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Recently, methane has been demonstrated as an effective n -type dopant for ZnO thin films deposited using the RF-magnetron sputtering method. It was shown that the major electrical doping effect of methane is caused by hydrogen released during methane decomposition. This work investigates the origin of the observed increase in conductivity of methane-doped ZnO films with the increase in thickness. The study is aimed at describing the nature of this thickness-dependent effect through a detailed analysis of the thickness-dependent morphology and crystalline structure. A combination of structural, electrical, and optical characterization revealed a transition from fine-grained films with a random orientation at early stages to partially (002)-textured films with columnar grains at later stages of growth. It is demonstrated that grain/sub-grain boundaries increase the electrical conductivity and that the contribution of such buried inner boundaries increases with increasing thickness. It is proposed that hydrogen diffuses along the grain and sub-grain boundaries during growth, leading to continuous doping of the buried interfaces. This hydrogen diffusion mechanism results in an apparent 'additional doping' of thicker films. The results provide new insights into the thickness-dependent conductivity of doped polycrystalline ZnO films mediated by hydrogen diffusion along internal interfaces. [ABSTRACT FROM AUTHOR]

The results of electrical and photoelectrical characterization of the interface and bulk properties of n+-ZnO/n-Si and poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/n+-ZnO/n-Si heterostructures are presented. It was found that the PEDOT:PSS layer deposited on the surface of zinc oxide increases the potential barrier at the ZnO/Si interface, leading to higher band bending in the silicon, which is important for solar cell applications. The recombination rate at the interface decreases because of the creation of an inversion layer in the silicon under operational conditions. The increase of the potential barrier in PEDOT:PSS/n+-ZnO/n-Si heterostructures results in the increase of the open-circuit voltage by 54–180%. The external quantum efficiency in PEDOT:PSS/n+-ZnO/n-Si heterostructures increases by 100% at 450 nm. [ABSTRACT FROM AUTHOR]

The effect of rare-earth clustering in dielectric media on the electroluminescence (EL) intensity, the charge trapping and the EL quenching was investigated using the example of Tb and Eu-implanted SiO2 layers. It was shown that the increase in the REOX cluster size induced by an increase in the furnace annealing temperature resulted in an increase in the concentration of electron traps with capture cross sections from 2×10-15 to 2×10-18 cm2. This is probably associated with an increase in the concentration of oxygen deficiency centers as well as with strained and dangling bonds in the SiO2 matrix which leads to an enhanced scattering of hot electrons and a decrease in the excitation cross section of the main EL lines of RE3+ ions. For the main EL lines of Tb3+ and Eu3+ ions the relation of the EL quenching to negative and positive charge generation in the SiO2 was considered. It was demonstrated that in case of REOX nanoclusters with small sizes (up to 5 nm) the EL quenching process can mainly be explained by a defect shell model which suggests the formation of negatively charged defect shells around the nanoclusters leading to a Coulomb repulsion of hot electrons and a suppression of the RE3+ excitation. At high levels of the injected charge (more than 2×1020 e/cm2) a second stage of the EL quenching was observed which was contributed to a positive charge accumulation in the SiO2 at a distance beyond the tunneling distance from the SiO2[Single_Bond]Si interface. In case of Eu-implanted SiO2 the quenching of the main EL line of Eu3+ is mostly correlated with positive charge trapping in the bulk of the dielectric. A model of EL quenching of the main Eu3+ line is proposed. [ABSTRACT FROM AUTHOR]

Exploiting CVD technique for carbon deposition from C2H2+H2+N2 mixture, a graphene-like film synthesized directly on SiO2 surface of SiO2-Si structure was obtained. The graphene-like film was grown under thin Ni layer that is easy exfoliated from graphene-SiO2-Si structure. Surface of the film was sufficiently smooth and reveals no winkles and holes; it has a good homogeneity and perfect adhesion to SiO2 layer. Studying the micro-Raman spectra showed a graphene-like structure of the film; using atomic force microscopic technique, the thickness of film was determined (0.6 nm). Using spectroscopic ellipsometry and simple Cauchy model enabled us to estimate optical parameters of this graphene-like film. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy and micro-Raman spectroscopy were applied for analysis of single graphene layer. Despite that Raman spectra showed the high quality of studied layers (ratio of intensities of the D and G peaks ID/ IG is better than <0.01), two semicircles on the Nyquist curve of the Ni-graphene-Ni structure suggest the existence of inhomogeneous regions. Exposure in ethanol and acetone vapors by different degrees affects the reactive and active resistance of graphene film. Moreover, the dynamic response behavior of impedance differs in the vapor of ethanol, acetone, and phenol. It ensures that impedance spectroscopy of graphene is a useful tool for detection of different gases. [ABSTRACT FROM AUTHOR]

In this paper, we explore the electrophysical and electroluminescence (EL) properties of thermally grown 350 nm thick SiO2 layers co-implanted with Si+ and C+ ions. The implanting fluencies were chosen in such a way that the peak concentration of excess Si and C of 5-10 at.% were achieved. Effect of hydrogen plasma treatment on electroluminescence and durability of SiO2 (Si,C) - Si-system is studied. Combined measurements of charge trapping and EL intensity as a function of the injected charge and current have been carried out with the aim of clarifying the mechanisms of electroluminescence. EL was demonstrated to have defect-related nature. Cross-sections of both electron traps and hole traps were determined. EL quenching at great levels of injected charge is associated with strong negative charge capture, following capture of positive charge leading to electrical breakdown of SiO2 structures. [ABSTRACT FROM AUTHOR]