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In this contribution, we show that silver substitution for copper in Cu(In,Ga)Se2 (CIGS) to form (Ag,Cu)(In,Ga)Se2 (ACIGS) leads to a reduction of the voltage loss expressed as Eg/q – V oc. This, in turn, leads to higher device efficiencies as compared to similar CIGS devices without Ag. We report $V_{{\rm{oc}}}$ at 814 mV at a conversion efficiency of 21% for our best ACIGS device with 20% of the group I element consisting of silver. Comparing ACIGS and CIGS devices with the same Ga/(Ga + In) ratio, the ACIGS devices exhibit about 0.05 eV higher bandgap. Alkali postdeposition treatment with KF leads to improvements in efficiency both for CIGS and ACIGS, but we find that the dose of KF needed for optimum device for ACIGS is 10–20% of the dose used for CIGS.

It is investigated if the performance of Cu(In,Ga)Se-2 (CIGSe) solar cells produced by co-evaporation can be improved by surface sulfurization in a postdeposition treatment. The expected benefit would be the formation of a sulfur/selenium gradient resulting in reduced interface recombination and increased open-circuit voltage. In the conditions used here it was, however, found that the reaction of the CIGSe layer in a sulfur environment results in the formation of a CuInS2 (CIS) surface phase containing no or very little selenium and gallium. At the same time, a significant pile up of gallium was observed at the CIGSe/CIS boundary. This surface structure was formed for a wide range of annealing conditions investigated in this paper. Increasing the temperature or extending the time of the dwell stage had a similar effect on the material. The gallium enrichment and CIS surface layer widens the surface bandgap and therefore increases the open-circuit voltage. At the same time, the fill factor is reduced, since the interface layer acts as an electron barrier. Due to the balance of these effects, the conversion efficiency could not be improved.

Light-induced metastabilities of Cu(In,Ga)Se2 (CIGS)-based thin film solar cells have been extensively researched for many years. It is commonly observed that junction capacitance and p-doping level in CIGS absorbers increase considerably after light soaking (LS). In this work, we focus on the LS behaviors of cells with different minority carrier lifetimes (τn). Experiments show that high efficiency cells with long τn lose open circuit voltage (Voc) and fill factor (FF) upon LS, whereas low efficiency cells with short τn lose less or even gain Voc and FF. The sodium content measured with glow discharge optical emission spectroscopy (GD-OES) increases in the region close to the CdS/CIGS interface with LS and may contribute to the observed LS behaviors. The change in electrical parameters is explained with simulations, which relate the Voc and FF changes to a reduced recombination rate in the space charge region due to the light-induced doping increase. The simulations also suggest that cells with higher n-doping in the CdS are less sensitive to changes in interface recombination rate and doping of CIGS, which agrees with the hypothesis that the CdS buffer deposition is important for the LS behavior.

The significant gain in efficiency by a KF post deposition treatment (PDT) on small cells, observed by several groups, can be scaled to full size modules. This is shown here by a significant gain for full size modules with KF PDT and a module reaching 17.2% (aperture area efficiency, externally confirmed). Another important topic is reducing the cell-to-module losses. Two different methods are presented and compared, a metal grid on top of the TCO and an improved TCO (ZnO:B). A sub-module (300×275 mm2) reaching 17.6% efficiency and a mini-module (50×50 mm2) reaching 18.7% efficiency is presented and confirms the reduction of cell-to-module losses.

We report a new certified world-record efficiency for thin-film Cu(In,Ga)Se2-based photovoltaic sub-modules of 17.4%(aperture area). The record efficiency of the 16 cm2, monolithically integrated, sub-module has been independently confirmedby Fraunhofer ISE. The record device is the result of extensive co-optimization of all processing steps. Duringthe optimization process, strong focus has been put on the scalability of processes to cost-effective mass production, asreflected, for example, in Cu(In,Ga)Se2 deposition time and substrate temperature. Device manufacturing as well as resultsof electrical and material characterization is discussed.

