The mechanism of SiGe film growth from Si2H6 and GeF4 was examined by ab initio B3LYP/6-31G** calculations using three cluster surface models. Energies of reaction and activation were calculated, and the process of SiGe film growth was analyzed. It was found that the reaction of GeF4 with Si2H6 formed GeF2 by much lower activation energy than decomposition of GeF4. In addition, GeF2 made activation energy of surface reactions lower than using only Si2H6.

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Sputtering systems for semiconductor manufacturing require high-vacuum conditions. Typically it takes a long time to recover high-vacuum conditions after a sputtering system is opened to air. To increase the operating efficiency of the system, the recovery time must be reduced. Therefore, in this study, a glow discharge cleaning technique is applied using a glow-mode plasma source in argon gas. The discharge current distribution inside the sputtering system is measured under various conditions. It was found that nonuniformity was decreased: when the number of electrodes was increased from one to two; when the pressure during the discharge was decreased to 3×10−3 Torr; and when the anode current or anode voltage was increased. By applying these results, a drastic reduction in pumping time is achieved. The pumping time to attain a pressure of 1.5×10−6 Torr is reduced from 17 to 6 h with concurrent use of 3.5 h of discharge cleaning.

Development of cathode active materials (CAM) with higher energy density has been desired in the development of next-generation batteries. In this respect, organic CAMs are probable candidates because of their lightweight frameworks without heavy elements. Herein, we examined the characteristics of two possible organic crystalsa naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) lithium salt dimer fused by the dithiin ring (DNP) and phenazinetetrone (PTO)by density functional theory (DFT)-based first-principles calculations. Based on the pristine crystals of fully oxidized molecules carrying no Li, we computationally explored the low-energy crystal structures at different states of charge (SOCs) during the lithiation (discharging), Li n (DNP), and Li n (PTO)2 (n = 0–14), with the DFT energetics. We then calculated the voltage (Li vacancy formation energy) profile and confirmed that our calculations can reasonably explain the experimental discharge curve, indicating the validity of our structure models. It is also demonstrated that deeper discharge destabilizes the lithiated structure. Calculated unit cell shapes suggested that the volume change is significant for early n (stage I), ∼10% for Li n (DNP), and ∼15% for Li n (PTO)2. On the other hand, the volume over this stage is almost kept by the adjustment of the DNP/PTO stacking manner according to the Li insertion, which is advantageous for the usage as CAMs. Li in Li n (DNP) mainly has fourfold coordination to the framework anions, while threefold coordination is dominant in Li n (PTO)2, implying that Li n (DNP) is more stable than Li n (PTO)2. We also evaluated the electronic density of states and the partial electron distributions of both materials with selected SOCs and demonstrated that the electronic conductivities of both materials seem similar. On the other hand, the calculated migration barriers of Li indicated that the PTO crystal has faster Li migration and thus higher rate capability than the DNP. These results suggest that Li n (PTO)2 exhibits better cathode performance. The present computational predictive approach reveals the voltage and structural as well as electronic characteristics of the potential organic CAMs, and suggests useful aspects for the material selection.

Rechargeable magnesium batteries (RMBs) are one of the promising energy-storage technologies for sustainable energy storage due to the abundant resources and intrinsically remarkable energy-storage properties of magnesium metal. However, to compete with alternative technologies, such as present lithiumion batteries, there is a need to improve their energy density. One of the approaches to accomplish the above demand is to use highvoltage cathodes. The poor anodic stability of the current etherbased electrolytes compatible with magnesium metal anodes limits their working voltage and the choice of electrode materials. In this study, we explored different organic solvent-based electrolytes to design anodically stable ether-based electrolyte solutions for RMB applications. Through comprehensive experimental and computational surveys, we found that the intrinsic electrochemical/chemical stabilities against magnesium metal and the well-balanced solvating ability were necessary to achieve the desired functionality. Based on this knowledge, we designed and synthesized glyme analogues bearing trifluoroalkyl groups. Consequently, we developed anodically stable electrolytes that support electrochemical magnesium deposition/dissolution by combining suitable fluorinated glyme-based solvents with appropriate conducting salts. These electrolytes showed a remarkable anodic limit of 4.4 V vs Mg 2+ /Mg (the highest ever reported to the best of our knowledge) and effectively suppressed the undesired corrosion of Al current collectors. However, these electrolytes could not be applied to RMBs with high-voltage oxide-based cathodes. Fragility against oxide-based cathodes caused undesired catalytic decomposition of the fluorinated solvents during charging.

To shorten the time for designing and developing new materials, fast evaluation of microstructure-property relation is required. In this research, we applied machine learning to perform crystal phase segmentation and extracted microstructure features of Cr-based duplex alloys from the scanning electron microscope (SEM) images. The results show that the accuracy of crystal phase segmentation was improved when the backscattered electron (BSE) images with controlled channeling contrast was used. This indicates that measurement conditions of the BSE images are important for obtaining high segmentation accuracy. The segmented images were used for the extraction of microstructure features. With the extracted features, the reliable prediction of mechanical properties of Cr-based duplex alloys was verified with a prediction error less than 10%. We demonstrated a method of using microstructure features extracted from SEM images for fast evaluation of microstructure-property relation.

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The structural and electrical properties of SiGe films deposited by reactive thermal chemical vapor deposition using a lamp heating system with a source gas mixture of GeF 4 and Si 2 H 6 were investigated. In the SiGe film depositions with respective GeF 4 and Si 2 H 6 flow rates of 0.06 and 3 sccm, the film structure changed from crystalline to amorphous during the film growth. The results of secondary ion mass spectroscopy analysis and high-temperature deposition suggest that the gas phase reactions cause the structural change. To suppress the gas phase reactions, lowpressure depositions are investigated. The SiGe film deposited at a relatively low pressure of 400 Pa shows good crystallinity. The thin-film transistor with this SiGe film also reveals a high p-channel mobility of about 10 cm 2 ÁV À1 Ás À1 . #