Search

A hybrid catalyst consisting of Zr-doped mesoporous silica (Zr-SBA-15) supports with intergrown Cu nanoparticles was used to study the effects of a catalysts chemical states on CO2 hydrogenation. T ...

Photoelectrochemical (PEC) water-splitting offers a promising method to convert the intermittent solar energy into renewable and storable chemical energy. However, the most studied semiconductors generally exhibit a poor PEC performance including low photocurrent, small photovoltage, and/or large onset potential. In this work, we demonstrate a significant enhancement of photovoltage and photocurrent together with a substantial decrease of onset potential by introducing electrocatalytic and p-type NiO nanoclusters on an n-type cubic silicon carbide (3C-SiC) photoanode. Under AM1.5G 100 mW cm(-2) illumination, the NiO-coated 3C-SiC photoanode exhibits a photocurrent density of 1.01 mA cm(-2) at 0.55 V versus reversible hydrogen electrode (V-RHE), a very low onset potential of 0.20 V-RHE and a high fill factor of 57% for PEC water splitting. Moreover, the 3C-SiC/NiO photoanode shows a high photovoltage of 1.0 V, which is the highest value among reported photovoltages. The faradaic efficiency measurements demonstrate that NiO also protects the 3C-SiC surface against photo-corrosion. The impedance measurements evidence that the 3C-SiC/NiO photoanode facilitates the charge transfer for water oxidation. The valence-band position measurements confirm the formation of the 3C-SiC/NiO p-n heterojunction, which promotes the separation of the photogenerated carriers and reduces carrier recombination, thus resulting in enhanced solar water-splitting. Funding Agencies|Swedish Research Council (Vetenskapsradet) [621-2014-5461, 2018-04670, 621-2014-5825]; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) [2016-00559]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [CH2016-6722]; AForsk Foundation [16-399]; Stiftelsen Olle Engkvist Byggmastare [189-0243]; EU project CHALLENGE; Knut and Alice Wallenberg Foundation [KAW 2014.0276]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

Efficient metal-ion-irradiation during film growth with the concurrent reduction of gas-ion-irradiation is realized for high power impulse magnetron sputtering by the use of a synchronized, but delayed, pulsed substrate bias. In this way, the growth of stress-free, single phase alpha -W thin films is demonstrated without additional substrate heating or post-annealing. By synchronizing the pulsed substrate bias to the metal-ion rich portion of the discharge, tungsten films with a 110 oriented crystal texture are obtained as compared to the 111 orientation obtained using a continuous substrate bias. At the same time, a reduction of Ar incorporation in the films are observed, resulting in the decrease of compressive film stress from sigma =1.80-1.43GPa when switching from continuous to synchronized bias. This trend is further enhanced by the increase of the synchronized bias voltage, whereby a much lower compressive stress sigma =0.71GPa is obtained at U-s=200V. In addition, switching the inert gas from Ar to Kr has led to fully relaxed, low tensile stress (0.03GPa) tungsten films with no measurable concentration of trapped gas atoms. Room-temperature electrical resistivity is correlated with the microstructural properties, showing lower resistivities for higher U-s and having the lowest resistivity (14.2 mu Omega cm) for the Kr sputtered tungsten films. These results illustrate the clear benefit of utilizing selective metal-ion-irradiation during film growth as an effective pathway to minimize the compressive stress induced by high-energetic gas ions/neutrals during low temperature growth of high melting temperature materials. Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [VR 2018-04139]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Japan Society for the Promotion of Science (JSPS)Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [17KK0136]

In the present study, we investigate the impact of pulse power (Ppulse) on the ion flux and the properties of TiN films using reactive high-power impulse magnetron sputtering. Ppulse was adjusted in the range of 5–25 kW, while keeping the total average power constant through regulating the pulsing frequency. It is found that the required N2 flow, to produce stoichiometric TiN, decreases as Ppulse is increased, which is due to a decrease in the deposition rate. The plasma conditions when stoichiometric TiN is formed were investigated in detail. In situ ion mass spectrometry measurements of the ion energy distribution functions reveal two distinct ion populations, ions originating from sputtered atoms (Ti+, Ti2+, and N+) and ions originating from the working gas (Ar+, Ar2+, and N2+). The average ion energies (Eave) of the sputtered ions show an increase with increasing Ppulse, while Eave for the gas ions remains almost unaffected. The relative flux intensity Ti2+/Ti+ showed an increasing trend, from 0.28 to 0.47, as Ppulse was increased from 5 to 25 kW. The ion flux changes affect the growth of the TiN film such that 111-textured films are grown for low Ppulse while higher Ppulse results in mixed orientations. In addition, the hardness of the deposited film increases with increasing Ppulse, while the compressive film stress increases significantly at a higher Ppulse. In this way, optimum deposition conditions were identified at Ppulse = 8.3 kW, where a relatively low compressive stress of 0.89 GPa and high hardness of 22.67 GPa were measured. Funding agencies: Swedish Research CouncilSwedish Research Council [VR 2018-04139]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at the Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

