Field-effect transistor based on organosoluble germanium nanoclusters

Synthesis and monolayer behavior of organogermanium clusters

Several organogermanium clusters (Or-GeCs) with different organic capping reagents have been synthesized, and their monolayer behaviors on a water surface studied. GeCl(4) and organic bromides were reacted in a one-pot process using magnesium to synthesize the corresponding Or-GeCs. The structures of the Or-GeCs were characterized by UV-vis, NMR, and FT-IR spectroscopy. GPC measurements were also collected, and the results revealed that the cores of the clusters were composed of a 3-D Ge-Ge network capped with organic reagents. Surface pressure (π)-area (A) isotherms and Brewster angle microscopy (BAM) measurements indicated that the Or-GeCs with alkyl capping regents formed an oil, whereas those with aromatic capping regents formed a solid-like monolayer at the air-water interface. It was concluded that the occurrence of a π-π interaction between the aromatic capping reagents was necessary for the formation of a solid-like film. Phenyl-GeCs, which contained a phenyl group capping reagent, were transferred onto a solid substrate using the Langmuir-Schaeffer method, and atomic force microscopy (AFM) images revealed a uniform film (root mean square roughness of 0.6 nm) of 3-4 nm in thickness. Furthermore, a multilayer phenyl-GeC film was prepared by repeating the deposition process.

Germanium and silicon nanocrystal thin-film field-effect transistors from solution

Germanium and silicon have lagged behind more popular II-VI and IV-VI semiconductor materials in the emerging field of semiconductor nanocrystal thin film devices. We report germanium and silicon nanocrystal field-effect transistors fabricated by synthesizing nanocrystals in a plasma, transferring them into solution, and casting thin films. Germanium devices show n-type, ambipolar, or p-type behavior depending on annealing temperature with electron and hole mobilities as large as 0.02 and 0.006 cm(2) V(-1) s(-1), respectively. Silicon devices exhibit n-type behavior without any postdeposition treatment, but are plagued by poor film morphology.

Solution-phase synthesis of germanium nanoclusters using sulfur

Sulfur is used to promote the formation of germanium nanocrystals from the robust organometallic precursor, triphenylgermanium chloride, at elevated temperatures (300 °C) in the surfactant/solvent hexadecylamine. Transmission electron microscopy shows that 8 nm germanium nanocrystals are produced that self-assemble into uniform-sized 60 nm germanium nanoclusters after purification. Electron diffraction studies show that the germanium nanoclusters have a diamond germanium crystal structure and energy dispersive x-ray spectroscopy shows that the nanoclusters are primarily composed of pure germanium.

Thermal behavior and film formation from an organogermanium polymer/nanoparticle precursor

In situ high-resolution transmission electron microscopy (HRTEM) was used to investigate the effect of heating on an organo-Ge polymer/nanoparticle composite material containing 4-8 nm diameter alkyl-terminated Ge nanoparticles. The product was obtained from the reduction of GeCl4 with Na(naphthalide) with subsequent capping of the -Cl surface with n-butyl Grignard reagent. The in situ HRTEM micrographs show that the product undergoes significant changes upon heating from room temperature to 600 degrees C. Two pronounced effects were observed: (i) Ge nanoparticles coalesce and remain crystalline throughout the entire temperature range, and (ii) the organo-Ge polymer acts as a source for the in situ formation of additional Ge nanoparticles. The in situ-formed Ge nanoparticles are approximately 2-3 nm in diameter. These in situ-formed nanoparticles (2-3 nm) are so dense that, together with the original ones, they build up an almost continuous crystalline film in the temperatures between 300 and 500 degrees C. Above 480 degrees C, melting of the in situ formed Ge nanoparticles (2-3 nm) is observed, while nanoparticles greater than 5 nm remain crystalline. After cooling to room temperature, the 2-3 nm Ge nanoparticles recrystallized.