Organic field-effect transistors (OFETs) with a pentacene/TPBi/pentacene sandwich structure were realized and characterized. Compared with the single pentacene layer transistors, these devices not only showed an obvious reduction of threshold voltage but also presented a significant enhancement of field-effect mobilities. The performance improvement was attributed to the high conductivity of the sandwich active layers, which were analyzed by applying the transfer line method. Meanwhile, the morphologies of pentacene films with and without the TPBi interlayer were characterized by atomic force microscopy, the smoother surface of the upper pentacene film was observed in pentacene/TPBi/pentacene. Moreover, by applying X-ray diffraction, a higher-order growth phase of the pentacene thin film was observed.

A high-precision printing and patterning carbon nanotube (CNT) cathode was prepared using the screen-printing method. Selective plasma etchings were introduced to improve field emission properties of the CNT cathode through the reactive ion etching (RIE) system. The field emission characteristics and mechanism of the cathode after etching treatment were studied. It was found that the reactive ion etching could effectively expose plentiful CNTs inside the cathode and protrude them from the surface. Moreover, with the increase of RIE operation pressure, CNT cathode field emission behavior changed from metal-insulation medium-vacuum (MIV) to a classical metallic-microprotrusion (MM) structure field emission model. The results showed that only the cathode with appropriate RIE operation pressure etching has a low operation field and a high emission current density.

In this work, pressure-induced phase transition and elastic properties of BeS II–VI compounds semiconductor are investigated by first-principle method. Phase transition of BeS from direct gap semiconductor phase (ZB) to indirect-gap semiconductor phase (RS) occurs at 51.45 GPa accompanied by 11.23% volume collapse. Phase transition is due to S atom’s weakened electron attraction. Once the shared charge center of shared electron reaches 0.58 of the distance between Be and S, will the phase be unstable. Moreover, the broadened anti-bonding state and reduced bonding state display that tetrahedral Be-S covalent bonds are weakened. And then, the ZB structure is destroyed and rebuilt to RS structure. Furthermore, changes of covalent bond would cause evident variation of elastic constants and shears on {1 0 0} and {1 1 0} planes.

The reverse leakage current mechanisms of Schottky diodes prepared using liquid gallium on as-grown and cleaved tungsten diselenide surfaces were investigated by current-voltage method for the first time. The major leakage mechanism has been identified as tunneling current along with a small contribution of thermionic emission current. The leakage tunneling current is found to be predominant in uncleaved diode compared to that in cleaved one. This is related to the magnitude of interface state density and interfacial inhomogeneities. The inhomogeneous nature of the interface of the fabricated diodes is ascribed to be the reason behind its soft reverse characteristics.

The AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) sample has been grown by MOCVD on (0 0 0 1) sapphire substrate. The structure features a 7 nm In0.046Ga0.954N interlayer determined by Rutherford backscattering (RBS). Since the polarization field in the InGaN interlayer is opposite to it in the AlGaN layer, an additional potential barrier is introduced between the two-dimensional electron gas (2DEG) channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. The GaN layers between the AlGaN layer and InGaN interlayer are divided into two layers consisting of GaN channel layer which provides high mobility 2DEG grown at 1070 °C and GaN spacer layer grown at the same temperature as InGaN interlayer (800 °C) to prevent indium diffusion. RBS measurement confirms that the 3 nm GaN spacer layer isolates the InGaN interlayer well and free from diffusion. Hall measurement has been performed, the mobility as high as 1552 cm2/V s at room temperature is obtained and the sheet carrier density is 1.55 × 1013 cm−2. The average sheet resistance is 331 Ω/sq, respectively. The mobility obtained in this paper is about 20% higher than similar structures reported.

Glassy samples of Se78−xTe20Sn2Pbx (0 ≤ x ≤ 6) system are prepared by melt quenching method. For non-isothermal study of crystallization kinetics, DSC scans have been taken at the heating rates 5, 10, 15 and 20 K/min in non-isothermal mode. Activation energy of crystallization (Ec) has been calculated using Kissinger method, Matusita-Sakka method and Augis-Bennett method. Various kinetic parameters of crystallization kinetics like peak crystallization temperature (Tc), Rate constants (K) and order parameter (n) are determined using these DSC scans. Thermodynamic parameters such as crystallization enthalpy (ΔHc) and entropy change during the crystallization (ΔS) are also evaluated. Results are discussed using chemical bond approach.

Schottky barrier diodes based on a composite of polyaniline with titanium oxide (TiO2) were fabricated using aluminum as a Schottky contact and gold as an ohmic contact. The observed current-voltage characteristics can be satisfactorily fitted using the modified Schottky equation. The current-voltage characteristics were studied to explain the rectification generation of the diode. The diode shows non-ideal I-V behavior with an ideality factor greater than unity. The conduction mechanism was determined and a Schottky-type conduction process was defined. The diode parameters such as saturation current density and ideality factor were found to be 9.28 x 10−4 A/cm2 and 6.33, respectively.

