Biorientation Research Articles

Design, fabrication and performance evaluation of graphene/Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> flexible thermoelectric films and in-plane heat dissipation devices

In-plane heat dissipation technology based on flexible thermoelectric film cooling is expected to provide a solution to efficient in-plane heat dissipation of electronic devices. However, the low electrical transport performance of flexible thermoelectric films and the difficulty in designing the structure of in-plane heat dissipation device seriously restrict the applications of this technology in heat dissipation of electronic devices. In this work, an epoxy/Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> flexible thermoelectric film is incorporated with graphene which can simultaneously regulate the electrical and thermal transport behaviors. It is found that the incorporating of graphene not only contributes to the preferential orientation of Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> grains along (000<i>l</i>), but also provides a fast carrier transport channel. The carrier concentration and mobility of graphene/Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> flexible thermoelectric film are simultaneously increased. Comparing with the epoxy/Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> flexible thermoelectric film, the highest power factor of the flexible thermoelectric film with 1.0% graphene at room temperature reaches 1.56 mW/(K<sup>2</sup>·m), increased by 71%, while the cooling temperature difference is doubled. Using this high-performance graphene/Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> flexible thermoelectric film cooling, a cascade structure high-efficiency in-plane heat dissipation device is designed and fabricated. The device can dissipate heat from the heat source area to the heat dissipation area step by step and reduce the temperature of the heat source area by 1.4–1.9 ℃, showing an efficient and stable in-plane heat dissipation capability.

Preferred orientation of Bi and effect of Sn-Bi microstructure on mechanical and thermomechanical properties in eutectic Sn-Bi alloy

The grain sizes and grain orientations of Sn and Bi phases in Sn-58Bi alloy are investigated. We find that the grain size of Bi is larger than that of Sn. Tensile test and two-dimensional simulation reveal that the ductility and yield stress decrease upon Bi coarsening after 504 h of thermal aging at 80 ∘C, and that thermal stress is crowed on the Sn-Bi phase boundaries and is higher in Bi phase than that in Sn phase. Moreover, [0001] preferred orientation of Bi phase along the normal direction of the free surface of the casting model is observed.

Nanostructured Bi Grown on Epitaxial Graphene/SiC.

Controllable growth of metal nanostructures on epitaxial graphene (EG) is particularly interesting and important for the applications in electric devices. Bi nanostructures on EG/SiC are fabricated through thermal decomposition of SiC and subsequent low-flux evaporation of Bi. The orientation, atomic structure, and thickness-dependent electronic states of Bi are investigated by scanning tunneling microscopy/spectroscopy. It is found that metallic Bi nanoflakes and nanorods prefer to grow on the SiC buffer layer region with higher diffusion barrier, but Bi nanoribbons are formed on regularly ordered EG. Although the thicker Bi nanoribbons of 11 monolayers on EG are still metallic, the thinner ones become semiconducting owing to the interfacial effect. This indicates that the electronic states and physical properties of Bi are substrate-dependent. The results are helpful for the design of Bi- and graphene-based electronic and spintronic devices.

Electro-dissolution of the Bi second phase in Sn5Bi solder alloy

This study investigated the electro-dissolution, supersaturation and recrystallization of the second phase Bi in the Sn5Bi solder under 4.0×103–6.0×103A/cm2 current stressing at 25°C. The ex-situ XRD analysis of the current stressed specimen, after being quenched with liquid nitrogen, reveals a reduction of the Bi orientation peaks. The SEM investigation shows the dissolution and supersaturation of the Bi phase during current stressing. The in-situ SEM investigation reveals that recrystallization of the Bi phase occurred in the unquenched specimen when the current stopped. The kinetics of the electro-dissolution were analyzed, and the results showed that the maximum dissolution rate occurred during the progress of current stressing.

Effects of Bi Excess on the Preferred Orientation and Electrical Properties of (Bi$_{3.84}$Nd$_{0.16}$)Ti$_3$O$_{12}$ Ceramics

Effects of Bi Excess on the Preferred Orientation and Electrical Properties of (Bi$_{3.84}$Nd$_{0.16}$)Ti$_3$O$_{12}$ Ceramics

The effects of annealing and growth temperature on the morphologies of Bi nanostructures on HOPG

We report on the growth of ultra-thin bismuth (Bi) films on the basal plane of highly ordered pyrolitic graphite (HOPG) substrates; we investigate the morphologies of films grown at room temperature and then annealed at high temperature, and the morphologies of Bi structures grown at high temperature. Films grown at room temperature nucleate flat islands on the HOPG terraces, and 1D nanorods from HOPG step edges, the islands and rods both have heights in the range 1–3 nm. During annealing, the flat islands break up into groups of aligned, ∼ 2.5 nm tall rods. For films grown at high temperature, terrace nucleation is almost nonexistent, and 1D structures grow from step edges, with heights up to 30 nm. Finally, we observe rods with distinctively different morphologies corresponding to (110) and (111) orientations, and infer a surface energy driven Bi(110) to Bi(111) orientation transition. We speculate that the dominant mechanism for the reorientation is coalescence.