The influence of the average Se-to-metal overpressure during three-stage co-evaporation of Cu(InxGa1−x)Se2 solar absorber layers has been investigated. Solar cell devices were fabricated using a baseline process consisting of chemical bath deposited CdS, magnetron sputtered intrinsic and Al-doped ZnO, and e-beam evaporated Ni/Al/Ni current collection grid. For the higher Se-to-metal rate ratios studied, an increased short-circuit current in combination with a decreased fill factor is observed, while the open-circuit voltage stays fairly constant. Based on quantum efficiency measurements, fitting of IV data to a one-diode model, and simulations, we suggest the observed effects to be due to a decreased effective doping in combination with a decreased bulk recombination with higher average Se-to-metal overpressures. This could e.g. be explained by a decreasing number of Se-vacancies or VSe–VCu divacancies with higher Se rate. For the range of lower average Se-to-metal rate ratios studied, device performance drops due to a decreased open-circuit voltage and, for the lowest Se rate investigated, fill factor. In addition to electrical characterization, the effects on absorber microstructure are discussed based on results obtained from X-ray diffraction and scanning electron microscopy.

Current available techniques for transmission electron microscopy (TEM) of tooth–biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. Objectives The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth–biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chemfil Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clearfil SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. Methods After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. Results The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct “fog” or “melted look”, which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct “keyhole” shape of enamel rods sectioned at 90°, delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. Significance The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial–hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.

Six mechanisms have been identified, which control how Ca-aluminate materials are integrated onto tissue; 1) Main reaction, the hydration step of CA, 2) Apatite formation in presence of phosphate ions in the biomaterial, 3) Apatite formation in the contact zone in presence of body liquid, 4) Transformation of hydrated Ca-aluminate into apatite and gibbsite, 5) Biological induced integration and ingrowth, i.e. bone formation at the contact zone, and 6) Mass increase reaction, especially important when un-hydrated CA is used as coatings or as augmentation pastes. These six mechanisms affect the integration differently depending on a) what type of tissue the biomaterial is in contact with, b) in what state (un-hydrated or hydrated) the CA is introduced, and c) what type of application is aimed at (cementation, dental fillings, endodontic fillings, sealants, coatings and augmentation products). Both a pure nanostructural mechanically controlled integration, and a chemically induced integration seem plausible.

Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition.The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process.The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri-Oss HA-coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra-Tech OsseoSpeed (Astra Tech AB, Mölndal, Sweden), Straumann SLA (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden).It was found that their surface properties had differences. The surfaces were covered with crystalline TiO(2) (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively.This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.

Calcium aluminate is the main constituent in calcium aluminate cements, used in a wide range of applications in construction and mining industries and recently also as biomedical implant. In applications that demand very precise reaction features, such as the biomedical ones, the phase purity is of very high importance. In this paper the formation of CaAl2O4 from CaCO3–Al2O3 powder mixtures has been studied, varying holding times between 1 and 40 h and temperatures between 1300 and 1500 °C. Phase formation was studied in samples both quenched from the holding temperatures and in samples slowly cooled. Samples were characterized by X-ray powder diffraction (XRPD), using Guinier-Hagg film data and the Rietveld method, and scanning (SEM) and transmission (TEM) electron microscopy. Samples for TEM with very high site accuracy were produced using focused ion beam microscopy. In addition to CA (CaAl2O4) the samples contained major amounts of CA2 (CaAl4O7), C12A7 (Ca12Al14O33) and minor amounts of un-reacted A (Al2O3). Trace amounts of C3A (Ca3Al2O6) were observed only for samples heated to 1500 °C. The amount of the Ca-rich phase C12A7 was found to decrease with time as it reacts with A and, to a less degree, CA2 to form CA. In agreement with previous studies the amount of CA2 formed decreases comparatively slowly with time. Its un-reactivity is due to that it is concentrated in isolated porous regions of sizes up to 100 μm. The formation of the Ca aluminates is found to be in response to local equilibriums within small inhomogeneous regions, with no specific phase acting as an intermediate phase. Samples quenched from 1500 °C were found to contain smaller amounts of poorly crystallized phases. A reaction between C and A takes place already at 900 °C, forming a meta-stable orthorhombic modification of CA. The orthorhombic unit cell with a = 8.732(2) A, b = 8.078(2) A, c = √3·a = 15.124(4) A was verified by electron diffraction, revealing frequent twinning and disorder of the crystallites.

