ICMCTF1998 Session D3: Electronic and Optical Applications of Diamond and Related Materials

Wednesday, April 29, 1998 8:30 AM in Room Forum/Senate/Committee
Wednesday Morning

Time Period WeM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF1998 Schedule

Start Invited? Item
8:30 AM Invited D3-1 Current Applications of Diamond in Vacuum Microelectronic Devices
D. Palmer, D. Temple (MCNC)
Research in the area of diamond and diamond-coated vacuum microelectronic devices has been extremely intense in recent years. The potential for significant performance enhancement in commercial and military applications such as microwave power tubes, sensors, high brightness electron beam sources for analytical instrumentation, and flat panel displays has driven much of this research. The enhanced electron emission characteristics and low voltage operation of diamond-based field emitters are generally attributed to the negative electron affinity (NEA) of the diamond surface. Diamond can also improve cathode reliability through decreased probability of vacuum arcs at lower operating voltages, and increased stability of the emission current due to the high chemical and mechanical stability of the diamond film surface. Diamond vacuum microelectronic devices can emit electrons from planar surfaces or micromachined structures. This work will give an overview of the body of research in diamond vacuum microelectronics, with an emphasis on experimental results. Prospects for future applications will be discussed.
9:10 AM D3-3 Effects of Growth Conditions on the Growth Rate and Properties of Nanocrystalline Diamond Films Synthesized by Microwave Plasma CVD
T.G. McCauley, D. Zhou, M. Gruen, L.C. Qin, A.R. Krauss (Argonne National Laboratory)

We have investigated the effects of several process parameters on the growth rate, surface roughness, grain size, and microstructure of diamond thin films prepared by microwave plasma-assisted chemical vapor deposition (MPCVD) on (100) Si from a 1% methane (CH4) precursor in argon (Ar), with and without the addition of molecular hydrogen (H2). Film deposition was carried out at pressures ranging from 55-150 Torr, plasma hydrogen contents of 0-99% H2, and input powers of 500-1200 watts. The resulting films were characterized by visible and UV Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Addition of hydrogen to the feed gas produces the most pronounced enhancement in growth rate and modification of film microstructure, up to a total hydrogen content of approximately 50 atomic percent. Pressure is also shown to have a strong effect on the crystallite size and orientation, as well as on the growth rate. The measured growth rates were virtually independent of microwave power in the range from 500-1200 watts. Nanocrystalline diamond films have potential applications in fields ranging from industrial tool and bearing coatings to encapsulation of integrated microelectromechanical (MEMs) flow transducers to cold cathode devices and flat panel display (FPD) applications.

The results presented here demonstrate that these films can be produced economically and with properties optimized for particular applications through precise control of the growth chemistry and conditions during deposition.

n*Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract W-31-109-ENG-38.

9:30 AM Invited D3-4 Morphological, Topographical and Electrical Properties Relevant to Cold Cathode Electron Emission in Nanocrystalline Diamond Thin Films
A.R. Krauss, O. Auciello, T. Corrigan, M. Ding, D.M. Gruen, T.G. McCauley (Argonne National Laboratory); R.P.H. Chang (Northwestern University); A. Breskin, R. Chechyk, E. Shefer (Weizmann Institute of Science, Israel); E. Grossman, Y. Lifshitz (Soreq Nuclear Research Institute, Israel); A. Karabutov, V. Konov, S. Pimenov (General Physics Institute, Russian Academy of Science, Russia)

