Frequency dispersion reduction and bond conversion on n-type GaAs by in situ surface oxide removal and passivation

The method of surface preparation on n-type GaAs, even with the presence of an amorphous-Si interfacial passivation layer, is shown to be a critical step in the removal of accumulation capacitance frequency dispersion. In situ deposition and analysis techniques were used to study different surface preparations, including NH4OH, Si-flux, and atomic hydrogen exposures, as well as Si passivation depositions prior to in situ atomic layer deposition of Al2O3. As–O bonding was removed and a bond conversion process with Si deposition is observed. The accumulation capacitance frequency dispersion was removed only when a Si interlayer and a specific surface clean were combined

GaAs interfacial self-cleaning by atomic layer deposition

The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial "self-cleaning" is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements

Microstructure of an Extruded Third-Generation Snack Made from a Whole Blue Corn and Corn Starch Mixture

Blue corn is a potential material for expanded snack production. Whole blue corn meal was mixed with corn starch and processed by extrusion to produce a third-generation snack. Optimum extrusion conditions were calculated with the response surface methodology using expansion index (EI), penetration force (PF), specific mechanical energy (SME) and total anthocyanins content (TAC). Optimum conditions (zone 1, 67°C; cooking zone, 123°C; zone 3, 75°C; feed moisture, 24.6%) were used to extrude the mixture in a single-screw extruder, and EI,PF,SME and TAC of the expanded pellet were compared against predicted optimum values. Starch structural changes in pellets and expanded were analyzed with DSC, viscosity profiles, x-ray diffraction and SEM. Extruded pellet did not differ (p>0.05) from the predicted. However, TAC was lower (p<0.05) in the expanded pellet. Structural analyses showed damage starch granular structure during extrusion and pellet expansion. Blue corn is a promising material for production of third-generation snacks

Interface studies of GaAs metal-oxide-semiconductor structures using atomic-layer-deposited HfO2/Al2O3 nanolaminate gate dielectric

A systematic capacitance-voltage study has been performed on GaAs metal-oxide-semiconductor (MOS) structures with atomic-layer-deposited HfO2/Al2O3 nanolaminates as gate dielectrics. A HfO2/Al2O3 nanolaminate gate dielectric improves the GaAs MOS characteristics such as dielectric constant, breakdown voltage, and frequency dispersion. A possible origin for the widely observed larger frequency dispersion on n-type GaAs than p-type GaAs is discussed. Further experiments show that the observed hysteresis is mainly from the mobile changes and traps induced by HfO2 in bulk oxide instead of those at oxide/GaAs interface

S passivation of GaAs and band bending reduction upon atomic layer deposition of HfO2/Al2O3 nanolaminates

A systematic study of the interface engineering and dielectric properties of nanolaminated hafnium aluminate on GaAs is presented. The dielectrics were deposited using atomic layer deposition of alternating cycles of HfO2 and Al2O3 on GaAs substrates. High resolution x-ray photoelectron spectroscopy (XPS) showed differences in space charge amounts at the interface for the two surface treatments [NH4OH or (NH4)(2)S]. In-situ XPS analysis shows that chemical bonding to oxygen across the nanolaminate film is independent of the interface formation conditions. In addition, the GaAs surface treated with (NH4)(2)S shows a decreased band bending and slightly thinner films with respect to NH4OH. (C) 2008 American Institute of Physics

2,3-Dimethoxy-5-methyl-1,4-benzoquinones and 2-methyl-1,4-naphthoquinones: glycation inhibitors with lipid peroxidation activity

Anti-glycation activity of our anti-oxidant quinone library was measured and several 2,3-dimethoxy-5-methyl-1,4-benzoquinones and 2-methyl-1,4-naphthoquinones were identified as novel inhibitors of glycation, of which 2,3-dimethoxy-5-methyl-1,4-benzoquinones 13b is the most potent glycation inhibitor with around 50 [mu]M of the IC50 valueNRC publication: Ye