Narrow Results

The interaction between the H₂ molecule and the PdAg, PdAu, PtAg and PtAu bimetallic dimers deposited on the MgO(100) surface is investigated using density functional theory (DFT). The bimetallic dimers, whose molecular axes are considered to be perpendicular to the support surface, are adsorbed on top of an oxygen atom. Within this adsorption mode, the dimers prefer the orientation in which their Pd or Pt end is closer to the oxygen atom. The Ag and Au ends of the MgO-supported dimers capture the H₂ molecule with small exoenergetic effects. The spontaneous dissociation of H₂ on these ends does not occur. Thus, the MgO support decreases the ability of the dimers to adsorb and dissociate the H₂ molecule. From a catalytic viewpoint, it means that the activity of small bimetallic clusters toward the dissociative adsorption of H₂ is reduced when they are arranged on MgO. On the other hand, the results of our calculations show that the presence of the MgO support strengthens the binding of H atoms inside the PdAu, PtAg and PtAu dimers.

The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [SiO₄], [BO₄], [AlO₄] and trigonal [BO₃]. A small amount of AlO₅ or AlO₆ units also existed. The glass system was characterized with lower dielectric constant (4.17 ~ 4.6) and dielectric loss (12.3 × 10^-4 ~ 14.77 × 10^-4) at 1 MHz. With the increase of MgO content, the quantity of AlO₅ or AlO₆ units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.

Low-temperature co-fired ceramics (LTCC) applied in millimeter/microwave and terahertz frequencies (5G/6G) have attracted a lot of attention recently. In this study, MgO-based dielectric ceramics were successfully sintered at 950°C with the sintering aids: x wt.% of LiF fluoride ($x=2$, 4, 6, 8, 10) and 0.5wt.% of BBSZ (Bi₂O₃–B₂O₃–SiO₂–ZnO) glass. BBSZ glass was introduced as another sintering aid to facilitate the sintering and densification. Crystalline structure and micro-morphology were investigated and analyzed. Dielectric properties (${\epsilon }_r$, $Q\times f$, ${\tau }_f$) at millimeter/microwave and terahertz wave frequencies were also studied. The ionic characteristics of Mg–O bond ($f_i$), the lattice energy (U) and the bond energy (E) were calculated and analyzed. It is suggested that the optimal $x=4$, where ${\epsilon }_r=10.5$, $Q\times f=120,000$GHz (@12GHz) and ${\tau }_f=-26$ppm/°C at millimeter/microwave range. When the frequency was up to terahertz (1.0THz), the ${\epsilon }_r$ values were 8.8–9.35 and the tan$\delta$ were $5.6\times 10^{-3}$–$8.7\times 10^{-3}$. The experimental results indicated that the low-temperature sintered MgO-based ceramics have potential for millimeter/microwave and terahertz communication applications.

We review recent developments in magnetic tunnel junctions with perpendicular easy axis (p-MTJs) for nonvolatile very large scale integrated circuits (VLSIs). So far, a number of material systems such as rare-earth/transition metal alloys, L1₀-ordered (Co, Fe)–Pt alloys, Co/(Pd, Pt) multilayers, and ferromagnetic-alloy/oxide stacks have been proposed as electrodes in p-MTJs. Among them, p-MTJs with single or double ferromagnetic-alloy/oxide stacks, particularly CoFeB–MgO, were shown to have high potential to satisfy major requirements for integration.