We report low-temperature electronic transport in batch-processed single-walled carbon nanotube (SWNT) field-effect transistors (FETs). SWNTs
are in situ synthesized and wired between submicrometer metallic electrodes in a single-step process involving hot-filament-assisted chemical
vapor deposition. FETs show a pronounced ambipolar field effect between 1 and 300 K. Moreover, the gate dependence exhibits hysteresis
at any temperature because of the extraction and trapping of charges. We find Schottky barriers at the SWNT/metal contact to be responsible
for the field effect. Below 30 K, potential barriers along the SWNT induce a Coulomb blockade at low drain-source bias, leading to the
suppression of the field-effect gain and inducing fluctuations in the transconductance.
We demonstrate epitaxially grown high-quality pure germanium (Ge) on bulk silicon (Si) substrates by ultra-high-vacuum chemical vapor deposition (UHVCVD) without involving growth of thick relaxed SiGe buffer layers. The Ge layer is grown on thin compressively strained SiGe layers with rapidly varying Ge mole fraction on Si substrates resulting in several SiGe interfaces between the Si substrate and the pure Ge layer at the surface. The presence of such interfaces between the Si substrate and the Ge layer results in blocking threading dislocation defects, leading to a defect-free pure Ge epitaxial layer on the top. Results from various material characterization techniques on these grown films are shown. In addition, capacitance-voltage (CV) measurements of metal-oxide-semiconductor (MOS) capacitors fabricated on this structure are also presented, showing that the grown structure is ideal for high-mobility metal-oxide-semiconductor field-effect transistor applications.
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