EE PhD Oral Examination - Justin Snapp, Thursday May 3, 3pm CISX 101 Auditorium

Sidewall Silicon Carbide Emitters for Integrated Terahertz Vacuum Microelectronics

 

Justin Snapp

Department of Electrical Engineering

Advisor: Prof. Thomas H. Lee

Co-Advisor: Prof. Roger T. Howe 

Thursday, May 3, 2012

3:00 pm (refreshments at  2:45 pm)

Paul G. Allen Auditorium (Allen CIS-X 101)

http://cis.stanford.edu/directions/

 

 

The frequency band from 250 GHz to 2.5 THz is rich in potential applications, but suffers from a lack of efficient sources. This "THz gap" arises from the sharp decrease in the efficiency of solid-state electronic amplifiers at frequencies above 100 GHz and the unavailability of compact, uncooled optical sources for wavelengths longer than the infrared.  Future THz systems hold great promise for leveraging the unique properties of THz waves, which are long enough in wavelength to be penetrating through clothing and skin, but short enough to be useful for imaging, resonant with complex molecular bonds, and low enough in energy to be safe and non-ionizing.   In additions to applications in security screening and medical imaging, continuous wave THz systems would also enable short-range extreme wideband communications.

 

We propose a micro-fabricated Barkhausen-Kurz (u-BK) oscillator as a promising candidate source. The u-BK oscillator has significant advantages over other vacuum electronic devices, promising high DC-to-THz efficiency and low startup current requirements.  This device achieves low impedance, even when operated at harmonics of the electron orbit frequency, by extracting energy over multiple passes of favorably phased electrons confined within a potential well. The need for an emitter integrated into a parabolic potential well poses a major fabrication challenge.  The basic fabrication process for the cavity and integrated poly-silicon carbide thermionic cathode has been demonstrated, providing the foundation for developing stable cathodes for injecting a sheet electron beam and for optimizing the electrode geometry for defining a parabolic potential well.

 

The talk will discuss why the proposed u-BK oscillator is a promising candidate for future efficient integrated THz circuits.  The fabrication process and results for the sidewall lateral emitter integratable into a silicon u-BK cavity process will be presented.  Experimental results from emission testing on integrated diode test structures under testing in a vacuum chamber will be shown.  Additionally future work towards the development of a fully realized integrated THz source will be discussed.  The demonstrated sidewall filament emitters allow the design of radically new vacuum electronics that combine electron emitters, coupled resonant cavities and lithographically shaped electrodes in a single substrate. This will enable a new class of efficient THz vacuum electronic integrated circuits.

Wednesday 12-1 Allen 101X seminar on NNIN iWSG Brazil trip with pizza

All --

I've attached a flyer for this Wednesday's noon seminar by Sonia
Buckley, Meredith Lee, and Jared Schwede on the their experiences at the
NNIN's International Winter School at the University of Campinas
(UNICAMP), Campinas, Sao Paulo, Brazil and a second week's stay in a
region along the Atlantic coast.

The seminar's jointly sponsored by NNIN, which will be adding pizza to
the Stanford Nano Society's usual generous order to accommodate the
larger crowd.

See you there!

Roger

Special Seminar - Dr. Sami Hendow, Monday May 14, 6:30PM, GCC (Please RSVP, Pizza will be served)

Special Seminar Presented by NATEA (North America Taiwanese Engineering & Science Association) and the Stanford Optical Society

 

 Micromachining with Nanosecond and Femtosecond Pulsed Lasers

 

Dr. Sami Hendow

 

Date: Monday, May 14, 6:30 PM

Venue: Graduate Community Center (750 Escondido Road, Stanford, CA 94305)

Agenda:

6:30 - 7:00 PM: Registration and Social Networking (Pizza will be served)

7:00 - 8:15 PM: Presentation including Q&A

Fee:

Free for members of NATEA and the Stanford Optical Society with RSVP

$5.00 for non-members with RSVP

$10 for all without RSVP

RSVP: http://goo.gl/dXPht (contact: borchyuan@gmail.com or cachang@stanford.edu)

Please RSVP prior to May 13 (Pizza will be served)

 

Abstract

Laser-material interactions using pulses that are nsec in durations or longer are dominated by thermal time constants. Ultrashort pulses, on the other hand, undergo a much faster photon-electron energy transfer where pulse energy is deposited at a rate much faster than the material's thermal time constant. We will show examples of micromachining of metal, silicon and ceramics using nsec pulses, and outline the effects of change of peak power, pulse energy and pulse width. We will also extend this discussion to oxide formation on the surface, as well as bursting where pulses are broken into short but rapidly deposited pulses. These effects will be contrasted when the micromachining operation is performed using psec and fsec ultrafast pulses.

