We report on the bottom-up, in-vacuum synthesis of nanoparticle layers on static substrates with areas of up to 150 & times; 200 mm(2) by gas-phase condensation combined with an additional PECVD source for the deposition of organic (plasma polymer) or inorganic dielectric matrix materials. Nanoparticles embedded in a thin-film matrix have a wide range of potential applications, from antiviral and antibacterial surfaces, to water treatment, (photo-)catalysis, sensing, and structured surfaces for condensation and heat transfer. Ag, Ti, and Pt nanoparticles are obtained from inert gas-phase-condensation (GPC) of sputtered atomic vapor, stemming from an inert gas flow sputtering (GFS) source. This method is suitable for the production of virtually all existing metals. Here, we present the stability and the homogeneity of the resulting nanoparticle layers (Ag- and Pt-NPs). To further inspect the homogeneity of the nanoparticle deposition process, Ag-NPs/SiOx multilayer nanocomposite layers (embedded nanoparticles in a dielectric matrix) are examined by X-ray diffraction. The synthesis/structure/morphology relations are presented for both the initial random deposition (Ag) as well as the highly porous structure (Ti) obtained during later stages of deposition. Nanoparticle size and structures are investigated and the control of nanoparticle size distribution by both pressure in the aggregation zone and discharge power is reported. Specific features of the setup are presented, and allow metal NPs coverage with inhomogeneity values < +/- 7% over up to 70 & times; 70 mm(2) area in static mode and 1250 & times; 70 mm(2) in rotation mode.

CdSexTe1-x/CdTe solar cells are fabricated in the pilot line at CTF Solar with an efficiency of up to 21 %. Investigations were made on samples both directly after device processing and after a hot open-circuit light soaking (hOCLS) treatment. The hOCLS treatment generally leads to a substantial improvement of the IV performance, but behavior is not always consistent between cells. Most cells maintain a stable Jsc, but some show a significant loss in this parameter. In this study we try to explain this difference using IV measurements, EQE, SEM cross sections, EBIC, XRF thickness measurements, and front band alignment determination from PES sputter depth profiles. Investigations indicate a reduction in current contribution from the front of the CdSexTe1-x absorber, arising from change of the p-n junction. The band alignment at the front interface is investigated for different samples and different treatment in hOCLS by a PES sputter depth profiling.

CdTe photovoltaics has enjoyed considerable performance improvements in the last several years due in large part to the incorporation of the CdSeTe alloy within the absorber layer. However, cell and module open-circuit voltage improvements are not nearly as large as some metrics suggest they should be. It has recently been shown by others that, in addition to substantially increased photoluminescence quantum yield -which would be expected to increase voltage - high selenium incorporation creates significant band tail states, which would be expected to decrease voltage. Using photoluminescence spectroscopy, this work aims to quantify this relationship as a function of selenium concentration, and potentially identify an optimal concentration which maximizes implied voltage. Also shown are multiple-microsecond lifetimes in CdTe-based polycrystalline absorber films deposited directly on the front contact with no passivating layers at either interface, an uncommon result in presently available literature.

Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O2 outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO3 film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale.

A novel additive manufacturing route using a tailored resin containing Poly(vinylidene fluoride) Trifluoroethylene (PVDF-TrFE) to 3D print piezoelectric films is demonstrated. Piezoelectric films are printed within 2 seconds in a single step by simultaneously focusing initiating and inhibiting excitations within the liquid resin to locally confine the photochemical reaction. The printed films are patterned with an array of holes with a diameter of 30 mu m and a pitch of 55 mu m. The piezoelectric response is homogeneous across the film, indicating that the print pattern does not impact the PVDF-TrFE microstructure. Although the printed films contain only a small volume fraction of PVDF-TrFE (3 wt.%), their piezoelectric response (d33 = 20.3 pC/N) is comparable to the highest literature values reported for PVDF-TrFE films. The printed PVDF-TrFE films are predominantly beta-phase, and no electrical poling, post-processing, piezoelectric or inorganic additives are used in the fabrication. Analysis using piezoresponse force microscopy (PFM) and scanning electron microscopy (SEM) reveals that the enhanced piezoelectric response is due to the preferential formation of oriented PVDF-TrFE phases during printing. These results demonstrate how the dedicated design of photoactive resins in combination with volumetric additive manufacturing can be applied to rapidly fabricate functional 3D structures. 3D printing of piezoelectric PVDF-TrFE films from a photochemical reaction. The microstructure films are printed in 2s by exciting the photo-active resin with an initiating (go) and inhibiting (stop) excitation wavelength, respectively.image

