Properties of amorphous silicon thin films synthesized by reactive particle beam assisted chemical vapor deposition

Amorphous silicon thin films were formed by chemical vapor deposition of reactive particle beam assisted inductively coupled plasma type with various reflector bias voltages. During the deposition, the substrate was heated at 150 °C. The effects of reflector bias voltage on the physical and chemical properties of the films were systematically studied. X-ray diffraction and Raman spectroscopy results showed that the deposited films were amorphous and the films under higher reflector voltage had higher internal energy to be easily crystallized. The chemical state of amorphous silicon films was revealed as metallic bonding of Si atoms by using X-ray photoelectron spectroscopy. An increase in reflector voltage induced an increase of surface morphology of films and optical bandgap and a decrease of photoconductivity.     

Microwave permittivity of MWCNT,Ca1 − xBaxBi2Nb2O9 (0 ≤ x ≤ 1) and MWCNT/ Ca1 − xBaxBi2Nb2O9 (0 ≤ x ≤ 1) layered composite thick films using microstrip ring resonator overlay method

Journal of Electroceramics - The microwave dielectric properties of the multiwalled carbon nanotubes (MWCNT) thick film, Ca1???xBaxBi2Nb2O9 (x?=?0, 0.2, 0.4, 0.6, 0.8,...     

Effect of Ag nanoparticles on the electron energy structure and electrical properties of poly(p-phenylene vinylene) (PPV)

The effects of inorganic nanoparticles on a conjugated polymer were investigated by measuring the electronic properties of poly(p-phenylene vinylene) (PPV) and PPV/Ag nanocomposites. Through hybridization, an enhancement in current density was achieved with PPV/Ag nanocomposites due to an increase in the electron affinity with Ag nanoparticle content. Furthermore, roughening of the surface morphology was observed with incorporation of Ag nanoparticles. This roughness induces an enhanced applied field at the thinner region of the film and an increase in the surface area with a resulting increase of electron injection, leading to current enhancement.     

The application of an ordered mesoporous silica film to a GaAs device

Pseudomorphic high electron mobility transistors (PHEMTs) are promising devices for use in millimeter-wave and optical communications systems due to their excellent high frequency and low-noise performances. In order to further improve the performance of these devices, their gate lengths must be reduced to the technological limit and a small gate resistance must be realized. However, shorter gates result in an increase of short channel effects that limit microwave performance. In order to reduce the gate resistance, T-shaped gates with large cross-sectional areas are required. However, the thickness and dielectric constant of the passivation layer have major impacts on the gate capacitance. In this study, an ordered mesoporous silica film was introduced as a passivation layer between T-gates. Si₃N₄ with a dielectric constant of 7.4 and ordered mesoporous silica with a dielectric constant of 2.48 were used as passivation layers. The Si₃N₄ dielectric layer and the ordered mesoporous silica film were stacked together and the device characteristics were investigated.     

Fabrication of sub 50-nm direct-patterned Pb(Zr,Ti)O<Subscript>3</Subscript> films by electron beam-induced metal-organic deposition

Direct-patterned lead zirconate titanate (PZT) films prepared from an electron beam sensitive stock solution were investigated for advanced stage applications in sub 50-nm patterned systems. The required electron beam dose for the direct-patterning of PZT precursor films was 4.5 mC/cm². The PZT precursor films with pattern size of 500 × 500 μm² were exposed to an electron beam for 2 h and annealed at 400°C for 30 min under an O₂ ambient. After exposure and annealing, values of the remnant polarization and coercive field were 7.0 μC/cm² and 97 kV/cm at 10 V, respectively. These results suggest a possible application of PZT films in micro- or nano-electromechanical systems.     

The incorporation of SiO2 nanoparticles in poly(p-phenylenevinylene)(PPV) for PPV/SiO2 nanocomposite

The changes in surface morphology and current-voltage characteristics of poly(p-phenylenevinylene)(PPV) thin film has been studied by varying the amount of incorporated SiO₂ nanoparticles. The electronic structure of carbon atom in PPV and PPV/SiO₂ nanocomposite films was studied by using near-edge X-ray absorption fine structure. The surface morphology of PPV/SiO₂ nanocomposite film was found to be greatly dependent on the amount of incorporated SiO₂ nanoparticles. The current–voltage behavior of PPV/SiO₂ nanocomposite film was mainly dependent on the surface morphology of the film. The excess content of SiO₂ nanoparticles in PPV/SiO₂ nanocomposite film was revealed to induce an agglomeration of SiO₂ nanoparticles where blocking of electronic conduction happens.     

