We present the temperature-dependent carrier mobility of atomically thin MoS2 field-effect transistors on crystalline hexagonal boron nitride (h-BN) and SiO2 substrates. Our results reveal distinct weak temperature dependence of the MoS2 devices on h-BN substrates. The room temperature mobility enhancement and reduced interface trap density of the single and bilayer MoS2 devices on h-BN substrates further indicate that reducing substrate traps is crucial for enhancing the mobility in atomically thin MoS2 devices.

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One-dimensional GeO 2 and Ge nanostructures, including nanotubes, nanowires, and branched nanowires, were synthesized using Au as catalysts. White products of GeO 2 and brown products of Ge were fabricated at temperature regions of 500-600 and 300-400 °C, respectively. For the first time, we report the formation of single-crystalline GeO 2 nanotubes and branched nanowires. Detailed growth mechanisms of the nanowires, nanotubes, and branched nanowires are presented. Fabrication of one-dimensional nanostructures with different configurations and compositions simultaneously from a single precursor enables the diversity of nanotube/ nanowire synthesis, as well as their potential applications in nanoscale photonic and electronic devices.

Ge nanocrystals embedded in lanthanide-based high-k dielectric ͑amorphous Lu 2 O 3 in this work͒ were formed using pulsed laser deposition followed by rapid thermal annealing in N 2 ambient. The formation and evolution of the Ge nanocrystals have been studied using transmission electron microscopy ͑TEM͒, x-ray photoelectron spectroscopy ͑XPS͒ in conjunction with depth profiling, and secondary ion mass spectroscopy ͑SIMS͒ analysis. Plan-view TEM images indicated that the formation of nanocrystals was first initiated during the deposition process. The annealing treatment significantly enhanced the nucleation of Ge nanocrystals, resulting in a high areal density of 7 ϫ 10 11 cm −2 Ge nanocrystals with a mean size of about 6 nm in diameter in the amorphous Lu 2 O 3 matrix. XPS depth profile analysis revealed that Ge nanocrystals were predominantly formed from the precipitation of Ge nuclei from the oxide phase. A low annealing temperature of 400 °C was sufficient to dissociate the GeO 2 and GeO x leading to the formation of Ge nanocrystals. An accumulation of Ge species close to the upper Ge/ Lu 2 O 3 interface was observed from XPS and SIMS depth profile analysis. Different charge storage behaviors observed from the memory capacitor devices before and after annealing could be correlated to the changes in structure and composition of the film. The memory capacitor device fabricated from the annealed sample showed efficient charge storage effect under a low operation voltage without significant initial charge decay.

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