Hydrogen Free, High sp 3 Content DLC Films Produced by Pulsed Laser Ablation of Amorphous Graphite
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HYDROGEN FREE, HIGH sp3 CONTENT DLC FILMS PRODUCED BY PULSED LASER ABLATION OF AMORPHOUS GRAPHITE J. Haverkamp, R. M. Mayo Department of Nuclear Engineering, North Carolina State University, Raleigh NC 27695-7909 J. Narayan, C. Jin Department of Materials Science and Engineering, North Carolina State University, Raleigh NC 27695-7916 Pulsed laser deposition is a unique technique for the deposition of a wide variety of thin films. These films include magnetic and optical films, novel semiconductors, high temperature superconductors, and diamond-like carbon films. Amorphous Carbon material is evaporated from a solid target and ionized by a high-energy KrF laser and ejected as a plasma plume. The plume expands outwards and deposits the target material on a silicon substrate. Plasma and flow parameters in this plume determine the quality of the film deposited on the substrate. In these experiments, a quadruple Langmuir probe is used to determine various plasma properties in the plume as a function of laser energy density on target, laser spot size on the target and probe position from target. These properties include electron temperature, ion flow speed, ion kinetic energy, plume peaking parameter, and ion density. Film analysis was conducted by electron energy loss spectroscopy (EELS) indicating that DLC films have been successfully deposited with an sp3 concentration as exceeding 72%. Introduction Diamond-like carbon(DLC) thin films are used in a variety of applications, including antireflection coatings for infrared windows[1], coatings for wear resistance in hip joints[2], and magnetic disk drive coatings[1]. Similar to pure diamond, DLC films have properties that include scratch resistance, high hardness, chemical inertness, optical transparency, high electrical resistivity and good thermal conductivity[1,3,4,5]. Diamond-like carbon films owe their diamond-like nature to a high degree of sp3 bonding[1]. An excellent method for the production of DLC thin films is pulsed laser deposition(PLD). The properties of the plasma plume created during PLD affect the quality of films produced. Therefore, there is interest in determining the properties of the plume created during PLD for a variety of operating conditions. For instance, the ion kinetic energy may affect sp3 fraction, and the plume forward peaking parameter describes the density profile of the plume and hence the thickness profile of the deposited film. A number of different techniques are used for the analysis of PLD plumes, including spectroscopy and probe methods. The quadruple Langmuir probe is used in this research to determine plume properties such as electron temperature, ion density, plume leading edge flow speed, ion kinetic energy, and the plume forward peaking value. Experiment North Carolina State University operates a pulsed laser evaporation and deposition facility under the auspices of the National Science Foundation Center for Advanced Materials and Smart Structures, directed by Professor Narayan. This facility is described in detail in several re
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