Exponential absorption edge in hydrogenated α-Si films

Optical and photoelectric measurements demonstrate that hydrogenated amorphous silicon prepared by glow discharge decomposition of silane has an exponential optical absorption edge, over the photon energy range 1.4–1.8 eV with a slope of 0.05–0.08 eV. Evidence is presented that the photogeneration efficiency is unity at room temperature and independent of electric field (10²?10⁴ V/cm^?1) and photon energy (1.2–2.2 eV).     

Vibrational spectra of crystalline H2SeO3 in the O-H stretching region

IR transmission, near-normal IR reflection and polarized Raman spectra of single crystals of selenious acid (H₂SeO₃) have been obtained at temperatures between 77°K and 335°K. The observed bands in the O-H stretching region have been assigned to two types of O-H….O bonds in the crystal structure. The spectral results appear to rule out correlation field splittings, intramolecular coupling, or Fermi resonance as explanations for the observed splitting. A proposed model based on intermolecular coupling of O-H….O vibrations to explain the splitting of the O-H stretching region is given.     

The Reaction of Ketenylidenetriphenylphosphorane (Ph3P˭C˭C˭O) with Acidic H‒E (E˭O,N) Bonds

Abstract

The reactivity of ketenylidenetriphenylphosphorane (1) with the protic reagents 2,4,6-trimethylphenol (7), 2,6-di-tert-butyl-4-methylphenol (8), and diphenylamine (9) has been explored. Three novel carbonyl-stabilized ylides have been synthesized and characterized. Crystal structures were obtained for Ph₃PCHC(O)O(C₆H₂Me₃) (11), Ph₃PCHC(O)O(C₆H₂t-Bu₂Me) (12), and Ph₃PCHC(O)NPh₂ (13), respectively. These products were then methylated in an attempt to develop a new route to low-valent carbon compounds. Crystals of [Ph₃PCH(CH₃)C(O)O(C₆H₂Me₃)]I (14) were isolated and characterized but this route did not prove to be synthetically useful, at least toward the goal of preparing low-valent carbon-centered materials. Finally, 1 was also reacted with the bulky tin reagent, bis[bis(trimethylsilyl)amido]tin(II), in the presence of 2,4,6-trimethylphenol. A complex mixture of products was obtained, from which crystals of an unusual chelated tin compound (15) were isolated and characterized using X-ray crystallography.     

Intracellular pH mapping with SNARF-1 and confocal microscopy. II: pH gradients within single cultured cells

Using the pH-sensitive dual-emission fluorophore, carboxy-seminaphthorhodaflour-1 (SNARF-1) coupled with a laser-scanning confocal microscope system it is now possible to map intracellular pH. We have applied this combination to investigate the pH levels and distribution within single isolated cultured proximal tubule, bovine aortic endothelial and rat aortic smooth muscle cells. The majority of cells showed a uniform cytosolic pH. However, pH gradients were evident between the cytosol and nuclear regions with the nuclear regions having a predominantly higher pH than the cytosol. High concentrations of nigericin removed this gradient and indicated that active control of intranuclear pH by the nuclear membrane occured, possibly via the K⁺/H⁺ exchangers.     

Excimer laser assisted selective epitaxy of GaP

An ArF excimer laser has been used to achieve homoepitaxy of GaP at 500° C using trimethylgallium and tertiarybutylphosphine as the precursor gases. Dependence of epitaxial growth on several parameters is examined. The crystalline properties of the films are determined using cross-sectional transmission electron microscopy. It is found that at 500° C, in the presence of laser radiation, higher growth rate and superior crystalline properties of GaP are achieved compared to purely thermal metalorganic vapor phase epitaxy under the same conditions. Electrical properties of p-n diodes fabricated via Zn doping have also been examined.