(a) A cartoon schematic showing the generation and detection of the acoustic wave. (b) The total pump-probe differential reflectivity response for an as-grown sample and a sample exposed to 1013 Ne++ ions/cm2. (c) Isolated oscillatory responses for samples exposed to various irradiation doses superimposed on the undamaged response.
Calculated (a) real and (c) and imaginary coefficients of the index of refraction, with the derivative of these values with respect to energy (c) and (d). (e) Values for these four optical constants (E = 1.415 eV) for increasing defect concentration as determined by our phenomenological model.
CAP profiles of radiation-induced optical modification versus depth for various doses. Inset: graphical representation of ΔA/A.
(a) Values of ΔA/A as a function of dose for four different depths (z = 270 nm, blue; z = 470 nm, black; z = 640 nm, red; and z = 750 nm, green) along the damage profile. Inset: Normalized damage profile calculated by TRIM. (b) Change in CAP amplitude plotted to emphasize the value of βdose, which is equal to the line slope and is listed for each depth in the legend.
Channeling data for samples exposed to radiation doses between 1013 and 1015 ions/cm2. The inset shows the damage profile for 5 × 1014 ions/cm2 extracted from the experimental channeling data, compared to TRIM simulation.
Plot of ΔA/A vs nd according to Eq. (5). Here, the slope (β) determines the rate of optical modification versus radiation-generated point defects.
CAP profiles for a single dose (1012 cm−2) showing the frequency-dependence of the radiation induced optical modification as the probe photon energy is detuned from the experimental band gap (Eg ≈ 1.41 eV).
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