Ion-induced electron-emission from diamond

Abstract

Electron emission from diamond surfaces has recently attracted much attention due to the outstanding physical and electrical properties of diamond (including the negative electron affinity (NEA) that some diamond surfaces exhibit). In general, induced electron emission from any material involves three stages: (I) the excitation of electrons in the bulk; (II) their transport to the surface and (III) the escape of the electrons into the vacuum. The ion induced electron emission (IIEE) yield (/spl gamma/) is defined as the number of emitted electrons per incident ion. It was found to depend on the electronic energy loss of the moving ion in the material. For clean metal surfaces /spl gamma/ is usually about 2-5, however for conducting, boron doped, hydrogenated diamond layers amazingly large values for the IIEE yield (reaching 150 for 200 keV proton bombardment) were recently reported. These large values suggest the use of diamond as a material for the realization of "single ion detectors". Furthermore, the unique way electron-hole pairs are created by ion impact, and the large depth inside the material where they are generated, may also shed light on the processes involved in the other forms of electron emission from diamond. Here the authors present results of IIEE from differently treated and different kinds of diamonds: (i) Boron doped CVD diamond on Si, grain size of the order of a few microns. (ii) Undoped CVD diamond layers, grain size of the order of a few microns. (iii) Boron doped CVD diamond thin layers with sub-micron grain size. (iv) Boron doped CVD diamond thin membranes (free standing) with sub-micron grain size, for which electrons emitted both backwards and forwards are measured.