The authors investigated the effects of annealing in Ar atmosphere at different temperatures (350–1100 °C) on the densification and leakage current characteristics of thermally oxidized SiO2 films on n-type 4H-SiC. A strong correlation between densification improvement and leakage current reduction was observed. Densification of the SiO2 films, which were characterized by spectroscopic ellipsometry, Fouriertransform infrared spectroscopy and atomic force microscopy, can be significantly improved after annealing at moderate temperature (600 °C). The leakage current is decreased by two orders of magnitude of the SiO2 thin film after annealing at 600 °C. Based on the studies, SiO2 film of the highest quality can be obtained after annealing at 600 °C. Improvements in the quality of the SiO2 thin films after annealing at 600 °C may be explained by the consumption and formation of carbon-related and oxygen-related defects during annealing.

Transparent conducting aluminum-doped and undoped ZnO thin films have been deposited by direct current (DC) sputtering technique from ZnO target onto glass substrate at room temperature and 400 °C. X-ray diffraction analysis shows that all films have a preferential growth along the c-axis of the hexagonal structure. The average grain size increases with the increasing deposition temperature and the doping of thin films. Analysis with AFM shows an improvement of the surface with the doping of thin films and deposition temperature. The root main square (RMS) surface roughness increases with deposition temperature. Al-doped ZnO (AZO) thin films have a lower electrical resistivity than that of ZnO thin films. 1/f noise measurement shows that ZnO thin film is more homogeneous than that of AZO.

α-Bi2O3 thin films were deposited on different substrates by atomic layer deposition method. The results of X-ray diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscope correspond to α-Bi2O3. The Fourier transform infrared spectroscopy analyses indicate that the reaction is rather complete during the deposition. Optical properties of the films have been investigated using ultraviolet-infrared transmittance spectra in the temperature range of 8–300 K. It is found that the band gap Eg decreases from 3.12 to 3.03 eV with the temperature. The parameters αB and ΘB of the Bose-Einstein model are 69.3 meV and 293.9 K, respectively. The band narrowing coefficient dEg/dT is −0.435 meV/K at room temperature. The present results can be considerable for future application of Bi2O3-based electro-optic and wide temperature range optoelectronic devices.

Cu0.62Zn0.38 foil was subjected to surface mechanical attrition treatment (SMAT) processing first. Growth behavior of ZnO nanostructure on the SMAT Cu0.62Zn0.38 surface during thermal oxidation was investigated in this paper. The original and SMAT Cu0.62Zn0.38 foils were thermally oxidized at 400 ~ 700 °C under various gaseous environments, including nitrogen and mixture of N2-O2 at a pressure of 1 atm. for 3 h. The oxidized specimens were characterized with a scanning electron microscope, an X-ray diffractometer and a transmission electron microscope. It is found that nanosheets are easily formed on the SMAT specimen surface. The favorable formation of nanosheets relates to twin lamellae structure of Cu0.62Zn0.38 formed during SMAT processing.

Pulsed thermography has been proven to be a fast and effective method to detect fluid ingress in aircraft honeycomb structure; however, water and hydraulic oil may have similar appearance in the thermal image sequence. It is meaningful to identify what kind of liquid ingress it is for aircraft maintenance. In this study, honeycomb specimens with glass fiber and aluminum skin are injected different kinds of liquids: water and oil. Pulsed thermography is adopted; a recognition method is proposed to first get the reference curve by linear fitting the beginning of the logarithmic curve, and then an algorithm based on the thermal contrast between liquid and reference is used to recognize what kind of fluid it is by calculating their thermal properties. It is verified with the results of theory and the finite element simulation.

The presence of metallic particles has been recognized as a dangerous threat in gas-insulated substation (GIS). Such particles are initially free and move toward higher electric field regions such as triple junction i.e., spacer-electrode-gas interface. However, once these particles reach the spacer surface, they adhere to the spacer easily due to electrostatic image forces. From insulation point of view, the triple junction is the weakest point in GIS. The presence of such metallic particles on the spacer surface deteriorates the insulation strength. Thus, in order to improve the reliability of GIS, it is important to identify the size and the position of the particle adhering to the insulating spacer surface. One of the most promising methods to carry out such identification is by recognizing the partial discharges (PDs) provoked by such particles. This paper is aimed to discuss the particle size and position estimation by using the PD patterns and statistical analysis. The PD patterns were acquired using IEC 60270 method. Measurements were made to determine various PD signals caused by particle of different sizes at different locations on the spacer surface. The acquired PD patterns were characterized by a number of statistical parameters. The results show that the implemented technique could be used to distinguish between various particle sizes and positions at different SF6 pressures with a fairly high accuracy.

We are interested in modeling the interaction between light and biological tissue from the Monte Carlo method which is an approach used to solve modeling problems in different physical domains. Through the Monte Carlo approach we are going to try to interpret the spectral response absorption, reflectance, transmittance of normal human tissue under its three dominant tints in the visible range (350–700) nm. Then we will focus on the spectral response of the human tissue with varicosities in order to determinate the optimal conditions of operating the semiconductor laser for esthetic aim.