Complex oxide heterointerfaces, which play host to an incredible variety of interface physical phenomena, are of great current interest in introducing new functionalities to systems. Here, coherent super‐tetragonal BiFeO3/LaAlO3 and rhombohedral BiFeO3/LaAlO3 heterointerfaces are investigated by using a combination of high‐angle annular dark‐field (HAADF) imaging and annular bright‐field (ABF) imaging in a spherical aberration (Cs) corrected scanning transmission electron microscope (STEM), and first‐principles calculations. The complicated ferroelectric polarization pinning and relaxation that occurs at both interfaces is revealed with atomic resolution, with a dramatic change in structure of BiFeO3, from cubic to super‐tetragonal‐like. The results enable a detailed explanation to be given of how non‐bulk phase structures are stabilized in thin films of this material.

Mach–Zehnder (MZ) waveguide interferometers integrated on SOI (silicon on insulator) for 1.3 μm operation are studied on the basis of the large cross-section single-mode rib waveguide condition and the free-carrier plasma dispersion effect in Si wafer direct bonding SOI by back-polishing. And the MZ interferometers are fabricated by using KOH anisotropic etching. Their insertion losses and modulation depths are measured to be 4.81 dB and 98%, respectively, at the wavelength of 1.3 μm when a forward bias voltage applied to a p+n junction is 0.95 V and the active zone length of the MZ interferometers is 816.0 μm.

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Electronic, elastic and piezoelectric properties of two-dimensional (2D) group-IV buckled monolayers (GeSi, SnSi and SnGe) are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d 11 of SnSi and SnGe are 5.04 pm/V and 5.42 pm/V, respectively, which are much larger than 2D MoS2 (3.6 pm/V) and are comparable with some frequently used bulk materials (e.g., wurtzite AlN 5.1 pm/V). Charge transfer is calculated by the Löwdin analysis and we find that the piezoelectric coefficients (d 11 and d31) are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

Additive manufacturing (AM) nickel-based superalloys have been demonstrated to equate or exceed mechanical properties of cast and wrought counterparts but their tribological potentials have not been fully realized. This study investigates fretting wear behaviors of Inconel 625 against the 42 CrMo4 stainless steel under flat-on-flat contacts. Inconel 625 is prepared by additive manufacturing (AM) using the electron beam selective melting. Results show that it has a high hardness (335 HV), superior tensile strength (952 MPa) and yield strength (793 MPa). Tribological tests indicate that the AM-Inconel 625 can suppress wear of the surface within a depth of only ~2.4 μm at a contact load of 106 N after 2 × 104 cycles. The excellent wear resistance is attributed to the improved strength and the formation of continuous tribo-layers containing a mixture of Fe2O3, Fe3O4, Cr2O3 and Mn2O3.