The precise control of the growth nanostructured thin films at low temperature is critical for the continued development of microelectronic enabled devices. In this study, nanocomposite Ni-Si-N thin films were deposited at low temperature by reactive high-power impulse magnetron sputtering. A composite Ni-Si target (15 at.% Si) in combination with a Ar/N2 plasma were used to deposit films onto Si(0 0 1) substrates, without any additional substrate heating or any post-annealing. The films microstructure changes from a polycrystalline to nanocomposite structure when the nitrogen content exceeds 16 at.%. X-ray diffraction and (scanning) transmission electron microscopy analyses reveal that the microstructure consists of nanocrystals, NixSi (x > 1) 7–8 nm in size, embedded in an amorphous SiNx matrix. It is proposed that this nanostructure is formed at low temperatures due to the repeated-nucleation of NixSi nanocrystals, the growth of which is restricted by the formation of the SiNx phase. X-ray photoelectron spectroscopy revealed the trace presence of a ternary solid solution mainly induced by the diffusion of Ni into the SiNx matrix. Four-probe electrical measurements reveal all the deposited films are electrically conducting.

N-doped nickel oxide (NiO:N) thin films were deposited on glass and silicon substrates by reactive DC magnetron sputtering in Ar/O 2 /N 2 gas atmosphere with a series of N 2 /O 2 gas ratio ranging from 0 to 80%. X-ray diffraction measurements have revealed that the films are constituted of Ni 1-x O grains and showed enhanced polycrystalline features with increasing N-doping concentration. For the first time, we report here that N-doping in the Ni-deficient NiO (Ni 1-x O) film leads to a band-gap narrowing from 3.6 to 2.3 eV. X-ray photoelectron spectroscopy (XPS) measurements proved that up to 4 atomic percent (at.%) nitrogen can be incorporated at least at the surface of the NiO:N samples. In addition, XPS valence band spectra and UV–vis transmission measurements have demonstrated that the band-gap narrowing may originates from the contribution of an intermediate band (IB) ∼2.4 eV just above the valence band maximum and the up-shifting of the valence band edge (∼0.3 eV) due to the introduction of occupied N 2 p states. Local I–V measurements, carried out by conductive AFM (C-AFM), have revealed that the extrinsic doping of N atoms within the oxide can be a good way to precisely control the electrical conductivity of such p- type materials.

A catalytically active nanoassembly comprising Cu-nanoparticles grown on integrated and active supports (large pore Zr-doped mesoporous SBA-15 silica) has been synthesized and used to promote CO2hydrogenation.

This study deals with the DC and HiPIMS reactive magnetron deposition process using a pure nickel target (99.995%) in an Ar-N2 gas mixture with varied nitrogen gas flow and bias voltage (floating or -100 V). The characterization of the NiN films has been carried out by X-ray diffraction (XRD), X-ray photoelectrons spectroscopy (XPS) and Energy dispersive X-ray Spectroscopy (EDXS). XRD measurements have highlighted the deformation of the Ni cubic cell as a function of nitrogen content, and a mixture of nitrided phases (Ni4N, Ni3N and Ni2N) appears for 20% N2 in the discharge. XPS and EDX are well correlated and permit us to determine three zones: metallic between 0 and 20% N2, Ni4N between 20% and 42% N2 and finally Ni3N for N2 above 50%. These three zones are in good agreement with deposition rates and optical emission spectroscopy measurements. Cyclic voltammetry has been performed in a conventional three-electrode cell using neutral, alkaline and acidic aqueous electrolytes. The NixN electrochemical behavior shows a pseudocapacitive charge storage mechanism in LiNO3 and KOH electrolytes using an appropriate voltage window, suitable for supercapacitors, whereas NixN exhibits reversible faradaic redox peaks beyond one potential in KOH, depicting NixN film as a battery-type electrode.

The effect of applying a positive voltage pulse (Urev = 10 - 150 V) directly after the negative high power impulse magnetron sputtering (HiPIMS) pulse (bipolar HiPIMS) is investigated for the reactive sputter deposition of TiN thin films. Energy-resolved mass spectroscopy analyses are performed to gain insight in the effect on the ion energy distribution function of the various ions. It is demonstrated that the energy of a large fraction of the ions can be tuned by a reverse target potential and gain energy corresponding to the applied Urev. Microscopy observations and x-ray reflectometry reveal densification of the films which results in an increase in the film hardness from 23.9 to 34 GPa as well as an increase in compressive film stress from 2.1 GPa to 4.7 GPa when comparing conventional HiPIMS with bipolar HiPIMS (Urev = 150 V).