Diamond and diamond-like carbon thin films have been found to be effective cold cathode electron emitters. The emission mechanism however, is not clear, and a number of models have been advanced to explain the process. In general, there are very few reliable "fingerprints" to determine apriori if a given film will or will not emit electrons. We have used transmission electron microscopy (TEM), photoelectron microscopy (PEEM), visible and UV Raman spectroscopy, scanning tunneling and atomic force microscopy, and UV photoelectron yield measurements to characterize a series of diamond thin films grown in a microwave CVD reactor using C60-Ar-H2, CH4-Ar-H2 and CH4-Ar-N2 plasmas, and have identified a set of morphological, topographical, electronic and electrical criteria which enable prediction of the cold cathode electron emission properties. For these films, emission appears to originate largely at grain boundaries, and a simple model for grain boundary emission is presented, based on the observed grain morphology and a recent calculation of grain boundary properties by P. Keblinski, D. Wolf, S. Philpot and H. Gleiter1. For diamond films grown by other methods such as dc plasma and arc jet deposition, there appear to be different emission sites and emission mechanisms which do not fit the model developed for the films deposited by microwave CVD.

1 P. Keblinski, D. Wolf, S. Philpot and H. Gleiter, J. Mater. Research, in press

*Work supported by the US Dept. of Energy, Office of Basic Energy Sciences under contract W-31-109-ENG-38, and by the Office of Naval Research under contract N00014-96-C0283.

10:10 AM D3-6 Break

10:30 AM D3-7 The Microstructural Dependance of the Opto-Electronic Properties of Nitrogenated Amorphous Carbon Nitride Thin Films
S.R.P. Silva, A.P. Burden, J.V. Anguita, R.D. Forrest (University of Surrey, United Kingdom); A. Papworth, A. Munindradasa, C.J. Kiely, G.A.J. Amaratunga (University of Liverpool, United Kingdom)
The microstructural properties of amorphous carbon nitride thin films deposited using a number of different plasma deposition systems are analysed in order to evaluate its impact on their opto-electronic properties. The microstructure, which is examined using infra red spectroscopy, electron energy loss spectroscopy, elastic recoil detection analysis and Rutherford Backscattering, is used to reconstruct a density of states (DOS) diagram for the carbon nitride films. Information obtained from optical absorption is then used together with electrical activation energy studies to refine the DOS. Using this DOS we attempt to predict the variation expected in the electronic conduction as a function of nitrogen content and temperature. The electrical data obtained for the amorphous carbon nitride thin films appear to be controlled by the heterojunction at the back contact as opposed to a Schottky barrier at the front contact. The bulk conduction within the films at high fields is fitted to Poole-Frenkel, Poole and Ionic conduction type behaviour in order to obtain the best fits to the data. It is interesting to note that when the metal-insulator-metal (MIM) data is fitted to a Fowler-Nordheim type conduction, which is expected for electron field emission from semiconductors, barriers to emission close to those observed for electron field emission are obtained for the MIM structures too.
11:10 AM D3-9 Diamond-Like Carbon Films with Extremely Low Stress
S. Kumar, D. Sarangi, O.S. Panwar, P.N. Dixit, R. Bhattacharyya (National Physical Laboratory, India)
We in this paper report different ways to realise thick diamond-like carbon (DLC) films with stress values lower than 0.5 GPa. Thick DLC films grown by conventional rf self bias technique often delaminate from the substrate due to the presence of high compressive stresses of the order of 3 - 5 GPa. We have made an indepth study of the delamination problem of DLC films at NPL and found that only for substrates kept away from the plasma (plume) it is possible to grow thick DLC films. This goes to show the heating of the substrates when in contact with the plasma appears to be one of the most important factor giving rise to the high stress values. Techniques that have produced consistently low stress values (0.2 - 0.5 GPa) in this laboratory are dc saddle field fast atom beam source and pulse plasma PECVD techniques. It is also possible to reduce stresses, when during the film growth, the first layer in contact with the substrate contained Si in some form. Stress measurement involving various graded and nanocomposite structures have been made. Electronic properties of the materials so produced has been estimated by evaluating Urbach energy using photothermal deflection spectroscopy (PDS) measurements. Presence of unbound hydrogen in these films, as measured by a nuclear technique, influencing the stress levels is also explored.
Time Period WeM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF1998 Schedule