(Left) Dark-field X-TEM images and (right) histogram showing the evolution of the intrinsic ([P] = 0) silicon nanocrystal ensemble size distribution with increasing isothermal (1050 °C) anneal time, tA in the range 3 to 100 s. The red lines are lognormal fits to the data, which provides the mean nanocrystal size, 〈d〉.
(Left) Normalized room temperature PL spectra (offset for clarity) and (right) PL peak emission energy for (bottom) intrinsic and (top) phosphorus doped silicon nanocrystals as a function of isothermal (1050 °C) anneal time (tA = 1, 5, 10, 50, 100, and 600 s).
(a) Integrated PL intensity for the intrinsic (open squares) and phosphorus doped (closed squares) silicon nanocrystals as a function of the isothermal (1050 °C) anneal time, (b), (c), and (d), respectively, show the evolution of the ratios of the PL full width at half maximum, PLFWHM(P)/PLFWHM(0), integrated PL intensities, IPL(P)/IPL(0) and the difference in peak emission energy, ΔE = E(P) – E(0) over the annealing time range. Lines are to guide the eye.
Evolution of the spectrally resolved PL decay rates for the phosphorus doped (red squares) and intrinsic (grey squares) silicon nanocrystals as a function of isothermal (1050 °C) anneal time. The inset shows a typical PL decay curve, the fit (red line) of which is derived from a stretched exponential function, giving characteristic lifetimes, τPL = w PL −1.
(Left axis) Evolution of the measured intrinsic (black squares) nanocrystal mean diameter and that estimated (for a 52% size increase) for the phosphorus doped (grey squares) nanocrystals. (Right axis) Ratio of the integrated PL intensities, (red squares) as a function of the isothermal (1050 °C) anneal time. The blue arrows and circle indicate the nanocrystal size at which = 1 and therefore provides an estimate of the “threshold size” (dthreshold ∼ 1.85 nm) above which the majority of nanocrystals contain free carriers after the ionization of substitutional phosphorus donors.
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