Polycrystalline Ba8Ga16MgxGe30−x compounds were synthesized by combining solid-state reaction with spark plasma sintering (SPS) method. The structural and electronic properties of Mg-substituted Ge type-I clathrate phase Ba8Ga16MgxGe30−x (x = 1, 2, 3, 4) were investigated experimentally and theoretically. Theoretically structural and electronic properties of Ba8Ga16MgxGe30−x were calculated by first-principles method based on the density-functional theory. The results indicate a strong preference for the occupation of the 6c sites by Mg. It is found that Mg substitution for Ge can lower the melting points and bulk modulus of this system. The formation energies and the binding energies decrease with increasing Mg content, suggesting that the Mg-doped Ba8Ga16Ge30 clathrates are stable in a limited range of composition. The calculated results show that these alloys are all indirect gap semiconductors and the values of band gap increase with the increase of Mg content. All specimens exhibit the behavior of the p-type conduction, which is originated from the presence of a shallow acceptor energy level. The electrical conductivity and the room-temperature carrier mobility decrease with increasing Mg content, while the room-temperature carrier concentration increases with increasing Mg content.

We investigated the electrical conduction and resistance switching mechanisms of TiOx thin films grown on three kinds of bottom electrode at room temperature (an inert Pt, an active Ti and fluorine tin oxide FTO electrodes). The bottom electrode materials strongly affect the I-V characteristics and switching parameters. The I-V characteristic is explained through the presence of interface states in the metal electrode devices (Pt and Ti) and the work function in the metal oxide device (FTO). The Pt device has the smallest VSET and largest switching ratio, while the Ti device shows the largest VSET and smallest switching ratio. XPS data shows non-lattice oxygen in TiOx films. Therefore, the proposed bipolar resistance switching arises from formation and rupture of filament paths, generated by the movement of oxygen vacancies. All devices depict the same electrical conductions, trap-controlled space-charge-limited, FN tunneling and Ohmic conductions for a high resistance state and a low resistance state, respectively. In this study, the rarely reported FN tunneling conduction in published TiOx-based ReRAM device was found, which can be attributed to an influence of the bottom electrode on the electronic distribution in devices.

This letter focuses on the evolution under illumination of the minority carrier lifetime and conversion efficiency of p-type gallium (Ga) co-doped solar grade multicrystalline silicon wafers and solar cells. We present experimental data regarding the concentration of boron-oxygen (B-O) defects in this silicon when subjected to illumination, and the concentration was found to depend on [B]-[P] rather than [B] or the net doping p0([B] + [Ga] – [P]). This result implies that the compensated B is unable to form the B-O defect. Minority carrier lifetime and EQE measurements at different degradation states indicate that the B-O defect and Fe-acceptor pairs are the two key centers contributed to LID in this material.

By combining the techniques of dielectric relaxation spectroscopy (DRS), measurement of both ac and dc conductivities, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), we have explored the effect of electrical ageing on poly (methyl methacrylate) (PMMA) films at temperature between 0 °C and 80 °C in the frequency range of 1 Hz–107 Hz. These results are discussed and correlated to FTIR and SEM observations.

Al/MoOx nanoenergetic multilayer films (nEMFs) were deposited by magnetron deposition method. The samples with bilayer thicknesses of 75 nm and 225 nm were prepared, respectively, and the total thickness is 3 μm. The as-deposited Al/MoOx nEMFs were characterized with varied analytical techniques, including SEM, XRD, XPS and DSC. Results show that the MoOx films are amorphous, and are composed of MoO3, Mo2O5 and MoO2. The values of heat release in samples are 3524 J/g and 2508 J/g, respectively, and the final products are Mo, MoO2, and Al2O3. Finally, the reaction paths and reaction kinetics of Al/MoOx exothermic reactions were discussed.

A Cu2ZnSnSe4 (CZTSe) thin film fabricated by selenization of stacked pure metal precursors through e-beam evaporation on Mo-coated soda lime glass substrates worked as thin film solar cell absorber. The selenization was carried out under element Se vapor circumstance at 570 °C for 20 min. The absorber went through chemical bath CdS deposition, sputtered ZnO, ITO and Al electrodes to become a solar cell. Unlike previous works, only simple three-layer metal precursors without any compound were used as evaporation sources. The synthesized CZTSe absorber layer phase was identified by X-ray diffraction. The solar cells were measured by AAA class solar simulator. The absorber layer thickness was measured by scanning electron microscope (SEM). Energy dispersive spectrometer (EDS) was also used for checking metal ratios in the absorber layer. The best efficiency was 4.2%. In this work, we found that there were voids in absorber film bottom. The Cu-top precursors will lead to larger grains, flatter surfaces and larger voids than Sn-top precursors. The Cu-top precursor may also contribute to better selenization which may help prevent Zn loss but cause Sn loss. Finally, this work also showed Cu-poor and Zn-rich will improve conversion efficiency.

The aim of our work is to obtain nano-structured cadmium oxide (CdO) thin films by sol-gel spin coating method and to investigate the effects of cadmium sulfide quantum dots (CdS QDs) doping on the structural modification and surface morphology evolution. X-ray diffraction (XRD) results show that the intensities of the peaks of the crystalline phase increase with the increase in CdS QDs concentrations. From scanning electron microscopy (SEM) images, the distinct variations in the morphology of the thin films were also observed. In addition, the evolution of surface morphology, roughness and granularity has been characterized by atomic force microscopy (AFM). Moreover, we have performed the optical characteristics of the thin films such as transparency, energy band gap and Urbach tail. The optical band gap of the thin films increases from 2.23 to 2.51 eV with the increase in CdS QDs concentrations due to the Moss–Burstein effect. The enhanced values of the transparency, energy band gap and crystallity indicate that addition of CdS QDs can be used to modify the optical, structural and morphological properties of CdO thin films.