This paper reports on the deposition and characterization of piezoelectric AlXSc1-XN (further: AlScN) films on Si substrates using AlSc alloy targets with 30 at.% Sc. Films were deposited on a Ø200 mm area with deposition rates of 200 nm/min using a reactive magnetron sputtering process with a unipolar–bipolar hybrid pulse mode of FEP. The homogeneity of film composition, structural properties and piezoelectric properties were investigated depending on process parameters, especially the pulse mode of powering in unipolar–bipolar hybrid pulse mode operation. Characterization methods include energy-dispersive spectrometry of X-ray (EDS), X-ray diffraction (XRD), piezoresponse force microscopy (PFM) and double-beam laser interferometry (DBLI). The film composition was Al0.695Sc0.295N. The films showed good homogeneity of film structure with full width at half maximum (FWHM) of AlScN(002) rocking curves at 2.2 ± 0.1° over the whole coating area when deposited with higher share of unipolar pulse mode during film growth. For a higher share of bipolar pulse mode, the films showed a much larger c-lattice parameter in the center of the coating area, indicating high in-plane compressive stress in the films. Rocking curve FWHM also showed similar values of 1.5° at the center to 3° at outer edge. The piezoelectric characterization method revealed homogenous d33,f of 11–12 pm/V for films deposited at a high share of unipolar pulse mode and distribution of 7–10 pm/V for a lower share of unipolar pulse mode. The films exhibited ferroelectric switching behavior with coercive fields of around 3–3.5 MV/cm and polarization of 80–120 µC/cm².

Porous thin films have various application fields, e.g., for energy conversion in fuel cells, energy storage in lithium ion batteries or supercapacitors as well for catalysis, filtration and sensing. We synthesized porous thin films by co-evaporating a low-vapor-pressure material (e.g., Si, Ni or C) together with zinc and depositing a compact layer of resulting composite. High-rate deposition process up to 100 nm/s was realized by electron beam physical vapor deposition (EB-PVD) of the materials from two graphite crucibles with a fast deflected electron beam in high vacuum. Immediately after deposition, the coated substrates were heated up in vacuum to a temperature above 500 degrees C and thereby zinc is removed selectively. Due to its higher vapor pressure against that of remaining component, zinc is expelled from the layer and vacancies are generated by so called vapor phase dealloying (VPD). We investigated the feasibility of VPD process for the elements silicon, nickel and carbon. The elemental composition and the morphology of the layers prior and after thermal annealing were analyzed by scanning electron microscopy, by energy-dispersive X-ray spectrometry and by X-ray diffraction.

This paper reports on how both the growth conditions and thickness of aluminum thin films impact the surface morphology and subsequent anodization behavior when sputtered onto Si and glass substrates up to a 1-mu m thickness, respectively. Specifically, the effects of oxygen incorporation during sputtering and variations between continuous vs. stepwise deposition are thoroughly investigated here. Previous studies demonstrated the tremendous impact of oxygen concentration while sputtering, which, in turn, allows minimizing the grain sizes for 200-nm-thick sputtered AlOx-films. The then anodized aluminum oxide (AAO) thin films can then be used, for instance to grow quasi defect-free, large-area gold nanorod arrays for plasmonic applications. The challenge when preparing thicker films as emphasized here, is to avoid gradients of oxygen concentration and grain size for any film thickness. We have developed reproducible protocols how to minimize such gradients: the deposition process is purposely interrupted after every 100/200/300-nm AlOx deposition step for approximately 5 min. to allow thermal relaxation under pure nitrogen atmosphere. The subsequent anodization and pore filling with gold then revealed highly improved properties for AAO-films up to the 1-mu m thickness, exhibiting a homogenous nanorod distribution with a very low number of defects.

Porous silicon thin films were fabricated by an innovative method using vacuum processing for the application as high capacity anode in lithium ion batteries. The deposition procedure comprises a co-evaporation of silicon and zinc, resulting in a deposition of a compound layer with deposition rates up to 100 nm/s and a subsequent thermal annealing. Due to its high vapor pressure, the zinc fraction is expelled and hence, a porous silicon matrix is formed. Herein, we introduce a novel and potentially scalable synthesis method for porous silicon films and show first analytical investigations concerning the layer morphology and the electrochemical properties. With the novel silicon anode excellent electrochemical performance, particularly high capacities of >= 3000 mAh/g, reasonable coulombic efficiencies of >= 90% in the initial cycle and comparably high cycle life > 150 cycles can be demonstrated, which reveals their great potential for battery anode applications.

