Since the invention of transistors in 1947, semiconductors have been developing for more than 70 years following Moore's Law, thanks to the progress of surface (wet) and vacuum (dry) technologies. Semiconductor devices moved from the micron generation to the nano generation in 1991. Now in the angstrom generation, both technologies are more critical. Semiconductor vacuum technology, believed to be “free from dirt” in the 1980s, has succeeded in the dry process revolution by overcoming the challenge of being far from a true vacuum. Polishing technology, ridiculed as “in pouring rain” in the 1990s, has succeeded in the wet process revolution by Dry-in/Dry-out. What, then, will be the revolutionary technology in the angstrom generation? One might be the fusion of dry and wet technologies. This paper examines the history of semiconductor manufacturing and vacuum systems that have evolved with semiconductor devices, assesses their present state, and predicts future breakthroughs.
The variation of local deposition rate has been studied for Ti films deposited on the inner wall of holes with an entrance size of 2×2 mm2. The deposition was performed by high-power impulse magnetron sputtering (HiPIMS) under peak current densities of 0.3, 0.9, and 2.5 A/cm to investigate the transport behavior of sputtered ions and neutral particles into the holes and its effect on deposition rate distribution and microstructure of the films on the inner wall. Ti ion content in the plasma increased with increasing peak current density. As the ion content increased, the deposition rate tended to decrease and the film microstructure become denser regardless of the hole depth. Normalized deposition rate increased with increasing ion content when the hole depth was deeper than 4 mm. The effect of the ion content on the growth of Ti films deposited on the inner wall was demonstrated.
We investigated oxygen reduction reaction (ORR) activity of Pt single atoms and Pt sub-nano clusters (Pt1, Pt2 Pt3) on pristine and various light-element doped graphene using first-principles calculations based on density functional theory. We revealed that ORR activity of these systems shows so-called volcano plot with adsorption energy of an OH which is an ORR intermediate as well as bulk metal catalysts. Additionally, we note that ORR activity of Pt1 is higher than those of Pt2 and Pt3, and a support effect caused by light-elements doped graphene is more clearly observed in the cases of Pt1. Therefore, the combination of Pt1 and proper light-element doped graphene support is a promising candidate for designing a new catalyst that competes with the current fuel cell catalyst ; bulk Pt catalyst.
Molybdenum disulfide (MoS2) has attracted much attentions since it possesses electrical properties as a semiconductor and it is easy to obtain atomically thin films from natural resources and its bandgap can be controlled by a number of layers. Authors created devices using this MoS2 as the channel material of field-effect transistors (FET), and tried to detect molecules from the change in the electrical characteristics. This paper describes that the electric properties such as the drain current, the threshold voltages, and the mobility are significantly changed when chlorine molecules and Tetracyanoquinodimethane (TCNQ) molecules are adsorbed on the surface of MoS2-FET.
We have studied the atomic structure and phase transition of a monolayer phase of In on Si(111), known as the hexagonal (√7×√3) phase. Low-energy electron diffraction and scanning tunneling microscopy observations revealed that the monolayer phase actually has an incommensurate structure with the In overlayer uniaxially contracted by 2% from (√7×√3). We observed the phase transition to the (√7×√7) phase at 250–210 K upon cooling. Angle-resolved photoelectron spectroscopy and in situ four-point-probe conductivity measurements demonstrated that the transition induces disappearance of the metallic surface states and a sharp drop in conductivity, respectively. These results indicate an electronic metal-insulator transition.
We have developed scanning tunneling potentiometry (STP) operating in ultrahigh vacuum conditions, which provides us a surface topography and the corresponding electrochemical potential distribution simultaneously in nanometer scale special resolution and µV-level potential sensitivity under a lateral electrical current flowing parallel to the sample surface. Using this setup, we have successfully performed an STP measurement on the Si(111)-7×7 reconstructed surface, which holds metallic surface states. Our observation indicates that not only steps but also phase boundaries of the Si(111)-7×7 surface work as an electrical resistance impeding the conductance through the surface states. From the evaluation of the ratio of conductivity across the one-dimensional line defects to that of the terrace on the Si(111)-7×7 surface, the conductivity of the phase boundary is found five times that of the monolayer-height step.
Atomic force microscopy has become one of the most widely used tools in the mechanical characterization of cells to quantify elastic and viscoelastic properties. Here we briefly review AFM techniques, such as force curve, stress relaxation, creep, and force modulation measurements, developed for examining the mechanical properties of cells and describe how specific features of cellular samples are characterized.