Phuoc Huu Le

By Phuoc Huu Le and Chih Wei Luo

Bismuth chalcogenides have been intensively studied for their high-performance thermoelectric properties and their novel topological surface states, which could significantly benefit novel applications in fields such as TE devices, spintronics, and quantum computing. This chapter reports recent advances in pulsed laser deposition (PLD) for the growth of bismuth chalcogenide (e.g., Bi2Te3, Bi2Se3, and Bi3Se2Te) thin films and their novel properties. It covers a wide range of fields such as thin film growth using PLD for fabricating polycrystalline and epitaxial films with different thermoelectric, nanomechanical, and magnetotransport properties as a function of the PLD processing conditions. Moreover, the proximity-induced superconductivities in Bi inclusions/bismuth chalcogenide thin films are also reported and discussed in detail.

Part of the book: Applications of Laser Ablation

By Phuoc Huu Le and Chih-Wei Luo

Ultrafast dynamics of carriers and phonons in topological insulator Bi2Se3, CuxBi2Se3 (x = 0, 0.1, 0.125) single crystals were studied by time-resolved pump-probe spectroscopy. The coherent optical phonon (A1g1) is found via the damped oscillation in the transient reflectivity changes (∆R/R) for CuxBi2Se3. The observed red shift of A1g1 phonon frequency suggests the intercalation of Cu atoms between a pair of the quintuple layers of Bi2Se3 crystals. Moreover, the relaxation processes of Dirac fermion near the Dirac point of Bi2Se3 are studied by optical pump and mid-infrared probe spectroscopy through analyzing the negative peak of the ∆R/R. The Dirac fermion-phonon coupling strength was found in the range of 0.08–0.19 and the strength is reduced as it gets closer to the Dirac point. The ultrafast dynamics and fundamental parameters revealed by time-resolved pump-probe spectroscopy are important for designing the optoelectronics in the mid-IR and THz ranges.

Part of the book: Two-dimensional Materials for Photodetector

By Phuoc Huu Le, Nguyen Trung Kien and Chien Nguyen Van

This chapter provides recent progress in developments of BiVO4- and Bi2Te3-based materials for high efficiency photoelectrodes and thermoelectric applications. The self-assembling nanostructured BiVO4-based materials and their heterostructures (e.g., WO3/BiVO4) are developed and studied toward high efficiency photoelectrochemical (PEC) water splitting via engineering the crystal and band structures and charge transfer processes across the heteroconjunctions. In addition, crystal and electronic structures, optical properties, and strategies to enhance photoelectrochemical properties of BiVO4 are presented. The nanocrystalline, nanostructured Bi2Te3-based thin films with controlled structure, and morphology for enhanced thermoelectric properties are also reported and discussed in details. We demonstrate that BiVO4-based materials and Bi2Te3-based thin films play significant roles for the developing renewable energy.

Part of the book: Bismuth

By Phuoc Huu Le and Jihperng Leu

This book chapter reports some spectacular and interesting 1D nanostructures of TiO2, which are grown by the anodic oxidation. Under suitable conditions, conventional one-step anodic oxidation is available to grow TiO2 nanotube arrays (TNAs) and TiO2 nanowires/nanotubes; meanwhile, two-step anodic oxidation allows fabricating some novel TNAs with spectacular morphologies such as highly ordered TNAs, bamboo-type TNAs, and lotus root-shaped TNAs. The formation mechanisms of these nanostructures during the anodic oxidation processes are elusive via studying effects of several key parameters such as oxidizing voltage, processing time, and electrolytes. In addition, the photocatalytic activity of the TNA-based nanomaterials is characterized by the degradation of pharmaceutical model, methylene blue, or the photoelectrochemical effect.

Part of the book: Titanium Dioxide

By Phuoc Huu Le and Chih-Wei Luo

This chapter reviews the nanostructuring fabrications and properties of indium-tin-oxide (ITO) thin films by femtosecond laser annealing. Fundamental mechanisms of laser-induced periodic surface structures (LIPSS) and other nanostructures on ITO films are presented and discussed in detail. ITO films with large-area surface ripple structures with a multiperiodic spacing of ~800, ~400, and ~200 nm were successfully fabricated by femtosecond laser pulses, without scanning. The ITO films exhibited significant enhancement in electrical conductivity by ~30 times because of the formation and distribution of indium metal-like clusters. This metallic content of the laser-induced nanodots and nanolines further causes the anisotropic transmission characteristics in the visible range. In addition, by varying the laser fluences, nanostructures with cotton, brick, and ripple forms are generated on the surface of ITO films, which produce cyan, yellow, and orange colors. Intriguingly, the ITO films with laser-induced nanostructures can significantly attenuate blue light, thus they are potential for applications such as eye protection and information security.

Part of the book: Methods for Film Synthesis and Coating Procedures

By Dang Long Quan and Phuoc Huu Le

The direct methanol fuel cell (DMFC) is among the most promising alternative energy sources for the near future owing to its advantages of simple construction, compact design, high energy density, and relatively high energy-conversion efficiency. Typically, the electrodes in DMFC is comprised of a Pt-based catalysts supported on great potential of carbon materials such as multi-walled carbon nanotubes (MWCNTs), carbon black (CB), graphene, etc. It is desired to develop an electrode with high surface area, good electrical conductivity and suitable porosity to allow good reactant flux and high stability in the fuel cell environment. This chapter will provide recent advances in Pt-based binary and ternary electrocatalysts on carbon supports for high-performance anodes in DMFC. Through studying the effects of composition-, support-, and shape dependent electrocatalysts, further fundamental understanding and mechanism in the development of anode catalysts for DMFC will be provided in details.

Part of the book: Electrocatalysis and Electrocatalysts for a Cleaner Environment

By Le Thi Cam Tuyen, Phuoc Huu Le and Sheng-Rui Jian

This book chapter reports recent advances in nanostructured Bi2Te3-based thermoelectric (TE) thin-films fabricated by pulsed laser deposition (PLD). By controlling the processing conditions in PLD growths, various fascinating Bi2Te3-based nanostructured films with promising or enhanced TE properties have been successfully fabricated, including super-assembling of Bi2Te3 hierarchical nanostructures, self-assembled Bi2Te3 films with well-aligned 0D to 3D nanoblocks, polycrystalline-nanostructured Bi2Se3 and Bi2Te3 thin-films, etc. In addition, a PLD-growth mechanism for fabricating the super-assembling Bi2Te3 thin-films is presented. This book chapter provides fundamental understanding the relationship amongst processing condition, structure-morphology, and TE property of PLD-growths Bi2Te3-based thin-films. It also presents an overview of TE materials and applications with the challenges and perspectives.

Part of the book: Materials at the Nanoscale