Surface Characterization of Silicon Carbide Following Shallow Implantation of Platinum Ions for High Temperature Hydroge
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0929-II03-03
Surface Characterization of Silicon Carbide Following Shallow Implantation of Platinum Ions for High Temperature Hydrogen Sensing Applications Claudiu Muntele, Satilmis Budak, Iulia Muntele, and Daryush Ila Physics, Alabama A&M University, 4900 Meridian Street, PO Box 1447, Normal, 35762 Abstract Silicon carbide is a promising wide-bandgap semiconductor intended for use in fabrication of high temperature, high power, and fast switching microelectronics components running without cooling. For hydrogen sensing applications, silicon carbide is generally used in conjunction with either palladium or platinum, both of them being good catalysts for hydrogen. Here we are reporting on the temperature-dependent depth profile modifications of tungsten electrical contacts deposited on silicon carbide substrates. Introduction Palladium and platinum are known as good catalysts for hydrogen, which makes them good active materials in designing hydrogen sensors. They are absorbing hydrogen from the surrounding environment and then release it back in a continuous process, since they do not form stable hydrides. A typical hydrogen sensor design would consist of an electrically insulating substrate on which a thin Pd or Pt layer is deposited along with electrical contacts for monitoring changes in its resistivity due to hydrogen absorption. This concept is rather crude and not very sensitive, therefore the insulating substrate is typically replaced by a semiconductor and a nonlinear (p-n, Schottky, or MOSFET) electronic device is then devised. This kind of device, while having a tremendous increase in sensitivity, becomes much more fragile and structurally unstable, especially in environments where high temperatures associated with corrosive or oxidizing gases are expected to be monitored. Recent literature [1] mentions Au, Ti, Ta, W as good choices for creating ohmic contacts on silicon carbide for hot environment applications. However, our previous work [2] show that Au and Ti contacts don’t maintain structural integrity for extended time when operating at 800°C. The work we present here deals with the evolution of the tungsten electrical contact layers deposited using e-beam evaporation from WC powder. We implanted and then heat treated (HT) our samples in air for 1 hr at 800 °C, using Rutherford Backscattering Spectrometry (RBS), Optical Absorption Spectrophotometry (OAS), and Raman Spectroscopy (RS) measurements to characterize the evolution of the deposit at the end of each preparation stage.
Experimental Semi-insulating 6H silicon carbide was masked and deposited (e-beam evaporation from WC powder in a graphite crucible) with a thin (sub micron) tungsten carbide layer to be used as electrical contacts. We carried out RBS measurements using 2.1 MeV 4He1+ ions in an IBM geometry with the particle detector placed at 170 deg. on both silicon carbide material and tungsten carbide deposits, RS on the tungsten deposits only, and OAS in the range 350 to 2000 nm on the silicon carbide chip only. Then, 1×1015 platinum ions
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