combustion synthesis at different temperatures of the substrate as a basis for understanding the nucleation and growth mechanisms of the diamond phase. The films and particles were studied by scanning and transmission electron microscopes and were characterized by Raman spectroscopy. The best results, namely, a polycrystalline diamond film and perfect octahedral 0crystals, were obtained at R(O₂/C₂H₂) = 1.0, gas flow rate F = 2. 2 l/min, distance between flame-corn and the surface of the substrate d = 2 mm. Raman shift: 1332 cm^-1, the crystal growth rate: 50Å/c. It has been stated that diamond particles on molybdenum surface can be grown at the surface temperature T = 873 - 1123K which is lower by about 100 - 150 K than the temperature reported in the known studies of the flame method. Thermal measuring is described in detail in this report.
DP-17 Effects of the Growth Parameters on Properties of Vertically Aligned Carbon Nanotube Grown by Plasma Enhanced Chemical Vapor Deposition J.H. Han, B.S. Moon, W.S. Yang, J.B. Yoo, C.Y. Park (Sungkyunkwan University, Korea) Much effort has been devoted lately to the synthesis and application of carbon nanotubes. Carbon nanotubes are potential candidates, particularly, for cold cathode field emitter because of their unique electrical, chemical and mechanical properties, and their high aspect ratios and small ratio of curvature at their tips. For applications such as flat panel displays and vacuum microelectronics, large-area films of nanotubes producing uniform field emissions across its surface are required. Above all, alignment of the carbon nanotubes is important to both fundamental studies and applications. Recently, we have successfully grown the vertically aligned carbon nanotube arrays on nickel-coated glass with and without Indium Tin Oxide (ITO) and silicon (100) at temperatures below 650 degrees Centigrade by plasma enhanced chemical vapor deposition (PECVD). In this work, a dc plasma was employed, and acetylene gas was used as the carbon source and ammonia gas was used ! ! as a catalyst and dilution gas. Nanotubes with controllable diameters from 10 to 100 nanometers and lengths from 0.1 to 10 micrometers were obtained. We studied the effect of growth parameters such as growth temperature, plasma intensity, pressure, flow rate, catalyst etching time, and composition of input gases on the properties of carbon nanotubes. Subsequently, the optimum growth conditions such as diameter, length, density, and uniformity, etc. of the highly oriented carbon nanotubes for good electron emission were obtained. The morphology of nanotube arrays was examined by atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and the microstructure analysis of nanotubes was investigated by transmission electron microscopy (TEM).
DP-18 Fidelity of Diamond Replicas on Silicon Substrate A.M. Pizzo Passaro, M.C. Salvadori, D.R. Martins, M. Cattani (Institute of Physics, University of Sap Paulo, Brazil) Up to now, most of the microelectromechanical system (MEMS) devices has been based on silicon. This is due to the technological know-how accumulated on the manipulation, machining and manufacturing of silicon. However, the silicon properties are poor, especially when compared with diamond, concerning to the wear resistance, chemical inertness, thermal conductivity, etc. So, fabrication of diamond microstructures is a promising field for MEMS. In this work we investigated the micrometric and nanometric fidelity of diamond replicas, obtained using silicon molds. This was done in order to verify the limit of accuracy of this technique in the fabrication of MEMS. We verified that the roughness (rms) of the diamond replicas is about 4 times the rms of the silicon substrate, which is around 6 nm. Lateral distances between two points on the silicon molds, around 50 (m, can be reproduced with a precision of 0.5%. We have also measured the fractal dimension of the replicas to analyze the growth dynamics of the interface between diamond and silicon substrate. The characterization was made by atomic force microscopy.
DP-19 Synthesis of High-quality Homoepitaxial Diamond by Means of the Combustion Flame Method S. Takeuchi, M. Murakawa (Nippon Institute of Technology, Japan) It has been known that relatively high-quality homoepitaxial diamond can be deposited homoepitaxially onto a high-temperature high-pressure diamond substrate by means of the combustion flame method. However, there is no known established method to evaluate the quality of the homoepitaxially deposited diamond, although it is known that exciton recombination radiation can be observed in the cathodoluminescence spectrum from type II diamond or high-quality CVD diamond. It is also known that the cathodoluminescence spectrum of diamond generally shows a sharp peak value of free-exciton recombination, indicating high crystallinity of the (100) face. In this study, we synthesized diamond by the combustion flame method using a (100) single-crystal diamond substrate, and evaluated the crystallinity of the deposited homoepitaxial diamond to obtain the values of free-exciton recombination, indicating the degree of diamond quality, in order to finally establish specific synthesizing conditions to fabricate high-quality homoepitaxial diamond.
