Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 113-117). / Infrared spectrum, especially mid-infrared range (2.512tm) covers the absorption peaks of many important chemicals including carbon monoxide, methane and water vapor. By analyzing the absorption spectrum of achemical, one can measure the concentration of the chemicals as well as distinguish the chemical species. The purpose of this work is to build a Si CMOS compatible integrated mid-infrared (MIR) platform for sensing. In this work, we evaluated the three major components (materials and devices) comprising an integrated mid-infrared (MIR) sensing platform: the light source, the waveguide sensor and the detector. To build an integrated MIR light source, we evaluated three approaches. 1) Germanium light source, which is the representative of the CMOS compatible semiconductor light source. By applying tensile strain as well as increasing doping and injection level, Ge is tuned to pseudo-direct or direct bandgap structure and the emission wavelength extends to MIR range. 2) Er-doped GaLaS (GLS) platform which is the representative of the rare earth doped material system. A new laser structure is designed for this system with a threshold power of 7.6 ptW and a slope efficiency of 10.26%. 3) Frequency comb generation which is a new area using nonlinearity to generate new frequencies. Thick Si3N4 material for comb structures are designed, fabricated and tested. In the waveguide sensor section, a waveguide structure based on chalcogenide glass (ChG) is built and tested. The sensing limit for methane reaches 2.5 vol. %. Besides, a ChG based small-footprint plasmonic optical switch is designed to work as an optical router for integrated spectrometer applications with a small (167 nm long) footprint. In the last part, a MIR PbTe based integrated detector has been successfully demonstrated for the first time. A further improvement in the material property and device structure yields a responsivity is about 1.4 A/W in the MIR regime. / by Zhaohong Han. / Ph. D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (leaves 88-90). / by Bugra Giritlioglu. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995. / Includes bibliographical references (leaves 78-80). / by Caroine S. Lee. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1988. / Includes bibliographical references. / by Giuseppe La Rosa. / M.S.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (leaves 35-36). / Recent research has allowed the use of electrode-active materials as actuators by harnessing reversible volumetric change due to intercalation during charging and discharging. These actuators provide a relatively large strain, 2-3%, while requiring less than ten volts to operate with a cycle time on the order of one hundred seconds. This technology can be used in any moderate bandwidth, high-force, high-strain application, including shape-morphing helicopter blades, boat hulls, satellites, and any other structure that benefits from shape change. An analysis is performed on the state of the technology, the intellectual property held, and the potential markets that exist. A recommendation is made to pursue the technology, while cognizant of the fact that it is still in a seed stage and requires significant time and financial investment before entering production. Two business models are proposed and rough market calculations are also presented. The basis of this project is work done at the Massachusetts Institute of Technology by Professor Yet-Ming Chiang and Professor Steven Hall. Industrialists, including but not limited to, William Fallon and Dan Ursenbach of Sikorsky Aircraft in Stratford, Connecticut are also involved in the project. / by John T. Wong. / M.Eng.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997. / Includes bibliographical references (leaf 75). / by Randy Logan. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1992. / Includes bibliographical references (leaves 245-247). / by Richard Roth. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1992. / Vita. / Includes bibliographical references. / by Richard Westhoff. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 109-116). / All scanning probe microscopes (SPMs) are affected by disturbances, or mechanical noise, in their environments which can limit their imaging resolution. This thesis introduces a general approach for suppressing out-of-plane disturbances that is applicable to non-contact and intermittent contact SPM imaging modes. In this approach, two distinct sensors simultaneously measure the probe-sample separation: one sensor measures a spatial average over a large sample area while the other responds locally to topography underneath the nanometer-scale probe. When the localized sensor is used to control the probe-sample separation in feedback, the spatially distributed sensor signal reveals only topography. This technique was implemented on a scanning tunneling microscope (STM) and required a custom micromachined scanning probe with an integrated interferometer for the spatially averaged measurement. The interferometer design is unique to SPM because it measures the probe-sample separation instead of the probe deflection. A robust microfabrication process with a novel breakout scheme was developed and resulted in 100 % device yield. For imaging, an STM setup with optical readout was built and characterized. The suppression improvement over conventional SPM imaging was measured to be 50 dB at 1 Hz, in agreement with predictions from classical feedback theory. Images are presented as acquired with each sensor signal in several environments, and the interferometer images show remarkable clarity when compared with the conventional tunneling images. / (cont.) The out-of-plane noise floor with this technique on the home-built microscope was 0.1 i rms. The results of this work suggest that the resolution of STM and other SPM modes, notably tapping mode atomic force microscopy (AFM), can be substantially improved, allowing low noise imaging of nanoscale topography in noisy environments and potentially enabling repeatable atomic scale imaging in ambient conditions. / by Andrew William Sparks. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (p. 115-126). / The introduction of certain controlled gradients in plastic properties is known to promote resistance to the onset of damage at contact surfaces during some tribological applications. Gradients in composition, microstructure and plastic properties can also be deleterious to contact-damage resistance in some situations. In order to realize such potentially beneficial or deleterious effects of plastic property gradients in tribological applications, it is essential first to develop a comprehensive understanding of the effects of yield strength and strain hardening exponent on frictionless normal indentation. To date, however, systematic studies of plasticity gradient effects on indentation response have not been completed. A comprehensive parametric study of the mechanics of indentation of plastically graded materials is completed in this work by recourse to finite element (FE) computations. On the basis of a large number of detailed computational simulations, a general methodology for assessing instrumented indentation response of plastically graded materials is formulated so that quantitative interpretations of depth-sensing indentation experiments could be performed. The specific case of linear gradient in yield strength is explored in detail. / (cont.) The FE analysis leads to a universal dimensionless function to predict load displacement curves for plastically graded engineering materials. Experimental validation of the analysis is performed by choosing the model system of an electrodeposited nanostructured Ni-W alloy, where the plastic property variation is introduced through a linear variation in grain size with distance through the thickness. The universal dimensionless function is shown to correlate with the shield factor which is used to predict crack behavior at the interface of plastically graded materials. Here in this work a general framework is proposed for the indentation of plastically graded materials based on energetic considerations. Possible mechanisms underlying indentation size effects are also explored including the surface energy terms in the proposed energy based framework so as to rationalize a broad range of experimental observations. Practical implications of the present work are highlighted. / by In-Suk Choi. / Ph.D.