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Dynamic random access memories (DRAMs) are currently used as the core memory in computing systems because of their high speed and density. Their demand should continue to grow owing to increased data usage. A unit cell in a DRAM consists of one transistor and one capacitor, and the data are stored in the capacitor. As the size of the unit cell decreases to improve the memory density by aggressive scaling, it is important to secure sufficient capacitance in the capacitor. In this regard, technological advances in the fabrication of capacitors are of great importance; accordingly, the materials and processing of high‐k thin films require developmental innovations. Besides, it is necessary to develop electrode materials that optimize the function of high‐k thin films. In this review, recent advances in achieving sufficient capacitance in DRAM capacitors are summarized from structural and material/process perspectives, and the future direction of DRAM capacitor development is discussed. Atomic layer deposition (ALD) is a key technique that enables the growth of functional thin films for DRAM capacitors; thus, recent advances in the deposition of high‐k and electrode thin films grown using the ALD technique are addressed. [ABSTRACT FROM AUTHOR]

The interface between a dielectric thin film and a metal electrode is studied to improve reliability as well as electrical properties of the metal–insulator–metal (MIM) capacitor in dynamic random‐access memory (DRAM) devices. The interfacial layers between a dielectric thin film and a metal electrode play important functional roles such as increasing the electrical barrier or preventing oxygen defects in high‐k dielectrics. By introducing an electrical barrier layer or a sacrificial layer at the metal–dielectric interface for engineering the electronic band, lattice, or dipole, various effects could be confirmed such as the conduction band offset (CBO), bandgap or mismatch modulation for controlling the dielectric loss depending on the AC frequency or leakage current of MIM capacitors. Upon the insertion of Al2O3 as an electrical barrier layer, CBO increased because of the band engineering. Further, upon the insertion of TiO2 as a sacrificial layer at the interface, CBO increased because of the dipole formation at the interface, attributed to the difference in electronegativity. Thus, a robust MIM capacitor for DRAM that maintains a low leakage current and has improved reliability which is realized using the proper combination of interfacial layers. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the applicability of concrete-filled steel tube (CFT) columns made from high-performance construction materials. KBC2016, South Korea’s current building code, limits the maximum compressive strength of concrete at 70 MPa and the maximum yield strength of steel at 650 MPa. Similar restrictions to material properties are imposed on major composite structural design parameters in other countries worldwide. With the recent acceleration of the pace of development in the field of material technology, the compressive strength of commercial concrete has been greatly improved and the problem of low tensile strength, known to be the major limitation of concrete, is being successfully addressed by adding fiber reinforcement to concrete. Therefore, the focus of this study was to experimentally determine the strength and ductility enhancement effects, which depend on material composition. To this end, we performed concentric axial loading tests on CFT stub columns made from steel with a yield strength of 800 MPa and steel fiber-reinforced high-strength concrete. By measuring the strain at the yield point of CFT steel during the test, we could determine whether steel yields earlier than ultimate failure load of the member, which is a key design concept of composite structures. The analysis results revealed that the yield point of steel preceded that of concrete on the stress-strain curve by the concurrent action of the strain increase at the maximum strength, attributable to the high compressive strength and steel fiber reinforcement, and the strain increase induced by the confining stress of the steel tube. Additionally, we performed parametric study using ABAQUS to establish the broad applications of CFT using high-performance materials, with the width-to-thickness ratio as the main parameter. Parametric study was undertaken as experimental investigation was not feasible, and we reviewed the criteria for limiting the width-to-thickness ratio as specified in the current building code. [ABSTRACT FROM AUTHOR]