Research ArticleAPPLIED SCIENCES AND ENGINEERING

High-pressure, high-temperature molecular doping of nanodiamond

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Science Advances  03 May 2019:
Vol. 5, no. 5, eaau6073
DOI: 10.1126/sciadv.aau6073
  • Fig. 1 Carbon precursor doping mechanism and characterization.

    (A) Schematic representing the synthesis and doping of carbon aerogels, including BF-TEM image with SAED inset. To incorporate them within the carbon aerogel grains, we introduce dopants simultaneously with resorcinol and formaldehyde. Upon conversion to diamond at high pressure and high temperature, dopants remain inside the diamond lattice as color centers. (B) A TEM image with SAED of the doped carbon aerogel illustrates the carbon precursor morphology and lack of crystallinity. (C) EDS spectra of the carbon aerogel as synthesized only show the presence of carbon, silicon, and oxygen. Copper signal comes from the TEM grid. arb. u., arbitrary units. (D) Schematic showing a 1070-nm heating laser or polarized 532-nm Raman and photoluminescence (PL) laser focused into the pressurized DAC, which is loaded with a carbon aerogel precursor, ruby for pressure measurements, and solid argon pressure media, contained by a rhenium gasket. CCD, charge-coupled device; NF, notch filter; HLB, holographic beamsplitter cube.

  • Fig. 2 Structural characterization after HPHT synthesis.

    (A and B) High-angle annular dark-field scanning transmission electron microscopy (STEM-HAADF) and BF-TEM illustrate the microstructure of the recovered diamond material. Arrows in the STEM-HAADF image point out example impurity atoms. The identity of these atoms was not individually confirmed spectroscopically, but EDS mapping and Z-contrast indicate that most are silicon. The inset in (B) contains SAED, exhibiting 2.08-Å lattice spacings that correspond to diamond (111) planes. Figures S1 and S2 detail the d-spacing assignments and provide additional TEM images, respectively. (C) Power-law background subtracted STEM-EELS of the region displayed in (A) showing the argon-L2,3 edge and carbon-K edge.

  • Fig. 3 Dopant distribution mapping.

    (A) Wide-area STEM-HAADF image and (B) the corresponding STEM-EDS elemental mapping of argon (red) and silicon (blue) of the recovered TEOS-doped carbon aerogel. The green squares correspond to the field of view of Fig. 2A. (C) Extracted sum spectrum from the green square area of STEM-EDS spectrum image region showing the overall elemental composition. The small concentration of aluminum likely comes from trace amounts of ruby during laser heating, and the Cu peak is from the sample grid and STEM pole piece. The argon peak includes both Kα and Kβ.

  • Fig. 4 PL of color centers.

    (A) High-resolution PL spectra of the SiV region comparing HPHT TEOS-doped and undoped carbon aerogels. (B) PL and Raman scattering of recovered nanodiamond synthesized from the TEOS-doped carbon aerogel after depressurization and removal from the DAC. Labels denote diamond Raman scattering and NV0, NV, and SiV color center ZPLs. (C) Experimental SiV ZPLs and the B3LYP/6-31G(d) average energy differences of the molecular orbitals, which exhibit largest contributions to the absorption peak responsible for the ZPL at different pressures. Error bars for both pressure and ZPL energy sit within the circular markers. The insets in (C) illustrate the contour plots (0.025 isodensity) of the LUMO (lowest unoccupied molecular orbital) (left) and the HOMO-2 (highest occupied molecular orbital) (right) molecular orbitals (the largest contribution; see table S1 and fig. S6) of a SiV-containing nanodiamond (C119SiH104), oriented perpendicular to the diamond <1,1,1> axis, as modeled with DFT. White, gray, and pink atoms are hydrogen, carbon, and silicon, respectively.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaau6073/DC1

    Additional computational details

    Fig. S1. SAED of the recovered nanodiamond material.

    Fig. S2. Additional TEM images of the recovered nanodiamond material.

    Fig. S3. Raman of the recovered nanodiamond material.

    Fig. S4. Low-energy EELS.

    Fig. S5. DFT modeling of the SiV defect in diamond under uniform hydrostatic pressure.

    Fig. S6. DFT modeling of the SiV excited states.

    Fig. S7. STEM-EDS composition maps.

    Fig. S8. Carbon-K edge scanning transmission x-ray microscopy of nanodiamond synthesized from undoped carbon aerogel on a lacey carbon TEM grid.

    Fig. S9. Poisson distribution of silicon incorporation per nanodiamond grain with varying size.

    Fig. S10. Integrated STEM-EEL spectrum image of the recovered silicon-doped carbon aerogel.

    Fig. S11. DFT modeling of surface capping scheme on SiV center excitations.

    Table S1. Time-dependent DFT transition energies and oscillator strengths.

    Table S2. Time-dependent DFT transition energies and oscillator strengths for ligand capping schemes.

    Table S3. DFT orbital differences for the ligand capping schemes.

    References (4360)

  • Supplementary Materials

    This PDF file includes:

    • Additional computational details
    • Fig. S1. SAED of the recovered nanodiamond material.
    • Fig. S2. Additional TEM images of the recovered nanodiamond material.
    • Fig. S3. Raman of the recovered nanodiamond material.
    • Fig. S4. Low-energy EELS.
    • Fig. S5. DFT modeling of the SiV defect in diamond under uniform hydrostatic pressure.
    • Fig. S6. DFT modeling of the SiV excited states.
    • Fig. S7. STEM-EDS composition maps.
    • Fig. S8. Carbon-K edge scanning transmission x-ray microscopy of nanodiamond synthesized from undoped carbon aerogel on a lacey carbon TEM grid.
    • Fig. S9. Poisson distribution of silicon incorporation per nanodiamond grain with varying size.
    • Fig. S10. Integrated STEM-EEL spectrum image of the recovered silicon-doped carbon aerogel.
    • Fig. S11. DFT modeling of surface capping scheme on SiV center excitations.
    • Table S1. Time-dependent DFT transition energies and oscillator strengths.
    • Table S2. Time-dependent DFT transition energies and oscillator strengths for ligand capping schemes.
    • Table S3. DFT orbital differences for the ligand capping schemes.
    • References (4360)

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