Wafer Scale Synthesis and High Resolution Structural Characterization of Atomically Thin MoS2 Layers

Synthesis of atomically thin MoS₂ layers and its derivatives with large‐area uniformity is an essential step to exploit the advanced properties of MoS₂ for their possible applications in electronic and optoelectronic devices. In this work, a facile method is reported for the continuous synthesis of atomically thin MoS₂ layers at wafer scale through thermolysis of a spin coated‐ammonium tetrathiomolybdate film. The thickness and surface morphology of the sheets are characterized by atomic force microscopy. The optical properties are studied by UV–Visible absorption, Raman and photoluminescence spectroscopies. The compositional analysis of the layers is done by X‐ray photo­emission spectroscopy. The atomic structure and morphology of the grains in the polycrystalline MoS₂ atomic layers are examined by high‐angle annular dark‐field scanning transmission electron microscopy. The electron mobilities of the sheets are evaluated using back‐gate field‐effect transistor configuration. The results indicate that this facile method is a promising approach to synthesize MoS₂ thin films at the wafer scale and can also be applied to synthesis of WS₂ and hybrid MoS₂‐WS₂ thin layers.     

Molecular absorption and photodesorption in pristine and functionalized large-area graphene layers

We studied the photodesorption behavior of pristine and nitric acid (HNO(3)) treated graphene layers fabricated by chemical vapor deposition (CVD). The decrease in electrical conductivity and a negative shift of the Dirac point in graphene layers illuminated with ultraviolet light are caused by molecular photodesorption, while the UV illumination does not degrade the carrier mobility of graphene layers. When graphene layers were treated with concentrated HNO(3), the photodesorption-induced current decrease became less significant than for pristine graphene layers. We suggest this is due to the passivation of oxygen-bearing functionalities to CVD grown graphene structural defects by HNO(3) functionalization, which prevents the further absorption of gas molecules. Our results provide a new strategy for stabilizing the electrical performance of CVD grown large-area graphene layers for applications ranging from nanoelectronics to optoelectronics.     

Exploring factors affecting consumers' adoption of wearable devices to track health data

Universal Access in the Information Society - Mobile health is a rapidly emerging topic due to technological advances, especially in mobile computing and communication technologies. Increased...