NRL Researchers Demystify the Nature of Metal-contacts to 2D Materials

2d materials illustration
In a recent study, ECE researchers from the Nanoelectronics Research Lab (NRL), investigated the nature of the physical contacts between 2D TMD semiconductors and a number of metals using a novel ab-initio technique specifically designed for such 2D layered materials.

Atomically-thin, two-dimensional (2D) transition metal dichalcogenides (TMD) have emerged as promising materials for future unprecedented electronic, optoelectronic and sensor applications. TMDs offer a wide range of material types, from semiconductors to half-metals and from metals to superconductors, with variable but uniform band gaps.

Besides, these ultra-thin TMDs have inherent flexibility and transparency, rendering them attractive to display electronics. These materials additionally have pristine surfaces that can boost device performance, especially in nanoscale transistors. However, such pristine surfaces also imply that interface bonding to these materials is predominantly van der Waals (vdW) type that are inherently weak (as compared to strong covalent bonds). The vdW bonding essentially implies that there actually exists a ‘vdW gap’ at such interfaces leading to some unusual electronic behavior that had remained inexplicable till date. Moreover, the vdW type interface bonding also leads to poor contact resistances between metals and 2D TMDs.

Ensuring low-resistance metal-contacts to such semiconductors is the primary hindrance to using this technology. In a recent study, ECE researchers from the Nanoelectronics Research Lab (NRL), led by Professor Kaustav Banerjee have investigated the nature of the physical contacts between 2D TMD semiconductors (such as monolayer molybdenum disulfide) and a number of metals using a novel ab-initio technique specifically designed for such 2D layered materials. The detailed study not only provides a pathway to identify the best contact metals for these semiconductors but also reveals some new physics of the interfaces that, in turn, determine the carrier transport across such interfaces. The formalism and the results in this work provide guidelines for novel 2D semiconductor device design and fabrication, a field that is on the rise because of limitations in scaling silicon semiconductor technology.

These results have been recently published in the prestigious journal, Physical Review X, by ECE PhD student Jiahao Kang, et al. The formalism has already yielded some of the highest performance 2D TMD-transistors.

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Electrical and Computer Engineering and Computer Engineering students receive honors at the College of Engineering’s “Senior Send-Off”

photo of kay and singh
College of Engineering (CoE) celebrates the undergraduate class of 2014 on June 13th with their annual “Senior Send-Off” event.

The event program and reception included honoring seniors, teaching assistants and faculty members.

The following Electrical & Computer Engineering (ECE) and Computer Engineering (CE) undergraduates received recognition:

  • College of Engineering Academic Honor (overall highest GPA): Joshua Eric Kay (ECE)
  • Hynes / Wood Award: Dahman Singh (ECE)
  • Outstanding Seniors (major highest GPA): Christopher Taylor Nelson (CE), Joshua Eric Kay (ECE)
  • College of Engineering High Honors: Kevin Michael Albers (ECE), Melissa Anne Johnson (ECE), Joshua Eric Kay (ECE), Christopher Taylor Nelson (CE), Alex Romin Sarraf (CE)
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ECE’s Ortoleva and CE’s Goodman receive “Outstanding Teaching Assistant” honors at the College of Engineering’s “Senior Send-Off”

photos of ortoleva and goodman
College of Engineering (CoE) celebrates the undergraduate class of 2014 on June 13th with their annual “Senior Send-Off” event.

The event program and reception included honoring seniors, teaching assistants and faculty members.

The following graduate students received “Outstanding Teaching Assistant (TA) recognitions from the graduating seniors in their program:

  • Sami Ortoleva — Electrical & Computer Engineering (ECE)
  • Eric Goodman — Computer Engineering (CE)
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GRIT talk – The Promise of Silicon Photonics

Photonics has transformed our work and our lives by enabling the Internet through low cost, high capacity fiber optic transmission. Photonics is now replacing electrical cables in data centers and thus enabling higher performance at lower cost. This talk will describe how we got to this point and what the future holds for photonics. In particular, a number of important breakthroughs in the past decade have focused attention on Si as a photonic platform. We review here recent progress in this field, focusing on efforts to make lasers, amplifiers, modulators and photodetectors on or in silicon. The impact silicon photonic integrated circuits could have on interconnects, telecommunications and on silicon electronics will be described.

Presented by GRIT talks — Research Worth Sharing. Ground-breaking Research/Innovative Technology.

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ECE Professors Gossard and Rodwell report highest performing III-V Metal-Oxide Semiconductor FETs

microscopic image of MOSFET
Researchers from University of California, Santa Barbara (UCSB) introduced the highest performing III-V metal-oxide semiconductor (MOS) field-effect transistors (FETs) this week at the 2014 Symposium on VLSI Technology.

The UCSB research promises to help deliver higher semiconductor performance at lower power consumption levels for next-generation, high-performance servers. The research is supported by the Semiconductor Research Corporation (SRC), the world’s leading university-research consortium for semiconductors and related technologies.

