ICMCTF2001 Session D3-1: Electrical, Optical and Thermal Characterization and Applications of Carbon and Related Materials

Thursday, May 3, 2001 1:30 PM in Room Royal Palm 4-6

Thursday Afternoon

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1:30 PM D3-1-1 Electronic Properties of Phosphorus-Doped Diamond Emitters in Triode-Type Field Emission Arrays
Chia-Fu Chen, Chia-Lun Tsai, Chien-Liang Lin (National Chiao Tung University, Taiwan)

Field emission display (FED) is evolving as a promising technique of flat panel displays in the future. Many factors affect the performance of field emitter arrays including the shape and work function of emission materials, distance between tip and gate, and the environmental vacuum condition. There is an increasing interest in the studies on field emission of diamond films. This is because diamond surfaces terminated with hydrogen atoms have negative affinity (NEA) in addition to superior properties such as chemical inertness and mechanical hardness. Therefore, this material is considered as highly promising applications in electron field emission devices.

In this work, we present a novel scheme that involves a new fabrication process of gate structure metal-insulator-semiconductor (MIS) diode using IC technology. Using a bias assisted microwave plasma chemical vapor deposition (BAMPCVD) system synthesized P-doped completes this process. Deposition of the diamond emitters in this MIS diode forms a dendrite-like diamond in gated field emission arrays (FEAs).

Moreover we compare the gate structure and P-doping concentrations for the influence of emission properties. It is demonstrated that turn-on voltage of electron emission decreases with increasing concentrations for P-doped diamond emitters. Next, the gate aperture diameter could significantly influence the electron field emission characteristics. We have successfully fabricated 4µm-pattern and 1µm-pattern device to enhance emission current density for a given voltage. The detail of result will be presented at conference.

1:50 PM D3-1-2 Field Emission from Amorphous Carbon Film Deposited by RF Plasma CVD Method on Various Metal Electrodes
Y. Show, T. Matsukawa, T. Ohya, M. Iwase, T. Izumi (Tokai University, JAPAN)

Amorphous carbon film is one of promising materials for the cold emitter of the field emission display (FED). It is need to deposit the amorphous carbon film on metal electrodes, which are formed on glass substrate, at low temperature to fabricate the FED. In this study, we have deposited the amorphous carbon films on the various metal electrodes below the temperature of 100 °C without sample cooling by the deposition of low growth pressure (5x10-3 torr). Moreover, we have studied the field emission from the amorphous carbon films on the metal electrodes.

The amorphous carbon films were deposited on the Al, Au and Ti electrodes from mixture gas of CH4 and H2 by using the RF plasma CVD equipment. Both gas flow rates of the CH4 and the H2 were 5 sccm. The RF power and the growth pressure were kept at 100 W and 5x10-3 torr, respectively. The negative bias of -30 V was applied to the substrate during the film deposition. The amorphous carbon films with the thickness of 100 nm were deposited by the deposition of 2 hours.

The amorphous carbon film, deposited on the Al electrode, did not exhibit the electron emission up to applied electric field of 20 V/µmm. On the other hand, the amorphous carbon films, deposited on the Au and the Ti electrodes, emitted the electrons by applying the electric field. The threshold electric field for the amorphous carbon film, deposited on the Au electrode, was 5 V/µmm, which was lower than that of Ti electrode. The emission current densities at the electric field of 20 V/µmm were 7x10-4 and 6x10-6 A/cm-2 for the Au and the Ti electrodes, respectively. Moreover, the stability of the field emission for the Au electrode was more stable than that of the Ti electrode. These results indicate that the high efficiency cold emitter is formed by using the Au electrode as the back contact.

