INFRARED WAVELENGTH-SELECTIVE PHOTODESORPTION ON DIAMOND SURFACES

We report first studies of photodesorption from diamond films using th e Vanderbilt Free-Electron Laser at two infrared wavelengths: 3.5 mu m , corresponding to localized absorption by C-H bonds at grain boundari es, and 5 mu m, corresponding to two-phonon absorption by the bulk dia mond, At 3.5 mu m, we observe two photodesorption thresholds at fluenc es well below the onset of ablation. In contrast, at 5 mu m, a single photodesorption threshold is identified at a fluence which is close to the second fluence threshold, observed at 3.5 mu m. These experiments shed light on the physics of wavelength selective desorption through non-electronic channels. (C) 1998 Elsevier Science B.V.