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Optimizing thermal anneals of Si-implanted β-Ga2O3 is critical for low resistance contacts and selective area doping. We report the impact of annealing ambient, temperature, and time on the activation of room temperature ion-implanted Si in β-Ga2O3 at concentrations from 5 × 1018 to 1 × 1020 cm−3, demonstrating full activation (>80% activation, mobilities >70 cm2/V s) with contact resistances below 0.29 Ω mm. Homoepitaxial β-Ga2O3 films, grown by plasma-assisted molecular beam epitaxy on Fe-doped (010) substrates, were implanted at multiple energies to yield 100 nm box profiles of 5 × 1018, 5 × 1019, and 1 × 1020 cm−3. Anneals were performed in an ultra-high vacuum-compatible quartz furnace at 1 bar with well-controlled gas compositions. To maintain β-Ga2O3 stability, pO2 must be greater than 10−9 bar. Anneals up to pO2 = 1 bar achieve full activation at 5 × 1018 cm−3, while 5 × 1019 cm−3 must be annealed with pO2 ≤ 10−4 bar, and 1 × 1020 cm−3 requires pO2 < 10−6 bar. Water vapor prevents activation and must be maintained below 10−8 bar. Activation is achieved for anneal temperatures as low as 850 °C with mobility increasing with anneal temperatures up to 1050 °C, though Si diffusion has been reported above 950 °C. At 950 °C, activation is maximized between 5 and 20 min with longer times resulting in decreased carrier activation (over-annealing). This over-annealing is significant for concentrations above 5 × 1019 cm−3 and occurs rapidly at 1 × 1020 cm−3. Rutherford backscattering spectrometry (channeling) suggests that damage recovery is seeded from remnant aligned β-Ga2O3 that remains after implantation; this conclusion is also supported by scanning transmission electron microscopy showing retention of the β-phase with inclusions that resemble the γ-phase. 

Most high-quality quantum dots (QDs) are synthesized in the organic phase, and are often coated with polymers for use in aqueous biological environments. QDs can exhibit fluorescence losses during phase transfer, but evaluating underlying mechanisms ( e.g. , oxidation, surface etching, loss of colloidal stability) can be challenging because of variation in synthesis methods. Here, fluorescence stability of QDs encapsulated in block co-polymer (BCP) micelles was investigated as a function of BCP terminal functionalization ( i.e. , –OH, –COOH, and –NH 2 groups) and synthesis method ( i.e. , electrohydrodynamic emulsification-mediated selfassembly (EE-SA), sonication, and manual shaking). Fluorescence losses, fluorescence intensity, energy spectra, and surface composition were assessed using spectrofluorometry and cathodoluminescence spectroscopy (CL) with integrated X-ray photoemission spectroscopy (XPS). QDs passivated using charged BCPs exhibited 50–80% lower fluorescence intensity than those displaying neutral groups ( e.g. , –OH), which CL/XPS revealed to result from oxidation of surface Cd to CdO. Fluorescence losses were higher for processes with slow formation speed, but minimized in the presence of poly(vinyl alcohol) (PVA) surfactant. These data suggest slower BCP aggregation kinetics rather than electrostatic chain repulsion facilitated QD oxidation. Thus, polymer coating method and BCP structure influence QD oxidation during phase transfer and should be selected to maximize fast aggregation kinetics.