DP-20 Fabrication of Diamond Nano-whiskers for Field Emitter E.S. Baik, Y.-J. Baik (Korea Institute of Science and Technology, Korea); S.W. Lee, D. Jeon (Myongji University, Korea) Since diamond has a negative electron affinity, it is considered as an excellent cold cathode. In this paper, we suggested a method for fabricating diamond nano whiskers, which could be used to define emission sites and enhance emission efficiency of electrons. We used thin metal deposits, in the present case Mo, as a mask to define nano-whiskers. Thin Mo was deposited using RF sputtering, whose thickness was about several tens Å. These samples were contacted with in the atmosphere of air plasma generated by RF electric source. The formation behavior was investigated with parameters of substrate bias, pressure, the amount of Mo deposits etc. The diameter and density of the whiskers were about 60nm and 10¹⁰/cm² respectively. The whiskers were very anisotrophic and emitted high density of electron at low threshold voltage. The possibility of phase change of diamond during the etching was also discussed.
DP-21 Control of Diamond Micro-Tip Geometry for Field Emitter E.S. Baik (Korea Institute of Science and Technology, Korea); D. Jeon (Myongji University, Korea); Y.-J. Baik (Korea Institute of Science and Technology, Korea) Recently we proposed a diamond micro tip array for field emitter, which was fabricated using simple lithography and dry etching technique (Baik et al. Dia. Rel. Mat. in press, 1999). This process was very simple and effective in producing high efficient electron emitting field emitter. In this work, We investigated the variables, which affected the tip geometry and consequent variation of electron emission efficiency. A patterned silicon oxide dot array (2µm in diameter, 300 X 300 array) was formed on diamond film of 5µm in thickness. The thickness of the oxide were 4000, 8000, and 12000Å respectively. Diamond etching was performed using air plasma generated by radio frequency source. We controlled with r.f. power and bias, pressure with in the range several tens mTorr. The air plasma reactively etched the diamond because of the oxygen component, but removed the silicon oxide mask slowly by physical sputtering. This difference in the etching rate between the diamond and the oxide mask led to the formation of a cone-shaped diamond tip. With increasing the thickness of silicon oxide and decreasing the working pressure, cone shaped diamond tips became sharpened. But r.f. power did not change the geometry of tip. Post treatment using hydrogen plasma was effective in cleaning the diamond tips and increasing the surface conductivity. The effect of the tip geometry on electron emission was also investigated.
DP-22 Tribological Properties of cBN Films Deposited by Unbalanced Magnetron Sputtering H.S. Kim (Korea Institute of Science and Technology, Korea); I.H. Choi (Korea University, Korea); Y.-J. Baik (Korea Institute of Science and Technology, Korea) Cubic boron nitride (cBN) films were deposited by unbalanced magnetron sputtering and their tribological behaviors were investigated. We used hBN as target material which was sputtered in argon plasma with various nitrogen contents. The r.f. power applied to the target and pulse DC bias applied to the substrates were varied from 300 to 550 W and from 0 to -300 V respectively. Friction and wear behaviors were measured with a rotating type ball-on-disc wear-rig in ambient air condition. Ball-on-disc experiments were performed at different sliding velocities and loading levels using steel balls (AISI 52100) and Al₂O₃ balls. The compositions of debris formed by using the different balls were analyzed by AES. The Main parameters affecting cBN formation were the r.f. power and pulse D.C. bias voltage. With increasing these parameters, the cBN content increased up to 80 %. The surface roughness of cBN-hBN mixed film showed very heterogeneous bi-mode morphology, composed of flat surface and globular nodules. As hBN content decreased, the nodules tended to disappear so that the surface was covered by the atomically flat area. The friction coefficients also decreased below 0.3 with cBN content. The comparison of friction behavior with the hardness of the films and the microstructural analysis of wear scar were also performed.
