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80 K DRCLS spectra of (0001) ZnO at various depth up to 1500 nm after (a) mechanical polishing with 6 μm to ¼ μm diamond slurry and (b) subsequent HF etching. Mechanical polishing decreases NBE luminescence efficiency and shifts defect peak intensity from ∼2.4 eV to ∼2.05 eV in near-surface regions, while HF etching increases (decreases) near-surface NBE (∼2.05 eV) emission intensities.
80 K DRCLS spectra comparison of polished ZnO sample d1 and subsequently HF etched ZnO sample d2. The spectra are normalized relative to NBE at 3.353 eV. Inset shows maximum relative deep level defect to NBE intensities versus sampling depth. HF etching decreases the deep band emission intensity by approximately an order of magnitude.
SPS spectra of (a) mechanically polished ZnO sample d1 and (b) subsequent HF etched ZnO sample d2. HF etching removes 2.0/2.05 eV and reduces 1.3 eV defect features.
T-SPS transient at 2.3 eV of polished and HF etched ZnO showing parameters for Eq. (2) .
Transient SPS defect densities calculated for each defect level using Eq. (2) .
Transient SPS defect densities converted to bulk densities using W = 139 nm.
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