Among diamond-based devices, the Schottky barrier diode (SBD) shows significant promise, achieving high breakdown voltages (9.5 MV center dot cm-1) center dot cm- 1 ) and reduced serial resistance (1 ohm ) through structural advancements. The performance of SBDs depends on the interface between the Schottky contact, surface termination, and diamond. Studies have highlighted the impact of interface configuration on Schottky barrier height (SBH), particularly for hydrogen (H) and oxygen (O)-terminated diamonds. H-terminated surfaces exhibit negative electron affinity (NEA), whereas O-terminated surfaces show positive electron affinity (PEA). This surface behaviour has a strong impact on electron affinity, surface conductivity, work function, and the SBH which are critical for device performance. To know more about the metal-surface-diamond interface, tungsten (W) and platinum (Pt) deposited by electron beam-induced deposition (EBID), in a FIB dual beam, were employed as Schottky contacts on H and O-terminated diamond. The resulting structure has a pseudo vertical configuration with a back ohmic contact on a p ++ boron-doped layer. The current-voltage (I-V) and X-ray photoelectron spectroscopy (XPS) measurements resulted in a SBH of 1.69 eV for Wand 1.76 eV for Pt, with an ideal factor (n) n ) of 1.22 and 1.18, respectively. These n values demonstrated a chemical reactivity between metal-surface-diamond. Finally, a combination of two techniques for the SBH estimation is discussed.

A new type of cermet coating, with potential use as low-cost solar thermal absorber has been developed using spray pyrolysis. It consists of crystalline silver nanoparticles embedded in amorphous zirconia and was obtained by spraying aqueous precursor solutions onto aluminized carbon steel sheets at 200 degrees C. It was found that simultaneous spraying of silver and zirconium solutions led to a considerable reduction, in the nanometer range, of silver particle size distribution. Hence, we comparatively studied the cermet coatings obtained by A) sequentially or B) simultaneously spraying silver and zirconium solutions. For the latter case, a zirconia anti-reflection layer was sprayed on top. Both coating systems were studied by SEM, AFM, HRTEM/EDS and UV-VIS-IR spectroscopy with respect to silver particle size distribution. Optical parameters like solar absorptance (AM 1.5) and thermal emittance (373 K) were determined from absolute hemispherical reflectance, and a per-formance coefficient was calculated in order to evaluate the solar selectivity of the coatings. The comparison showed that smaller silver particles lead to an increase in solar selectivity and that the size reduction is due to an effective encapsulation by zirconia of the silver particles when spraying silver and zirconium precursors simultaneously. Furthermore, HRTEM confirmed the metallic and crystalline state of the silver nanoparticles embedded in amorphous zirconia.

Tungsten carbide (WC) contacts deposited on oxygenated diamond surface have shown great importance in the field of diamond-based Schottky diodes. In previous works, high temperature stability up to 600 K, an ideality factor close to 1 with a Schottky Barrier Height (SBH) of similar to 1.5 eV have been demonstrated by electrical measurements. Annealing at higher temperature lead to the deterioration of the contact behaviour in terms of SBH and ideality factor. The reaction between deposited material and diamond or the desorption of oxygen at the interface has been tentatively linked to this phenomenon. In this work, the composition of the WC/O-diamond interfaces annealed at 600 K are analysed by X-ray photoelectron spectroscopy (XPS) depth profile with low energy Ar + ion sputtering for the first time. The microstructure of the contact is analysed by high-resolution transmission electron microscopy (HR-TEM). The formation of a metastable cubic-WC phase at the interface and the presence of interface oxygen is evidenced. The SBH of the WC/O-diamond contact is estimated by XPS at 1.6 +/- 0.2 eV in agreement with I/V measurements.

gamma-Alumina is a promising candidate for fabricating the gate of the diamond metal oxide semiconductor field effect transistor based on oxygen termination due to its high bandgap of 6.7 eV and high static dielectric constant of 9. Besides these properties, having a sufficient barrier for holes is mandatory to avoid carriers leakage through the gate. However, the band offset of the diamond/alumina heterojunction can be affected by the alumina crystallinity and interface bonds, which depend on multiple factors such as deposition and annealing temperature or diamond surface treatment prior to deposition. In this work, the heterojunction of atomic layer deposited alumina and (1 0 0) p-diamond is studied using X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy studies reveal that the deposited alumina layer is 35 nm thick and present the gamma phase. The valence band offset between diamond and gamma-alumina is evaluated on a single sample with a new methodology based on an ion etching XPS depth profile. The obtained value for the valence band offset of diamond and gamma-alumina is 3.4 eV.

A limited series of uniform composition CdSeTe alloys and a CdMgTe alloy were grown via molecular beam epitaxy and measured with x-ray photoemission spectroscopy to determine valence band offsets (VBO) with CdTe. We present an alternative to the Kraut method for VBO determination in ternary alloy systems, which does not require determination of the valence band maxima, often a significant source of error in VBO determination. VBOs determined using two different etching sources agreed well with temperature dependent current-voltage data as well as with recent theoretical work, and a linear fit of the VBO data presented here predicts a VBO between CdTe/CdSe a factor two to three times smaller than previously reported.

