ION-BEAM-INDUCED SURFACE MODIFICATION OF CHEMICAL-VAPOR-DEPOSITION DIAMOND FOR X-RAY-BEAM POSITION MONITOR APPLICATIONS

The Advanced Photon Source at Argonne National Laboratory is a third-g eneration synchrotron facility that generates powerful x-ray beams on its undulator beamlines for a variety of scientific and industrial use r research programs. It is very important to know the position and the angle of the x-ray beam during experiments. Due to very high heat flu x levels, several patented x-ray beam position monitors (XBPMs) exploi ting beneficial characteristics of chemical vapor deposition (CVD) dia mond have been developed. These XBPMs have a thin layer of low-atomic- mass metallic coating so that photoemission from the x rays generates a minute but measurable current for position determination. Another co ncept has been the graphitization of the CVD diamond surface to create a very thin, intrinsic conducting layer that can stand much higher te mperatures and have minimal x-ray transmission losses compared to coat ed metallic layers. In the present study, a laboratory sputter ion sou rce was used to transform selected surfaces of a CVD diamond substrate into graphite. The effect of 1-5 keV argon ion bombardment on CVD dia mond surfaces at various target temperatures from 200 to 500 degrees C was studied using Auger electron spectroscopy and in situ electrical resistivity measurements. Graphitization after the ion bombardment was confirmed, and optimum conditions for graphitization were studied. Ra man spectroscopy was applied to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. It w as found that the target temperature plays an important role in the st ability and electrical conductivity of the irradiated CVD diamonds. (C ) 1997 American Vacuum Society.