Yuanyuan Xie

A Multilayered Silicon-Reduced Graphene Oxide Electrode for High Performance Lithium-Ion Batteries

A multilayered structural silicon-reduced graphene oxide electrode with superior electrochemical performance was synthesized from bulk Si particles through inexpensive electroless etching and graphene self-encapsulating approach. The prepared composite electrode presents a stable charge-discharge performance with high rate, showing a reversible capacity of 2787 mAh g(-1) at a charging rate of 100 mA g(-1), and a stable capacity over 1000 mAh g(-1) was retained at 1 A g(-1) after 50 cycles with a high columbic efficiency of 99% during the whole cycling process. This superior performance can be attributed to its novel multilayered structure with porous Si particles encapsulated, which can effectively accommodate the large volume change during the lithiation process and provide increased electrical conductivity. This facile low-cost approach offers a promising route to develop an optimized carbon encapsulated Si electrode for future industrial applications.

On the physical and chemical details of alumina atomic layer deposition: A combined experimental and numerical approach

Alumina thin film is typically studied as a model atomic layer deposition (ALD) process due to its high dielectric constant, high thermal stability, and good adhesion on various wafer surfaces. Despite extensive applications of alumina ALD in microelectronics industries, details on the physical and chemical processes are not yet well understood. ALD experiments are not able to shed adequate light on the detailed information regarding the transient ALD process. Most of current numerical approaches lack detailed surface reaction mechanisms, and their results are not well correlated with experimental observations. In this paper, the authors present a combined experimental and numerical study on the details of flow and surface reactions in alumina ALD using trimethylaluminum and water as precursors. Results obtained from experiments and simulations are compared and correlated. By experiments, growth rate on five samples under different deposition conditions is characterized. The deposition rate from numerical...

Atomic layer deposition of Al2O3 process emissions

The ALD process emissions and the associated chemical reaction mechanism in the ALD of the Al2O3 system are studied and reported. In gaseous emissions, 3.22 vol% of CH4 and 6.01 × 10−2 vol% of C2H6 are found. Net peak emissions of aerosols are found between 1 × 103 and 1 × 104 # cm−3 and net total emissions of 25 cycles are in the range of 6.0 × 105 and 2.5 × 106 particles. Most aerosols are determined as ultrafine particles with diameter smaller than 100 nm. Purging time has significant impacts on emission concentrations but no effect on size distribution. Both main and side chemical reactions are observed in the ALD system. X-ray photoelectron spectroscopy (XPS) shows that besides O–Al which represents the existence of Al2O3, a significant amount of C-containing by-products are also generated. Chemical bonds observed in C-containing products are C–H, C–O and CO. The main reactions can be considered stable to a certain extent, while side reactions accelerate along internal tubes and finally exceed the speed of the main reactions near the outlet of the ALD system. These results could help us to understand the potential environmental impacts of ALD nanotechnology and guide the technologys sustainable scale-up in the future.