Plasmonic response of free charges confined in nanostructures of plasmonic materials is a powerful means for manipulating the light-material interaction at the nanoscale and hence has influence on various relevant technologies. In particular, plasmonic materials responsive in the mid-infrared range are technologically important as the mid-infrared is home to the vibrational resonance of molecules and also thermal radiation of hot objects. However, the development of the field is practically challenged with the lack of low-loss materials supporting high quality plasmons in this range of the spectrum. Here, we demonstrate that degenerately doped InN nanocrystals (NCs) support tunable and low-loss plasmon resonance spanning the entire midwave infrared range. Modulating free-carrier concentration is achieved by engineering nitrogen-vacancy defects (InN1-x, 0.017 amp;lt; x amp;lt; 0.085) in highly degenerate NCs using a nonequilibrium gas-phase growth process. Despite the significant reduction in the carrier mobility relative to intrinsic InN, the mobility in degenerate InN NCs (amp;gt;60 cm(2)/(V s)) remains considerably higher than the carrier mobility reported for other materials NCs such as doped metal oxides, chalcogenides, and noble metals. These findings demonstrate feasibility of controlled tuning of infrared plasmon resonances in a low-loss material of III-V compounds and open a gateway to further studies of these materials nanostructures for infrared plasmonic applications. Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 14.0276]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (faculty Grant SFO-Mat-LiU) [2009-00971]; EPSRC [EP/M024938/1]

In this contribution, based on the analyses of the discharge behavior as well as final properties of the deposited Ni-O films during reactive high power impulse magnetron sputtering discharge, we have demonstrated that monitoring the oxygen flow rate leads to 4 different regimes of discharge. Tuning the oxygen partial pressure allows deposition of a large range of chemical compositions from pure nickel to nickel-deficient NiOx (x > 1) in the poisoned mode. Investigation of the plasma dynamics by time-resolved optical emission spectroscopy suggests that the discharge behavior in the poisoned mode principally comes from the higher contribution of both oxygen and argon ions in the total ionic current, leading to a change in the ion induced secondary electron emission coefficient. Additionally, material characterizations have revealed that optoelectronic properties of NiOx films can be easily tuned by adjusting the O/Ni ratio, which is influenced by the change of the oxygen flow rate. Stoichiometric NiO films...

High power impulse magnetron sputtering (HiPIMS) has already demonstrated great potential for synthesizing the high-energy crystalline phase of titanium dioxide (rutile TiO2) due to large quantities of highly energetic ions present in the discharge. In this work, it is shown that the metastable anatase phase can also be obtained by HiPIMS. The required deposition conditions have been identified by systematically studying the phase formation, microstructure and chemical composition as a function of mode of target operation as well as of substrate temperature, working pressure, and peak current density. It is found that films deposited in the metal and transition modes are predominantly amorphous and contain substoichiometric TiO x compounds, while in compound mode they are well-crystallized and present only O2− ions bound to Ti4+, i.e. pure TiO2. Anatase TiO2 films are obtained for working pressures between 1 and 2 Pa, a peak current density of ~1 A cm−2 and deposition temperatures lower than 300 °C. Rutile is favored at lower pressures ( 2 A cm−2), while amorphous films are obtained at higher pressures (5 Pa). Microstructural characterization of selected films is also presented.

chap 6; International audience; Vibration‐powered generators are typically inertial spring and mass systems which employ three main transduction mechanisms to extract energy from vibrations: piezoelectric, electromagnetic and electrostatic. This chapter presents a short overview of the microelectromechanical systems (MEMS) energy harvesters employing both piezoelectric and electromagnetic effects both proposed in the literature and developed in the framework of the Nanofunction project. It presents a short overview of state‐of‐the‐art vibration energy transducers employing the piezoelectric effect. The chapter illustrates the near‐field characterization techniques as well as electromechanical modeling and simulation required for the design of the energy harvesting transducers. It reviews the electromagnetic generators presented in the literature including large‐scale discrete devices and integrated versions, where the results achieved on vibration energy harvester exploiting both electromagnetic and piezoelectric effects are derived. Modeling and simulation results are presented to demonstrate the feasibility of the proposed device concepts.

This paper presents for the first time the scaling rules of piezoelectric nanowires (NWs), as the active transducer element for sensors and mechanical energy harvesters. Moreover, to keep close to realistic structures, non-linear effects associated to large displacements were taken into account, as well as the influence of NW variability, based on experimental data. We demonstrate that well-above-state-of-the-art sensitivities and resolutions can be achieved for sensing applications, and that large energy conversion efficiencies can be obtained for mechanical energy harvesters (about 7 times larger than that of their bulk counterpart).