Hyung Soo Ahn

Nanomaterials have facilitated the development of innovative technologies in various industries. However, most research has been limited to nanoscale phenomena, and the effects of nanomaterials on microscale crystal growth remain obscure. In this study, we demonstrated a straight 2H–Si microneedle with a longitudinal growth rate of 6.7 × 10⁴ Å·s⁻¹, which could not be explained by conventional crystal growth mechanisms, through AlN nanowires. The AlN nanowires were grown using the hydride vapor-phase epitaxy method, which induced the formation of Al membranes when NH₃ supply was ceased. At this time, an elliptical Al membrane was created within 0.166 s, in accordance with the principle of Plateau–Rayleigh instability. The average spacing of the Al membrane was 4 μm, and approximately 10 000 elliptical Al membranes absorbed SiCl almost simultaneously to form a 40 mm 2H–Si microneedle within 100 min of growth time. Therefore, we realized straight 2H–Si microneedles with a growth rate of 6.7 × 10⁴ Å·s⁻¹. Differing from the conventional growth mechanism, this new growth method sheds light on the mechanism by which nanoscale phenomena contribute to the growth of microscale crystals.

Nanomaterials have facilitated the development of innovative technologies in various industries. However, most research has been limited to nanoscale phenomena, and the effects of nanoscale phenomena on microscale crystal growth remain obscure. In this study, we demonstrated a straight 2H-Si microneedle with a longitudinal growth rate of 6.7 × 10⁴ Å·s^-1, which could not be explained by conventional crystal growth mechanisms, through AlN nanowires. The AlN nanowires were grown using the hydride vapor-phase epitaxy method, which induced the formation of Al membranes when NH₃ supply was ceased. At this time, an elliptical Al membrane was created within 0.166 s, in accordance with the principle of Plateau–Rayleigh instability. The average spacing of the Al membrane was 4 μm, and approximately 10,000 elliptical Al membranes absorbed SiCl almost simultaneously to form a 40-mm 2H-Si microneedle within 100 min of growth time. Therefore, we realized straight 2H–Si microneedles with a growth rate of 6.7 × 10⁴ Å·s^-1. Differing from the conventional growth mechanism, this new growth method sheds light on the mechanism by which nanoscale phenomena contribute to the growth of microscale crystals.

Electricity generation using the piezoelectric effect is an important energy harvesting method. In this study, a solar radiation pressure‐driven crater‐shaped light pressure electric generator (LPEG) device with a Pb(Zr_0.52, Ti_0.48)O₃ (PZT) piezoelectric layer and grained Ag layer is fabricated on GaAs(100) wafer. The electrical output of the device is improved by adsorbing Au nanoparticles (AuNPs) on the Ag layer with the surface of closely connected Ag nanoparticles (AgNPs). By controlling the size and concentration of the AuNPs, a maximum power density of 867.5 µW cm⁻² is obtained under a solar simulator (AM 1.5G), which represents a 151.7% improvement over the case without AuNP adsorption. The results of Raman spectra, finite‐difference time‐domain (FDTD) simulations, and COMSOL Multiphysics demonstrate that the newly formed hotspots between AgNPs─AuNPs and AuNPs─AuNPs enhance the electric field of the incident light significantly and extend the region where the electric field is maximally amplified to 600–800 nm, resulting in increased solar radiation pressure on the PZT piezoelectric layer.

Although hexagonal (2H) silicon (Si) semiconductors exhibit excellent optical properties owing to their quasi-direct bandgap, their growth conditions, which require extremely high pressures, preclude their widespread use in industrial applications. The current study, therefore, proposes a novel approach for the facile growth of hexagonal Si at atmospheric pressure via a unique phenomenon known as Al-based nano absorber. A mixed-source hydride vapor phase epitaxy (HVPE) method was used for the growth of the hexagonal Si single crystals employing a rapid interaction between GaCl₃, AlCl, and SiCl_n gases at a high temperature of 1200 °C using a source mixture of Ga, Al, and Si. In this process, the Al-based nano absorber was formed, which resulted in the absorbance of Si atoms, rather than the growth of Al-based nano absorber, to form the Si crystals due to the subsequent lack of GaCl₃ and AlCl sources. The hexagonal Si structure of these Si crystals was confirmed using field emission scanning electron microscopy, high-resolution x-ray diffraction spectroscopy, and Raman spectroscopy. Thus, the current study establishes atmospheric pressure mixed-source HVPE as a facile approach for growing various allotropic crystals such as Si, C, or Ge via absorption of other atoms by an Al-based nano absorber.