BaO Thin Film Research Articles

Nano-architectured BaO thin film electrode synthesized via SILAR technique for supercapacitor application

Nano-architectured BaO thin film electrode synthesized via SILAR technique for supercapacitor application

Surface Reactions on Pt during NOx Storage−Reduction Studied by Polarization-Modulation Infrared Reflection−Absorption Spectroscopy

NOx storage−reduction (NSR) cycles on a model catalyst, consisting of Pt particles on a BaO thin film deposited on a polished Al substrate, have been investigated by means of in situ polarization-modulation infrared reflection−absorption spectroscopy (PM-IRRAS). The method affords simultaneous time-resolved detection of bulk Ba species and species in gas-phase and on the Pt surface. The study revealed the special role of atop NO adsorption sites on platinum for NO oxidation leading to efficient NOx storage on the Ba component, and a gradual change in adsorbate composition resulting in a transition from N2O- to NO2-formation reaction on Pt during lean periods.

Quantum Yield Investigation of Ag−BaO Thin Film

Ag−BaO thin films have been fabricated by evaporating silver into BaO semiconductor thin film in ultrahigh vacuum and the quantum yield distribution in the visible region between 1.5 and 3.7 eV has been measured. The quantum yield spectra have a peak when the energy of the incident light is 2.5 eV. The direct transitions and surface plasmon resonance of silver nanoparticles appear to be very important in determining the shape of quantum yield spectra. The explanation for the small discrepancy between the experimental result and the theoretical data is given.

Theoretical study on the photoelectric emission spectra of a field-assisted Au–BaO thin film

The dependence of the spectral distribution of photoelectron emission from gold nano-particles embedded in BaO semiconductor thin film on applied voltage and surface plasmon resonance of gold nano-particles is predicted and investigated theoretically. The photoelectron emission response curves to light wavelength between 0.2 and 0.8 μ m are given. The dependence of the wavelength threshold on the size of gold nano-particles and external field strength is also shown. The reason that the theoretical photoelectron emission spectra is in the visible region is explained. The probabilities increased for photoexcited electrons to overcome the barrier and escape from the surface are discussed. This could be of importance in designing field-assisted thin film and finding their optimum operation conditions.

Theoretical study on the quantum yield spectra of a field-assisted Au–BaO thin film

The theoretical quantum yield curves response to the wavelength of the incident light between 0.2 and 0.9 μm are predicted. The greater value of the external voltage is applied, the higher peaks in theoretical spectral distribution are obtained. The theoretical results show that an increasing in sizes of gold nano-particles, obviously causes the quantum yields of this thin film to increase, makes the full widths at the half-maximum become narrow, and leads to the emergence of exactly Gaussian in form. The spectral distributions of the quantum yield of this field-assisted Au–BaO thin film are mainly determined by the surface plasmon resonance of the gold nano-particles embedded in BaO and the direction photon–electron transition. It may be helpful to design the field-assisted Au–BaO thin film and choose an optimum operation condition.

Influence of external field and particle size upon theoretical photoelectron emission spectral response of silver nano-particles embedded in BaO thin film

The dependence of the spectral distribution of photoelectron emission from silver nano-particles embedded in BaO semiconductor thin film on external voltage and the size of silver nano-particles is predicted and investigated theoretically. The photoelectron emission response curves to light of wavelength between 0.2 and 0.8μm are given. The dependence of the wavelength threshold on the size of silver nano-particles and external field strength is also shown. Photoemission in the visible spectrum is explained as due to the optical resonance absorption in the silver particles. This could be of importance in designing field-assisted photocathodes and finding their optimum operation conditions.

Synthesis of a BaO thin film supported on MgO(001) using a shell-model amorphisation and recrystallisation strategy

An amorphisation and recrystallisation strategy with a shell model representation of ionic polarisability has been used to generate models for thin BaO films supported on an MgO(001) substrate. The resulting BaO thin film includes a complex 〈101〉 dislocation network, the core structures of which have mixed screw-edge and pure edge character. The atomistic core structures of two such dislocations are deconvoluted and presented using graphical techniques. Intermixing of cations across the interfacial plane is observed to be of the order of 1–3%. The amorphisation and recrystallisation strategy improves upon the analogous rigid ion approach in that it enables the ions to retain significant mobility even after recrystallisation enabling additional annealing steps to be performed to allow the ions to rearrange further into low energy configurations. Conversely, the computational cost of such calculations is considerably higher.

