Contact angle goniometry is conducted for epitaxial graphene on SiC. Although only a single layer of epitaxial graphene exists on SiC, the contact angle drastically changes from 69 degrees on SiC substrates to 92 degrees on graphene. It is found that there is no thickness dependence of the contact angle from the measurements of single-, bi-, and multilayer graphene and highly ordered pyrolytic graphite (HOPG). After graphene is treated with oxygen plasma, the level of damage is investigated by Raman spectroscopy and the correlation between the level of disorder and wettability is reported. By using a low-power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices.

Graphene has attracted much interest in both academia and industry. The challenge of making it semiconducting is crucial for applications in electronic devices. A promising approach is to reduce its physical size down to the nanometer scale. Here, we present the surface-assisted bottom-up fabrication of atomically precise armchair graphene nanoribbons (AGNRs) with predefined widths, namely 7-, 14- and 21-AGNRs, on Ag(111) as well as their spatially resolved width-dependent electronic structures. STM/STS measurements reveal their associated electron scattering patterns and the energy gaps over 1 eV. The mechanism to form such AGNRs is addressed based on the observed intermediate products. Our results provide new insights into the local properties of AGNRs, and have implications for the understanding of their electrical properties and potential applications.

Sb2Se3 is a promising absorber material for photovoltaic cells because of its optimum band gap, strong optical absorption, simple phase and composition, and earth-abundant and nontoxic constituents. However, this material is rarely explored for photovoltaic application. Here we report Sb2Se3 solar cells fabricated from thermal evaporation. The rationale to choose thermal evaporation for Sb2Se3 film deposition was first discussed, followed by detailed characterization of Sb2Se3 film deposited onto FTO with different substrate temperatures. We then studied the optical absorption, photosensitivity, and band position of Sb2Se3 film, and finally a prototype photovoltaic device FTO/Sb2Se3/CdS/ZnO/ZnO:Al/Au was constructed, achieving an encouraging 2.1% solar conversion efficiency.

The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.