Distortion analysis on an improved mask technology for X-ray lithography

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaves 90-91).by Kevin P. Pipe.S.B.and M.Eng

Bipolar thermoelectric devices

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 124-133).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.The work presented here is a theoretical and experimental study of heat production and transport in bipolar electrical devices, with detailed treatment of thermoelectric effects. Both homojunction and heterojunction devices are considered, and particular attention is given to semiconductor laser diodes. The mechanisms that govern both internal heat exchange and heat transfer between a device and its environment are examined, leading to structures which are optimized for thermal management.by Kevin Patrick Pipe.Ph.D

Emission and detection of surface acoustic waves by AlGaN/GaN high electron mobility transistors

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98689/1/ApplPhysLett_99_243507.pd

Enhanced optical field intensity distribution in organic photovoltaic devices using external coatings

An external dielectric coating is shown to enhance energy conversion in an organic photovoltaic cell with metal anode and cathode by increasing the optical field intensity in the organic layers. Improved light incoupling in the device is modeled using transfer matrix simulations and is confirmed by in situ measurement of the photocurrent during growth of the coating. The optical field intensity in optimized cell geometries is predicted to exceed that in analogous devices using indium tin oxide, both cell types having equivalent anode sheet resistance, suggesting a broader range of compatible substrates (e.g., metal foils) and device processing techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87812/2/233502_1.pd

Organic light-emitting device on a scanning probe cantilever

Organic light-emitting devices (OLEDs) were fabricated on scanning probe cantilevers using a combination of thermally evaporated molecular organic compounds and metallic electrodes. Ion beam milling was used to define the emissive region in the shape of a ring having a diameter of less than 5 μm5μm and a narrow width. Stable light emission was observed from the device at forward bias, with a current-voltage response similar to that of archetypal OLEDs. Based on this device, a novel electrically pumped scanning optical microscopy tool is suggested.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87792/2/111117_1.pd

On Determinism of Game Engines used for Simulation-based Autonomous Vehicle Verification

Game engines are increasingly used as simulation platforms by the autonomous vehicle (AV) community to develop vehicle control systems and test environments. A key requirement for simulation-based development and verification is determinism, since a deterministic process will always produce the same output given the same initial conditions and event history. Thus, in a deterministic simulation environment, tests are rendered repeatable and yield simulation results that are trustworthy and straightforward to debug. However, game engines are seldom deterministic. This paper reviews and identifies the potential causes of non-deterministic behaviours in game engines. A case study using CARLA, an open-source autonomous driving simulation environment powered by Unreal Engine, is presented to highlight its inherent shortcomings in providing sufficient precision in experimental results. Different configurations and utilisations of the software and hardware are explored to determine an operational domain where the simulation precision is sufficiently low i.e.\ variance between repeated executions becomes negligible for development and testing work. Finally, a method of a general nature is proposed, that can be used to find the domains of permissible variance in game engine simulations for any given system configuration.Comment: 17 pages, 9 figures, 1 tabl

Thermoelectric and bulk mobility measurements in pentacene thin films

Low-noise thermoelectric and electrical measurements were used to derive the dependences of Seebeck coefficient and hole mobility on carrier concentration and grain size in the "bulk" regions of thermally evaporated pentacene thin films (in contrast to the channel field-effect mobility typically measured using thin-film transistor geometries). Distinct charge transport regimes were observed for larger (0.5 and 0.8 ??m) and smaller (0.2 ??m) grain sizes, attributed to carrier-dopant scattering and percolation, respectively.clos

Computational Sprinting

Although transistor density continues to increase, voltage scaling has stalled and thus power density is increasing each technology generation. Particularly in mobile devices, which have limited cooling options, these trends lead to a utilization wall in which sustained chip performance is limited primarily by power rather than area. However, many mobile applications do not demand sustained performance; rather they comprise short bursts of computation in response to sporadic user activity. To improve responsiveness for such applications, this paper explores activating otherwise powered-down cores for sub-second bursts of intense parallel computation. The approach exploits the concept of computational sprinting, in which a chip temporarily exceeds its sustainable thermal power budget to provide instantaneous throughput, after which the chip must return to nominal operation to cool down. To demonstrate the feasibility of this approach, we analyze the thermal and electrical characteristics of a smart-phone-like system that nominally operates a single core (~1W peak), but can sprint with up to 16 cores for hundreds of milliseconds. We describe a thermal design that incorporates phase-change materials to provide thermal capacitance to enable such sprints. We analyze image recognition kernels to show that parallel sprinting has the potential to achieve the task response time of a 16W chip within the thermal constraints of a 1W mobile platform

Temperature mapping and thermal lensing in large-mode, high-power laser diodes

The authors use high-resolution charge-coupled device based thermoreflectance to derive two dimensional facet temperature maps of a λ = 1.55 μmλ=1.55μm InGaAsP/InPInGaAsP∕InP watt-class laser that has a large (>5×5 μm2)(>5×5μm2) fundamental optical mode. Recognizing that temperature rise in the laser will lead to refractive index increase, they use the measured temperature profiles as an input to a finite-element mode solver, predicting bias-dependent spatial mode behavior that agrees well with experimental observations. These results demonstrate the general usefulness of high-resolution thermal imaging for studying spatial mode dynamics in photonic devices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87806/2/201110_1.pd

Thermal and Electrical Transport in Ultralow Density Single‐Walled Carbon Nanotube Networks

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98216/1/adma_201300059_sm_suppl.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/98216/2/2926_ftp.pd