Vertical structure of Sb-intercalated quasi-freestanding graphene on SiC(0001)

Using the normal incidence x-ray standing wave technique as well as low energy electron microscopy we have investigated the structure of quasi-freestanding monolayer graphene (QFMLG) obtained by intercalation of antimony under the $(6\sqrt{3}\times6\sqrt{3})R30^\circ$ reconstructed graphitized 6H-SiC(0001) surface, also known as zeroth-layer graphene. We found that Sb intercalation decouples the QFMLG very well from the substrate. The distance from the QFMLG to the Sb layer almost equals the expected van der Waals bonding distance of C and Sb. The Sb intercalation layer itself is mono-atomic, very flat, and located much closer to the substrate, at almost the distance of a covalent Sb-Si bond length. All data is consistent with Sb located on top of the uppermost Si atoms of the SiC bulk

Quasi‐Freestanding Graphene via Sulfur Intercalation: Evidence for a Transition State

Abstract Sulfur intercalation of a carbon rich (63×63)R30∘ reconstruction on silicon carbide, also known as buffer layer, is reported. In a two‐zone furnace a sulfur rich precursor is heated and the gaseous species is transported for intercalation by an argon flow to the sample. Successful intercalation can be confirmed by X‐ray photoelectron spectroscopy and low‐energy electron diffraction. Angle‐resolved photoelectron spectroscopy reveals a p‐type doping of the intercalated samples. In some cases only partial intercalation appears with non‐intercalated sulfur on top of the remaining buffer layer areas. Further annealing of such samples leads to a migration of the non‐intercalated sulfur under the buffer layer areas, indicating that the sulfur bonded to the buffer layer constitutes a transition state

Fabrication of nanoparticle-containing films and nano layers for alloying and joining

Nanoparticles (NPs) can improve mechanical properties of construction elements. However, the integration is not trivial due to the nanoscopic nature of the particles and the different material properties of particle and device: new processing routes have to be found for homogeneous incorporation. Therefore, a wet chemical synthesis is established to incorporate various ceramic NPs such as TiO2, TiC, SiC, and WC in copper films in desired concentrations. Depending on the kind and concentration of NPs, hardness and wear resistance of copper are enhanced. The resulting metal matrix composite films are thus of high interest for various applications such as reinforced electrical contacts and in aerospace and automotive technology. The energy released in an exothermic reaction of a reactive multilayer system (RMS) can be used as a precise and well-defined local heat source for joining the surface of polymers. In this case, a RMS consisting of alternating layers of nickel and aluminum is used. The design of the RMS is adjusted in a way that despite the intensive but very short reaction no damaging of the polymers occurs. The joining process takes only milliseconds and does not require any pre- or post-treatment of the polymers. With the optimal joining parameters, e.g., the joining load, for fiber non-reinforced polymers tensile strengths can be achieved, which lead to a material failure by tensile attempts. Preliminary tests of fiber reinforced polymers result in a tensile strength that is characteristic for adhesive polymer bonding. Model simulations show that only the first few micrometers of the materials surface are in a liquid state for a very short period of time. In addition to the applied joining load, the materials composition and specifically the resulting solidification process of the liquid polymer phase result in a strong bond between polymer samples that have to be joined. Materials with different thermal expansion coefficients are difficult to join thermally. Among them is the joining of solar cells. It is conventionally carried out by heating the whole assembly. Due to the thermal differences between tabbing wire and silicon, deformations as well as changes in the microstructure can occur. In the worst case, damage of the whole assembly is possible. Upon inspection of the joining process, the high energy consumption of the process itself is also critical

High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

We show full Li/S cells with the use of balanced and high capacity electrodes to address high powerelectro-mobile applications. The anode is made of an assembly comprising of silicon nanowires asactive material densely and conformally grown on a 3D carbon mesh as a light-weight current collector,offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growthis guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3Dsubstrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anodein Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combinedwith high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflatebasedelectrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacityof 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles(capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNWLi/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lowerdegradation is due to a lower self-reduction of polysulfides after continuous charging/discharging

High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging

High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging

Domain Boundary Formation Within an Intercalated Pb Monolayer Featuring Charge-Neutral Epitaxial Graphene

The synthesis of new graphene-based quantum materials by intercalation is an auspicious approach. However, an accompanying proximity coupling depends crucially on the structural details of the new heterostructure. It is studied in detail the Pb monolayer structure after intercalation into the graphene buffer layer on the SiC(0001) interface by means of photoelectron spectroscopy, x-ray standing waves, and scanning tunneling microscopy. A coherent fraction close to unity proves the formation of a flat Pb monolayer on the SiC surface. An interlayer distance of 3.67 Å to the suspended graphene underlines the formation of a truly van der Waals heterostructure. The 2D Pb layer reveals a quasi ten-fold periodicity due to the formation of a grain boundary network, ensuring the saturation of the Si surface bonds. Moreover, the densely-packed Pb layer also efficiently minimizes the doping influence by the SiC substrate, both from the surface dangling bonds and the SiC surface polarization, giving rise to charge-neutral monolayer graphene. The observation of a long-ranged ((Formula presented.)) reconstruction on the graphene lattice at tunneling conditions close to Fermi energy is most likely a result of a nesting condition to be perfectly fulfilled