DP-23 Influences of Metal Doping on Wear Performance of Diamond-like Carbon Films Deposited by Unbalanced Magnetron Sputtering D.Y. Wang, C.L. Chang (National Chung Hsing University, Taiwan, ROC) The ultra-low friction coefficient and high surface hardness make the diamond-like carbon (DLC) coating, either hydrogenated (a-C:H) or non-hydrogenated (a-C), one of the most promising surface technologies for processing of advanced structure materials. In this study, metal-doped DLC films (a-C:Me) were synthesized by the unbalanced magnetron sputtering of metal and graphite targets simultaneously. An interface layer of a graded metal/metal-nitride/metal-carbonitride thin film was deposited from the same metal target to improve the adhesion between DLC and steel substrates. The inclusion of metal dopants improves the toughness of DLC films as a result of residual stress reduction. Influences of metal doping on wear properties of DLC films were investigated. The composition of metal inclusion in DLC coatings was analyzed by electron probe microanalysis (EPMA) and secondary-ion mass spectroscopy (SIMS). The microstructure was analyzed by scanning electron microscopy (SEM) and x-ray diffractometry (XRD). A ball-on-disk tribometer was used to measure friction coefficients, wear rates, and adhesion strength of the metal-doped DLC films.
DP-24 Simultaneous Growth of Diamond and Graphite T. Badzian, A. Badzian, R. Roy (Materials Research Laboratory, The Pennsylvania State University); Shang-Cong Cheng (Materials Characterization Laboratory, The Pennsylvania State University) Early CVD diamond growth processes suffered from codeposition of diamond and graphite. Increase of atomic hydrogen concentrations in CVD reactors resulted in elimination of graphite codeposition. More recently the role of metals in diamond synthesis from the gas phase has revealed new phenomena. Simultaneous growth of diamond on silicon substrate and graphite fibers on iron substrate placed beside each other takes place under the same plasma ball ignited in the CH₄/H₂ gas mixture in a microwave reactor. Even more simultaneous processes take place during etching by hydrogen of graphite powder and nickel mesh. Growth of single crystal graphite free standing plates has been achieved in such processes. The plates resemble a knife blade and grow fast in the <11100> directions (zigzag edge) with long crystals exceeding 100 micrometers. The armchair features are seen at the side edges. It seems that growth from the gas phase of extensive flat plates (over one micrometer in linear dimension) of graphite has never been reported. The single crystal nature of these thin plates, transparent to electrons, has been confirmed by electron diffraction. Diamond crystals nucleate a graphite and they grow simultaneously. We suggest that the paradoxical growth of graphite in a hydrogen plasma, under conditions in which graphite is usually etched away, is possible because of a protective coating by a Ni-C-H phase. Such a coating could well be an unstable solid condensed Me-C-H° phase, which presumably exists because the plasma provides atomic H. The coating (probably a few atomic layers thick) enables carbon atoms to be transported to the growing graphite surface. Carbon is transported as Ni-C-H gaseous molecules formed during etching of graphite and Ni. Diamond nucleates on graphite covered by the Ni-C-H° phase and grows under or out of the same Ni-C-H coating.
DP-25 Tribological Characterization of Diamond-like Nanocomposite Coatings D.J. Kester, M.P. Kirk, C.L. Brodbeck, J.D. Peck, M.D. McClure (Advanced Refractory Technologies, Inc.) Diamond-like nanocomposites are amorphous thin films containing C, Si, H, and O. They are deposited using plasma enhanced chemical vapor deposition (PECVD). Tribological characterization of coatings deposited under several sets of conditions was performed. Ball-on-disk testing of coated M-2 tool steel was done using WC and 52100 steel balls. Tests were run with a 20N load to 100,000 cycles. Wear factors were in the range of 1-5 × 10^-8 mm³/Nm. Hardness and modulus was measured using nanoindentation, with hardness values ranging from 14-20 GPa. Coating stress was found to be below 1000 MPa. Coatings had low friction (COF=0.04-0.1) and low surface energy, ranging from 20 to 40 mN/m. Current applications of the coatings will be discussed.