 

About the speaker      

Sami Hendow is an independent consultant. Recently, he was with Multiwave Photonics as Sr. Director responsible for Engineering and Application Development. Prior to that he was Engineering Program Manager with Spectra-Physics developing solid state and fiber amplified lasers. Before that, he was Sr. Scientist at Northrop Grumman working on the qualification of fiber lasers and power scaling by coherent beam combining of fiber laser arrays. Over the last 25 years, he has developed several products and has published about sixty articles and patents related to lasers and photonics technologies. Sami has a PhD in Optical Sciences from the University of Arizona. He is Chair of 2013 Fiber Lasers Conference, SPIE Photonics West, and member of conference program committees of the SPIE's Laser Applications in Microelectronic and Optoelectronic Manufacturing, and LIA's Laser Microprocessing Conference, ICALEO.

http://photons.stanford.edu

Re: Etch area update, 4/27

Dear lab members,

For some of you the Intlvac Ion Beam Mill Etcher at the Stanford Nanocenter (across the road from SNF) might be an alternative. It is a very versatile tool accessible to academic and industrial users. Ion beam processing is a controllable thin film etching technique with independent control of ion energy, ion current density, and incidence angle.
More details can be found at http://www.stanford.edu/group/snc/equipment/ion%20beam%20mill.html

Please contact me at mbaennin@stanford.edu if you are interested in using the ion mill or have any questions.

Best,
Matthias


-----------------------------------
Matthias Baenninger, PhD
Goldhaber-Gordon Group
Stanford University
McCullough Bldg., Room 224
476 Lomita Mall
Stanford
CA 94305-4008
-----------------------------------



----- Original Message -----
From: "Mary Tang" <mtang@stanford.edu>
To: labmembers@snf.stanford.edu
Sent: Friday, 27 April, 2012 10:26:47 PM
Subject: Etch area update, 4/27

Hi all --

I've been told that people want more detail about the status of certain
etch tools. So, I'll try to expand on the daily postings (which can be
found at http://toolstatus.blogspot.com/ and is linked from the SNF home
page).

STSetch2: This is the item of greatest need and concern. As you may
know, the system suffered a massive vacuum chamber leak which took
several weeks to fix. But then, the RF generator which has been
replaced just before shutdown, was found to be out of calibration.
Actually, the generator was good, but we suspect the DeviceNet
communications interface board which was moved from the original to the
replacement generator might also have stored calibrations. So, this
generator was sent out for recalibration. Both this and the original
generator are due back next week, the first one on Monday at 4:30 pm,
the second a few days later. The first, unfortunately, had been delayed
a week, in large part because of recent changes in Procurement
requirements from suppliers. (Ironically, Elmer had made the repair
service feel so bad for our situation, they discounted the price as a
courtesy -- which then required Procurement to authorize the change -
MORE delay!!) Plan A is to install the repaired generator Tuesday and
requalify. If Plan A doesn't work, then Plan B is to try the second
generator, which should have arrived. And yes, a Plan C is in the works.

Lampoly: This generator is also out for repair. It was due back today,
but is delayed into next week because of changes in Procurement procedures.

Amtetcher: The long pumpdowns are due to the hexode not cooling down.
The hexode heats to 30 C when the chamber is open and cools down 23 C
for the etch. The hexode is slightly heated to reduce water adsorption
during the 10 minutes of so of loading wafers when the chamber is
open. To control temperature, the hexode has a valve which controls
the flow of a hot circulating water loop (30 C) and a cold loop (20C).
This valve appears to be leaky or not sealing. Unfortunately, it is an
obsolete part, so some research into possible replacements needs to be
done. In the meantime, because it is a lot more important to keep the
hexode at temperature for etching than it is to heat during loading, the
heating has been disabled for now -- so the hexode will remain at 23 C
whether the chamber is open or closed. We believe this should not
affect most, if any processes, significantly. A quick requalification
was performed to verify etch rates were good.

If you have specific needs or concerns, please contact a staff member --
we can provide more information, and possibly offer suggestions on
backups either at SNF or elsewhere.

Thanks for your attention --

Team Etch

Etch area update, 4/27

Hi all --

I've been told that people want more detail about the status of certain
etch tools. So, I'll try to expand on the daily postings (which can be
found at http://toolstatus.blogspot.com/ and is linked from the SNF home
page).

STSetch2: This is the item of greatest need and concern. As you may
know, the system suffered a massive vacuum chamber leak which took
several weeks to fix. But then, the RF generator which has been
replaced just before shutdown, was found to be out of calibration.
Actually, the generator was good, but we suspect the DeviceNet
communications interface board which was moved from the original to the
replacement generator might also have stored calibrations. So, this
generator was sent out for recalibration. Both this and the original
generator are due back next week, the first one on Monday at 4:30 pm,
the second a few days later. The first, unfortunately, had been delayed
a week, in large part because of recent changes in Procurement
requirements from suppliers. (Ironically, Elmer had made the repair
service feel so bad for our situation, they discounted the price as a
courtesy -- which then required Procurement to authorize the change -
MORE delay!!) Plan A is to install the repaired generator Tuesday and
requalify. If Plan A doesn't work, then Plan B is to try the second
generator, which should have arrived. And yes, a Plan C is in the works.

