Using a photolithographic fabrication process microminiature Joule–Thomson refrigerators have been fabricated substantially smaller in size than hitherto and with refrigeration capacities of the order of 25 mW. The devices are 0.5×2×15 mm in size, they operate on nitrogen gas and cool to 88 K in 45 s. The fabrication process allows mass production of the devices at low cost. It was found that the theoretical models used for the design of the refrigerators are adequate at this level of miniaturization.

Germanium (Ge) nanowires were fabricated directly on stainless steel current collectors for Li-ion batteries without any additional catalytic seeds. Substrates of stainless steel are unconventional materials for the direct growth of nanowires for battery applications. Stainless steel substrates were activated for nanowire growth by annealing them in air at a temperature of 450 °C to form a catalytic iron oxide surface layer. Large yields of Ge nanowires were obtained from oxidized stainless steel via a liquidinjection chemical vapor deposition process, with diphenylgermane (DPG) as a Ge precursor. Fabricated Ge nanowires have uniform morphology and are single-crystalline. The capacity retention from a nanowire anode tested at 0.2 C is very stable, highlighted by reversible capacities of ∼1014 and 894 mAh/g after the 50th and 250th cycles, respectively. The large specific capacity values are one of the highest achieved for binder-free Ge nanomaterial-based anode materials. The high specific capacity values, good capacity retention, and voltage stability observed resulted from the excellent adhesion of the nanowires to the stainless steel current collectors, ensuring good electrical contact and electrical conductivity. Achieving such electrochemical performance from Ge nanowires grown via a significantly simplified direct growth process on a functional conductive substrate demonstrates the potential of directly grown Ge nanowires as a high-performing anode material for Li-ion batteries.

The effect of particle size, morphology and Crates on 3D structured Co 3 O 4 inverse opal conversion mode anode materials

This paper details the application of phosphorus monolayer doping of silicon on insulator substrates. There have been no previous publications dedicated to the topic of MLD on SOI, which allows for the impact of reduced substrate dimensions to be probed. The doping was done through functionalization of the substrates with chemically bound allyldiphenylphosphine dopant molecules. Following functionalization, the samples were capped and annealed to enable the diffusion of dopant atoms into the substrate and their activation. Electrical and material characterisation was carried out to determine the impact of MLD on surface quality and activation results produced by the process. MLD has proven to be highly applicable to SOI substrates producing doping levels in excess of 1 × 1019 cm−3 with minimal impact on surface quality. Hall effect data proved that reducing SOI dimensions from 66 to 13 nm lead to an increase in carrier concentration values due to the reduced volume available to the dopant for diffusion. Dopant trapping was found at both Si–SiO2 interfaces and will be problematic when attempting to reach doping levels achieved by rival techniques.

Reported here is a new chemical route for the wet chemical functionalization of germanium (Ge), whereby arsanilic acid is covalently bound to a chlorine (Cl)-terminated surface. This new route is used to deliver high concentrations of arsenic (As) dopants to Ge, via monolayer doping (MLD). Doping, or the introduction of Group III or Group V impurity atoms into the crystal lattice of Group IV semiconductors, is essential to allow control over the electronic properties of the material to enable transistor devices to be switched on and off. MLD is a diffusion-based method for the introduction of these impurity atoms via surface-bound molecules, which offers a nondestructive alternative to ion implantation, the current industry doping standard, making it suitable for sub-10 nm structures. Ge, given its higher carrier mobilities, is a leading candidate to replace Si as the channel material in future devices. Combining the new chemical route with the existing MLD process yields active carrier concentrations of dopants (>1 × 1019 atoms/cm3) that rival those of ion implantation. It is shown that the dose of dopant delivered to Ge is also controllable by changing the size of the precursor molecule. X-ray photoelectron spectroscopy (XPS) data and density functional theory (DFT) calculations support the formation of a covalent bond between the arsanilic acid and the Cl-terminated Ge surface. Atomic force microscopy (AFM) indicates that the integrity of the surface is maintained throughout the chemical procedure, and electrochemical capacitance voltage (ECV) data shows a carrier concentration of 1.9 × 1019 atoms/cm3 corroborated by sheet resistance measurements.