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The influence of low kinetic energy hydrogen ion irradiation on the chemical composition and luminescence intensity of MoS2 nanoflowers (NFs) hydrothermally synthesized is reported. X‐ray photoelectron spectroscopy (XPS) core‐level analysis of the as‐synthesized MoS2 NFs reveals the presence of the 2H‐MoS2 (semiconductor) crystal phase and MoOx. Furthermore, the relative amounts of oxygen and potassium decrease for increasing hydrogen ion irradiation time, whereas the photoluminescence (PL) intensity observed at 1.71 eV increased approximately three times. [ABSTRACT FROM AUTHOR]

The future demands for smart‐cities applications impose maximising the resources utilisation. This study achieves two main objectives to comply with fifth‐generation networks goals. First one is to enhance the Narrowband‐Internet of Things (NB‐IoT) spectral‐efficiency. The second is to alleviate the burden of two issues: The signalling during each transmission request for smart‐meters (SM) and queuing burden. First, we model the uplink scheduler for the NB‐IoT access network using state‐machine modelling methodology on Simulink environment. The simulation result is verified and validated with trusted modelling technique. Second, we optimise the NB‐IoT uplink scheduler which exploits the periodicity nature of SMs applications with putting envisage considering the emergency conditions. This is done by proposing integrated scheduling protocol which classifies the IoT traffic types and rearranges the transmission times of different SMs utilities and draws a map for the transmission schedule of them to better utilise the sparse time resources. The proposal comprises architecture, signalling, and algorithms. The optimisation is evaluated in term of numbers of SMs versus four spectral performance indicators; utilisation, efficiency, setup‐success‐percentage, and session‐drop‐rate according to a case study. The simulation results prove the ability of our proposal to increase the spectrum‐utilisation to 17.47%. This enhancement reflects on spectral‐efficiency that improved doubled. [ABSTRACT FROM AUTHOR]

The quest for low cost solar cells has resulted in attempts to use lower purity silicon rather than conventional electronic grade material. The metallic content of such 'solar silicon' is usually much higher than electronic grade material and this compromises the efficiency of photovoltaic conversion via a variety of recombination mechanisms. Molybdenum is a common metallic contaminant in Si which is difficult to getter because of its low diffusivity. It is known that Mo incorporates into the Si lattice as single interstitial atoms, introducing a deep donor level into the gap. In this work, we show that Mo in silicon can also form nano-precipitates which may represent a new general class of efficient recombination centres. We have observed the Mo precipitates by TEM as 5-10 nm clusters in Si samples into which molybdenum was introduced during growth or by ion implantation and annealing. In general, such precipitates can form in Si samples containing metals with low diffusivity during high-temperature treatments and subsequent cooling. We report the carrier capture and emission properties of Mo nano-precipitates, which show that these could be very effective recombination centres for minority carriers in p-type Si. In particular we present data and analysis of minority carrier charge exchange at these nano-dimension metallic defects. [ABSTRACT FROM AUTHOR]

Propagation of pre-existing micro cracks and their associated residual contact stresses, generated from the wafer sawing process, is the leading cause for photovoltaic (PV) silicon wafer/cell breakage during handling and processing. In the current work, the impact of a single micro crack on the fracture strength of PV silicon wafer is investigated based on a controlled flaw method. Radial/median cracks with controllable scales are introduced through microindentation at the center of a PV silicon sample to simulate micro cracks resulting from wafer sawing, handling, or thermal processing. Results indicate that the fracture strength of PV silicon wafer decreases linearly with the increasing of the microindentation load (radial crack scale). In addition, it is found that the impurity carbon plays an important role in the contact cracking-fracture process. The fracture strength increased ≈21% when the substitutional carbon concentration is increased from 1.2 × 1018 to 6.4 × 1018 cm−3. [ABSTRACT FROM AUTHOR]

Nanocrystalline (nc) Cu and Cu–1% Nb bulk materials are synthesized using a combination of cryogenic and room temperature ball milling. The grain size values of these in situ consolidated Cu and Cu–1% Nb, determined using transmission electron microscopy, are found to be 22 nm and 18 nm, respectively. In this investigation, isochronal heat treatments are performed for 1 h to establish grain size and microstructural changes as a function of temperature. The annealing of nc Cu–1% Nb at a temperature of 1073 K reveals a slight increase in the average grain size from 18 to 45 nm. The grain size of nc Cu, however, increases from 22 nm to about 3 μm after annealing at the same conditions. The present results indicate that solute entrapment plays a major role in thermal stability of the high purity contaminant‐free Cu with the addition of only 1 at% Nb after annealing for 1 h up to a homologous temperature of 0.8. Kinetic stabilization via clustering of Nb atoms on the grain boundaries and the triple junctions is also observed after annealing at high temperature for longer times. [ABSTRACT FROM AUTHOR]