Nanocrystalline Cd0.8Zn0.2S thin films were prepared by chemical-bath-deposited method and the effect of time on the properties of Cd0.8Zn0.2S thin films was studied. The X-ray diffraction (XRD) patterns show that the synthesized films have a cubical (zinc blende) phase. The mean crystallite size and the internal lattice strain were calculated. Atomic force microscopy (AFM) studies showed that the surface roughness of the films increase with increasing thickness. The optical constants of Cd0.8Zn0.2S films were determined and the analysis of the result showed that Cd0.8Zn0.2S thin films have direct transition and the values of energy gap indicates quantum confinement effect.

The mechanically activated self-propagating high-temperature synthesis (MASHS) technique and the mechanically activated annealing process (M2AP) were used to produce NiAl intermetallic compound. Rietveld analysis of X-ray diffraction data was used to characterize the mechanically activated powders, MASHS and M2AP end-products. Two-phase (B2+L12) nickel aluminide intermetallic compounds were synthesized by the mechanically activated volume combustion synthesis (MASHS). A single phase B2 NiAl was formed when mechanically activated annealing process (M2AP) was performed. Starting from a mixture of elemental pure powders, both M2AP and MASHS milling processes lead to nanostructured powders. Structural analysis deduced from the Rietveld refinement of X-ray diffraction patterns of NiAl compounds synthesized by SHS after a milling of 6 h show the formation of β-NiAl phase with a cell parameter a = (0.2885 ± 1.2618 × 10−4) nm. The average crystallite size is D = (44.6421 ± 2.4263) nm and the microstrains values are close to those of metallic alloys τ = (0.2142 ± 1.6186 × 10−2)%. Finally, scanning electron microscopy (SEM) was carried out to characterize the microstructure of end-products.

The objective of this study was to evaluate in situ structural and thermal changes of dental restorative materials at periodical time intervals. The commercial materials included zinc oxide eugenol (ZOE), zinc phosphate type I (ZnPO4), glass ionomer cement type II (GIC) and resin-based nano-omposite (Filtek Z350 XT). These materials were processed according to manufacturer’s instructions. For the structural analysis Fourier transform infrared spectroscopy (FTIR) was used at high resolution. TGA was used to evaluate thermal weight-loss. The FTIR spectra were collected at periodic time intervals. FTIR spectra showed that with time passing all materials exhibited an increase in peak intensities and a new appearance of shoulders and shifting of peaks for example, ZnPO4 (P-O), ZOE (C═O, C═N, C-O-C), GIC (COO–, C-H, Si-OH), composites (C═O, C═C, C═N, C-N-H). The peaks were replaced by bands and these bands became broader with time interval. Composites showed a degree of conversion and new peaks corresponded to the cross-linking of polymer composites. TGA analysis showed that significant changes in weight loss of set materials were observed after 24 h, where ZOE showed continuous changes in thermal degradation. The spectral changes and thermal degradation with time interval elucidated in situ setting behaviour and understanding of their bonding compatibility with tooth structure and change in relation to time.

In this article, we report on the design and construction of an in situ break-junction sample holder for transmission electron microscopy. The holder is based on the differential-screw mechanism. The technical details and a comprehensive consideration to all relevant critical issues surrounding the instrumentation procedure are presented. An application of the newly developed instrument is demonstrated using the example of a micro-scale gold wire. We also provide a detailed discussion on the challenges involved and the pitfalls to avoid in developing similar in situ holders.

The electrical contact resistance of a vertical binary contact between stainless steel balls with a low mechanical load was investigated. Using a statistical approach, we measured the voltage at which the dielectric breakdown occurs within a thin surface oxide layer and the distribution of the contact resistance. Electrical load-bearing conduction through a thin insulating layer was found to occur through two possible sequential processes. In both cases, once a conduction path is formed, the melting of bridges as in conventional contact theory is involved. This suggests that conduction through an oxide layer with a low mechanical load depends mainly on breakdown-induced bridges. Furthermore, the distribution of such path’s resistance shows the log-normal distribution with a long tail toward high resistance.

For liquid droplets of sub-micrometer dimensions, the study of wetting properties (quantified by contact angle, disjoining pressure, spreading coefficient, etc.) is possible using the relatively new technique known as scanning polarization force microscopy (SPFM). This non-contact scanning probe microscopy technique was successfully implemented in our laboratory in order to study the wetting properties of glycerol and sulfuric acid on the surface of highly oriented pyrolytic graphite (HOPG) and glycerol on aluminum film deposited on mica. An AC polarization bias of 3 V at 3 kHz frequency was applied between a conductive atomic force microscope tip and the substrate. The resulting polarization force was measured with high accuracy, allowing non-contact topography profile measurements of liquid micro- and nanodroplets. The dependence of the contact angle on droplet height was determined in order to calculate the values of the spreading coefficient and the disjoining pressure between the liquid and substrates. The calculated potential energies give disjoining pressure values of ∼0.4 atm for glycerol on HOPG, ∼0.47 atm for glycerol on aluminum and ∼13 atm for H2SO4 on HOPG. In the case of H2SO4 on HOPG the strength of the force appears to be thirty times bigger than that for glycerol on HOPG and aluminum.

We study the solutions and bifurcations of the Jeffcott rotor with a rubbing effect. The model of horizontal rotor possesses such nonlinear effects as inertia, dry friction, and contact loss between the rotor and stator. By the exceeding of the rotor-stator radius clearance, the rotor can penetrate into the limiting rubbers with a fractional power in the restore force. The system response is analyzed by a bifurcation diagram. The specific cases are additionally clarified by means standard methods and quantified by the test 0-1 which is sensitive to chaotic behaviour.