Electromagnetic shielder compatible ZnO transparent conducting oxides hybridized with various sizes of Ag metal nanoparticles

In this paper, the effect of different sizes of Ag-nanoparticles dispersed in ZnO matrix using sol–gel method has been focused. Low-temperature crystallized ZnO thin films was achieved by sol–gel process, using zinc acetate dihydrate and 2-methoxyethanol as starting precursor and solvent, respectively. Various sizes of Ag-nanoparticles could be prepared by the spontaneous reduction method with changing the preparation temperatures and mole concentrations of Ag 2-ethylhexanoate in dimethyl sulfoxide solvent. The crystallographic structure of the Ag–ZnO hybrid film was analyzed by X-ray diffraction. Ag-nanoparticle size and optical property of Ag–ZnO hybrid films were measured by UV–vis spectrophotometer.     

Study of PEDOT:PSS-SnO2 nanocomposite film as an anode for polymer electronics

Poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate)(PEDOT:PSS) is a candidate material for applications in molecular electronics, such as organic field effect devices, organic photovoltaics, and organic light emitting devices. The properties of 3.5–4.0 nm sized SnO₂ nanoparticles doped PEDOT:PSS films were investigated for anode application. Sheet resistance was decreased and rms roughness was slightly increased with the incorporation of SnO₂ nanoparticles. However, the connectivity of conducting grains was improved by the plasticizing effect of surface –OH groups of SnO₂ nanoparticle. Using photoemission spectroscopy and near edge X-ray absorption fine structure (NEXAFS), the electronic structure of the films is studied comparatively on the C 1s NEXAFS, secondary electron emission cut off, and valence band spectra. The start of electron emission retarded and valence band maximum was increased in the PEDOT:PSS-SnO₂ nanocomposite films. These changes in the electronic structure resulted from emitted electron screening of core-hole in the PEDOT:PSS energy band and electron donation of SnO₂ nanoparticles.     

Thermoelectric Properties of Nb-Doped Ordered Mesoporous TiO<Subscript>2</Subscript>

Mesoporous materials have pores with diameters between 2 nm and 50 nm, the presence of which generally decreases the thermal conductivity of the material. By incorporating mesoporous structures into thermoelectric materials, the thermoelectric properties of these materials can be improved. Although TiO₂ is an ordinary insulator, reduced TiO₂ shows better electrical conductivity and is therefore a potential thermoelectric material. Furthermore, the addition of a dopant to TiO₂ can improve its electrical conductivity. We hypothesized that, by doping ordered mesoporous TiO₂ films with niobium, we would be able to minimize the thermal conductivity and maximize the electrical conductivity. To investigate the effects of Nb doping and a mesoporous structure on the thermoelectric characteristics of TiO₂ films, Nb-doped mesoporous films were investigated using x-ray diffraction, ellipsometry, four-point probe measurements, and thermal conductivity analysis. We found that Nb doping of ordered mesoporous TiO₂ films improved their thermoelectric properties.     

Effect of PrBa2Cu3O7?x buffer layer thickness on the properties of YBa2Cu3O7?x thin films grown on sapphire by laser ablation

Superconducting YBa₂Cu₃O_7–x (YBCO) thin films were deposited onr-plane A1₂O₃ substrates with PrBa₂Cu₃O_7–x (PBCO) buffer layer by XeCl excimer laser ablation. The thickness of PBCO buffer layer was systematically changed to investigate the superconducting properties of YBCO thin films on sapphire. The structure and surface morphology of the films were characterized by X-ray diffraction and scanning electron microscopy (SEM). Superconducting transition temperatures were varied depending on the buffer layer thickness. Interdiffusion between laser-ablated YBCO thin films and A1₂O₃ substrates had been studied by Auger electron spectroscopy (AES). The results of this study show that diffusion does not occur between the YBCO thin film and the substrate even with 20 Å thick PBCO buffer layer.