Subject: Change in raith schedule for Thursday June 14, 2007 : I will be starting my 1 PM session at 2 PM to attend Arvind Sundaramurthy's. PhD defense.
From: James Conway <jwc@snf.stanford.edu>
Date: Wed, 13 Jun 2007 10:38:59 -0700

Greetings Raith Users:

I will be starting my Thursday afternoon RAITH session an hour later than scheduled in order to attend Arvind Sundaramurthy's  PhD defense public session in CIS X 101.

I hope to start my session between 2  and 2:15 PM tomorrow afternoon and am happy to 'share the ride' with other chip users.

Thank you,

James Conway

P. S. Arvind was the second or third person to come onto the RAITH 150 when commissioned in June of 2002. He completed his project using the RAITH 150 here at Stanford.  He produced the smallest gap structure every printed on any RAITH 150 to my knowledge demonstrating sub-10 nm gap features in his device.


Here is his abstract:


Bowtie Nanoantennas: Optical Resonators at Visible Wavelengths

Arvind Sundaramurthy

Ph.D. Oral Exam

Dept. of Electrical Engineering, Edward.L.Ginzton Lab, Stanford University.

Advisor: Prof. Gordon.S.Kino.

Date & Time: 14 June 07, 1:15pm(Refreshments served at 1:00pm).

Location: CIS-X Auditorium.

Abstract:

       The resolving power of an optical system is fundamentally limited by diffraction. According to the Rayleigh criterion, two points on a sample cannot be resolved unless they are spaced apart by 0.61*lambda where lambda is the wavelength of incident light in air. Antennas efficiently confine and enhance the propagating fields incident on them into a region that is a fraction of the incident wavelength.  In this talk we present our work on bowtie nanoantennas that resonate at optical frequencies. The bowtie nanoantennas consisting of two opposing triangles facing each other tip-to-tip, are fabricated by electron beam lithography(EBL) with triangle lengths of 75nm and gap widths ranging from 16nm to 500nm.  We experimentally studied the scattering response of the bowtie antennas using total internal reflection(TIR) microscopy. We observed that the resonant scattering wavelength is a strong function of the gap width in the antennas.

       We simultaneously studied the currents, field distribution and scattering efficiencies in the Au bowties using finite difference time domain(FDTD) simulations. The experimentally observed resonant wavelengths in the antennas were in excellent agreement with the FDTD simulations. We propose a model that predicts the change in resonant wavelength with gap based on the current distribution in the antennas.

       We then study the field enhancement in the bowties by measuring the efficiency of two photon enhanced photoluminescence(TPPL) emitted by the Au bowties. We experimentally determined the enhancement factor(|E|^2 >10^3) in the antennas for the first time and these were in good agreement with the FDTD computations of the enhancements.

       We studied the light confinement and enhancement in the bowties by two-photon polymerization(TPP) of SU-8 resist. We coated the bowties with SU-8 optical resist and excited them with pulsed laser light focused to a diffraction limited spot. We observed minimum resist features that were <30nm exposed at low incident average powers(27 microwatts). The experimental results compare very well with FDTD computations.

       Finally we demonstrate a novel method for fabricating bowtie antennas on an atomic force microscope (AFM) tip, to produce a scanning probe optical microscope. We use the microscope for Raman spectroscopy and imaging of an isolated single wall carbon nanotube (SWCNT) with an optical resolution of ~24nm . The scanning probe microscope with the bowtie nanoantenna has a superior light collection efficiency compared to aperture based microscopes.