Narrow Results

First-principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA) were carried out to investigate the energy band gap structure of Si and Ge nanofilms. Calculation results show that the band gaps of Si(111) and Ge(110) nanofilms are indirect structures and independent of film thickness, the band gaps of Si(110) and Ge(100) nanofilms could be transfered into the direct structure for nanofilm thickness of less than a certain value, and the band gaps of Si(100) and Ge(111) nanofilms are the direct structures in the present model thickness range (about 7 nm). Moreover, the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects. It will be a good way to obtain direct band gap emission in Si and Ge materials, and to develop Si and Ge laser on Si chip.

Size-dependent elastic properties of Ni nanofilms are investigated by molecular dynamics (MD) simulations with embedded atom method (EAM). The surface effects are considered by calculating the surface relaxation, surface energy, and surface stress. The Young's modulus and yield stress are obtained as functions of thickness and crystallographic orientation. It is shown that the surface relaxation has important effects on the the elastic properties at nanoscale. When the surface relaxation is outward, the Young's modulus decreases with the film thickness decreasing, and vice versa. The results also show that the yield stresses of the films increase with the films becoming thinner. With the thickness of the nanofilms decreasing, the surface effects on the elastic properties become dominant.

The nanocomposite Al₂O₃–Y₂O₃ films were prepared on the surface of carbon steel by an electrochemical process and a sintering process. High-resolution field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films, indicating that the films have nanostructures and the deposited alumina layers have a composition close to the stoichiometry of Al₂O₃. SEM and mass gain measurement are adopted to study the oxidation resistance of films on carbon steel. It is proved that this kind of film is effective in protecting the substrate from oxidation. The mechanisms accounting for such effects have been discussed.

ZnIn₂S₄ nanofilms were grown on In₂S₃ substrates. The band gap of ZnIn₂S₄ barriers was approximately 2.8 eV at room temperature. The morphology and structure of the obtained nanofilms were already investigated via transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction analyses.^1,2 In this paper, thermal analyses are performed via a photothermal technique, which has been used to indirectly evaluate the specific heat capacity of the obtained Zn-doped nanofilms. The yielded value for an optimal zinc-to-indium ratio, x (0.33), at the mean room temperature (T_∞ = 301 K), was C_s ≈ 411.5 J K^-1kg^-1.

As a new nanomaterial, HgWO₄ nanofilms are prepared by the self-inventive technique of collodion nanoparticles-dispersal and film-formation. Their photoluminescent properties are enhanced and then controlled through nano-TiO₂ doping. These approaches not only ensure film uniformity and fluorescence (FL) enhancement, but also realize a FL increase/decrease conversion effect. The relationships between HgWO₄ nanofilms' PL intensities and TiO₂ doped amounts are in good agreement with Gaussion function, and maximum PL intensities of HgWO₄ nanofilms are located at 3.8% ratio of TiO₂ nanoparticles.

Amorphous alumina films are isotropic and have no grain boundaries, which make them have smooth surfaces, excellent properties, and wide applications in protective coatings, catalysis, and microelectronics. However, high-quality alumina films were usually prepared by vapor-phase approaches which need expensive equipment and long production time. Additionally, amorphous films are long-range disordered, which makes the study of structure–property relationships challenging. Here, a simple sol–gel method is employed to obtain high-quality amorphous Al₂O₃ thin films. The microstructure, morphology, and mechanical properties of amorphous Al₂O₃ thin films were systematically investigated. All the Al₂O₃ thin films heat-treated at 600–800^∘C are in amorphous state with ultrasmooth surface (Ra values about 0.29–0.43 nm) and high mechanical properties (elastic modulus ∼170GPa, hardness ∼20GPa). The mechanical properties (E and H) of Al₂O₃ films gradually increase with the increase of heat-treating temperature. Additionally, the Al coordination of the amorphous alumina films are analyzed by solid-state NMR and correlated with the mechanical properties. The results show that in amorphous alumina, the presence of tetrahedral Al ([4]Al) and octahedral Al ([6]Al) is helpful to improve the mechanical properties, while the five-coordinated Al ([5]Al) is not conducive to improve the mechanical properties. The results demonstrate that sol–gel method is an attractive alternative to time-consuming and expensive vapor-phase approaches and are useful for scale-up to applications and research of amorphous alumina films.

Adaptive and functional polymers have drawn much attention in many fields due to their unique properties. Through nanotechnology, there have been reports of fabricating various adaptive polymer nanostructures, such as nanofibres and nanofilms, in recent years. In this chapter, fabrication of nanofibres and nanofilms by concentrating on the electrospinning and self-assembly methods, are first introduced. At the same time, the principles and parameters of electrospinning as well as self-assembly are discussed. Secondly, the morphologies and structures of nanofibres and nanofibrous nonwovens are described briefly. Thirdly, we will present a brief review on the development of some typical adaptive polymer nanofibres and nanofilms, and in particularly, adaptive shape memory polymeric nanofibres and nanofibrous nonwovens; nonlinear optical nanofibres; responsive and adaptive porphyrin based nanostructures; adaptive nanocomposites and functional polymer nanofilms. Finally, the applications of nanofibres and nanofilms are introduced. Thus, a comprehensive understanding of adaptive nanofibres and nanofilms can be obtained in this chapter.