DP-26 Effects of Argon Dilution of the Ethanol/Hydrogen Gas Feed on the Growth of Diamond by Hot-Filament CVD A.C. Peterlevitz, M.C. Tosin, S.F. Durrant, H.J. Ceragioli, V. Baranauskas (Faculdade de Engenharia Eletrica e Computacao, Universidade Estadual de Campinas, Brazil) Noble gases are present in high concentrations in natural gems, and their isotopic concentrations are used to identify the origin and the geo-genesis of diamond and carbides. In this work, we studied the effects on the growth kinetics and the properties of diamond films obtained by the introduction of argon at high concentrations (up to 50 % vol.) into the feed mixture (ethanol and hydrogen) of a hot-filament CVD reactor. An interesting aspect of this work is the understanding of the chemistry of the crystallization process. Atomic hydrogen produced at the filament always tends to attach to the carbon-free bonds, producing hydrogen terminated carbon chains -C-C- that are open. In contrast, the noble gases allow the chains to close onto themselves, which could produce fullerene-type structures, instead of diamond, which may (or may not) aid diamond growth. Another important aspect is that energy loss is minimized since the dissociation of molecular hydrogen is minimized. A critical discussion of the results obtained in the characterization of the samples by scanning electron microscopy (SEM), photoluminescence and micro-Raman spectroscopy will be presented.
DP-27 Characterization and Field Emission of Co-deposited Cs Incorporated DLC Thin Film by Cs⁺ and C^- Ion Beam D.W. Han, H.K. Baik, S.M. Jeong (Yonsei University, Korea) Diamond-like carbon (DLC) films have been studied as a cathode emitter material of field emission display (FED) due to a possibility of negative electron affinity (NEA). There have been making an attempt to addition of different kinds of element to improve electron transport inside the film considered more important in these days. In this study, the improvement of electron transport through the Cs atom in DLC film was investigated. Cs incorporated DLC thin films were synthesized by Cs⁺and C^-ion beam. The Cs⁺ion flux was varied under the constant condition that C^-and Cs⁺ion energy are 300eV and 50eV, respectively. Film properties were characterized by Raman, XPS, AES, SEM. It was shown that the films have higher sp²fraction with the increase of Cs ion flux. And the charge transfer from Cs to C inside the film was increased as Cs⁺ion flux increase. Charge transfer occurred by orbital overlap between s orbital of Cs and ? orbital of C. It is believed that the increase of charge transfer and geometrical field enhancement induced field emission characteristics.
DP-28 Nucleation Enhancement of Diamond using Natural Hematite in the CVD Process V. Baranauskas, H.J. Ceragioli, A.C. Peterlevitz, S.F. Durrant, M.C. Tosin (Faculdade de Engenharia Eletrica e Computacao, Universidade Estadual de Campinas, Brazil) Diamond growth on non-diamond substrates requires initially a heterogeneous nucleation step on the substrate surface and, depending on the substrate material, the nucleation time may be very long and the nuclei density may also be very low, compromissing the film quality. Seeding of the substrates prior to CVD, typically using diamond grains, is commonly employed to increase nucleation of the growing film. Alternative methods are of great interest. In this work, we demonstrate the feasibility of using natural hematite to increase nucleation on silicon. This mineral in lamelae form minimizes damage to the substrate surface. Such a process is shown to produce a high nucleation density. The resulting nuclei and films were monitored using Raman spectroscopy and characterized by optical, scanning electron (SEM) and atomic force (AFM) microscopies.
DP-29 Structural and Photoluminescent Properties of In-built Carbon Structures in Thick Porous Silicon V. Baranauskas, M.C. Tosin, A.C. Peterlevitz, H.J. Ceragioli, S.F. Durrant (Faculdade de Engenharia Eletrica e Computacao, Universidade Estadual de Campinas, Brazil) In this work, we studied the properties of nanoporous carbon embedded in very thick porous silicon (PS) films of very high porosity. PS was obtained by etching pores into crystalline Si wafers in a process controlled to prevent crack formation during etching and drying. The nanoporous carbon was made by introducing diluted polyfurfuryl alcohol into the PS micro pores and submitting the samples to pyrolysis at different temperatures (in the 400 K to 700 K range). Such a composite structure of two type-IV materials in nanoporous form may find a large number of future applications, ranging from luminescent devices to molecular sieves. Critical discussion ot the results of surface and cross-section analyses of samples by scanning electron microscopy (SEM), micro-photoluminescence and micro-Raman spectroscopy will be given.
