Electrically Detected Electron-Spin-Echo Envelope Modulation: A Highly Sensitive Technique for Resolving Complex Interface Structures

We show that the electrical detection of electron-spin-echo envelope modulation (ESEEM) is a highly sensitive tool to study interfaces. Taking the $\mathrm{Si}/{\mathrm{SiO}}_2$ interface defects in phosphorus-doped crystalline silicon as an example, we find that the main features of the observed echo modulation pattern allow us to develop a microscopic model for the dangling-bond-like $P_{b0}$ center by comparison with the results of ab initio calculations. The ESEEM spectrum is found to be far more sensitive to the defect characteristics than the spectrally resolved hyperfine splitting itself.

Figure 1

Continuous wave (cw) EDMR spectra of the $c\mathrm{\text{−}}\mathrm{Si}\mathrm{\text{:}}\mathrm{P}$ samples with ${}^{29}\mathrm{Si}$ fractions of 4.7%, 20% and 100% for ${\overrightarrow{B}}_0\Vert [100]$. The upper panel shows a fitted decomposition of the 4.7% spectrum (dashed lines). For the 20% ${}^{29}\mathrm{Si}$ sample two pairs of hf-split peaks (horizontal arrows) are attributed to $P_{b0}$ and $P_{b1}$ spins. Vertical arrows indicate the spectral positions where ESEEM experiments have been performed.

Figure 2

(a) ESEEM signals (black lines) on the ${}^{31}\mathrm{P}$ resonance for ${\overrightarrow{B}}_0\Vert [100]$ and ${\overrightarrow{B}}_0\Vert [110]$ in the 20% ${}^{29}\mathrm{Si}$ sample. (b) ESEEM signals on the $P_{b0}$ resonance for three samples with different ${}^{29}\mathrm{Si}$ concentrations for ${\overrightarrow{B}}_0\Vert [100]$. The inset shows the modulation depths as a ($\approx$ linear) function of the ${}^{29}\mathrm{Si}$ concentration for the main oscillation frequency.

Figure 3

Magnetization density $m(\overrightarrow{r})$ of the most likely microscopic structure of the $P_{b0}$ center at the $\mathrm{Si}/{\mathrm{SiO}}_2$ (100) interface as determined from the comparison of ESEEM (100% ${}^{29}\mathrm{Si}$ sample) and theory: monolayer step with a dimerized upper part. View along $[01\overline{1}]$ (a) and [111] (b). The lattice sites of nuclei contributing to the ESEEM signal are indicated.

Figure 4

ESEEM signal of the 100% ${}^{29}\mathrm{Si}$ sample (black solid line) with fits (red lines) taking into account three and seven nuclear spins. The corresponding fitting parameters are listed in Table . Calculated ESEEM signals of the $P_{b0}$ at a dimerized monolayer-step structure ($b_0$) and on a flat surface (a).