Bone-anchored titanium implants have been used for anchorage of amputation prostheses for more than one and a half decades. Histo-logical and ultrastructural analyses were performed on a forearm amputation prosthesis after being in use for more than 11 years.The implant was retrieved from the ulnar bone after a fatigue fracture of the titanium implant, and was clinically stable at the time of removal. The histological findings showed a large amount of bone within the threads and a high degree of apposition of mineralized bone to the implant surface. Ultrastructural analysis of thin samples prepared by focused ion-beam microscopy revealed an electron-dense layer at the interface and direct apposition of crystalline hydroxyapatite at the implant surface.Our observations in this retrieval study provide a structural correlate to the functional properties and clinical results of amputation prostheses.

Vertebral compression fractures were simulated by making a hole into sheep vertebrae and by injecting a stabilizing material. The injectable bio-ceramic Xeraspine™ was evaluated together with a commercially available PMMA (Vertebroplastic™) as the reference material. The Vertebrae were harvested after 7 days and prepared for microscopy. The samples were deposited with gold on the surface and thereafter subjected to SEM and EDX analysis. It was found that the Xeraspine-bone interface was composed of a mixture of elements. The Vertebroplastic implant was embedded in a carbon containing tissue, likely a soft tissue capsule. The Xeraspine sample was subjected to high resolution analysis in the TEM combined with EDX measurements. The TEM sample was prepared with a novel technique for preparation of the tissue-material interface (FIB). In the TEM analysis it was found that the interface region consists of ZrO2 together with a mixture possibly consisting of katoite and apatite formed during setting and/or originating from the boneapatite.

A method for producing ordered carbon nanopillar arrays is presented. The method is based on ion irradiation through a small anodic porous alumina membrane, resulting in carbon deposition within the centers of the pores on a gold covered SiO 2 / Si substrate. Samples were irradiated by 4 MeV Cl 2 + ions with fluences of 10 15 – 10 16 ions / cm 2 . The combined use of pick’n place positioning of the small porous alumina templates and ion beam irradiation is well suited for post-processing on silicon based integrated circuits. It provides fast local deposition at low temperature of high-density ordered carbon nanopillar arrays in larger silicon based systems, e.g., for field emitting or biosensors applications.

A non-bioactive implant device can easily be changed to in vitro bioactive with a thin coating of crystalline TiO2. This crystalline coating can be deposited very thin with great step coverage at a low temperature with Atomic Layer Deposition (ALD). An anatase TiO2 coating was built up atomic layer by atomic layer using TiI4 and H2O as precursors in a hot wall furnace. Several hundreds of cycles resulted in a 10-30nm well defined TiO2 of anatase phase on both Si and Ti substrates. These coatings were shown to be bioactive when immersed in simulated body fluid in vitro, as hydroxyapatite (HA) formed on the surface. The surface roughness of the substrates affected the adhesion of the HA. The adhesion was low on the smooth Si but much better on the 100 times rougher Ti. The ALD technique is promising for coating substrates of all shapes with bioactive crystalline TiO2 at a low temperature.

Transmission electron microscopy (TEM) investigations of intact interfaces of cells and brittle biomaterials have proven difficult using common TEM preparation techniques. This paper describes a technique to fabricate thin sections for TEM investigation of intact interfaces between human monocytes and sintered hydroxylapatite by the use of focused ion beam (FIB) microscopy. The interfaces were examined using energy filtered TEM.

Electrical contacts of NiSi0.82Ge0.18 to p+-Si0.82Ge0.18 were fabricated and characterised. Lateral growth of the NiSi0.82Ge0.18 under SiO2 isolation was observed. A three-dimensional model was employed to extract the contact resistivity by considering both the lateral growth and the presence of a recessed NiSi0.82Ge0.18 step into the Si0.82Ge0.18. The contact resistivity extracted was 5.0 × 10− 8 and 1.4 × 10− 7 Ω cm2 for small contacts of circular geometry and large contacts of square shape, respectively. Possible causes responsible for this 3-fold difference in contact resistivity were discussed. An underestimate of the contact resistivity by 35% was found if a two-dimensional model was used without taking into account the complex interface morphology.

