Microscaled and nanoscaled platinum sensors

We show small and robust platinum resistive heaters and thermometers that are defined by microlithography on silicon substrates. These devices can be used for a wide range of applications, including thermal sensor arrays, programmable thermal sources, and even incandescent light emitters. To explore the miniaturization of such devices, we have developed microscaled and nanoscaled platinum resistor arrays with wire widths as small as 75 nm, fabricated lithographically to provide highly localized heating and accurate resistance (and hence temperature) measurements. We present some of these potential applications of microfabricated platinum resistors in sensing and spectroscopy

Enhancement of antimonide-based p-channel quantum-well field effect transistors using process-induced sprain

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 55-57).For decades, the scaling of silicon CMOS has brought impressive growth to the semiconductor industry, as well as a wealth of technological innovations. However, the continued scaling of CMOS devices to the nanometer regime is now threatened by intrinsic limitations to the use of silicon as the channel material. Hence, there is a strong interest in III-V semiconductor materials to replace silicon as the channel material as a result of their outstanding electron transport properties. While III-V materials have demonstrated impressive n-channel field-effect transistors (FETs), the same success has not yet been translated to the development of a high-performance III-V pchannel FET. This is because while many III-V's have high electron mobilities, they generally have very poor hole mobilities. The development of a high-performance III-V p-channel FET is critical to the realization of a future-generation III-V CMOS architecture. Among the III-Vs, the antimonides have the highest hole mobilities. This makes them attractive for developing a 111-V p-channel FET. This thesis examines the use of process-induced uniaxial strain combined with biaxial strain introduced during growth of the heterostructure as an approach to enhance antimonide-based FETs. Using a compressively stressed silicon nitride layer to induce uniaxial strain in the device, stressed devices with an InGaSb channel were fabricated and compared with unstressed devices processed in parallel. Enhancements of >50% in the intrinsic transconductance were observed as well as reductions of >30% in the source-drain resistance. This work illustrates the effectiveness of uniaxial strain in improving the performance of antimonide FETs.by Luke Guo.S.M

Thermal Blood Clot Formation and use in Microfluidic Device Valving Applications

The present invention provides a method of forming a blood-clot microvalve by heating blood in a capillary tube of a microfluidic device. Also described are methods of modulating liquid flow in a capillary tube by forming and removing a blood-clot microvalve

Hybridization gap versus hidden order gap in URu2_2Si2_2 as revealed by optical spectroscopy

We present the in-plane optical reflectance measurement on single crystals of URu$_2$As$_2$. The study revealed a strong temperature-dependent spectral evolution. Above 50 K, the low frequency optical conductivity is rather flat without a clear Drude-like response, indicating a very short transport life time of the free carriers. Well below the coherence temperature, there appears an abrupt spectral weight suppression below 400 cm$^{-1}$, yielding evidence for the formation of a hybridization energy gap arising from the mixing of the conduction electron and narrow f-electron bands. A small part of the suppressed spectral weight was transferred to the low frequency side, leading to a narrow Drude component, while the majority of the suppressed spectral weight was transferred to the high frequency side centered near 4000 cm$^{-1}$. Below the hidden order temperature, another very prominent energy gap structure was observed, which leads to the removal of a large part of the Drude component and a sharp reduction of the carrier scattering rate. The study revealed that the hybridization gap and the hidden orger gap are distinctly different: they occur at different energy scales and exhibit completely different spectral characteristics.Comment: 5 page

A Generic Framework for Constraint-Driven Data Selection in Mobile Crowd Photographing

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Mobile crowd photographing (MCP) is an emerging area of interest for researchers as the built-in cameras of mobile devices are becoming one of the commonly used visual logging approaches in our daily lives. In order to meet diverse MCP application requirements and constraints of sensing targets, a multifacet task model should be defined for a generic MCP data collection framework. Furthermore, MCP collects pictures in a distributed way in which a large number of contributors upload pictures whenever and wherever it is suitable. This inevitably leads to evolving picture streams. This paper investigates the multiconstraint-driven data selection problem in MCP picture aggregation and proposes a pyramid-tree (PTree) model which can efficiently select an optimal subset from the evolving picture streams based on varied coverage needs of MCP tasks. By utilizing the PTree model in a generic MCP data collection framework, which is called CrowdPic, we test and evaluate the effectiveness, efficiency, and flexibility of the proposed framework through crowdsourcing-based and simulation-based experiments. Both the theoretical analysis and simulation results indicate that the PTree-based framework can effectively select a subset with high utility coverage and low redundancy ratio from the streaming data. The overall framework is also proved flexible and applicable to a wide range of MCP task scenarios