C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75 x 10(3) Omega(-1) cm(-1)) were obtained for GIZO films with In/Zn ratio >= 1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85-0.90 for the GIZO films.

CuS and ZrO2/CuS thin films have been deposited at 200 °C in ambient atmosphere by spray pyrolysis onto stainless steel S304 and aluminum AA1050 sheets in order to be used as prospective solar absorbers for thermal energy harvesting. Zirconia has been deposited as a top layer working as an antireflection coating increasing the solar absorption and protecting the underlying copper sulfide layer, which works as the solar light absorbing material. Solar selectivity of the samples was evaluated measuring the total hemispherical reflectivity in the ultraviolet‐visible infrared range and calculating solar absorptance and thermal emittance. The solar selectivity was optimized by tuning the film thickness of the coating stack. X‐ray diffraction, SEM and X‐ray photoelectron spectroscopy analyses have been used to proof crystal phase, coverage, film thickness, and surface contamination of optimized samples, revealing that the copper sulfide film is CuS covellite and the optimized film thicknesses are in the range of 50 nm for the ZrO2 top layer and 140 nm for the CuS layer. Copyright © 2016 John Wiley & Sons, Ltd.

Optical properties of ZnO-CdTe electrochemically prepared on a core-shell nanostructure (NS) were studied. Numerical simulations based on effective medium approximation give higher absorption than ZnO-CdS samples and a sensitive dependence on CdTe content. The absorption edges for deep black samples found by transmittance (T(λ)) and diffuse reflectance (Rdiff(λ)) measurements were at 1.33eV and 1.55eV, respectively. A split-off band edge was also found by Rdiff(λ) at ∼2.5eV. The red shift observed in T(λ), previously observed in ZnO-CdS, and may confirm the enhancement of sub-bandgap absorption due to the NS nature of samples.

The effects of the CuxS stoichiometry, 1≤x≤2, on the optical, electrical, and solar thermal properties of copper sulphide thin films, which have been deposited by chemical spray pyrolysis onto glass, have been studied. A full 32 factorial design has been applied to determine the effects of the substrate temperature and deposition time on the electrical and optical properties of the sulphide thin films. The sulphide film properties are strongly related to the CuxS stoichiometry, and this relationship is dependent on the substrate temperature. Therefore, the electrical resistivity of the films varies in the range of 10−4Ωcm to 10−1Ωcm as × increases from 1 to 2. The relationship between the stoichiometry and conductivity has been established with infrared reflectance, solar absorptance and thermal emittance. The optical constants have been obtained using optical models (Classical Drude).

Due to its potential use as selective surface in solar thermal absorbers, cobalt has been electrodeposited into porous alumina obtained by anodization of aluminum sheet. A 32 factorial design has been applied to find out the effects of the electrochemical variables, electrodeposition time and applied cell potential, on optical properties and to optimize the solar energy selectivity of the obtained surfaces. Effective-medium optical models have been used to reproduce their reflectance spectra and to estimate the thickness of the different layers that form the selective surface.

The optical properties of bare ZnO nanorods and sensitized nanostructures, with Cu2O and CdS, are comparatively studied. These nanostructures may show improved photovoltaic performance compared to planar ones. ZnO nanorod arrays were grown by electrochemical deposition. In a second step, Cu2O was also deposited electrochemically, while for CdS successive ion layer adsorption and reaction techniques were used. The experimental results are interpreted using numerical simulation based on an effective medium theory. Bare nanorod samples reveal mainly the direct ultraviolet absorption edge of ZnO (between 3.25 and 3.30 eV) and a monotonically increasing transmittance from the ultraviolet into the red. This increase is originated in light scattering, probably by the nanometric structure of the samples. For the sensitized samples reduced transmittance in the solar spectrum region is observed and several well-defined absorption edges appear. Spectral absorption edge shifts are interpreted comparing with numerical simulations. For CdS the measured shifts are larger than the ones obtained from numerical simulations. The difference may be due to the combined influence of sub-bandgap absorption, light scattering in the nanorod array and quantum confinement in the nanocrystalline structure of sensitizer layers. For Cu2O its more complex electronic structure gives larger dispersion in the results although major absorption edges are clearly observed.