Microstructure and Ferroelectric Properties of Direct-Patternable Bi3.25La0.75Ti3O12 Films Prepared by Photochemical Metal-Organic Deposition

The microstructure and ferroelectric properties of Bi 3.25 La 0.75 Ti 3 O 12 films prepared by photochemical metal-organic deposition using photosensitive precursors were characterized. The diffraction intensities showed a distribution similar to Bi 3.25 La 0.75 Ti 3 O 12 ceramics, and Pt(111) was found to not influence the growth orientation of Bi 3.25 La 0.75 Ti 3 O 12 films. The values of measured remnant polarization and dielectric constant of Bi 3.25 La 0.75 Ti 3 O 12 films annealed at 650 and 700°C were 8.7, 16.0 μC/cm 2 and 172, 276, respectively. The films remained free of fatigue up to 10 9 switching cycles. These results suggest the possible application of ferroelectric Bi 3.25 La 0.75 Ti 3 O 12 film, relatively easily and without high cost process such as dry etching.

Effect of Dysprosium Substitution on the Properties of Bismuth Titanate Thin Films Prepared by Sol-Gel Method

Dysprosium-substituted bismuth titanate (Bi 3.2 Dy 0.8 Ti 3 O 12 , BDT) thin films were successfully deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by a sol–gel method. The effects of dysprosium-substitution on the microstructure and ferroelectric properties of Bi 4 Ti 3 O 12 thin films were investigated. X-Ray diffraction analysis reveals that the highly degree of (117) orientation can be obtained for BDT thin films. The improved ferroelectric properties can be attributed to the enhanced degree of (117) orientation of Bi 3.2 Dy 0.8 Ti 3 O 12 thin films. The highly (117)-oriented Bi 3.2 Dy 0.8 Ti 3 O 12 thin films exhibit high remanent polarization (2P r) of 52 μ C/cm 2 and low coercive field (2E c) of 120 kV/cm. The corresponding results show that the obtained Bi 3.2 Dy 0.8 Ti 3 O 12 thin film exhibited excellent ferroelectric properties and, thus, was suitable for application to non-volatile ferroelectric random access memory applications.

Effect of yttrium doping on microstructure and ferroelectric properties of Bi 4Ti 3O 12 thin film

Bi 4 − x Y x Ti 3O 12 thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by sol–gel method and rapid thermal annealing. The effects of yttrium-substitution and annealing temperature (500–800 °C) on the microstructure and electrical properties of bismuth titanate thin films were investigated. X-ray diffraction analysis reveals that the degree of (117) orientation increases as the yttrium content increased. The improved ferroelectric properties can be attributed to the enhanced degree of (117) orientation of Bi 4 − x Y x Ti 3O 12 thin films. The highly (117)-oriented Bi 3.2Y 0.8Ti 3O 12 thin films exhibit high remanent polarization (2P r) of 58 μC/cm 2 and low coercive field (2E c) of 116 kV/cm, with fatigue-free characteristics up to > 10 8 switching cycles. The corresponding results show that the obtained Bi 3.2Y 0.8Ti 3O 12 thin film exhibited excellent ferroelectric properties and, thus, was suitable for application to non-volatile ferroelectric random access memory applications.

Effects of TiO2 Seeding Layer on Crystalline Orientation and Ferroelectric Properties of Bi3.15Nd0.85Ti3O12 Thin Films Fabricated by a Sol–Gel Method

The effect of a 20‐nm thick TiO2 seeding layer on the growth of a Bi3.15Nd0.85Ti3O12 (BNT) thin film on Pt(111) thin‐film substrates has been studied. Under otherwise identical deposition process conditions, the BNT film could be turned from a highly random orientation to a (200) preference orientation by adding the seeding layer. Field‐emission scanning electron microscope result reveals that the BNT thin film with the TiO2 seeding layer is composed of fine grains with smaller sizes about 80–150 nm in diameter. The Pr and Ec values of the BNT thin film and BNT film with the TiO2 seeding layer were 36 and 16 μC/cm2, and 96.9 and 92 kV/cm at a voltage of 12 V, respectively. The fatigue test exhibited a very strong fatigue endurance up to 109 cycles for both films. The leakage current densities were generally in the order of 10−6–10−5 A/cm2 for both samples.

