Jyh-Shen Tsay

Electric field controlled magnetic devices have attracted interest in the area of magnetic recording research, owing to their lower power consumption and high stability. While heterostructures composed of Co and carbon materials exhibit unique properties, our understanding of the magnetic properties of Co on graphene with a wavelike structure and related electric field-controlled phenomena remains limited. Here, we demonstrate the preparation of a customized Co/graphene structure, in which the controllability of the coercive force is enhanced. Taking the coercive force and geometric factor of Co into consideration, a shape-dependent magnetic anisotropy is proposed, which sufficiently explains the correlation between the coercive force and the aspect ratios of the Co stripes. For the magnetic field perpendicular to the bottom lines of canyons, the adjustment capability of the coercive force is enhanced under conditions of a more negatively charged surface. Based on the large electric field and related magnetic anisotropy energy, a ferro-ionic control (FeIC) model is proposed, which describes the relationship between the electric potential and coercive force in electrified conditions. Based on a FeIC model with a preferred orientation, we propose a design of an integrated FeIC inductor with field tunability that could strongly impact the field of integrated-circuit design, resulting in wider applications and functionalities of chips.

By adding a rubrene layer, the highly stable IP combined with the tunable OP ferromagnetic resonance spectra for Ni( x )/rubrene/Si bilayers make them promising materials for use in microwave magnetic devices and spintronics with controllable PMA.

For Ni/rubrene bilayers on Si(100) substrate with alternating stack arrangement, the magnetic interaction of Ni layer is governed by a spinterface where an appreciable shift of valence band of bilayer has been found.

In this study, we demonstrate inverted PTB7:PC₇₁BM polymer solar cells featuring a solution-processed s-MoO₃ hole transport layer that can, after thermal aging at 85 °C, retain their initial power conversion efficiency for at least 2200 h.

Because of the ease of formation, and good lattice match with Si, metal silicides often form high-quality epitaxial layers and have established themselves over the years as important technological materials with industrial applications. For the fabrication of silicon-based devices, the contact between metal electrodes and Si is a key issue. The properties of thin films on silicon substrates are strongly dependent on their microstructure and local chemistry. However, a concrete understanding of the influence of a silver layer on different transition metal/silicon interfaces is not currently available. We propose, for the first time, a new model called molecular-incident reaction effect (MoIRE) model that successfully explains the different chemical reactions for Co/Si and Ni/Si interfaces by the introduction of a √3×√3 R30o-Ag layer. The interaction transfer of silicon atoms forms a Co silicide for Co/√3×√3 R30o-Ag/Si(111) with a thickness of a few nanometers, thus greatly reducing the temperature needed for the formation of a layered CoSi2 silicide compared to that for typical CoSi2 silicide formation at a Co/Si interface. Based on the MoIRE mechanism, the introduction of the √3×√3 R30o-Ag layer as an intermediate layer permits the silicidation temperature needed to produce a NiSi layer to be reduced to 400 K from typically above 600 K. This approach is advantageous for the formation of a silicide at the Ni/Si interface at low temperature. Based on the MoIRE model for silicide formation at Ni/√3×√3 R30o-Ag/Si(111), we propose a technique for the synthesis Ni silicide layers at lower temperatures with simpler fabrication steps due to the difference in the properties between Co and Ni. This mechanism of low-temperature fabrication includes the formation of (1) a √3×√3 R30o-Ag and (2) a NiSi layer. The findings presented herein will be useful for more efficiently forming salicides in integrated circuit fabrication, as well as for developing superconducting circuits and quantum bits for quantum computing.

By way of introducing heterogeneous interfaces, the stabilization of crystallographic phases is critical to a viable strategy for developing materials with novel characteristics, such as occurrence of new structure phase, anomalous enhancement in magnetic moment, enhancement of efficiency as nanoportals. Because of the different lattice structures at the interface, heterogeneous interfaces serve as a platform for controlling pseudomorphic growth, nanostructure evolution and formation of strained clusters. However, our knowledge related to the strain accumulation phenomenon in ultrathin Fe layers on face-centered cubic (fcc) substrates remains limited. For Fe deposited on Ir(111), here we found the existence of strain accumulation at the interface and demonstrate a strain driven phase transition in which fcc-Fe is transformed to a bcc phase. By substituting the bulk modulus and the shear modulus and the experimental results of lattice parameters in cubic geometry, we obtain the strain energy density for different Fe thicknesses. A limited distortion mechanism is proposed for correlating the increasing interfacial strain energy, the surface energy, and a critical thickness. The calculation shows that the strained layers undergo a phase transition to the bulk structure above the critical thickness. The results are well consistent with experimental measurements. The strain driven phase transition and mechanism presented herein provide a fundamental understanding of strain accumulation at the bcc/fcc interface.

A schematic plot elucidating the effects of the enhanced film quality and reducing defect density by inserting rubrene on the enlargement of the magnetic domains as well as the reduced coercive force.

Due to the widespread applications of biosensors, such as in magnetic resonance imaging, cancer detection and drug delivery, the use of superparamagnetic materials for preparing biosensors has increased greatly. We report herein on a strategy toward fabrication of a nanoscale biosensor composed of superparamagnetic films. On increasing the film thickness of magnetic layers, a phase transition typically occurs from either a low-Curie-temperature state or a superparamagnetic state to a ferromagnetic state. A new finding is demonstrated wherein a phase transition of such a superparamagnetic phase can be induced by controlling the thickness of ultrathin ferromagnetic layers with perpendicular magnetic anisotropy. Both the M–H curve with zero coercive force at 300 K and deviations of the normalized hysteresis loop at 2 K confirm the superparamagnetic state of Co/Ir(111) at room temperature. An overstrained film transforming into clusters (OFTC) model based on the new finding and our experimental evidence is proposed for modeling this phenomenon. From the energetic point of view of the OFTC model, we propose a limited distortion mechanism that can be useful in determining the critical thickness for the phase transition. This mechanism considers the balance between interfacial strain energy and surface free energy. A method for producing superparamagnetic films by taking advantage of the accumulation of strain and relaxation is reported.

Compound formation at a metal/semiconductor interface plays crucial roles in the properties of many material systems. Applications of Ni silicides span numerous areas and have the potential to be used as new functionalities. However, the magnetic properties of ultrathin Ni layers on silicon surfaces and related chemical compositions at the interface are not fully understood and the influence of Ag additives on the reactivity of Ni/Si(111) remain unclear. We report herein on the fact that the dominant species produced at the interface is NiSi, which is produced by the spontaneous formation of strong bonds between Ni and Si atoms. Assuming that a Ni layer is formed over a NiSi layer with the total coverage as a constraint, we established a chemical shift-related concentration model that, in effect, represents a practical method for determining the amount of ultrathin Ni silicides that are produced at the buried interface. The formation of Ag-Si particles provide a viable strategy for enhancing silicide formation via a specific interaction transfer mechanism, even at room temperature. The mechanism is related to differences in the enthalpies of formation ΔH_Ag-Si, ΔH_Ni-Ag, and ΔH_Ni-Si, for these phases and provides insights into strategies for producing ultrathin silicides at a buried interface.