In this work, hafnium oxide (HfO
2
) thin films are deposited on p-type Si substrates by remote plasma atomic layer deposition on p-type Si at 250 °C, followed by a rapid thermal annealing in nitrogen. Effect of post-annealing temperature on the crystallization of HfO
2
films and HfO
2
/Si interfaces is investigated. The crystallization of the HfO
2
films and HfO
2
/Si interface is studied by field emission transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. The experimental results show that during annealing, the oxygen diffuse from HfO
2
to Si interface. For annealing temperature below 400 °C, the HfO
2
film and interfacial layer are amorphous, and the latter consists of HfO
2
and silicon dioxide (SiO
2
). At annealing temperature of 450-550 °C, the HfO
2
film become multiphase polycrystalline, and a crystalline SiO
2
is found at the interface. Finally, at annealing temperature beyond 550 °C, the HfO
2
film is dominated by single-phase polycrystalline, and the interfacial layer is completely transformed to crystalline SiO
2
.
Halide segregation is a critical bottleneck that hampers the application of mixed-halide perovskite nanocrystals (NCs) in both electroluminescent and downconversion red-light-emitting diodes. Herein, we report a strategy that combines precursor and surface engineering to obtain pure-red-emitting (peaked at 624 nm) NCs with a photoluminescence quantum yield of up to 92% and strongly suppresses the halide segregation of mixed-halide NCs under light irradiation. Red-light-emitting diodes (LED) using these mixed-halide NCs as phosphors exhibit color-stable emission with a negligible peak shift and spectral broadening during operation over 240 min. By contrast, a dramatic peak shift and spectral broadening were observed after 10 min of operation in LEDs based on mixed-halide NCs synthesized by a traditional method. Our strategy is critical to achieving photo-and band-gap-stable mixed-halide perovskite NCs for a variety of optoelectronic applications such as micro-LEDs.
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