article · ACS Applied Electronic Materials
Researchers have developed a fabrication method to integrate silicon-germanium Mie resonators and germanium quantum dots into a single ultrathin film layer. The process begins with solid-state dewetting of a germanium layer deposited by molecular beam epitaxy on an ultrathin silicon-on-insulator substrate, creating SiGe core nanocrystals. Thermal oxidation is then used to form SiO2-SiGe-SiO2 shells around the nanocrystals through germanium condensation. Finally, molecular beam epitaxy grows germanium quantum dots onto the surface, yielding concentric core and multishell nanocrystals decorated with tiny quantum dots. Structural characterisation using high-resolution transmission electron microscopy and high-angle annular dark-field imaging confirmed the complex architecture. When tested, the engineered nanostructures demonstrated a functional photovoltaic effect across the visible light spectrum.
Combining light-trapping resonators and light-absorbing quantum dots into an ultrathin layer is a major challenge in materials science. Achieving this within a single film enables thinner, more efficient optical components, which can support the development of next-generation compact photodetectors and thin solar cells that generate electricity from visible light.
The work shows potential applications in ultrathin solar cells, optoelectronics, optical sensing, and high-performance, self-powered photodetectors. Developers of advanced sensors and energy-harvesting hardware could utilise these single-layer nanostructures. Because the findings reflect laboratory fabrication and initial demonstration of a photovoltaic effect, the technology is at an early stage of development and requires further integration and performance validation before commercial use.
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To efficiently integrate SiGe-based Mie resonators and germanium quantum dots into a single-layer structure for ultrathin solar cells and high performance self-powered photodetectors, we introduce an innovative method involving solid-state dewetting and germanium (Ge) condensation within SiGe nanocrystals. This results in the growth of SiGe/SiO2-SiGe-SiO2 core/shells nanocrystals decorated with Ge quantum dots. The process begins with solid-state dewetting, initiating the growth of SiGe core nanocrystals (Mie resonators) from a Ge layer initially deposited via molecular beam epitaxy on an ultrathin silicon-on-insulator (UT-SOI) film. Subsequently, SiO2-SiGe-SiO2 shells form through thermal oxidation, encapsulating the SiGe nanocrystals by germanium condensation. Finally, Ge quantum dots are grown by molecular beam epitaxy (MBE), resulting in concentric core/multishell nanocrystals embellished with minuscule Ge quantum dots. Our original nanostructure, validated via HR-TEM and HAADF analysis, represents a significant breakthrough in the integration of both Ge QDs and SiGe Mie resonators in one ultrathin layer for optoelectronic applications. Remarkably, these engineered nanostructures demonstrate a photovoltaic effect in the visible spectrum. Anticipating significant potential, this distinctive configuration holds promise for fostering advancements in optoelectronics and sensing applications.
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DOI: 10.1021/acsaelm.4c00126
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