The UCSB team’s III-V MOSFETs, for the first time in the industry, exhibit on-current, off-current and operating voltage comparable to or exceeding production silicon devices — while being constructed at small dimensions relevant to the VLSI (very-large-scale integration) industry.

For the past decade, III-V MOSFETs have been widely studied by a large number of research groups, but no research group had reported a III-V MOSFET with a performance equal to, let alone surpassing, that of a silicon MOSFET of similar size. In particular, UCSB’s transistors possess 25 nanometer (nm) gate lengths, an on-current of 0.5mA and off-current of 100nA per micron of transistor width and require only 0.5 volt to operate.

“The goal in developing new transistors is to reach or beat performance goals while making the transistor smaller—it is no good getting high performance in a big transistor,” said Mark Rodwell, professor of Electrical and Computer Engineering at UCSB. “In time, the UCSB III-V MOSFET should perform significantly better than silicon FinFETs of equal size.”

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ECE Professor João Hespanha part of project team given a five-year $4M NSF “Frontier” award

roseline logo
NSF announces the award given to Roseline project team that will tackle the challenge of timekeeping in cyber-physical systems (CPS) — often called the “Internet of Things” — in which objects and devices are equipped with embedded software and are able to communicate with and be controlled by wireless digital networks.

The research team, led by engineering faculty from UCLA and EE / CS faculty from UCSB, CMU and U. of Utah, will work to improve the accuracy, efficiency, robustness and security with which computers maintain their knowledge of physical time and synchronize it with these networked devices.

Timekeeping presents a particular challenge in this emerging field, which depends on precise knowledge of time in order to infer location, control communications and accurately coordinate activities in a broad and growing range of applications, from autonomous cars and aircraft autopilot systems to advanced robotic and medical devices, energy-efficient buildings and an array of other industrial initiatives.

“It is widely appreciated that constraints on energy storage and communication bandwidth typically limit the performance of cyber-physical systems, what we are now starting to discover is that the accuracy of clocks can also limit their performance,” commented João Hespanha, professor of electrical and computer engineering at UC Santa Barbara and co-PI for the project. “RoseLine will enable us to discover what these limitations may be and how to overcome them in practice.”

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ECE Graduate and NASA Astronaut, José Hernández, delivers the College of Engineering’s 2014 Commencement Address

photo of jose hernandez giving the commencement address
The following are highlights from the transcript of the speech delivered by NASA Astronaut José Hernández (Master of Science, Electrical and Computer Engineering, 1986) at the Engineering & Sciences commencement ceremony on Saturday, June 14, 2014.

DREAMING OF BECOMING AN ASTRONAUT AND HIS FATHER’S FIVE INGREDIENT RECIPE:

1) If you want to reach for the stars my father said, the first ingredient is to define my goal and decide what I wanted to be when I grew up: I of course had the fresh images on my mind of the last Apollo mission, Apollo 17. I recalled the images of Gene Cernan walking on the surface of the moon, talking to mission control Houston and the newscaster, Walter Cronkite, narrating the mission. These images are what inspired me to want to become an astronaut.

2) If you want to reach for the stars he said, the second ingredient is to recognize how far I was from my goal: I thought about it for a while and without thinking told him that I probably couldn’t be any further away given our social-economic status. Instead of getting mad at me he gave me a smile and said: I’m glad you recognize this because….

3) If you want to reach for the stars he said, the third ingredient is to draw yourself a roadmap from where you are to where you want to be. This roadmap should have as much detail as possible and will serve as your guide throughout life.

4) If you want to reach for the stars he said, the fourth ingredient he is to prepare yourself with the appropriate level of education. He went on the say that there was no substitute for a good education.

5) Finally, if you want to reach for the stars he said, the fifth ingredient is to develop a work ethic second to none. He reminded me of how hard I worked in the fields during the weekends and summers and pointed to my books and asked me to put that same effort in my studies and that upon graduating college to put that effort in my job. Always, always, he said give people more than what they expect. This should be your normal mode of operation.

Mix all this he said and this is the recipe to reach for your stars.

I remembered going to bed so happy that evening because my parents thought I could become an astronaut therefore I was determined to become one.

JOSÉ HERNÁNDEZ ADDS HIS OWN SIXTH INGREDIENT TO HIS FATHER’S RECIPE:

6) Perhaps a sixth ingredient I would add to my father’s recipe is perseverance. You see, I’m here to tell you that NASA rejected my astronaut application not once, twice three or even six times but 11 times! It was not until my twelfth attempt that I finally succeeded in becoming an astronaut.

