X. Y. Qi

Thickness and dielectric constant of dead layer in Pt/(Ba0.7Sr0.3)TiO3/YBa2Cu3O7−x capacitor

Pt/(Ba0.7Sr0.3)TiO3 (BST)/YBa2Cu3O7−x capacitors were prepared and investigated for the dead-layer (DL) thickness (td) and the DL dielectric constant (ed). Based on the series capacitor model, the td/ed ratio of 0.066 nm and the bulk BST ferroelectric-layer dielectric constant of 1370 were obtained through the measurements of the capacitance–voltage characteristics. The td×ed value of 120 nm was obtained through the measurements of the current–voltage characteristics. Combining these data, the DL thickness and the DL dielectric constant are respectively estimated to be 2.8 nm and 42.6.

Sb-induced bicrystal ZnO nanobelts

Zinc oxide bicrystal nanobelts of wurtzite structure were synthesized by simple thermal evaporation of a powder mixture of Zn and Sb2O3. The bicrystal nanobelts were found to have a growth direction of [2¯113], widths of 80–200 nm, and lengths up to several hundreds of micrometers. Energy dispersive x-ray spectroscopy and high angle annular dark field images showed that antimony was rich in the grain boundary of the bicrystal nanobelts. It was discovered that both sides of the bicrystal nanobelts were O-terminated toward the grain boundary. The mechanism of formation of the bicrystal nanobelts was also discussed.

In situ transmission electron microscopy study of electric-field-induced 90° domain switching in BaTiO3 single crystals

The 90° domain switching in single crystalline BaTiO3 under an external static electric field has been investigated by in situ transmission electron microscopy using a special homemade transmission electron microscope stage. With the initial domains gradually disappearing, new domains that are 90° away from the initial ones are observed to occur with polarizations being switched to the direction of the external electric field, and domain boundaries being changed from ⟨101⟩ to ⟨1¯01⟩ in order to maintain a “head-to-tail” arrangement.

Direct determination of the polarization direction of domains in BaTiO3 single crystal

The polarization directions of domains in BaTiO3 single crystal are determined by convergent-beam electron diffraction directly. The intensity distributions in the (001) and (001¯) diffraction disks are different, which is due to the noncentrosymmetric unit cell of ferroelectrics. The in situ transmission electron microscopy observations on the evolution of domains under external fields indicate that the disk with a little brighter center fringes is the (001) disk and the polarization vector is toward this disk. The method provides a straightforward criterion for polarization direction determination of ferroelectric domains.

Nanoscale strain analysis of strained-Si metal-oxide-semiconductor field effect transistors by large angle convergent-beam electron diffraction

In this letter we report the characterization of local compressive strain in p-type strained-silicon channel metal-oxide-semiconductor field effect transistors by large angle convergent-beam electron diffraction. The compressive strain was induced into the channel region of gate length of 80nm strained-Si p-type metal-oxide-semiconductor field effect transistor by Ge preamorphization implantation for source/drain extension. A method to distinguish between compressive strain and shear strain in the cross-sectional transmission electron microscopy specimens is proposed.

Metallic oxide p-I-n junctions with ferroelectric as the barrier

The authors report the formation of the metallic oxide p-I-n junctions with the ferroelectric (Ba,Sr)TiO3 (BST) as the barrier. The junctions with different thicknesses of BST are investigated. With appropriate thickness, the junctions possess definite parameters, such as the negligible reversed current density (⩽10−7A∕cm2), large breakdown voltage (>7V), and ultrahigh rectification (>2×104) in the bias voltage ⩽2.0V and temperature range from 5to300K. It is under consideration that the built-in field V0, the ferroelectric reversed polarized field Vrp, and the resistivity of the BST layer together decide the transport properties of the junctions.