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Boron‐doped diamond layers are grown on freestanding heteroepitaxial diamond substrates by microwave plasma chemical vapor deposition (MPCVD) to verify the high potential of large‐size heteroepitaxial diamond as an ultimate semiconductor material. Due to the high crystallinity and atomically flat surface morphology of the substrate, the MPCVD‐grown boron‐doped diamond layer exhibit excellent surface properties and crystallinity, as measured by X‐ray diffraction and atomic force microscopy. The temperature‐dependent Hall effect measurements are conducted at temperature ranges between 300–800 K with cloverleaf‐shaped van der Pauw geometry. The hole concentration of boron‐doped diamond samples is between 1.1 × 1015 and 5 × 1019 cm−3 at room temperature, and the resistivity is controlled between 10−1 and 20 Ω cm by changing boron to carbon ratio. A specific contact resistance as low as 1.41 × 10−4 Ω cm2 is obtained via annealing at 500 °C. The activation energy of the boron‐doped diamond layers is reduced from 0.35 to 0.12 eV as the amount of boron dopant increases, which is attributed to the formation of impurity band. Finally, the change in the carrier mobility of boron‐doped heteroepitaxial diamond is discussed based on the scattering mechanism.

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In this study, the staged seismic performance evaluations were conducted to the 91 high speed railway tunnels in use for checking whether to comply with the recent design criteria or not. In addition, the seismic fragility functions of the tunnels were developed to allow the probabilistic risk assessment. The results of the staged seismic performance evaluations which consist of a preliminary assessment and a detailed assessment, show that the tunnels comply with the recent design criteria. With reference to the results of previous studies, a form of the proposed seismic fragility functions was set as a log-normal distribution by PGA, and the parameters of the functions were determined by using the probability of damage for the design PGA level. The seismic fragility functions were developed for each types (Cut & Cover, NATM) of tunnels. The seismic fragility functions from this study and the existing research results (FEMA, 2004) were compared to evaluate the seismic performance level of the tunnels, as a result the tunnels of this study were relatively superior to the ASSM tunnels on the seismic performance.

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