Abstract
Long submicron diamond rods (SDRs) in long conical shape have been fabricated by mask-free plasma etching process. Both undoped and doped polished polycrystalline diamond were etched in oxygen plasma generated by a radio-frequency power of 100 W at 13.56 MHz. The SDR is coated with a Fe2O3 layer, as characterized by Auger electron spectroscopy, X-ray photoemission microscopy. We propose that a “self-forming” mask of Fe2O3 is generated during the etching process in which iron atoms sputtered from the substrate holder are deposited and oxidized on the diamond surface forming “micromask”. The “micromask” protects the underlying diamond and promotes the formation of SDRs.The boron doped single crystalline diamond rods (SCDRs) were used to fabricate Al/diamond Schottky diodes. Each SCDR was extracted from a grain in the polycrystalline film. The as-scratched SCDR was confirmed to be single crystalline diamond by electron diffraction measurements. Al/Ti and Al metals were deposited to form ohmic and Schottky contacts, respectively. A hydrogen plasma treatment is an essential step prior to the formation of Al/diamond Schottky contact in order to improve the device performance. The submicron scale Al/diamond Schottky diode exhibits a very high current density of 1.4 x104 A/cm2 at a forward bias (VF) voltage of -3V.Vertically aligned boron doped SDRs on the polycrystalline diamond film were used to investigated their field emission properties. The SDRs are ~4.5 □m in height and ~383 nm in diameter. Iron oxide is coated on SDRs in the formation of one-dimensional SDRs during oxygen plasma etching. The as-etched SDRs suffer with high turn-on field (ETO) and low field emission current density (JFE) due to the iron oxide. 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, the SDRs exhibit a low ETO value of 4.5V/□m (at 10 □A/cm2) and a high JFE value of 30 mA/cm2 (at 8.5 V/□m). However, the FE emitter is only stable for a short period of time at high current stress owing to the rounding of the tips of SDRs.MSM photodiodes fabricated on submicron scale diamond rods (SDRs) was respectively characterized under the illumination of tungsten light, white light and 254nm UV light. Al metals were deposited on both side of a SDR to form a MSM structure. The as-scratched SDR was confirmed to be three single crystalline diamond grains by electron diffraction measurements showing different fuzzy spot patterns at different part of a SDR. A high photocurrent of 10-6 A at a bias of 3 V was measured when the MSM photodiode was exposed to tungsten light and white light. The submicron scale Al/diamond MSM photodiode exhibits a very high responsibility of 778 A/W at a forward bias (VF) voltage of -1V when exposed to 254nm UV light.