The purpose of this paper is to understand metal/germanium (Ge) junction characteristics. Electrode metals with a wide work function range were deposited on Ge. All metal/$p\text{-}\mathrm{Ge}$ and metal/$n\text{-}\mathrm{Ge}$ junctions have shown Ohmic and Schottky characteristics, respectively, with the strong Fermi-level pinning. The charge neutrality level (CNL) at metal/Ge interface is close to the branch point calculated for the bulk Ge. Moreover, the pinning level is hardly modulated by annealing in forming gas, forming metal-germanide/Ge interfaces or changing the substrate orientation. These results suggest that Fermi level at metal/Ge interface is intrinsically pinned at the CNL characterized by the metal-induced gap states model.

A model for the physical origin of the dipole formed at high-$k/{\text{SiO}}_2$ interface is proposed. In our model, an areal density difference of oxygen atoms at high-$k/{\text{SiO}}_2$ interface is considered as an intrinsic origin of the dipole formation. The oxygen movement from higher-oxygen-density side to a lower-oxygen-density one will determine the direction of interface dipole. The bonding energy relaxation at the interface explains why the oxygen density difference is the driving force of the oxygen movement. Our model enables the prediction of the dipole directions for candidate gate dielectrics, including those so far not reported.

The contact properties between metal and graphene were examined. The electrical measurement on a multiprobe device with different contact areas revealed that the current flow preferentially entered graphene at the edge of the contact metal. The analysis using the cross-bridge Kelvin (CBK) structure suggested that a transition from the edge conduction to area conduction occurred for a contact length shorter than the transfer length of $\sim 1\mu \text{m}$ . The contact resistivity for Ni was measured as $\sim 5\times {10}^{-6}\Omega {\text{cm}}^2$ using the CBK. A simple calculation suggests that a contact resistivity less than ${10}^{-9}\Omega {\text{cm}}^2$ is required for miniaturized graphene field effect transistors.

The authors investigated the dielectric constant change of ${\mathrm{Hf}}_{(1-x)}{\mathrm{Si}}_x{\mathrm{O}}_2$ film as functions of Si concentration and annealing temperature. As a result, the dielectric constant of ${\mathrm{Hf}}_{(1-x)}{\mathrm{Si}}_x{\mathrm{O}}_2$ was increased when doped with a small amount of Si after $800°\mathrm{C}$ annealing. The authors revealed that the dielectric constant enhancement of ${\mathrm{Hf}}_{(1-x)}{\mathrm{Si}}_x{\mathrm{O}}_2$ films is related to the phase transformation from the monoclinic to the tetragonal phase of $\mathrm{Hf}{\mathrm{O}}_2$ . By using the Clausius-Mossotti relation, it is concluded that the dielectric constant enhancement through the structural phase transformation is derived from the molar volume shrinkage rather than the molar polarizability increase.

The mobility of graphene transferred on a SiO₂/Si substrate is limited to ∼10 000 cm²V⁻¹s⁻¹. Without understanding the graphene/SiO₂ interaction, it is difficult to improve the electrical transport properties. Although surface structures on SiO₂ such as silanol and siloxane groups are recognized, the relation between the surface treatment of SiO₂ and graphene characteristics has not yet been elucidated. This paper discusses the electrical transport properties of graphene on specific surface structures of SiO₂ prepared by O₂-plasma treatments and reoxidization.