20 research outputs found
Effects of molecular contamination and sp carbon on oxidation of (100) single-crystal diamond surfaces
The efficacy of oxygen (O) surface terminations of specific moieties and
densities on diamond depends on factors such as crystallinity, roughness, and
crystal orientation. Given the wide breadth of diamond-like materials and
O-termination techniques, it can be difficult to discern which method would
yield the highest and most consistent O coverage on a particular subset of
diamond. We first review the relevant physical parameters for O-terminating
single-crystalline diamond (SCD) surfaces and summarize prior oxidation work on
(100) SCD. We then report on our experimental study on X-ray Photoelectron
Spectroscopy (XPS) characterization of (100) diamond surfaces treated with
oxidation methods that include wet chemical oxidation, photochemical oxidation
with UV illumination, and steam oxidation using atomic layer deposition. We
describe a rigorous XPS peak-fitting procedure for measuring the
functionalization of O-terminated samples and recommend that the reporting of
peak energy positions, line shapes, and full-width-half-maximum values of the
individual components, along with the residuals, are important for evaluating
the quality of the peak fit. Two chemical parameters on the surface, sp C
and molecular contaminants, are also crucial towards interpreting the O
coverage on the diamond surface and may account for the inconsistency in prior
reported values in literature
Progress on preferential etching and phosphorus doping of single crystal diamond
Phosphorus is incorporated into single crystal diamond during epitaxial growth at higher concentrations on the (111) crystallographic surface than on the (001) crystallographic surface. To form n+-type regions in diamond for semiconductor devices it is beneficial to deposit on the (111) surface. However, diamond deposition is faster and of higher quality on the (001) surface. A preferential etch method is described that forms inverted pyramids on the (001) surface of a substrate diamond crystal, which opens (111) faces for improved phosphorus incorporation. The preferential etching occurs on the surface in regions where a nickel film is deposited. The etching is performed in a microwave generated hydrogen plasma operating at 160 Torr with the substrate temperature in the range of 800-950 °C. The epitaxial growth of diamond with high phosphorus concentrations exceeding 1020 cm-3 is performed using a microwave plasma-assisted chemical vapor deposition process. Successful growth conditions were achieved with a feedgas mixture of 0.25% methane, 500 ppm phosphine and hydrogen at a pressure of 160 Torr and a substrate temperature of 950-1000°C. The room temperature resistivity of the phosphorus-doped diamond is 120-150 Ω-cm and the activation energy is 0.027 eV
Enhancement of Ohmic heating by Hall current in magnetized capacitively coupled discharges
In low-pressure capacitively coupled discharges, a heating mode transition from a pressure-heating dominated state to an Ohmic-heating dominated state is known by applying a small transverse magnetic field. Here we demonstrate via particle-in-cell simulations and a moment analysis of the Boltzmann equation that the enhancement of Ohmic heating is induced by the Hall current in the direction. As the magnetic field increases, the Ohmic heating in the direction dominates the total electron power absorption. The Ohmic heating induced by the Hall current can be well approximated from the Ohmic heating of unmagnetized capacitively coupled discharges
Dopant uniformity and concentration in boron doped single crystal diamond films
High quality single crystal boron-doped diamond films are deposited in a microwave plasma-assisted CVD reactor with feedgas mixtures including hydrogen, methane, diborane, and carbon dioxide at reactor pressures of 160 Torr. The effect of diborane levels and other growth parameters on the incorporated boron levels are investigated, and the doping efficiency is calculated over a wide range of boron concentrations. The boron level is investigated using infrared absorption, and compared to SIMS measurements, and defects are shown to affect the doping uniformity
Deposition of thick boron-doped homoepitaxial single crystal diamond by microwave plasma chemical vapor deposition
The deposition of high quality single crystal boron-doped diamond is studied. The experimental conditions for the synthesis of 1-2 mm thick boron-doped diamond are investigated using a high power density microwave plasma-assisted chemical vapor deposition reactor. The boron-doped diamond is deposited at a rate of 8-11.5 m/h using 1 ppm diborane in the feed gas as the boron source, and the capability to overgrow defects is demonstrated. The experimental study also investigates the deposition of diamond with both 10 ppm diborane and 2.5-500 ppm of nitrogen added to the feedgas. Synthesized material properties are measured including the electrical conductivity using a four-point probe and the substitutional boron content using infrared absorption