Preferential orientation and thermoelectric properties of p-type Bi 0.4Sb 1.6Te 3 system alloys by mechanical alloying and equal channel angular extrusion

The p-type Bi 0.4Sb 1.6Te 3 system compounds with fine microstructure were prepared by mechanical alloying (MA) and equal channel angular extrusion (ECAE) in the present work. A preferentially orientated microstructure that the (1 1 0) plane preferentially orientated along the perpendicular direction to extrusion and the basal planes (0 0 l) preferentially orientated along the extrusion direction was formed in the ECAE process, and the orientation factors F of the basal planes (0 0 l) of the extruded alloys was about 0.36. The electrical and thermal transmission performances were strongly affected by the preferential orientation and the thermoelectric properties in the extrusion direction were obviously improved by the ECAE process. The maximum dimensionless figure of merit of the 4 wt.% Te-doped Bi 0.4Sb 1.6Te 3 alloys was obtained in the extrusion direction at testing temperature 343 K, ZT = 0.979.

Bi0.5(Na1-XKX)0.5TiO3の結晶配向に影響を及ぼす要因

Bi0.5(Na1-XKX)0.5TiO3の結晶配向に影響を及ぼす要因

Effective Deposition Potential Induced Size-Dependent Orientation Growth of Bi−Sb Alloy Nanowire Arrays

The influence of effective deposition potential on the orientation and diameter of Bi(1-x)Sbx alloy nanowire arrays by pulsed electrodeposition technique was reported. X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy analysis show that the orientation of the Bi(1-x)Sbx nanowires can be turned from the [110] to the [202] direction by increasing the effective deposition potential, and the nanowires fully fill in the pores of the AAM in the lower potential region, while in the higher potential region the nanowires partly fill the pores of the AAM. The origin of those phenomena and the growth mechanism of the nanowire are discussed together with composition analysis.

Effects of annealing schedule on orientation of Bi 3.2Nd 0.8Ti 3O 12 ferroelectric film prepared by chemical solution deposition process

Fatigue-free Bi 3.2Nd 0.8Ti 3O 12 ferroelectric thin films were successfully prepared on p-Si(1 1 1) substrate using chemical solution deposition process. The orientation and formation of thin film under different annealing schedules were studied. XRD analysis indicated that (2 0 0)-oriented films with degree of orientation of I (2 0 0) / I (1 1 7) = 2.097 and 0.466 were obtained by preannealing for 10 min at 400 °C followed by rapid thermal annealing for 3, 10 and 20 min at 700 °C, respectively, (0 0 8)-oriented films with degree of orientation of I (0 0 8) / I (1 1 7) = 1.706 were obtained by rapid thermal annealing for 3 min at 700 °C without preannealing, and (0 0 8)-oriented films with degree of orientation of I (0 0 8) / I (1 1 7) = 0.719 were obtained by preheating the film from room temperature at 20 °C/min followed by annealing for 10 min at 700 °C. The a-axis and c-axis orientation decreased as increase of annealing time due to effects of (1 1 1)-oriented substrate. AFM analysis further indicated that preannealing at 400 °C for 10 min followed by rapid thermal annealing for 3 min at 700 °C resulted in formation of platelike crystallite parallel to substrate surface, however rapid thermal annealing for 3 min at 700 °C without preannealing resulted in columnar crystallite perpendicular to substrate surface.

Effects of Heating Process on Crystalline Orientation and Electrical Properties of (Bi,La)4Ti3O12 Thin Films Derived by Chemical Solution Deposition Method

(Bi,La)4Ti3O12 (BLT) thin films were prepared on Pt-coated Si (Pt/Ti/SiO2/Si(100)) substrates by chemical solution deposition method. The effect of heating process on structural and electrical properties of BLT thin films was investigated. The c-axis preferentially oriented films were obtained by lower drying temperature with heating from bottom by a hot plate or IR lamp heater. On the other hand, randomly oriented films were obtained by higher drying temperature with heating from top of films by IR lamp heater or with heating substrate all around by tube type furnace. The orientation of BLT thin films deposited on Pt-coated substrates can be controlled by heating process.

PLA法により作製したBi<SUB>2</SUB>Sr<SUB>2</SUB>Ca<SUB>(<I>n</I>−1)</SUB>Cu<I><SUB>n</SUB></I>O<I><SUB>y</SUB></I>薄膜の超伝導特性と面内配向性

PLA法により作製したBi<SUB>2</SUB>Sr<SUB>2</SUB>Ca<SUB>(<I>n</I>−1)</SUB>Cu<I><SUB>n</SUB></I>O<I><SUB>y</SUB></I>薄膜の超伝導特性と面内配向性