Indium (III) oxide (In2O3) thin films have been obtained after heat treatment of In(OH)(3) precursor layers grown by a potential cycling electrodeposition (PCED) method from a dimethylsulfoxide (DMSO) based electrolytic solution onto fluorine-doped tin oxide (FTO) coated glass substrates. X-ray diffraction (XRD) measurements indicate the formation of a polycrystalline In2O3 phase with a cubic structure. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed a smooth morphology of the In2O3 thin films after an optimized heat treatment had been developed. The surface composition and chemical state of the semiconductor films was established by X-ray photoelectron spectroscopy analysis. The nature of the semiconductor material, flat band potential and donor density were determined from Mott-Schottky plots. This study reveals that the In2O3 films exhibited n-type conductivity with an average donor density of 2.2 x 10(17) cm(-3). The optical characteristics were determined through transmittance spectra. The direct and indirect band gap values obtained are according to the accepted values for the In2O3 films of 2.83 and 3.54 eV for the indirect and direct band gap values. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Reflectance of selective surfaces is numerically simulated from a continuous atomic concentration profile and then compared with experimental data, from a solar selective surface for solar thermal applications. The propagation of electromagnetic radiation is solved by using finite differences equation. Several theoretical models for optical properties of composite materials are compared and a proper mixing procedure is achieved. Results from Bruggeman effective medium theory are verified by comparison with experimental data. These data was obtained from Ni electrochemically impregnated into nanoporous alumina anodized onto an aluminum substrate. Concentration profile was measured using X-ray Photoelectron Spectroscopy. The procedure allows deducing measured reflectance from a very detailed model of the surface in depth, which uses three materials at the same time. This model could be used as a layout for a general three constituents mix for improving properties of solar thermal surfaces. (C) 2012 Published by Elsevier Ltd.

Highly transparent polycrystalline Al-doped ZnO thin films were deposited in open atmosphere by chemical spray pyrolysis on fused silica and glass substrates at 623 K. The influence of Al doping, 0 to 5%, was studied. XPS results revealed a linear relationship between Al content in the precursor solutions and Al content in the films. XPS depth profiling showed that any carbon contamination is restricted to the uppermost surface of the films. Optical transmission measurements revealed an increasing number of dispersion centres as well as a band gap shift to higher values with increasing Al content in the films. At fixed Al concentration, the comparison of the absorption coefficient for increasing film thickness showed that the films are very homogeneous, not changing their materials properties such as absorption coefficient and band gap.

Nickel oxide thin films have been deposited in an open atmosphere onto glass substrates by chemical spray pyrolysis using aqueous nickel acetate solutions and air as driving gas. The films show a strong variation in the surface morphology depending on the substrate temperature and the precursor solution flux. At 350°C substrate temperature, a reticular tissue-like film morphology is obtained, becoming the reticular nickel oxide fibres of the film thicker with increasing precursor solution flux. At 450°C substrate temperature, the film growth rate is 4 times slower and a highly symmetric self-ordering of the material at nanometer length scale occurs. These films consist of interconnected grains separated by pores, both of about 100nm in size. XRD and TEM revealed that the films are cubic NiO, being the crystallite size around 10nm. The optical band gap of the films decreases strongly for increasing film thickness from 4.3eV to 3.65eV.

In the present work, n-type silicon nanowire (n-SiNW) arrays have been synthesized by self-assembly electroless metal deposition (EMD) nanoelectrochemistry. The synthesized n-SiNW arrays have been submitted to scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and optical studies. Initial probes of the solar device conversion properties and the photovoltaic parameters such as short-circuit current, open-circuit potential, and fill factor of the n-SiNW arrays have been explored using a liquid-junction in a photoelectrochemical (PEC) system under white light. Moreover, a direct comparison between the PEC performance of a polished n-Si(100) and the synthesized n-SiNW array photoelectrodes has been done. The PEC performance was significantly enhanced on the n-SiNWs photoelectrodes compared with that on polished n-Si(100).

Cermet (Ag‐ZrO 2 ) coatings have been deposited by spray pyrolysis on an aluminized steel (AS) sheet of large area, using two different coating procedures: i) first spraying silver particles, and above that layer a film of zirconia, or ii) simultaneously spraying zirconia and the silver particles using a unique spray solution with Zr and Ag precursors. XPS surface and subsurface analysis, with the help of mild Ar + etching, has shown that the silver particles are metallic. On the surface of the silver particles exists a very thin oxide layer of silver zirconate. After Ar + etching, the Ag‐ZrO 2 coating material exhibits two phases showing differential charging. Both types of coatings reveal similar XPS spectra during analysis, albeit the coating obtained from the unique spray solution presents XPS peaks of slightly smaller width. SEM observations show that smaller silver particles with a smaller particle size distribution are obtained when spraying with a unique spray solution. Copyright © 2010 John Wiley & Sons, Ltd.

The chemical spray pyrolysis technique has been used to deposit thin films of MgO, NiO and ZrO2 on galvanized steel substrate. These films have been studied as barrier coatings against the degradation of the galvanized steel sheet during long term outdoor exposure. The corrosion protective effect of the coatings is discussed taking into account results from scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–VIS–NIR–MIR spectroscopy. By means of SEM, it has been observed that the coatings are dense and compact but the MgO coatings revealed film cracking. XPS and FTIR analysis have shown that the NiO coating has no residuals from the precursor solution, as inclusions of water or carbon. The MgO coating reveal traces of hydration. With respect to specific applications, the solar absorption and thermal emittance have been determined. The corrosion behaviour of the coatings has been estimated with electrochemical methods as potentiodynamic polarization and amperometry curves. Polarization resistances and corrosion rates were calculated and indicate a decreased pitting of the aluminized steel when coated with nickel oxide or zirconia.