Ultrathin flexible glass is a material with fascinating properties. However, the handling of the glass as well as the reliable and cost effective deposition of coatings onto its surface are decisive for creating attractive application cases. Indium-tin-oxide coatings were deposited onto the glass in a specially designed roll-to- roll coating machine. The substrate was heated while it was moved through the deposition zone. The minimum sheet resistance and the resistivity of these layers were 11 Omega(squ) and 1.5 x 10(-4) Omega cm, respectively. The surface topography of the samples was investigated by scanning electron microscopy and atomic force microscopy. The measurement revealed that the roughness of the samples shows a minimum for substrate temperatures of 190 degrees C during the deposition.

AlxSc1-xN films were deposited by reactive pulse magnetron co-sputtering from aluminum and scandium targets without additional substrate heating at deposition rates between 100 and 150 nm/min. With increasing incorporation of scandium into the hexagonal wurtzite structure, the piezoelectric properties are drastically improved. The piezoelectric charge coefficient d(33) is increased from 8.4 pC/N for AlN up to 23.6 pC/N for AlxSc1-xN with 33% scandium. Between 35 and 43% scandium content a relative broad maximum with high piezoelectric coefficients between 26.9 and 273 pC/N was detected. A further increase of scandium concentration above 50% results in the formation of the cubic and centrosymmetric rock salt structure and therefore the complete loss of piezoelectric properties.By FE-SEM, XRD and TEM investigations it was shown that up to up to 43% scandium concentration the wurtzite structure becomes more and more disordered and the c/a ratio is decreased from 1.6 to 1.27. Nevertheless, no aluminum or scandium segregation could be detected by high resolution TEM investigations. The Young's modulus of the wurtzite phase is reduced with increasing scandium concentration from 340 GPa to 185 GPa. The drastic improvement of the piezoelectric properties can be explained by weakening of the chemical bonding and by high distortion of the wurtzite structure. (C) 2016 Elsevier B.V. All rights reserved.

Results of investigations on thin films of titanium oxide are presented in which the layers were deposited at a very high deposition rate of approximately 50–100nm/s. The high-performance coating process is based upon electron beam evaporation, a dual crucible, and a spotless arc that burns in the metal vapor and reactive gas between the evaporating titanium electrodes that are heated by the electron beam. Electron beam power, arc current and oxygen flow rate were varied and the resulting coatings investigated with regard to their composition, optical properties, and microstructure. Even at such high deposition rates, transparent and dense layers with a high refractive index (2.4) could be produced. Amorphous TiO2 coatings were obtained at a substrate temperature below 150°C while crystalline layers of the anatase form could be deposited at a substrate temperature in the range of 200 to 300°C. The data regarding the chemical composition of the titanium oxide layers are compared with a mathematical model of reactive vapor deposition. An estimate based on the model shows that the incorporation coefficient of oxygen, which gives its deposit probability in the coating, is approximately 0.25 for stoichiometric TiO2 layers. Possible applications of the PVD process presented are foreseen for large-area optical coating systems and large-scale application of photo-induced effects.

This paper reports on the deposition of AlN and AlXSc1−XN films by pulse magnetron sputtering. The first part will focus on the AlXSc1−XN deposition process in comparison to the already established AlN process. The effect of doping AlN with Sc regarding piezoelectric and mechanical properties is presented. The films show the expected increase of piezoelectric properties as well as the softening of the material with higher Sc concentrations. Above a threshold concentration of around 40 % Sc in the AlXSc1−XN films, there exists a separation into two phases, an Al-rich and a Sc-rich wurtzite phase, which is shown by XRD. At Sc concentrations higher than 50 %, the films are not piezoelectric, as the films are composed primarily of the cubic ScN phase. The second main part of this paper evaluates the films for application in energy harvesting. Especially the Sc doping allows a significant increase in the energy generated in our test setup. Directly measuring the AC voltage at resonance depending on load resistance with base excitation of ±2.5 µm, 350 µW power have been generated under optimum conditions compared to 70 µW for pure AlN. For a more application oriented measuring setup, a standard and a SSHI-based (“Synchronised Switch Harvesting on Inductor”) AC/DC converter circuit have been tested. The SSHI interface showed a significant improvement to 180 % compared to the standard interface.

This paper reports on the deposition of AlN and AlXSc1-XN films by pulse magnetron sputtering. The influence of process parameters on the film properties and the evaluation of the films for micro energy harvesting are presented. For AlN it is shown, that film stress can be varied in a considerable range between compressive and tensile stress while maintaining good piezoelectric properties. Additionally, the effect of doping AlN with Sc regarding piezoelectric and mechanical properties is presented. The films show the expected increase of piezoelectric properties as well as the softening of the material with higher Sc concentrations. Above a threshold concentration of around 40% Sc in the AlXSc1-XN films, there exists a separation into two phases, an Al-rich and a Sc-rich wurtzite phase, which is shown by XRD. At Sc concentrations higher than 50%, the films are not piezoelectric, as the films are composed primarily of the cubic ScN phase. Sc doping allows to significantly increase the energy generated in test setup. Up to 350 mu W power have been generated under optimum conditions.

