Size dependence of nanostructures: Impact of bond order deficiency

A selective laser melting and solution heat treatment refined Al-12Si alloy with a controllable ultrafine eutectic microstructure and 25% tensile ductility

Dynamic self-organization phenomena in complex ionized gas systems: new paradigms and technological aspects

Silicon atomic force microscope (AFM) cantilevers having integrated solid-state heaters were originally developed for application to data storage, but have since been applied to metrology, thermophysical property measurements, and nanoscale manufacturing. These applications beyond data storage have strict requirements for mechanical characterization and precise temperature calibration of the cantilever. This paper describes detailed mechanical, electrical, and thermal characterization and calibration of AFM cantilevers having integrated solid-state heaters. Analysis of the cantilever response to electrical excitation in both time and frequency domains aids in resolving heat transfer mechanisms in the cantilever. Raman spectroscopy provides local temperature measurement along the cantilever with resolution near 1 mum and 5degC and also provides local surface stress measurements. Observation of the cantilever mechanical thermal noise spectrum at room temperature and while heated provides insight into cantilever mechanical behavior and compares well with finite-element analysis. The characterization and calibration methodology reported here expands the use of heated AFM cantilevers, particularly the uses for nanomanufacturing and sensing

Electrical, Thermal, and Mechanical Characterization of Silicon Microcantilever Heaters

Fast-charging and high-energy-density batteries pose significant safety concerns due to high rates of heat generation. Understanding how localized high temperatures affect the battery is critical but remains challenging, mainly due to the difficulty of probing battery internal temperature with high spatial resolution. Here we introduce a method to induce and sense localized high temperature inside a lithium battery using micro-Raman spectroscopy. We discover that temperature hotspots can induce significant lithium metal growth as compared to the surrounding lower temperature area due to the locally enhanced surface exchange current density. More importantly, localized high temperature can be one of the factors to cause battery internal shorting, which further elevates the temperature and increases the risk of thermal runaway. This work provides important insights on the effects of heterogeneous temperatures within batteries and aids the development of safer batteries, thermal management schemes, and diagnostic tools.

/pdf/fast-lithium-growth-and-short-circuit-induced-by-localized-23abbiq6g0.pdf

Fast lithium growth and short circuit induced by localized-temperature hotspots in lithium batteries

In this work we present a detailed structural characterization by Raman spectroscopy of hydrogenated amorphous silicon (a-Si:H) and of nanostructured silicon (ns-Si:H) thin films grown in radio-frequency plasma. The ns-Si:H thin films, also called polymorphous Si thin films, consist of a two-phase mixture of amorphous and ordered Si. The Raman spectra were measured at increasing laser intensities. Very low laser power densities (∼1 kW/cm2) were used to thoroughly analyze the structure of as-deposited thin films. Higher Raman laser powers were found to induce the crystallization of the films, which was characterized by the appearance of a sharp peak around 500 cm−1. This was attained faster in the ns-Si:H than in the conventional a-Si:H thin films because the silicon-ordered particles cause a heterogeneous nucleation process in which they act as seeds for crystallization. The laser power densities for film crystallization, crystal size, and surface temperature were determined from this Raman analysis. The ...

Crystal size and temperature measurements in nanostructured silicon using Raman spectroscopy

A method for the detection of dust particles occurring in silane–argon gas mixture plasmas is presented. It is based on the spectral analysis of the radio-frequency current. The amplitudes of the fundamental (13.56 MHz) and second harmonics (40.68 MHz) are very sensitive to the presence of the earlier nanoparticles when their size is in the range of 2–3 nm even if their influence on the capacitive character of the impedance is negligible. This method is nonperturbative, with a temporal resolution in the microsecond range, very easy to implement, and can thus be used for industrial reactors.

Detection of particles of less than 5 nm in diameter formed in an argon-silane capacitively coupled radio-frequency discharge

Effect of small crystal size and surface temperature on the Raman spectra of amorphous and nanostructured Si thin films deposited by radiofrequency plasmas

G. Viera

Papers

Crystal size and temperature measurements in nanostructured silicon using Raman spectroscopy

Detection of particles of less than 5 nm in diameter formed in an argon-silane capacitively coupled radio-frequency discharge

Effect of small crystal size and surface temperature on the Raman spectra of amorphous and nanostructured Si thin films deposited by radiofrequency plasmas