Resonance photoconductivity in Fe-doped InP

A photoconductivity peak at 0.44 eV is observed in Fe-doped InP. This peak is attributed to electrons which are optically excited from the Fe²⁺⁵E ground state to vibronic levels of the ⁵T₂ excited state, and thermally excited from there to the conduction band. The lineshape is nearly Gaussian and is well fitted by assuming a vibronic coupling energy of about 0.06 eV in the ⁵T₂ state. In analogy with results in the II–VI compounds this coupling may be dominated by interaction with non-symmetric lattice modes which produce a dynamic Jahn-Teller effect.     

FTIR Spectroscopy,SAXS and Electrical Conductivity Studies of the Hydrolysis and Condensation of Zirconium and Titanium Alkoxides

A continuous flowing-rapid mixing technique was combined with FTIR, SAXS and electrical conductivity to study the early stages of polymer formation and growth during the acid-catalyzed hydrolysis and condensation of titanium and zirconium alkoxides. Reaction times as short as 80 milliseconds were investigated. FTIR spectroscopy was used to monitor the water and M−OR concentrations during the reaction. Hydrolysis of ∼25–50% of the alkoxy groups was facile. The FTIR and SAXS data showed that condensation was also very rapid. The activity and mobility of the ions in the solution were monitored by electrical conductivity measurements. The decrease in the normalized solution conductivity during the reaction correlated with the loss of [M−OR]. Furthermore, the radius of gyration of the growing polymers increased rapidly in regimes where the conductivity and [M−OR] decreased fastest. This finding suggests that the mobility of some of the charge carrying species decreases because of the growth in size of the polymers. Managed by Lockheed-Martin Energy Systems, Inc.     

Quantitative analysis of surface donors in ZnO

At low temperatures, typically up to 30 K or even higher, the electrical properties of bulk ZnO samples are nearly always dominated by a conductive near-surface region. Here we show that a single, low-temperature Hall-effect measurement, say at 20 K, and a reasonable assumption regarding the upper limit of the surface compensation ratio, yields a value of surface donor concentration N_D,surf accurate to within about a factor two. Examples are given for bulk materials grown by the vapor-phase, melt, and hydrothermal processes.