Photoluminescence Detection of Surface Oxidation Processes on InGaN/GaN Nanowire Arrays.

InGaN/GaN nanowire arrays (NWA) exhibit efficient photoluminescence (PL) in the green spectral range, which extends to temperatures well beyond 200 °C. Previous work has shown that their PL is effectively quenched when oxidizing gas species such as O, NO, and O abound in the ambient air. In the present work we extend our investigations to reducing gas species, in particular to alcohols and aliphatic hydrocarbons with C to C chain lengths.

Self-Test Procedures for Gas Sensors Embedded in Microreactor Systems.

Metal oxide (MOX) gas sensors sensitively respond to a wide variety of combustible, explosive and poisonous gases. However, due to the lack of a built-in self-test capability, MOX gas sensors have not yet been able to penetrate safety-critical applications. In the present work we report on gas sensing experiments performed on MOX gas sensors embedded in ceramic micro-reaction chambers.

Photoluminescence Probing of Complex HO Adsorption on InGaN/GaN Nanowires.

We demonstrate that the complex adsorption behavior of HO on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, HO adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, HO adsorbates act as efficient photoluminescence enhancers.

Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors.

In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology.

The surface conductivity at the diamond/aqueous electrolyte interface.

We investigate the origin of the surface conductivity of H-terminated diamond films immersed in aqueous electrolyte. We demonstrate that in contrast to the in air situation, charge transfer across the diamond interface does not govern the surface conductivity in aqueous electrolyte when a gate electrode controls the diamond/electrolyte interfacial potential. Instead, this almost ideally polarizable interface allows the capacitive charging of the surface.