INFRARED SURFACE-PLASMONS ON PLATINUM SILICIDE

It is shown that surface plasmons (SPs) are supported on thin PtSi films. Using a prism-air gap-sample configuration, p-polarised infra-red light (3.39-mu-m) has been coupled with approximately 95% efficiency to SPs on the silicide electrode of PtSi-Si Schottky barrier structures. Stimulating SPs offers both a means of optically characterising silicide films and of enhancing optical absorption with a view to significantly increasing the Schottky barrier photoresponse.

Surface enhanced Raman evidence for Ag+ complexes of adenine, deoxyadenosine and 5'-dAMP formed in silver colloids

We report the formation of highly scattering silver complexes of adenine, deoxyadenosine and 5'-dAMP under alkaline pH conditions in the colloidal silver solutions which are used for surface-enhanced Raman spectroscopy. These complexes, and other pH-dependent phenomena, help to explain the diversity of previously reported adenine SERS spectra. Using conditions which promote complex formation allows nucleotides to be detected at <1 ppm, even in solutions with high salt concentrations.

Near-surface temperature cycling of stone and its implications for scales of surface deterioration

Many previous studies into internal temperature gradients within stone have assumed smooth, exponential increases and decreases in sub-surface temperatures in response, for example, to diurnal patterns of heating and cooling and these have been used to explain phenomena such as large-scale contour scaling. This high-resolution experimental study, in which a porous limestone block was subjected to alternate surface heating and cooling using an infrared lamp, demonstrates that internal temperature gradients in response to short-term environmental cycles (measured in minutes) can in fact be complex and inconsistent. Results confirm the significance of very steep temperature/stress gradients within the outer 10 mm or less of exposed stone. Below this the data indicate complex patterns of temperature reversals, the amplitudes of which are attenuated with depth and which are influenced in their intensity and location by variations in the relative duration of heating and cooling phases. It is suggested that the reversals might represent ‘interference patterns’ between incoming and outgoing thermal waves, but whatever their origin they are potentially important because they occur within the zone in which many stone decay processes, especially salt weathering, operate. These processes invariably respond to temperature and moisture fluctuations, and short-term interruptions to insolation could, for example, trigger these fluctuations on numerous occasions over a day. In particular, the reversals occur at a scale that is commensurate with decay by multiple flaking and could indicate an underlying control on this previously little-researched pattern of weathering. In the context of this publication, however, the main lesson to be learned from this study is that differing scales of behaviour require different scales of enquiry.

Mapping Irreversible Electrochemical Processes on the Nanoscale: Ionic Phenomena in Li Ion Conductive Glass Ceramics

A scanning probe microscopy approach for mapping local irreversible electrochemical processes based on detection of bias-induced frequency shifts of cantilevers in contact with the electrochemically active surface is demonstrated. Using Li ion conductive glass ceramic as a model, we demonstrate near unity transference numbers for ionic transport and establish detection limits for current-based and strain-based detection. The tip-induced electrochemical process is shown to be a first-order transformation and nucleation potential is close to the Li metal reduction potential. Spatial variability of the nucleation bias is explored and linked to the local phase composition. These studies both provide insight into nanoscale ionic phenomena in practical Li-ion electrolyte and also open pathways for probing irreversible electrochemical, bias-induced, and thermal transformations in nanoscale systems.

Real-space mapping of dynamic phenomena during hysteresis loop measurements: Dynamic switching spectroscopy piezoresponse force microscopy

Dynamic switching spectroscopy piezoresponse force microscopy is developed to separate thermodynamic and kinetic effects in local bias-induced phase transitions. The approaches for visualization and analysis of five-dimensional data are discussed. The spatial and voltage variability of relaxation behavior of the a-c domain lead zirconate-titanate surface suggest the interpretation in terms of surface charge dynamics. This approach is applicable to local studies of dynamic behavior in any system with reversible bias-induced phase transitions ranging from ferroelectrics and multiferroics to ionic systems such as batteries, fuel cells, and electroresistive materials. (C) 2011 American Institute of Physics. [doi:10.1063/1.3590919]

Investigation of Finish-cut of Microelectrodischarge Milling for Nano Surface Finish

In this article, the machining conditions to achieve nanometric surface roughness in finish cut microelectrodischarge milling were investigated. For a constant gap voltage, the effect of feed rate and capacitance was studied on average surface roughness (Ra) and maximum peak-to-valley roughness height (Ry). Statistical models were developed using a three-level, two-factor experimental design. The developed models minimized Ra and Ry by desirability function approach. Maximum desirability was found to be more than 98%. The minimum values of Ra and Ry were 23 and 173 nm, respectively, for 1.00 μm s-1 feed rate and 0.01 nF capacitance. Verification experiments were conducted to check the accuracy of the models, where the responses were found to be very close to the predicted values. Thus, the developed models can be used to generate nanometric level surface finish, which are useful for many applications in microelectromechanical systems.