A large improvement in Cu2ZnSnSe4 solar cell efficiency is presented based on the introduction of a Ge superficial nanolayer. This improvement is explained by three complementary effects: the formation of a liquid Ge‐related phase, the possible reduction of Sn multicharge states, and the formation of GeOx nanoinclusions, which lead to an impressive solar cell (VOC) increase.

Robust nanostructures for future devices will depend increasingly on their reliability. While great strides have been achieved for precisely evaluating electronic, magnetic, photonic, elasticity and strength properties, the same levels for fracture resistance have been lacking. Additionally, one of the self‐limiting features of materials by computational design is the knowledge that the atomistic potential is an appropriate one. A key property in establishing both of these goals is an experimentally‐determined effective surface energy or the work per unit fracture area. The difficulty with this property, which depends on extended defects such as dislocations, is measuring it accurately at the sub‐micrometer scale. In this Full Paper the discovery of an interesting size effect in compression tests on silicon pillars with sub‐micrometer diameters is presented: in uniaxial compression tests, pillars having a diameter exceeding a critical value develop cracks, whereas smaller pillars show ductility comparable to that of metals. The critical diameter is between 310 and 400 nm. To explain this transition a model based on dislocation shielding is proposed. For the first time, a quantitative method for evaluating the fracture toughness of such nanostructures is developed. This leads to the ability to propose plausible mechanisms for dislocation‐mediated fracture behavior in such small volumes.

Codeposition of hydrocarbons is a severe problem during focused electron beam writing of pure metal nanostructures. When using organometallic precursors, a low metal content carbonaceous matrix embedding and separating numerous nanosized metal clusters is formed. In this work, we present a new and easy approach to obtain high purity gold lines: the use of inorganic PF3AuCl as a precursor. Electrical resistivities as low as 22 μΩ cm at 295 K (ten times the bulk Au value) were obtained. This is to our knowledge the best value for focused electron beam deposition obtained from the vapor phase so far. No special care was taken to prevent hydrocarbon contamination. The deposited nanostructure consists of gold grains varying in size and percolation with beam parameters.

A detailed study explaining the beneficial effects of low temperature post deposition annealing combined with selective surface etchings for Cu 2 ZnSnSe 4 (CZTSe) based solar cells is presented. After performing a selective oxidizing surface etching to remove ZnSe secondary phases typically formed during the synthesis processes an additional 200ºC annealing step is necessary to increase device performance from below 3% power conversion efficiency up to 8.3% for the best case. This significant increase in efficiency can be explained by changes in the surface chemistry which results in strong improvement of the CdS/CZTSe heterojunction commonly used in this kind of absorber/buffer/window heterojunction solar cells. XPS measurements reveal that the 200ºC annealing promotes a Cu depletion and Zn enrichment of the etched CZTSe absorber surface relative to the CZTSe bulk. Raman measurements confirm a change in Cu/Zn ordering and increase in defect density. Furthermore, TEM microstructural investigations indicate a change of grain boundaries composition by a reduction of their Cu content after the 200ºC annealing treatment. Additionally, insights in the CdS/CZTSe interface are gained showing a significant amount of Cu in the CdS buffer layer which further helps the formation of a Cu-depleted surface and seems to play an important role in the formation of the pn-heterojunction.

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Due to substantial phonon scattering induced by various structural defects, the in-plane thermal conductivity (K) of graphene films (GFs) is still inferior to the commercial pyrolytic graphite sheet (PGS). Here, the problem is solved by engineering the structures of GFs in the aspects of grain size, film alignment, and thickness, and interlayer binding energy. The maximum K of GFs reaches to 3200 W m K and outperforms PGS by 60%. The superior K of GFs is strongly related to its large and intact grains, which are over four times larger than the best PGS. The large smooth features about 11 µm and good layer alignment of GFs also benefit on reducing phonon scattering induced by wrinkles/defects. In addition, the presence of substantial turbostratic-stacking graphene is found up to 37% in thin GFs. The lacking of order in turbostratic-stacking graphene leads to very weak interlayer binding energy, which can significantly decrease the phonon interfacial scattering. The GFs also demonstrate excellent flexibility and high tensile strength, which is about three times higher than PGS. Therefore, GFs with optimized structures and properties show great potentials in thermal management of form-factor-driven electronics and other high-power-driven systems.

The reactions of coronene dehydrogenation and fusion upon heat treatment in the temperature range of 500–700 °C were studied using XRD, TEM, Raman, IR, and NEXAFS spectroscopy. The formation of a coronene dimer (dicoronylene) was observed at temperatures 530–550 °C; dicoronylene can easily be separated using sublimation with a temperature gradient. An insoluble and not sublimable black precipitate was found to form at higher temperatures. Analysis of the data shows that dimerization of coronene is followed at 550–600 °C by oligomerization into larger molecules. Above 600 °C amorphization of the material and formation of graphitic nanoparticles was observed. Coronene fusion by annealing is proposed as a road to synthesis of larger polycyclic aromatic hydrocarbons and nanographenes.

The authors have experimentally investigated the compressive strength of GaAs pillars with a diameter of 1 m by uniaxial compression tests. The tests were performed at room temperature and, contrary to macroscopic tests, the micropillars were found to exhibit ductile plasticity comparable to that of metal single crystal micropillars. The yield stress was 1.8± 0.4 GPa and, for one pillar that was more closely examined, a total deformation of 24% was observed. In the diffraction patterns from transmission electron microscopy studies of this pillar, a high density of twins was observed.