The phase development and defect formation during the silicidation reaction of sputter-deposited Er films on Si with ∼20-nm-thick Ta and TaN capping layers were examined. TaN capping effectively prevented the oxygen incorporation from the annealing atmosphere, which resulted in complete conversion to the ErSi2-x phase. However, significant oxygen penetration through the Ta capping layer inhibited the ErSi2-x formation, and incurred the growth of several Er-Si-O phases, even consuming the ErSi2-x layer formed earlier. Both samples produced a number of small recessed defects at an early silicidation stage. However, large rectangular or square-shaped surface defects, which were either pitlike or pyramidal depending on the capping layer identity, were developed as the annealing temperature increased. The origin of different defect generation mechanisms was suggested based on the capping layer-dependent silicidation kinetics.

Vertical stacking and lateral growth of molybdenum disulfide (MoS ) are controlled with remarkable precision, and MoS nanotubes are directly converted from nanofibers. Predictive synthesis is enabled by identifying the specific thermodynamic region where the Boudouard reaction becomes favored. It reveals how the chemical potential of each species in the MoSCO system can predict phase behaviors.

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This study examined the effects of the Zn ratio on the microstructure of InGaZnO (IGZO) films and the device performance of their transistors. IGZO films with various Zn ratios were produced by co-sputtering InGaO and ZnO at different ZnO powers. The combination of transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses elucidated that as the Zn ratio increased from 0 to 0.69, the microstructure changed from amorphous IGZO to nanocrystalline IGZO and then to columnar ZnO. The dynamic transitions of the microstructure, in turn, profoundly affected the electrical properties including the mobility and carrier concentration. The sample with a mixing ratio of 0.25:0.2:0.55 (In:Ga:Zn) exhibited the best performance with a mobility of nearly 30 cm 2 /VÁs. Transparent oxide semiconductors (TAOS) have recently gained much attention owing to their technologically important features, including their high electron mobility, high transparency, capability for low temperature processing, etc. These materials are excellent candidates for the active layer of thin film transistors for display applications. 1,2 In particular, amorphous InGaZnO 4 (IGZO) has been the focus of many research and development efforts since Hosono and colleagues first demonstrated the possibility of using it as the active layer of TFTs. 3 Some such studies include the optimization of sputtering conditions (O 2 pressure, sputtering power, etc) and post-annealing conditions. 1,4 Nevertheless, systematic composition engineering of this material by modulating the cation ratio still remains incomplete.For the development of IGZO-based transistors with enhanced device performance, it is important to understand the roles of the main metallic elements (In, Ga, and Zn) of the material. Some recent studies unfolded that as the In ratio increased, the carrier concentration escalated sensitively and thus led to an increase in both the on-current and off-current, suggesting that In played the role of charge carrier generators. 5,6 Increasing the Ga ratio seems to have the opposite effect: With the Ga content increasing, the carrier concentration drastically decreases since Ga suppresses oxygen vacancy formation. 5-10 Thus, the In/Ga ratio is known to be critical for determining the carrier concentration of IGZO films. However, what remains relatively unexplored are the effects of modulating the Zn ratio on the film properties. It would be intriguing to investigate how the microstructure evolves and the electrical properties change as the Zn ratio changes over a wide range.In this study, we delved into the effects of the Zn ratio on the characteristics (microstructure, carrier concentration, and Hall mobility) of IGZO films and the device performance of their TFTs. We produced IGZO films with various Zn ratios via co-sputtering InGaO (IGO) and ZnO at different ZnO target powers. Combining X-ray diffraction (XRD), transmission electron microscopy (TEM), and Hall Effect measurements helped us to fully characterize the evolution of the film microstruct...

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material has been impeded by its several shortcomings. The most serious problem is a poor cyclic stability, which arises from a large volume change occurring due to extensive reactions between Si and Li during charging/discharging cycles. Such a volume change usually leads to fracture and exfoliation between Si anode and current collector, causing capacity fading or sometimes a catastrophic failure. [4][5][6] Among several approaches to mitigate this problem, nanostructured silicon, such as nanoparticles, [ 7,8 ] nanowires [ 9,10 ] or thin fi lms, [ 11,12 ] has drawn much attention. Anodes with such a structure have been reported to endure longer cycles as much of the strain could be released through the large surfaces. [13][14][15] In another (more practical) approach, researchers have introduced electrochemically inactive elements such as transition metals into the Si anode, as a multilayer for thin-fi lm batteries [16][17][18] or mixed powder via mechanical milling. [19][20][21] Multifold advantages are expected from the alloyed anode: the inactive element(s) could fi rst serve as a buffer by reducing the extent of volume changes due to a reduction in the volume of the active material and lending a high mechanical strength to the highly expanding structure. In addition, the presence of the transition metals could improve the electrical conductivity. Several studies based on such alloyed Si anode have reported a signifi cant improvement in cycle-life performance; however, much work, both on engineering andThe results of employing (Ti, Fe)-alloyed Si thin-fi lm anode for Li-ion batteries are reported. The material demonstrates an impressive cyclic stability with stable operation for more than 500 cycles at a capacity higher than 1400 mAh g −1 . Materials characterization using scanning electron microscopy and transmission electron microscopy illuminates an intriguing materials process behind the performance: ripple-like pattern formation via electrochemically driven segregation of the inactive elements (Ti and Fe). The ripple structure plays a buffer role by suppressing loss of the active material upon further cycling, allowing the anode to gradually transform into an array of microbumps. The morphological evolution helps the anode endure long cycles (even up to 1000 cycles) without catastrophic failure as the bumps shrank slowly and steadily, consistent with the electrochemical data.

The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm2), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current.