Search

In this work, SiC nanowire (NW) FETs are prepared and their electrical measurements are presented. From the samples fabricated on the same substrate, various I-Vs shapes are obtained (linear, non linear symmetric, and asymmetric). With the assistance of simulation, we show that this is a result of different values of Schottky Barrier Heights (SBH) at Source (S) / Drain (D) contacts of FETs. An origin for this might be a non uniformity in annealing, NW doping level and high interface traps density (that pins the Fermi level) as well as the high sensitivity of the metal-NW contacts to local surface contaminations.

Experimental and simulated I-V characteristics of silicon carbide (SiC) nanowire-based field-effect transistors (NWFETs) are presented. SiC NWs were fabricated by using the vapor-liquid-solid mechanism in a chemical vapor deposition system. The diameter of fabricated SiC NWs varied from 60 up to 100 nm while they were some micrometers long. Their I-V characteristics were simulated with SILVACO software, and special attention was paid to explore the role of NW doping level and NW/dielectric interface quality. The fabricated SiC-based NWFETs exhibit a mediocre gating effect and were not switched-off by varying the gate voltage. Based on the simulations, this is a result of the high unintentional doping (estimated at 1times1019 cm-3) and the poor NW/dielectric interface quality. Moreover, a homemade algorithm was used to investigate the ideal properties of SiC-based NWFETs in ballistic transport regime, with NW lengths of 5-15 nm and a constant diameter of 4 nm for which the carrier transport is fully controlled by quantum effects. This algorithm self-consistently solves the Poisson equation with the quantum nonequilibrium Green function formalism. In the ballistic regime, devices with undoped SiC NWs exhibit superior theoretical performances (transconductance: ~43.2times10-6 A/V and ION/IOFF=1.6times105 for a device with 9-nm NW length) based on their simulated characteristics.

In view of the current industrial process for the conventional ethanol fermentation, in which raw starch materials are heated at 120 degrees C for 2 h, conditions for an alternative process were set: an overall time from saccharification to ethanol fermentation of within 3-4 days, an operation temperature of below 60 degrees C, an ethanol yield of over 93%, and a ratio of raw material to fermentation volume of within 1:4. To meet these conditions, previously a steeping method of starch materials in 0.5N HCl solution at 60 degrees C for 12 h were used, followed by combined actions of ..cap alpha..-amylase and glucoamylase. The ethanol yield from uncooked cassava starch treated under the conditions described was 95% after fermentation for 3 days with Saccharomyces cerevisiae. However, the use of a relatively higher concentration of acid for steeping is still a problem and gelatinization of starch materials is insufficient. This communication, therefore, describes effects of alkali steeping and structural change of starch granules on the ethanol fermentation. 8 references.