2:10 PM D3-1-3 Structure and Field Emission Properties of Decorated C:N Nanotubes Tuned by Diameter Variations
R. Kurt, J.-M. Bonard, A. Karimi (Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland)
We demonstrate here the possibility of tuning the field emission of nanotube emitters. Plasma enhanced hot filament chemical vapour deposition (PE-HF-CVD) combined with micro-contact printing of catalysts was performed to deposited patterned films nitrogenated carbon (C:N) tubes. The systematic study of a transition between different kinds of twisted nanostructures as a function of the local substrate temperature ranging from 700°C up to 820°C is presented. The morphology, the diameter as well as the properties of the synthesised tubular structures showed strong dependence on this parameter. The diameter of the twisted C:N tubes can easily adjusted in a large range starting from 1 µm down to 10 nm. By means of electron microscopy a new type of decoration covering all tubular structures was observed. Buckled lattice fringes revealed the crystalline but disordered graphitic like character of the hollow C:N nanotubes. The chemical composition of the deposits was derived from electron energy loss spectroscopy (EELS) reaching a maximum N/C ration of approximately 0.04. Raman spectroscopy confirmed a respective transition in the microscopic order. Furthermore field emission in vacuum was studied resulting in a spectacular correlation to the deposition temperature and therefore the diameter of the C:N tubes. For arrays of nanotubes thinner than 50 nm an onset field below 3 V/µm was observed and a field amplification factor β of 1200 was determined in that case. Another big advantage concerning application is the very good long-term stability and the up-scalability.
2:30 PM D3-1-4 Comparison of Field Emission Behaviors of Graphite, Vitreous Carbon and Diamond Powders
S.-H. Lee, K.-R. Lee, K.Y. Eun (Korea Institute of Science and Technology (KIST), Korea)
Many efforts to implement carbon base cold cathode were reported due to their advantages such as low turn-on electric field, high resistance of back sputtering. However, improvement of the uniformity and stability of the emission still remains as a prerequisite for the application of carbon cold cathode. Field emission behavior of crystalline diamond and DLC films of various doping levels were investigated. However, their emission behaviors could not be compared due to the difference in surface morphology and electrical properties of the film surface and the interface between substrate and the film. Furthermore, their emission behaviors was not stable and reproducible, resulting in preventing systematic investigation on the emission mechanism. In the present work, powders of graphite, vitreous carbon and diamond (average grain size 20um) were coated on Mo coated glass by screen printing method using conducting epoxy binder. Morphology of the coated surface were identical in all materials. Their emission behavior was compared under the same measurement condition. Graphite showed the best emission behavior of low turn-on electric field (3 MV/m), reproducible emission behavior as measured by repeated I-V measurements, and stable emission current for long time. On the other hand, diamond exhibited high turn-on electric field of 17 MV/m and unstable emission behavior. This result shows that field emission from carbon materials are not related with the fraction of sp3 bonds but the electrical conductivity of the materials.
2:50 PM D3-1-5 CVD Diamond for Components and Emitters
J. Davidson, W. Kang, K. Holmes, A. Wisitsora-At, P. Taylor, T. Fisher (Vanderbilt University)
An attractive feature of diamond films is their ability to be an excellent dielectric (undoped, resistivity > 1014 ohm-cm to > 400?C) or an interesting semiconductor/ conductor (doped, resistivity ~ < 1 to 1Kohm-cm). Even as polycrystalline/ nanocrystalline films (depending on process deposition conditions), their breakdown strength (as dielectric) and power density capability are interestingly large numbers, particularly for the domain of high temperature, high power applications. The development of nominally conventional patterning processes to manipulate the diamond films into capacitors, resistors and emitter configurations has led to an ability to characterize diamond based components of practical form and function. In this paper, characteristics of two of these diamond microelectronic elements, diamond capacitors and diamond emitters are reported. The potential energy storage capability will be described from test results on diamond capacitors and the behavior of a diamond triode transistor will be presented.
3:30 PM D3-1-7 Infrared Absorption and the Effect of Carbon Isotope in Polycrystalline Diamond Sheets
E. Titus (Indian Institute of Technology, India); A.K. Sikder (University of South Florida); U. Paltnikar, M.K. Singh, D.S. Misra (Indian Institute of Technology, India)

The transparency of diamond to a wide range of electromagnetic spectrum makes it an ideal material for fabricating IR windows and optical coatings. The polycrystalline diamond films however contain grain boundaries and defects not present in single crystal stones. The impurities and defects in CVD diamond can induce significant amount of absorption that renders these less perfect diamond useless as IR windows. A detailed study of the influence of nitrogen, hydrogen on optical and thermal properties is there for essential for commercializing its novel properties. Studies of isotopic effect in the properties of diamond films are also equally important.

Diamond sheets were grown by hot filament chemical vapour deposition technique. Methane (CH4) and Hydrogen (H2) were used as precursor gases. 13CH4 were used to study the isotopic effect. Sheets were characterized using scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The mid-infrared spectral region contains detailed information on molecular vibrations and hence the chemical structures present in the polycrystalline film. Using Fourier Transform Infrared (FTIR) spectroscopy we have studied the one phonon infrared absorption bands for the nitrogen related peaks. Nitrogen also added in a controlled manner to the gas mixture inorder to ascertain the origin of C-N bands. The spectra show several features that have not been reported earlier. The shifts in C-N bands were noticed in one phonon region with the addition of 13C. The effect of isotope on thermal conductivity has also been studied. Quantitative calculation of hydrogen in the sheets using elastic recoil detection analysis and FTIR spectroscopy shows that the total hydrogen concentration in the sheets is nearly one order of magnitude higher than the bonded hydrogen. A correlation has been made with thermal and optical properties and the impurities in the sheets.

3:50 PM D3-1-8 The FTIR Studies of Oriented Diamond Films Grown on Si Substrate Using Temperature Gradient Across the Substrate
E. Titus (Indian Institute of Technology, India); A.K. Sikder (University of South Florida); U. Paltnikar, D.S. Misra (Indian Institute of Technology, India)

For practical applications in optics and electronics, large area single crystal (synthesized) diamond thin films on Si or other suitable substrates are very desirable. However due to the lattice mismatch and random nucleation, usually only polycrystalline diamond films were deposited on Si substrates in the past. These polycrystalline diamond films are formed by inter growth of disjointed diamond crystallites and usually have very rough surfaces. Depending on the deposition conditions, the morphology of these diamond films can be altered.

We have grown (100) oriented diamond films using temperature gradient across the Si(100) substrates by hot filament chemical vapour deposition method. Si substrates were treated with 2µm diamond powder. The temperature gradient was developed across the substrates by heating the sample at one end. The heating was done using a thin film heater on the backside of the sample. Deposition was carried out with 0.8% CH4 in balance hydrogen at average substrate temperature 890°C with varying deposition pressure from 60-140 Torr. Films were characrized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). XRD shows very strong (400) reflection in all the samples. SEM results shows smooth diamond surface comprised of (100) platelets. Because the (100) diamond plates were grown on top of the silicon substrate which is (100) oriented, their faces were more or less aligned parallel with the substrate surface resulting in a relatively smoother diamond surfaces. FTIR studies were carried out in order to determine the impurities present in it. Quantitative analysis was done for the calculation of hydrogen present in the sample. Comparative studies were done between the samples grown by temperature gradient method and steady temperature method.

Time Period ThA Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2001 Schedule