Atomic and electronic structures of barium oxide on Si(0 0 1) studied by metastable impact electron spectroscopy (MIES) and coaxial impact collision ion scattering spectroscopy (CAICISS)

The BaO thin film was grown on the Si(001) surface and its surface properties were investigated using metastable impact electron spectroscopy (MIES) and coaxial impact collision ion scattering spectroscopy (CAICISS). The BaO surface reduced by annealing at 600°C in ultrahigh vacuum is covered with a metallic Ba overlayer and exhibits the work function as small as 0.5eV. The semiconducting property recovers upon oxygenation of this surface as revealed from the MIES spectra. It is found that film quality is degraded considerably after several reduction/oxygenation cycles. Probably, this is because a template BaSi2 structure is broken gradually as a consequence of the solid-state reaction between BaO and BaSi2, which is induced by the migration of chemisorbed oxygen to the interface.

Theoretical Study on Effect of the Size of Silver Nanoparticles on the Localized Surface Plasmon Resonance Spectrum of Silver Nanoparticles Embedded in BaO Thin Film

Theoretical Study on Effect of the Size of Silver Nanoparticles on the Localized Surface Plasmon Resonance Spectrum of Silver Nanoparticles Embedded in BaO Thin Film

Transient optical relaxation of the Cu–BaO thin film

The pump–probe technique was used for measuring the transient optical relaxation of Cu–BaO composite thin film which was stimulated by femtosecond laser pulses. The experimental results were obtained that the optical transmissivity of the thin film rapidly decreased and a negative peak emerged during the time delay. The relaxation process consisted of two components: a fast recovery with a time of 500 fs and a subsequent slow one with over several picoseconds. An amended theoretical value of the electron–phonon coupling constant g of Cu nanometer particles in the composite thin film is given as 1.3×10 17 W/m 3 K according to the experimental results. The optical relaxation is a process in which nonequilibrium electrons, originating from Cu nanometer particles and excited by ultrashort laser pulses, return to the equilibrium state.

Nonequilibrium electron relaxation in composite thin film containing silver nano-scale particles

Under the stimulation of laser pulses with a wavelength of 647 nm and a pulse duration of 150 fs, the optical transient response of Ag–BaO thin film was obtained by the pump-probe method. Optical relaxation is a process in which nonequilibrium electrons, excited by laser pulses and originating from Ag nano-scale particles, return to the equilibrium state. Its optical transient relaxation consists of a faster part and a slower one. The faster part is only 200 fs and is caused by nonequilibrium electrons entering the matrix. The slower part is 1.6 ps and is caused by nonequilibrium electrons scattering with the lattice and the interface between the Ag nano-scale particles and the matrix. From calculated results, the theoretical curve was coincident with experimental one. The thin film containing Ag nano-scale particles embedded in BaO semiconductor matrix has extremely fast photoelectron response time.

Strain reduction in supported materials; the formation of cracks and dislocations

Supported materials have been constructed by successively depositing ions onto a surface in conjunction with dynamics simulation and energy minimisation. In particular, the growth of SrO/SrO, CaO/SrO (–6.9% misfit) and BaO/SrO (+7.0% misfit) were studied as model systems to examine the influence of the misfit on the structure and stability of epitaxial thin films. At low (theoretical monolayer) coverage, the CaO formed islands on the SrO(001) surface in contrast to the strips formed by BaO. At higher coverages cracks formed within the CaO, while dislocations appeared within the BaO thin film, in both cases to help reduce the strain within the materials. A mechanism for the formation of the dislocation is presented. For one particular CaO/SrO(001) interface, a cubic-hexagonal transformation of the CaO is observed, enabling the misfit to be perfectly accommodated.

Coherent Phonons in Ag-BaO Thin Films

Coherent acoustic phonons have been observed in Ag nanoscale particles (NSPs) embedded in BaO thin film by means of the femtosecond time-resolved pump-probe technique. The oscillatory component in the signal corresponds to a very low-frequency acoustic phonon mode of Ag NSPs. The generation of coherent acoustic phonons is attributed to the resonant excitation of localized surface plasmon.

Ultrafast optical response of the Au–BaO thin film stimulated by femtosecond pulse laser

The pump-probe method was applied to study the dependence of the transient optical transmissivity upon time delay for the Au–BaO composite thin film stimulated by a femtosecond pulsed laser. It was observed that the light absorption of the thin film increased rapidly and then resumed its initial value in several picoseconds. Optical relaxation is a process in which nonequilibrium electrons, excited by laser pulses and originating from Au ultrafine particles, return to the equilibrium state. In this article, the value of the electron-phonon coupling constant g of gold ultrafine particles in the composite thin film was calculated theoretically.