Subnanometer Thick Native sp² Carbon on Oxidized Diamond Surfaces

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Oxygen-terminated diamond surfaces are crucial for applications like quantum sensing and semiconductor devices.
• Characterizing the topmost atomic layers (<1 nm) of diamond surfaces is difficult with traditional methods like XPS and FTIR.
• Understanding surface termination is key to controlling diamond's electronic and chemical properties.

Purpose of the Study:

• To investigate the chemical composition of the shallowest regions (<10 nm) of oxygen- and hydrogen-terminated diamond surfaces.
• To differentiate bonding configurations of surface functional groups using advanced spectroscopic techniques.
• To determine the location and extent of oxygen bonding on diamond surfaces.

Main Methods:

• Utilized angle-resolved X-ray photoelectron spectroscopy (AR-XPS) on single-crystalline (100) diamond grown by chemical vapor deposition (CVD).
• Employed consistent peak-fitting methodologies to analyze spectral data.
• Analyzed Auger electron spectra and D-parameter calculations to quantify layer thickness.

Main Results:

• Identified and characterized sp2 carbon, ether, hydroxyl, carbonyl, and C-H groups on both oxygen- and hydrogen-terminated diamond surfaces.
• Quantified the sp2 carbon layer on oxygen-terminated diamond to be 0.3 ± 0.1 nm thick.
• Demonstrated that oxygen primarily bonds to this sp2 carbon layer, not directly to the bulk sp3 diamond carbon.

Conclusions:

• AR-XPS is effective for probing the chemical states within the first ten nanometers of terminated diamond surfaces.
• The findings reveal a distinct structural and chemical arrangement at the oxygen-terminated diamond interface.
• This work clarifies the bonding sites of oxygen on diamond, impacting the design of diamond-based devices.