Simultaneous Field Emission and Photoemission Characterization of N-Doped CVD Diamond
- PDF / 1,586,512 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 27 Downloads / 152 Views
diamond produced by Okano et al, a number of possible mechanisms have been recently proposed and studied. Possible mechanisms include emission from a midgap defect subband [3, 4], back contact injection into the conduction band[5], creation of electroformed conducting channels [6], and emission due to sharp asperities (created during dielectric breakdown) with high field enhancement factors [7]. Building on our recent studies of the field emission state identification of p-type diamond field emitters [8] we have applied our Kratos Analytical AXIS 165 imaging electron spectrometer to better understand field emission from N (urea) doped diamond materials EXPERIMENTAL DETAILS In this report we present electron spectroscopy studies of the field emission from two N (urea) doped diamond thin films (each about 2.5 x 2.5 mm in area) deposited on silicon using the process as reported by Okano et al.[1]. Each sample was mounted on 4-mm diameter support opposed by a grounded electroformed nickel mesh at about 100ltm above the sample surface. The grid used was (sample 02) 200 x 200 lines per inch (lpi) with 78% optical transparency or (sample 03) 250 x 250 lpi with a 70% optical transparency. In the field emission test structure, the diamond thin film sample under study was electrically biased to negative high voltage, such that field emission was achieved. Both the kinetic energy, and the spatial distribution of the emission were measured. The diamond-grid gap spacing was adjusted to be uniform and the gap spacing for samples 02 and 03 were found to be 135 g.tm and 94[tm, respectively. An analytical study [9] of the electric field uniformity (the ratio of minimum field strength to maximum) finds that for a smooth, equipotential sample surface the field uniformity will be greater than 99.5% for the 250 lpi grid at 135tim (02) and greater than 98.8% for the 200 lpi grid at 94 itm (03). Al Ka x-ray photoelectron spectroscopy (XPS) found that both samples had dominant carbon signatures, and 59
Mat. Res. Soc. Symp. Proc. Vol. 509 ©1998 Materials Research Society
also showed significant oxygen content (> 20 atomic %). Tungsten impurity was detected in sample 02 (- 3 atomic %). This impurity presumably originated in the hot (tungsten) filament CVD process. RESULTS Sample 02 After the XPS impurity analysis was complete, sample 02 was mounted in the field emission test structure and the "applied" electric field (defined as the applied potential divided by the gap) was gradually increased. As the applied field was increased, field emission electron (kinetic) energy spectroscopy measurements were made. Up to 8V/micron, no field emission was observed. Further increase in the applied field resulted in an electric discharge which damaged the nickel grid mesh. This event, which we attribute to arcing, produced a lO0ltm diameter hole in the mesh. After arcing, the field emission threshold decreased to below 4.5 V/g.Lm. A linear FowlerNordheim behavior was observed (fig. 1) over a wide range of emission current. Shown in figure 1 is the de
Data Loading...
