Diamond surfaces when are hydrogen-terminated exhibit very low/negative electron affinity (NEA) reducing the effective work function[1,2]. The NEA character favours the electron/photo emission [1]. For this, the diamond film application as cold photocathode is well proved[3-5], thanks also to its chemical stability and mechanical robustness. In this work, a comparative study between two different deposition techniques, the well known MicroWave Plasma Enhanced CVD (MWPECVD)[6] and the novel pulsed spray techniques[7], are presented and discussed showing advantages and drawbacks. The first technique permits to obtain thin nano- and/or poly-crystalline diamond films (at high deposition temperature, 650-900 °C) with excellent homogeneity and adhesion, while the second one allows to spray thin layer of diamond nanocrystals (at low work temperature, 120 °C), with lower adhesion and uniformity on the substrate. Samples of nanocrystalline diamond films and nanodiamond layers (obtained with the two techniques, respectively) have been characterized by Raman spectroscopy and atomic force microscopy (AFM). Photoemission measurements have been carried out in the UV spectral range, from 150 to 210 nm. The absolute quantum efficiency (QE) of the samples was evaluated by means of a calibrated standard photodiode (NIST). Preliminary results show QE values higher for nanodiamonds layer with respect to nanocrystalline diamond film.
Comparative photoemission study between nanocrystalline diamond films and nanodiamond layers
L Velardi;A Massaro;GS Senesi;
2014
Abstract
Diamond surfaces when are hydrogen-terminated exhibit very low/negative electron affinity (NEA) reducing the effective work function[1,2]. The NEA character favours the electron/photo emission [1]. For this, the diamond film application as cold photocathode is well proved[3-5], thanks also to its chemical stability and mechanical robustness. In this work, a comparative study between two different deposition techniques, the well known MicroWave Plasma Enhanced CVD (MWPECVD)[6] and the novel pulsed spray techniques[7], are presented and discussed showing advantages and drawbacks. The first technique permits to obtain thin nano- and/or poly-crystalline diamond films (at high deposition temperature, 650-900 °C) with excellent homogeneity and adhesion, while the second one allows to spray thin layer of diamond nanocrystals (at low work temperature, 120 °C), with lower adhesion and uniformity on the substrate. Samples of nanocrystalline diamond films and nanodiamond layers (obtained with the two techniques, respectively) have been characterized by Raman spectroscopy and atomic force microscopy (AFM). Photoemission measurements have been carried out in the UV spectral range, from 150 to 210 nm. The absolute quantum efficiency (QE) of the samples was evaluated by means of a calibrated standard photodiode (NIST). Preliminary results show QE values higher for nanodiamonds layer with respect to nanocrystalline diamond film.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
