Research ArticleMATERIALS ENGINEERING

Atomically engineered electron spin lifetimes of 30 s in silicon

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Science Advances  31 Mar 2017:
Vol. 3, no. 3, e1602811
DOI: 10.1126/sciadv.1602811
  • Fig. 1 Charge sensor for independent readout of two P donor quantum dots.

    (A) Overview STM image of the device template after STM lithography showing four electrostatic gates (G1, G2, GT, and GSET) and a SET charge sensor with source (S) and drain (D) leads. Two donor incorporation sites, D1 and D2 separated by 20 nm, were patterned 19 nm away from the SET. (B and C) Closeup STM images of D1 and D2 with the underlying Si(001)-(2 × 1) surface reconstruction. Both dot templates consist of three and four contiguous desorbed dimers (green ellipses) along two adjacent dimer rows. Assuming a 0.25–monolayer (ML) doping density (31), we estimate that a maximum of three P can be incorporated in D1 and D2. (D) Charge stability diagram (VSD = 300 μV, VGT = 100 mV, and VGSET = 0 mV) showing the current through the SET as a function of the voltage applied to G1 and G2. We observe two sets of parallel lines of breaks in the SET current where either the D1 (yellow dashed lines) or D2 (blue dashed lines) electrochemical potentials align with that of the SET.

  • Fig. 2 Extending T1 using single electron spins bound to multidonor quantum dots.

    (A) Measured charge stability diagram showing the positions in gate space where readout is performed on D1 and D2, recorded at VSD = 1.5 mV, VGT = −200 mV, and VGSET = 20 mV. The red and blue stars (circles) are the readout positions for D1 and D2 if the other dot is unoccupied (occupied). (B) Measured spin relaxation rates, T1−1, of the first electron bound to D1 (red squares) and D2 (blue squares) and the third electron bound to D2 (green squares) as a function of magnetic field. The data follow T1−1 = K5B5 with K5 = 0.00059 ± 0.00002 s−1 T−5, K5 = 0.0028 ± 0.0001 s−1 T−5, and K5 = 1.3 ± 0.1 s−1 T−5 for D1 (1e), D2 (1e), and D2 (3e), respectively. The black line shows the fit (K5 = 0.0095 s−1 T−5) to the spin relaxation times of the single donor device in the study by Watson et al. (2) measured at the same magnetic field direction used in this experiment.

  • Fig. 3 High-fidelity sequential readout of two electron spins confined to a 3P/2P DQD.

    (A) Twenty readout traces showing the real-time current through the SET during the sequential single-shot readout of D1 and D2 for a magnetic field of B = 1.5 T and VSD = 170 μV. A spin-up is assigned to D1 or D2 if a current pulse occurs during the read phase. (B and C) Histograms (black circles) of the peak current during the readout of (B) D1 and (C) D2 for 7500 readout cycles. The two well-separated peaks allow |↓〉 and |↑〉 electrons to be distinguished with high fidelity. The blue and green lines show the separated histograms for the |↓〉 and |↑〉 current traces, which were simulated using the experimental parameters.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/3/e1602811/DC1

    section S1. Extraction of the electron temperature, gate lever arms, and addition energies of D1 and D2.

    section S2. Fidelity of the sequential readout of D1 and D2.

    section S3. Comparison of the spin relaxation times of previous donor devices.

    fig. S1. Extraction of the electron temperature and gate lever arms from the thermal broadening of the SET Fermi level.

    fig. S2. Extraction of the addition energy for the second and third electrons on D2.

    fig. S3. Atomistic tight-binding calculations of the addition spectrum of 2P, 3P, and 4P donor dots.

    fig. S4. Extraction of the spin-dependent tunnel times during readout of D1 and D2.

    fig. S5. Optimization of the readout time.

    fig. S6. Electrical readout fidelity of D1 and D2.

    fig. S7. Deviation from the B5 field dependence in donor devices.

    table S1. Comparison of lever arms (α), addition voltages (ΔVadd), and addition energies (Eadd) of D1 and D2 for each electron transition for two different cooldowns.

    References (3234)

  • Supplementary Materials

    This PDF file includes:

    • section S1. Extraction of the electron temperature, gate lever arms, and addition energies of D1 and D2.
    • section S2. Fidelity of the sequential readout of D1 and D2.
    • section S3. Comparison of the spin relaxation times of previous donor devices.
    • fig. S1. Extraction of the electron temperature and gate lever arms from the thermal broadening of the SET Fermi level.
    • fig. S2. Extraction of the addition energy for the second and third electrons on D2.
    • fig. S3. Atomistic tight-binding calculations of the addition spectrum of 2P, 3P, and 4P donor dots.
    • fig. S4. Extraction of the spin-dependent tunnel times during readout of D1 and D2.
    • fig. S5. Optimization of the readout time.
    • fig. S6. Electrical readout fidelity of D1 and D2.
    • fig. S7. Deviation from the B5 field dependence in donor devices.
    • table S1. Comparison of lever arms (α), addition voltages (ΔVadd), and addition energies (Eadd) of D1 and D2 for each electron transition for two different cooldowns.
    • References (32–34)

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