Extended Data Fig. 2: DEER spectra for depth calibration of shallow NVs.
From: Coherence enhancement of solid-state qubits by local manipulation of the electron spin bath
a, Schematics showing the principle of DEER measurement. An extra π-pulse is applied at the middle of the spin-echo sequence, flipping the surrounding electron spins. Thus, the magnetic field from electron spins is sensed by the NV centre. b, Typical results of DEER spectra and spin-echo of a single shallow NV. Additional decoherence caused by the electron spins obviously appears in the DEER. c, Normalized DEER spectra for eliminating unwanted oscillations and peaks caused by the 13C residual spins or misalignment of biased magnetic field. d, Two typical normalized DEER spectra demonstrated in log-log plot of two shallow NV centres. The transition time is clearly observed, which reflects the depth of the NV centres. The dashed and dotted lines represent the powers of 2 and 2/3, respectively. e, The graph summarizing seven measured NV centres, which shows a positive relation between T2 and the depth. The red curve is used for guiding the eyes.
