Liquid-Modulated Photothermal Phenomena in Porous Silicon Nanostructures Studied by μ-Raman Spectroscopy

Exploring the Influence of Solvents on Electrochemically Etched Porous Silicon Based on Photoluminescence and Surface Morphology Analysis

Porous silicon (PSi) has promising applications in optoelectronic devices due to its efficient photoluminescence (PL). This study systematically investigates the effects of various organic solvents and their concentrations during electrochemical etching on the resulting PL and surface morphology of PSi. Ethanol, n-butanol, ethylene glycol (EG) and N,N-dimethylformamide (DMF) were employed as solvents in hydrofluoric acid (HF)-based silicon etching. The PL peak position exhibited progressive blue-shifting with increasing ethanol and EG concentrations, accompanied by reductions in the secondary peak intensity and emission linewidth. Comparatively, changes in n-butanol concentration only slightly impacted the main PL peak position. Additionally, distinct morphological transitions were observed for different solvents, with ethanol and n-butanol facilitating uniform single-layer porous structures at higher concentrations in contrast to the excessive etching caused by EG and DMF resulting in PL quenching. These results highlight the complex interdependencies between solvent parameters such as polarity, volatility and viscosity in modulating PSi properties through their influence on surface wetting, diffusion and etching kinetics. The findings provide meaningful guidelines for selecting suitable solvent conditions to tune PSi characteristics for optimized device performance.

Raman Spectroscopy of Glass Beads in Ammonium Nitrate Solution and Compensation of Signal Losses

In the present study, the influence of disperse systems on Raman scattering was investigated. How an increasing particle concentration weakens the quantitative signal of the Raman spectrum is shown. Furthermore, the change in the position of the optimal measurement point in the fluid was considered in detail. Additional transmission measurements can be used to derive a simple and robust correction method that allows the actual concentration of the continuous phase to be determined with a standard deviation of 2.6%.

Plasmonic Nanofluids: Enhancing Photothermal Gradients toward Liquid Robots

In situ energy generation in soft, flexible, autonomous devices is challenging due to the need for highly stretchable and fault-resistant components. Nanofluids with pyro-, tribo-, or thermoelectric properties have recently emerged as promising solutions for realizing liquid-based energy harvesters. Yet, large thermal gradients are required for the efficient performance of these systems. In this work, we show that oil-based plasmonic nanofluids uniquely combine high photothermal efficiency with strong heat localization. In particular, we report that oleic acid-based nanofluids containing TiN nanoclusters (0.3 wt %) exhibit 89% photothermal efficiency and can realize thermal gradients as large as 15.5 K/cm under solar irradiation. We experimentally and numerically investigate the photothermal behavior of the nanofluid as a function of solid fraction concentration and irradiation wavelength, clarifying the interplay of thermal and optical properties and demonstrating a dramatic improvement compared with water-based nanofluids. Overall, these results open unprecedented opportunities for the development of liquid-based energy generation systems for soft, stand-alone devices.

The Process and Mechanism of Preparing Nanoporous Silicon: Helium Ion Implantation

Ion implantation is an effective way to control performance in semiconductor technology. In this paper, the fabrication of 1~5 nm porous silicon by helium ion implantation was systemically studied, and the growth mechanism and regulation mechanism of helium bubbles in monocrystalline silicon at low temperatures were revealed. In this work, 100 keV He ions (1~7.5 × 10¹⁶ ions/cm²) were implanted into monocrystalline silicon at 115 °C~220 °C. There were three distinct stages in the growth of helium bubbles, showing different mechanisms of helium bubble formation. The minimum average diameter of a helium bubble is approximately 2.3 nm, and the maximum number density of the helium bubble is 4.2 × 10²³ m^-3 at 175 °C. The porous structure may not be obtained at injection temperatures below 115 °C or injection doses below 2.5 × 10¹⁶ ions/cm². In the process, both the ion implantation temperature and ion implantation dose affect the growth of helium bubbles in monocrystalline silicon. Our findings suggest an effective approach to the fabrication of 1~5 nm nanoporous silicon, challenging the classic view of the relationship between process temperature or dose and pore size of porous silicon, and some new theories are summarized.