The morphological stability of NiSi1−uGeu ternary alloy films formed by reacting Ni with single-crystal (sc) and polycrystalline (poly) Si1−xGeu is studied (u can be different from x). The agglomeration of NiSi1−uGeu films on Si0.7Ge0.3 occurs at 550°C after rapid thermal processing for 30 s, independently of the crystallinity of the Si1−xGeu. This behavior distinctly different from NiSi: NiSi films on poly-Si display a poorer morphological stability and degrade at lower temperatures than NiSi on sc-Si. On strained Si1−xGex, the presence of Ge simultaneously gives rise to two effects of different origin: mechanical and thermodynamic. The main driving forces behind the agglomeration of NiSi1−uGeu on sc-Si1−xGex are found to be the stored strain energy in the Si1−xGex and the larger (absolute) free energy of formation of NiSi compared to NiGe. The latter constitutes the principal driving force behind the agglomeration of NiSi1−uGeu on poly-Si1−xGex and is not affected by the degree of crystallinity of Si1−x...

The influence of a Nb layer between Si and Ti on the formation of TiSi2 in small-feature contacts and of the substrate doping level has been studied using transmission electron microscopy in combination with convergent-beam electron diffraction. For an As dose of 2.5×1016 cm−2, a mixture of C49 and partially agglomerated C54 TiSi2 grains was found in some of the 5×5 μm2 contact windows, while only C49 existed in the 0.7×0.7 μm2 windows. Agglomeration is shown to lead to possible C49−C54 coexistence, as well as erroneous interpretation of the C54 nucleation density. Decreasing the As dose to 5×1015 cm−2 leads to a thicker TiSi2 layer, but does not have a major influence on phase formation in the small windows, although only C54 TiSi2 was found in the large ones. In the presence of a thin Nb layer between Ti and poly-Si, C40 (Ti,Nb)Si2 was consistently found in all contacts, indicating that formation does not depend on the contact size at least down to 0.5 μm2. Surprisingly, Ti was found on both sides of th...

Continuous and uniform Ni(Si,Ge) layers are formed on polycrystalline Si and Si0.42Ge0.58 substrate films at 500 degreesC by rapid thermal processing. The germanosilicide is identified as NiSi0.42G ...

In this paper we present results of the efficiency optimization study performed in our production line for CIGS solar modules. For three different Ga/(Ga+In) ratios two different grading settings were tested. Results indicate high impact of these parameters on efficiency, in the range of 0.5% (abs.). Increasing the Ga content in the film, results in an increase of module voltage. This is almost completely compensated by the decrease of Isc. The resulting change in efficiency is FF driven. The FF increases slightly with higher overall Ga content, but the grading plays a more important role. For the grading setting 1, which was steeper than the setting 2, the FF and consequently efficiency were significantly improved. Optimum Ga content and grading has been defined accordingly.

The purpose of this study was to compare the integration in bone of uncoated free form fabricated cobalt chromium (CoCr) implants to the same implant with a calcium aluminate coating. The implants of cylindrical design with a pyramidal surface structure were press-fit into the limbs of New Zealand white rabbits. After 6 weeks, the rabbits were sacrificed, and samples were retrieved and embedded. Ground sections were subjected to histological analysis and histomorphometry. The section counter part was used for preparing an electron transparent transmission electron microscopy sample by focused ion beam milling. Calcium aluminate dip coating provided a significantly greater degree of bone contact than that of the native CoCr. The gibbsite hydrate formed in the hardening reaction of the calcium aluminate was found to be the exclusive crystalline phase material in direct contact with bone.

