Infrared wavelength-selective photodesorption on diamond surfaces

We report first studies of photodesorption from diamond films using the Vanderbilt Free-Electron Laser at two infrared wavelengths: 3.5 mm, corresponding to localized absorption by C–H bonds at grain boundaries, and 5 mm, corresponding to two-phonon absorption by the bulk diamond. At 3.5 mm, we observe two photodesorption thresholds at fluences well below the onset of ablation. In contrast, at 5 mm, a single photodesorption threshold is identified at a fluence which is close to the second fluence threshold, observed at 3.5 mm. These experiments shed light on the physics of wavelength selective desorption through non-electronic channels. q1998 Elsevier Science B.V.