Lampoly: This generator is also out for repair. It was due back today,
but is delayed into next week because of changes in Procurement procedures.

Amtetcher: The long pumpdowns are due to the hexode not cooling down.
The hexode heats to 30 C when the chamber is open and cools down 23 C
for the etch. The hexode is slightly heated to reduce water adsorption
during the 10 minutes of so of loading wafers when the chamber is
open. To control temperature, the hexode has a valve which controls
the flow of a hot circulating water loop (30 C) and a cold loop (20C).
This valve appears to be leaky or not sealing. Unfortunately, it is an
obsolete part, so some research into possible replacements needs to be
done. In the meantime, because it is a lot more important to keep the
hexode at temperature for etching than it is to heat during loading, the
heating has been disabled for now -- so the hexode will remain at 23 C
whether the chamber is open or closed. We believe this should not
affect most, if any processes, significantly. A quick requalification
was performed to verify etch rates were good.

If you have specific needs or concerns, please contact a staff member --
we can provide more information, and possibly offer suggestions on
backups either at SNF or elsewhere.

Thanks for your attention --

Team Etch

"Green Container" at Shipping and Receiving for Recycling Small Electronic Devices

Dear All,

 

This past Monday, we received our own “Green Container” for Small Electronic Devices and more…

 

This container is housed between the back doors of the loading dock and the US Mail slots of the Allen Building.

 

The waste that is accepted and can be happily recycled are:

 

·         Cellular phones

·         Personal digital assistants (i.e. Palm Pilots),

·         Pagers, CDs, DVDs, Telephones,

·         Empty Printer/Toner/Ink jet Cartridges,

·         Other small non-capital electronic waste

 

Waste NOT accepted are:

 

·         Computers, Monitors, and other capital electronic equipment

 

Please contact your Department Property Administrator for appropriate disposal of capital equipment

 

Kenny Green kennygee@stanford.edu – DPA for the Allen Building / Allen Building

Maureen Baran mbaran@stanford.edu – DPA for SNF.

 

One last thing, if you want to recycle your “curley q” light bulbs you can.  We ask that you wrap them up in a plastic bag so if they break in transport they are contained.

 

Thank you,

 

Maureen

 

 

 

Special Seminar - Prof. Ci-Ling Pan (National Tsing Hua University, Taiwan), Friday May 11, 4:15PM, CISX 101

Special Seminar Presented by the Stanford Optical Society

Recent Progress in Photonic-Network-Compatible Sub-THz-wave wireless links at data rate of 20 Gb/s

 

Prof. Ci-Ling Pan

National Tsing Hua University, Taiwan

Friday, May 11, 4:15 PM, CISX 101 Auditorium

Refreshments at 4PM

 

 

To meet the rapidly growing demand of gigabits wireless access applications, sub-THz or millimeter wave (MMW) carriers in W-band (75-110 GHz) or above are essential for obtaining the necessary broad transmission bandwidth. Thanks to the almost unlimited bandwidth and very low propagation loss in optical fiber, radio-over-fiber (RoF) communication system is now an efficient and cost-effective way to distribute synchronized photonic MMW signals from the central office to multiple base stations. In this talk, we will review our recent work on Photonic Wireless communication Link at 100 GHz or 0.1 THz. Key technologies are photonic MMW sources and photonic MMW transmitters will be described.  Wireless data transmission at a data rate beyond 20-Gb/s via bias modulation of such novel device has been successfully achieved for both downlink and uplink. We have also demonstrated an optical ultra-wide band Impulse-Radio Fiber-to-the-antenna (UWB-IR FTTA) system for in-building and in-home applications, operating from 75 to 110 GHz.

About the speaker

Ci-Ling Pan is Tsing Hua Chair Professor, Chairperson of the Department of Physics and Institute of Astronomy, National Tsing Hua University (NTHU), Hsinchu, Taiwan. He also held joint appointment at the Institute of Photonics Technologies and served as Director of the Photonics Research Center of NTHU. Prof. Pan taught at National Chiao Tung University, Taiwan, 1981-2009. He also held visiting professorship at Osaka University and Chinese University of Hong Kong in 2004 and 2008, respectively. In the past decade, the main foci of Prof. Pan's research activities have been Ultrafast and THz Photonics. Recent research highlights include developments of functional liquid crystal THz photonic devices, femtosoeocnd-laser recrystallization and activation of silicon as well as novel THz generators and detectors. The latter were used in diverse applications such as diagnostics of technologically important materials for photovoltaics, assessing burn trauma and optical-network-compatible W-band (100 GHz or 0.1 THz) wireless communication Link at a data rate beyond 20 Gbit/s. Prof. Pan is a Fellow of APS, IEEE, OSA, and SPIE.

 

http://photons.stanford.edu