The aim of this work was to investigate the in vitro bioactivity of two different experimental dental luting cement formulations based on calcium aluminate (CA) in comparison with glass ionomer cement (GIC). One of the CA-based formulations was a hybrid between CA and GIC.Samples were submerged in phosphate buffered saline and stored at 37 degrees C for four periods of time: 1 h, 1 day, 7 days and 4 weeks. After storage the samples were analyzed in order to investigate if a surface layer of hydroxyapatite had formed. The analysis techniques used included grazing incidence X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy.Both the CA-containing formulations were found to be bioactive. The highest degree of bioactivity was found on the sample with only CA as active substance. A relatively thick and totally covering layer was already formed after 24 h. On the hybrid material hydroxyapatite was found after 7 days. The GIC showed no bioactivity during the test period.The utilization of a bioactive material for tooth restorations will give an opportunity for remineralization and a natural and durable seal of the tooth-material interface. Materials based on CA exhibit bioactivity.

This study has been carried out to investigate the bioactivity of rutile and to deposit hydroxyapatite (HA) on heat-treated titanium through a biomimetic method. Biomimetic deposition of HA has gained large interest because of its low deposition temperature and good step coverage; however, it demands a substrate with bioactive properties. Commercially pure titanium is not bioactive but it can acquire bioactive properties through various surface treatments. In the present study, titanium plates were heat-treated at 800 degrees C to achieve rutile TiO(2) surfaces. These samples were immersed in a phosphate-buffered saline solution for seven days in order to deposit a HA layer on the surface. The rutile TiO(2) surfaces were found to be highly bioactive: after seven days of immersion, a layer of HA several micrometers thick covered the plates. The HA surfaces were confirmed by electron microscopy and X-ray diffraction. A scratch test was used to assess the adhesion of the HA coatings. This is a standard method to provide a measure of the coating-to-substrate adhesion and was found to be a useful method to test the thin HA coatings deposited on the bioactive surfaces. The critical pressure of the layer was estimated to be 2.4+/-0.1GPa.

A key feature in the understanding of the mechanisms of integration of implant materials is a deepened in-sight of the elemental and molecular composition of the interface zone between the implant and tissue. To analyze the interface at the ultrastructural level, transmission electron microscopy (TEM) is needed. However, techniques to fabricate thin foils for TEM are difficult and time consuming. By using focused ion beam microscopy (FIB) for site-specific preparation of TEM-samples, intact interfaces between bioceramics and calcified tissue can be prepared. The site-specific accuracy of the technique is about 1 mm. By using a dual-beam FIB, which is a combined scanning electron and focused ion beam microscope, the sample can be imaged with both electrons and ions (generating both secondary electrons and ions). Results from interface studies between Ca-aluminate based orthopaedic cement, dental materials, HA-coated Ti-implants and bone are presented. The interfaces were imaged in scanning-TEM and bright field mode, the crystal structures were determined using electron diffraction and elemental composition analyzed with energy dispersive spectroscopy. The technique fulfils a demand to correlate the surface properties of bioceramic implants with the structure and composition of preserved interfaces with tissues.

NiSi1-xGex films on compressively strained as well as relaxed undoped Si1-xGex epitaxially grown substrates with x=0.06-0.30 on Si(001) wafers have been studied with respect to the relative orienta ...

The reactions of Ni with polycrystalline Si, Si0.82Ge0.18 and Si0.818Ge0.18C0.002 films in two different configurations during rapid thermal processing were studied. For the usually studied planar configuration with 20 nm thick Ni on 130–290 nm thick Si1-x-yGexCy, NiSi1-xGex(C) forms at 450°C on either Si0.82Ge0.18 or Si0.818Ge0.18C0.002, comparable to NiSi formed on Si. However, the agglomeration of NiSi1-xGex(C) on Si0.818Ge0.18C0.002 occurs at 625°C, about 50°C higher than that of NiSi1-xGex on Si0.82Ge0.18. For thin-film lateral diffusion couples, a 200-nm thick Ni film was in contact with 80–130 nm thick Si1-x-yGexCy through 1–10 μm sized contact openings in a 170 nm thick SiO2 isolation. While the Ni3Si phase was formed for both the Si0.82Ge0.18 and Si0.818Ge0.18C0.002 samples, the presence of 0.2 at.% C caused a slightly slower lateral growth.

The formation of NiSi1-xGex on Si1-xGex(111) substrates with x=0, 0.05, and 0.20 at an annealing temperature of 500 degrees C has been studied by x-ray diffraction, transmission electron microscopy ...