Browsing by Author "Cross, Graham L.W."

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    Distribution of shallow NV centers in diamond revealed by photoluminescence spectroscopy and nanomachining
    (Elsevier, 2020-04-27) Jadidi, Majid Fazeli; Özer, H. Özgür; Goel, Saurav; Kilpatrick, Jason I.; McEvoy, Niall; McCloskey, David; Donegan, John F.; Cross, Graham L.W.
    We performed nanomachining combined with photoluminescence spectroscopy to understand the depth distribution of nitrogen-vacancy (NV) centers formed by low energy nitrogen ion irradiation of the diamond surface. NV− and NV0 fluorescence signals collected from the surface progressively machined by a diamond tip in an atomic force microscope (AFM) initially rise to a maximum at 5 nm depth before returning to background levels at 10 nm. This maximum corresponds to the defect depth distribution predicted by a SRIM simulation using a 2.5 keV implantation energy per nitrogen atom. Full extinguishing of implantation produced NV− and NV0 zero phonon line peaks occurred beyond 10 nm machining depth, coinciding with the end of easy surface material removal and onset of significant tip wear. The wear ratio of for NV active, ion irradiated diamond compared to the single-crystal diamond tip was surprisingly found to be 22:1. The reported results constitute the first integrated study of in-situ machining and wear characterization via optical properties of the diamond surface containing shallow formed NV centers. We discuss possible metrology applications for diamond tools used in precision manufacturing.
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    High-performance diamond “Supertools” with extreme tool-life
    (Elsevier, 2025-04) Durazo-Cardenas, Isidro; Goel, Saurav; Shore, Paul; Kirkwood, Leigh; Cross, Graham L.W.
    The use of diamond as a cutting tool is pervasive in modern ultra-high-precision machining applications, particularly for generating sub-micron accurate features through the Single Point Diamond Machining (SPDM) method. Beyond SPDM, diamond is also widely employed in contact profilometry (imaging), nanoindentation, nanoimpact, nanoscratching, and lithography applications. Interestingly, a particular type of diamond, commonly used in what the fabrication industry calls “supertools,” consistently demonstrates a lifespan up to 300% longer than that of standard diamond tools. Despite this remarkable performance, the reasons behind the enhanced durability of these unique diamond tools have remained unclear. This paper provides the first experimental explanation for the exceptional properties of these “supertools”. Using Fourier Transform Infrared Spectroscopy (FTIR), we establish that such diamond possess higher overall concentration of nitrogen, particularly Defect Type A (type IaA) and Defect Type C (type Ib). Counterintuitively, they also exhibit lower residual stresses, as revealed through cross-polar examination. Moreover, the diamond tip misalignment error, estimated using Laue backscattering analysis, was found to be insignificant in governing the tool wear resistance. These findings suggest that the wear resistance of natural diamonds can be predicted by screening for high levels of nitrogen defects (combination of Type A and Type C). This insight offers valuable potential for selecting superior diamonds for high-value manufacturing.