DP-30 A Study on the Deposition of Diamondlike Carbon Film Using rf Magnetron Sputtering Assisted by Ar Ion Beam H.S. Jung, H.H. Park (Yonsei university, Korea) The increasing importance of application of diamondlike carbon (DLC) film requires an in-depth study on the correlation between deposition condition and film properties. To accomplish this aim, the characterization of ion beam assist deposited DLC film has been undertaken. In this manuscript, the hydrogen-free DLC films were prepared by concurrent Ar ion bombardment during radio frequency (RF) magnetron sputtering. The Ar ions were produced by Kaufman ion beam source at the different ion energy range in order to study the Ar ion-induced modification of DLC films.@To observe the effect of Ar ion beam on the film properties, surface morphology, electrical and optical properties of DLC film were investigated. We report that Ar ion beam assistance has a significant influence on the film properties with Ar ion energy range.
DP-31 Characterization of Nitrogen Content Diamond-like Carbon FEAs Using a Magnetic Filtered Arc Method C.F. Chen, C.L. Lin, C.H. Shen, Y.W. Li (National Chiao Tung University, Taiwan,ROC) Uniform and large area pyramid-shape diamond-like carbon field emission arrays are successfully deposited using the magnetic filtered cathodic arc deposition (MFCAD) system. Nitrogen gas is used as the doping source to deposit the diamond-like carbon films containing nitrogen on the inverted pyramid-shape SiO₂ substrates. Experimental results indicate that the current-voltage value of field emission arrays is closely related to the diamond-like film quality. The quality of diamond-like carbon worsens when increasing the flow rate of nitrogen. Consequently, the film composition gradually transforms from diamond-like carbon to sp² and graphite, implying that nitrogen increases the sp² bonding carbon content of the diamond-like carbon. The detail of result will be presented.
DP-32 Electrical Properties of Filtered Cathodic Arc Diamond-like Carbon Films Y.W. Li, Y.J. Tseng, C.F. Chen (National Chiao Tung University, Taiwan,ROC) This work employs a magnetic filter cathodic arc deposition (MFCAD), that satisfies the requirements of magnetic storage devices to investigate how substrate bias, hydrogen-doping and nitrogen-doping affect the electrical properties of diamond-like carbon films. After deposition, a resistance meter (Keithley 617) was used to analyze the electrical properties. Analysis results indicate that increasing the substrate bias and/or incorporating nitrogen doping into the films degrade the lower resistance of the films. This degradation implies that the films contain more sp² bonded carbon. In addition, the hydrogen flow affects the films to a lesser extent. Therefore, increasing the hydrogen gas flow rate during the process degrades the higher resistance of the film. We conclude that hydrogen can prevent the nucleation of sp² carbon or graphite phase and stabilize sp³ diamond-like carbon growth.
DP-33 The Synthesis and Characterization of Boron Nitride Thin Films by Direct Dual Ion Beam Deposition H.K. Baik, D.Y. Lee, Y.H. Kim, I.K.K Kim, D.J. Choi (Yonsei University, Republic of Korea) In this study, we investigated the properties of boron nitride thin films synthesized using co-deposition with positive nitrogen ion beam and negative boron ion beam whose flux and energy independently controllable. The mixed compound of boron nitride containing nitrogen composition from 0 ~ 20 at. % was used as sputtering target. Nitrogen and argon mixed gas were supported by kafuman-type gas ion gun for the purpose of nitrogen source and ion beam bombardment effect respectively. Comparing with various phases of boron nitride (c-BN, h-BN, a-BN etc.), the deposition was performed changing ion beam energy, flux, and substrate temperature.the main object of our study was the fabrication of c-BN films with low stress at room temperature. In addition to the ion beam effects, we expect charge phenomena induced by positive and negative ion enhance the crystallinity of c-BN films.The transformation of phase was characterized by FTIR, XRD and the change of chemical properties was measured by XPS, AES. Especially, we studied the properties of amorphous boron nitride films and its possibility of application to various field such as tribological and electrical areas by nanoindentation and I-V measurement.

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