Abstract
One-dimensional boron-doped sub-micron diamond rods (SDRs) with excellent field emission current density 35mA/cm2 (at 8.5 V/μm) and turn on field 4.3 V/μm ( at 10 μA/cm2)are fabricated on polycrystalline diamond/Si by oxygen plasma etching and subsequent HCl etching. SDRs are fabricated on the polycrystalline diamond/Si substrate, made from HFCVD, by using oxygen plasma etching in capacitance coupled plasma (CCP) chamber operated at a radio frequency (RF) of 13.56 MHz. The RF power source is operated at 100 W. The total oxygen gas pressure is kept at 15 mtorr and the self-bias voltage is -1300 V during etching. The one-dimensional SDRs are further wet-etched by HCl(37%) at 90℃for 30 minutes. Field emission properties are measured at 10-6 torr with a spacing of 100μm between the copper anode and cathode. Experimental results indicate that field emission characteristics are better for longer SDRs. The SDRs’ length (diameter) change from 4.2μm (420nm) to 4.8μm (370nm) as the plasma self-bias voltage increase from -1000V to -1300V, associate with better field emission characteristics. Nevertheless, the as-etched SDRs suffer with high turn-on field (ETO) and low field emission current density (JFE) due to residual iron oxide on the rods’ surfaces. A huge improvement in the field emission characteristics can be achieved by removing iron oxide using a wet-etch process in a diluted HCl (37%). After the wet-etch, field emission current density (JFE) increases from 1 mA/cm2 to 35mA/cm2 under the same filed 8.5 V/μm and turn-on field (ETO) reduces from 6V/μm to 4.3 V/μm ( at 10 μA/cm2). Stability test shows a stable period exists in the beginning and after that the current density decay significantly and approach saturation at last. The stable period become smaller and the near saturation time become shorter with increasing applied field.