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Optimal Control and Coordination of Small UAVs for Vision-based Target Tracking

Small unmanned aerial vehicles (UAVs) are relatively inexpensive mobile sensing platforms capable of reliably and autonomously performing numerous tasks, including mapping, search and rescue, surveillance and tracking, and real-time monitoring. The general problem of interest that we address is that of using small, fixed-wing UAVs to perform vision-based target tracking, which entails that one or more camera-equipped UAVs is responsible for autonomously tracking a moving ground target. In the single-UAV setting, the underactuated UAV must maintain proximity and visibility of an unpredictable ground target while having a limited sensing region. We briefly describe solutions from two different vantage points. The first regards the problem as a two-player zero-sum game and the second as a stochastic optimal control problem. The resulting control policies have been successfully field-tested, thereby verifying the efficacy of both approaches while highlighting the advantages of one approach over the other.

When employing two UAVs, one can fuse vision-based measurements to improve the estimate of the target’s position. Due to the richness of this problem, the primary focus of this talk is on optimally coordinating two UAVs to gather the best joint vision-based measurements of a moving ground target, which is first done in a simplified deterministic setting. The results in this setting show that the key optimal control strategy is the coordination of the UAVs’ distances to the target and not of the viewing angles, which is traditionally assumed, thereby showing the advantage of solving the optimal control problem over using heuristics. To generate a control policy robust to real-world conditions, we formulate the same control objective using higher order stochastic kinematic models. Since grid-based solutions are infeasible for a stochastic optimal control problem of this dimension, we employ a simulation-based dynamic programming technique that relies on regression to form the optimal policy maps, thereby demonstrating an effective solution to a multi-vehicle coordination problem that until recently seemed intractable on account of its dimension. The results show that distance coordination is again the key optimal control strategy and that the policy offers considerable advantages over uncoordinated control policies, namely reduced variability in the cost and a reduction in the severity and frequency of high-cost events.

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ECE’s Rodwell and Johnson to receive “Outstanding Faculty” honors at the College of Engineering’s “Senior Send-Off”

photo of mark rodwell and john johnson

College of Engineering (CoE) celebrates the undergraduate class of 2014 on Friday, June 13th with their annual “Senior Send-Off” event.

The event program and reception includes honoring seniors, teaching assistants and faculty members.

The following Electrical & Computer Engineering (ECE) and Computer Engineering (CE) faculty to receive “Outstanding Faculty” recognition by the graduating seniors in their program:

  • Mark Rodwell (ECE) — instructs Circuits and Electronics I & II (ECE 137A/B) and Communication Electronics (ECE 145/218A)
  • John Johnson (CE) — instructs Senior Computer Systems Project (ECE 189A/B) and Sensor & Peripheral Interface Design (ECE 153B)
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Four teams given top prizes at the 2014 ECE 188, ECE 189 and CS 189 Senior Capstone Project Presentation Day

IR Scout, Autoponix, String Cheese, and NP Compete teams given awards at the 2014 Senior Capstone Project Presentation event held on June 5th, 2014 in the Engineering Science Building and Courtyard.

During their senior year, all Computer Engineering (ECE & CS 189A/B) and some Electrical & Computer Engineering (ECE 188A/B) students take a two quarter Senior Project course also know as the Senior “Capstone” Project.

The Capstone project gives students the opportunity to put their education into practice. Students, working in small teams, design and engineer innovative hardware and software systems. At the end of the Spring quarter the final projects are presented at a full-day, industry-sponsored event where student groups publicly present their projects and participate in an outdoor lunchtime project demonstration and poster event.

This year’s project team awardees:

photo of ir scout team
Best Electrical & Computer Engineering ECE188A/B Capstone Project Prize

IR Scout: Scouting Hazardous Environments Thermal Imaging. Team – Josh Kay, Azim Muqtadir, Ryan Stevenson
 
 
 
 
photo of string cheese and np-compete teams
Weihan David Wang Computer Engineering / Computer Science / Electrical Engineering Capstone Poster Prize (co-winners)

NP-Compete (CS 189): a platform to enable users to broadcast video peer-to-peer, using minimal centralized server resources, and only their web browser. Team: Daniel Vicory (lead), Nicole Theokari, Omar Masri, Jerry Medina, Justin Liang

String Cheese (CS 189): a UAV capable of surveying a farmer’s field that detects environmental hazards in order to fix them before they harm the crop or the environment. Team: Alexander Huitric (lead), EJ Fernandes, Drew Hascall, Jasen Worden

photo of autoponix team
James Cheng-Yuan Hong Best Computer Engineering ECE189A/B Capstone Project Prize

AutoPonix: an automated water quality monitor and adjustment system for the maintenance of an aquaponics system. Team: Greg Swanson (leader), Ludim Castillo, Ryan Born, Manuel Perez, Alex King
 
 
photo of string cheese team
George Chen Best Computer Engineering / Computer Science CS189A/B Capstone Project Prize

String Cheese: a UAV capable of surveying a farmer’s field that detects environmental hazards in order to fix them before they harm the crop or the environment. Team: Alexander Huitric (lead), EJ Fernandes, Drew Hascall, Jasen Worden

You can learn more about the other amazing projects at the following webpages:

2014 Capstone Senior Project Presentation Day
Electrical and Computer Engineering Senior Projects
Computer Engineering and Computer Science Senior Projects

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