We have investigated CdTe thin film solar cells without activation treatment and with CdCl2 activation treatment at temperatures between 370 and 430 °C using a constant activation time of 25 min. For this purpose, CdS/CdTe layers were deposited by closed-space-sublimation on FTO coated float glass. The solar cells were characterized by measurements of the JV characteristics and quantum efficiencies. In addition, ion polished cross sections of the solar cells were prepared for high-resolution FE-SEM imaging of the microstructure and the simultaneous registration of electron beam induced current (EBIC) signal distribution. By measurement of the EBIC signal distribution, it can be shown that without activation treatment the CdTe grain boundaries itself and grain boundary near regions exhibit no EBIC signal, whereas centres of some singular grains already show a distinct EBIC signal. In contrast, after the chlorine activation treatment, the grain boundary near regions exhibit a significant higher EBIC signal than the centre of the grains. The results can be discussed as a direct evidence for defect passivation of grain boundary near regions by the chlorine activation treatment. At activation temperature of 430 °C, additionally, a significant grain growth and agglomeration of the CdS layer can be recognized, which is linked with the formation of voids within the CdS layer and a deterioration of pn junction properties.

For deposition of thin oxide coatings there are a lot of qualified PVD processes today. If high productivity or large-area coating is necessary for economic reasons processes with high deposition rate are reasonable. Using electron beam (EB) evaporation all inorganic materials can be evaporated with high rates. Microstructure of coatings deposited by EB-evaporation depends on substrate temperature during layer growth and melting temperature of coating material. Particularly in case of high melting materials columnar and porous microstructure is obtained. For large area coating several plasma sources have been developed in order to enhance energy of condensing particles and to get denser layer microstructure.Spotless arc Activated Deposition (SAD) combines electron beam high-rate evaporation using axial gun and a spotless arc discharge burning in metal vapor on hot evaporating cathode [2]. The SAD process is suitable for evaporation of high-melting metals like titanium, zirconium or tantalum providing high deposition rate up to 2000 nm/s. Moreover plasma-activation enables reactive mode of operation and deposition of oxides, nitrides or other compounds with a high rate in the range of 20 to 100 nm/s. A Spotless arc is an arc discharge burning in metal vapor which is obtained if the cathode temperature is high enough to enable high thermionic electron emission current density. Spotless mode results in relatively low cathodic arc current density and droplets known from arc evaporators with cold cathode are completely avoided [3]. Nevertheless high DC arc current up to 2000 A is possible.Recent work has shown that SAD process is well suited for deposition of titanium dioxide coatings based on evaporation of titanium and reactive processing in oxygen atmosphere [4]. TiO2 layers were deposited at very high deposition rates between 40 and 70 nm/s. Depending on process conditions amorphous coatings or crystalline phases were obtained. Coatings consisting of anatase phase show very good properties concerning photoinduced superhydrophilicity and photocatalysis. Transparent layers with high refractive indexes in the range of 2.30 and 2.58 could be reached.

We report 12% efficient CdS/CdTe thin film solar cells prepared by low temperature close space sublimation (CSS). Both semiconductor films, CdS and CdTe, were deposited by high vacuum CSS in superstrate configuration on glass substrates with fluorine doped tin oxide (FTO) front contact. The CdTe deposition was carried out at a substrate temperature (Tsub) of ≤340 ∘C, which is much lower than that used in conventional processes (>500 ∘C). The CdTe films were treated with the usual CdCl2 activation process. Different optimal annealing times and temperatures were found for low-temperature cells (Tsub≤ 340 ∘C) compared to high-temperature cells (Tsub = 520 ∘C). The influence of the activation step on the morphology of high-temperature and low-temperature CdTe is determined by XRD, AFM, SEM top views, and SEM cross-sections. Grain growth, strong recrystallization, and a reduction of planar defects during the activation step are observed, especially for low-temperature CdTe. Further, the influence of CdS deposition parameters on the solar cell performance is investigated by using three different sets of parameters with different deposition rates and substrate temperatures for the CdS preparation. Efficiencies about 10.9% with a copper-free back contact and 12.0% with a copper-containing back contact were achieved using the low temperature CdTe process.