Papers

AVS1996 Session FP-TuA: Field Emitter Displays

Tuesday, October 15, 1996 2:00 PM in Room 204B

Tuesday Afternoon

Start	Invited?	Item
2:00 PM		FP-TuA-1 Potential for Diamond-Based Field Emission Displays J. Jaskie (Motorola) Field Emission Displays that use conventional Spindt tip geometries are becoming an industrial reality. Engineering evaluation displays are now available and several companies are currently building production facilities. The evolution of Field Emission Displays will be toward low work function emitters that allow improved performance and lower cost. Diamond-Like Carbon (DLC), or amorphous carbon, has been demonstrated in laboratories to show attractive combinations of robustness and low effective barrier to electron emission. This promises to lower the cost and improve the performance of future displays. The status of this material and its importance to Field Emission Displays will be discussed.
2:40 PM		FP-TuA-3 The Relationship between the Spatially Resolved Field Emission Characteristics and the Raman Spectra of a Nano-crystalline Diamond Cold Cathode A. Talin, L. Pan, K. McCarty, T. Felter (Sandia National Laboratories); R. Bunshah (University of California, Los Angeles) Spatially resolved electron field emission measurements from a nano-crystalline diamond film grown by plasma-enhanced chemical transport deposition have been obtained using a scanning probe apparatus with micrometer resolution. Macroscopic regions with a high emission site density, and turn-on fields below 3 volts per micron, comprised approximately one half of the total sample area. The emitting and the non-emitting regions of the specimen are differentiated distinctly by Raman spectra and subtly by morphologies. Both areas are largely sp3-bonded, but only the non-emitting regions exhibit the sharp line of better diamond at 1332 cm\super -1\
3:00 PM		FP-TuA-4 Electron Emission from Doped Amorphous Diamond S. Camphausen, M. Ding (North Carolina State University); S. Bozeman (Commonwealth Scientific Corporation); J. Bruley (Lehigh University); J. Cuomo, L. Krasnobaev (North Carolina State University) Doped amorphous diamond (a-D) films were synthesized on sapphire, molybdenum and silicon substrates using a filtered cathodic arc. Phosphorus and nitrogen were incorporated in the films during growth. Phosphorus doping was achieved by using a cathode made of graphite with embedded phosphorus pellets. Nitrogen was incorporated by using a nitrogen background gas at pressures from 10 \super -3\ to 10 \super -5\ Torr. This doping resulted in a significant drop in resistivity from 10 \super 7\ \Omega\ cm (for undoped a-D) to 10 - 20 \Omega\ cm for the doped samples. Secondary ion mass spectroscopy (SIMS) was used to determine doping concentration. Transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were used to characterize the structure of the doped amorphous diamond films. Electrical properties were investigated using a four point probe, field emission and secondary electron emission.
3:40 PM		FP-TuA-6 Electronic Structure of Lithium-Containing Amorphous Hydrogenated Carbon Films J. Thiele, P. Oelhafen (University of Basel, Switzerland) Materials exhibiting a negative electron affinity offer a promising way for the development of small-scale field emitting devices for use in flat panel displays. Quite generally, a negative electron affinity is likely to be found in wide band-gap semiconductors. Besides crystalline materials, e. g. GaAs or diamond, amorphous carbon is under discussion as a possible material. However, the fields necessary for emission and the electron currents obtained with amorphous carbon films are not yet satisfactory. Here lithium-containing amorphous hydrogenated carbon films have been deposited onto silicon and metal substrates. Films were synthesized by parallel deposition of hydrocarbon ions from an ion source and lithium evaporation from dispensers. Parameters of deposition were chosen such as to obtain a carbon matrix with a high content of sp\super 3\-coordinated carbon. The films have been investigated in-situ by X-ray and ultraviolet photoelectron spectroscopy. Parallel shifts of core level and valence band spectra to higher binding energies with respect to the spectra of pure amorphous hydrogenated carbon (a-C:H) indicate a shift of the Fermi level due to lithium incorporation. From the on-set of the valence band spectra at low kinetic energy the work function of the samples could be determined. The work function is reduced from 3.5 eV in pure a-C:H to 2.5 eV in samples containing 20 at.% lithium. The resulting energy level scheme of pure and lithium-containing a-C:H suggests the possibility of preparing films with a negative electron affinity. Clear indication for a negative electron affinity is found in the UPS valence band spectra of some samples.
4:00 PM		FP-TuA-7 Novel Materials for Field Emission M. Park, L. Krasnobaev, J. Cuomo (North Carolina State University) The oxides of copper have been examined for electron emission applications. We report on the field emission and secondary electron emission from both cupric oxide (CuO) & cuprous oxide (Cu\sub 2\O) systems on flat and field emission tip surfaces. The oxides were grown by rf glow discharge in a mixture of argon and oxygen with the substrate, temperature, bias, gas composition and time controlled to optimize the process. The effect of thin electropositive layers on the surface of both oxide systems was also examined. X-ray diffraction, cross-sectional TEM, field emission and secondary electron emission measurement were performed to characterize these films.
4:20 PM		FP-TuA-8 Nanoscale Characterization of Field Emissiom from Diamond Films by Scanning Probe Microscopy in High Vacuum. T. Inoue (Electrotechnical Laboratory, Japan); R. Carpick (Lawrence Berkeley National Laboratory and University of California, Berkeley); D. Ogletree, M. Salmeron (Lawrence Berkeley National Laboratory) Field emission (FE) is greatly enhanced when cathodes are coated with diamond or diamond-like carbon (DLC) films. The exact mechanism of emission enhancement is unresolved, but current ideas involve either the formation of regions with very low work function, the formation of nano-asperities which locally enhance the electric field, or some combination of both. We have studied field emission from diamond films using an atomic force microscope with electrically conducting tips in vacuum. Non-contact images were made by biasing the tip and using electrostatic forces to maintain a tip-surface separation of ~ 100 nm while recording both surface topography and field emission currents. Contact images were made while measuring surface conductivity. Both contact (ohmic) and non-contact (FE) I-V data were acquired, as well as I-Z data. This technique can provide new insights into emission mechanisms by correlating field emission, surface topography and surface conductivity on the sub-micron scale. Data from AFM-FE studies of diamond films will be presented. A very small fraction of the cathode surface shows significant emission at fields < 5 MV/m, while most of the surface does not show emission even at fields up to ~ 500 MV/m. Contact I-V curves of emitting regions show rectifiying behavior, while non-emitting regions do not.
4:40 PM		FP-TuA-9 Field Emission from Amorphous Diamond Films Deposited By Laser Ablation onto Mo M. Ding, A. Myers, W. Choi, R. Vispute, S. Camphausen, J. Narayan, J. Cuomo, J. Hren (North Carolina State University) Previous studies have shown that carbon films deposited onto needle-shaped Si emitters by filtered cathodic arc are amorphous but have a high sp2 content. These results can be ascribed to the poor thermal conductivity inherent to this geometry and material. Our present studies overcome this difficulty by depositing amorphous diamond films onto needle-shaped Mo emitters by laser ablation. The eximer laser used (KrF, l 3D 248 nm) was focused to a fluence of 25 J/cm2 with a pulse repetition rate of 10 Hz. Monitoring films were grown onto sapphire substrates and appeared transparent with a resistivity greater than 10/super 7-8/ Ohm-cm. Field electron emission from coated Mo emitters showed considerable improvement compared with the same emitters before deposition. Electron energy loss spectroscopy showed the films to be amorphous carbon with a high sp3 content. High resolution transmission microscopy and diffraction confirmed that the microstructure of the films at both the tips and shanks were amorphous.