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Plasmatability High-Purity CVD Diamond Material

Introduction:

Plasmability has undertaken a short R&D study to assess the quality of CVD diamond plates grown in our
Austin Texas facility using our IcemakerTM CVD reactors. The analysis was carried out at the laboratory
facilities of GIA (Gemological Institute of America) facility in New York.

EPR Measurements indicate sub-ppb nitrogen incorporation

Using the Plasmability CVD growth system, we successfully achieved nitrogen incorporation levels under 1 ppb in single crystal diamond samples with a thickness of 0.5 mm. Nitrogen content analysis was measured utilizing a high-precision Bruker EMXmicro Electron Paramagnetic Resonance (EPR) instrument and Photoluminescence (PL) spectroscopy (Renishaw InVia Raman confocal microspectrometer).

The focus of our EPR analysis was primarily on single substitutional nitrogen (Ns0), the dominant defect in CVD diamond. EPR is a bulk technique that can provide average Ns0 concentrations ([Ns0]) with a sensitivity down to ~ 0.05 ppb (parts per billion). This is accomplished by comparing the strength of the Ns0 EPR signal from a specific sample to that of a reference sample with a known concentration.

Sample

[Ns0] (ppb)

P0698-704

0.1   (+0.1)

P0700-701

0.04  (+0.05)

P0708-702

0.10  (+0.03)

Figure 1. EPR measurements of CVD diamond plates grown at Plasmability

Photoluminescence Measurements show no detectable nitrogen or silicon vacancy defects

Photoluminescence (PL) data was obtained at a temperature of 77 K using both a 514 nm laser and a 457 laser.  Both measurements show no detectable signal for  NV0 (575 nm), NV- (637 nm), and SiV- (737 nm) centers. Further spectra collected at higher power (saturated Raman peak) did not reveal any defect-related emissions.

Figure 2. Photoluminescence spectra obtained at liquid nitrogen temperature (77 K) using a 514 nm green laser for excitation. The zoomed in spectra show only Raman features associated with the diamond (552 nm) and liquid nitrogen (LN2). No defect-related PL features were detected.

Figure 3. Photoluminescence spectra obtained at liquid nitrogen temperature (77 K) using a 457 nm blue laser for excitation. The zoomed in spectra show only Raman features from diamond (468 nm) and the liquid nitrogen (LN2). No defect-related PL peaks were detected.