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The effect of the size of the B powder and the Mg powder on MgB2 phase formation has been studied by the technique of in situ high-temperature resistivity (HT-ρ(T)) measurement. Two characteristic temperatures indicating the phase formation, the onset point, Tonset, and the completion point, TPF, were directly determined during the continuous heating process. These two temperatures of the samples synthesized using nanometer-size B powder (Nano-B) and micrometer-size B powder (Micro-B) with nanometer-size Mg (Nano-Mg) are almost the same, i.e. Tonset = 713 K and TPF~763 K, respectively, indicating that the phase formation temperature of MgB2 does not primarily depend on the particle size of the B powder. A similar process was then carried out on Mg powders with the same B powder. An exponential relationship between the onset phase formation temperature and the Mg powder size is clearly shown, which can be fully fitted by a modulated diffusion equation and which gives Q = 421 kJ mol−1 describing the grain boundary activation energy of Mg diffusing into B. We also find that the MgB2 crystallites along the [101] direction have the lowest formation energy, revealed by x-ray diffraction (XRD) analysis on raw Mg powders, and the corresponding MgB2 crystallites aligned along [101] will be formed preferentially in the sintering process. This result is useful for the understanding of MgB2 phase formation in the solid reaction process.

In this paper, ground-signal-ground type through-silicon vias (TSVs) exploiting air gaps as insulation layers are designed, analyzed and simulated for applications in millimeter wave. The compact wideband equivalent-circuit model and passive elements (RLGC) parameters based on the physical parameters are presented with the frequency up to 100 GHz. The parasitic capacitance of TSVs can be approximated as the dielectric capacitance of air gaps when the thickness of air gaps is greater than 0.75 μm. Therefore, the applied voltage of TSVs only needs to achieve the flatband voltage, and there is no need to indicate the threshold voltage. This is due to the small permittivity of air gaps. The proposed model shows good agreement with the simulation results of ADS and Ansoft's HFSS over a wide frequency range.

The through silicon via (TSV) technology has proven to be the critical enabler to realize a three-dimensional (3D) gigscale system with higher performance but shorter interconnect length. However, the received digital signal after transmission through a TSV channel, composed of redistribution layers (RDLs), TSVs, and bumps, is degraded at a high data-rate due to the non-idealities of the channel. We propose the Chebyshev multisection transformers to reduce the signal reflection of TSV channel when operating frequency goes up to 20 GHz, by which signal reflection coefficient (S11) and signal transmission coefficient (S21) are improved remarkably by 150% and 73.3%, respectively. Both the time delay and power dissipation are also reduced by 4% and 13.3%, respectively. The resistance-inductance-conductance-capacitance (RLGC) elements of the TSV channel are iterated from scattering (S)-parameters, and the proposed method of weakening the signal reflection is verified using high frequency simulator structure (HFSS) simulation software by Ansoft.

The effects of the Dzyaloshinski—Moriya (DM) interaction on the ground-state properties of the anisotropic XY chain in a transverse field have been studied by means of correlation functions and entanglement. Different from the case without the DM interaction, the excitation spectra k of this model are not symmetrical in the momentum space and are not always positive. As a result, besides the ferromagnetic (FM) and the paramagnetic (PM) phases, a gapless chiral phase is induced. In the chiral phase, the von Neumann entropy is proportional to log2 L (L is the length of a subchain) with the coefficient A ≈ 1/3, which is the same as that of the XY chain in a transverse field without the DM interaction for γ = 0 and 0 < h ≤ 1. And in the vicinity of the critical point between the chiral phase and the FM (or PM) phase, the behaviors of the nearest-neighbor concurrence and its derivative are like those for the anisotropy transition.

Chiral phase and quantum phase transitions of anisotropic XY chains with the XZY − YZX type of three-site interaction are studied. The phase diagram is obtained by the study of the Lee–Yang zeros, order parameters, and ground-state energy. Besides the paramagnetic and ferromagnetic phases, a new chiral phase is found after the introduction of three-site interactions. In the new phase, we find that the fidelity is zero and the von Neumann entropy SL is proportional to Alog2L with the coefficient A≈1/3 the same as that in the anisotropy transition line of XY chain without three-site interactions. From the ferromagnetic phase to the paramagnetic phase, the quantum critical behavior is same as that identified for the XY spin model without three-site interactions. In this critical line, SL is proportional to Alog2L with A≈1/6, the same as that in the Ising transition line of the XY chain without three-site interactions. From the ferromagnetic phase to the chiral phase and from the chiral phase to the paramagnetic phase, the quantum phase transitions are similar to the anisotropy transitions.