Electron stimulated desorption on diamond 100/as a negative hydrogen source

The electron-stimulated desorption of negatively charged hydrogen ions from diamond surfaces is studied with respect to an application as a bright ion source. Bombarding an 100.-oriented, boron-doped single crystal diamond with 40-mA electrons at energies up to 12 keV, a maximum ion current of 700 pA negative hydrogen is obtained. A supply of 1.0=10y4 mbar atomic deuterium results in a steady-state ion current of 30 pA. The ionization cross section has been proven to vary one order of magnitude between 3.5=10y18 cm2 and 5=10y19 cm2 with hydrogen coverage of the surface. This effect might be caused by the changing electron affinity of the diamond. q1999 Elsevier Science B.V. All rights reserved