Bit-patterned perpendicular magnetic media

Zhenzhong Sun, Su Gupta and Dawen Li, MINT Center, The University of Alabama, Tuscaloosa, ALWork performed at Georgia Tech Nanotechnology Research Center

The project targets to employ E-beam lithography topattern perpendicular anisotropy Co80Pt20 films intonanopillar arrays as bit-patterned perpendicularmagnetic media for next-generation recording mediawith ultra-high data storage capacity. The magneticCo80Pt20 thin films were deposited by sputtering, andnegative resist HSQ was spin-coated on the top ofCo80Pt20 films for electron-beam lithography. TheSEM images reveal that as density increase thenanopillar diameters get larger. These nanopillararrays act as masks for ion miller etching. Afteretching, the magnetic properties of Co80Pt20nanopillar arrays were characterized by alternatinggradient field magnetometer (AGM) and magneto-optical Kerr effect magnetometer (MOKE).Furthermore, magnetic force microscopy (MFM) wasused to study the domain structure. Our results showthat E-beam lithography provides a promising way topattern perpendicular magnetic media.

Multi-s light source based on grating coupled laser diodes with wavelength selective elements.

• As in previous year, the work was focused on developing a multi-s emitter for different applications such as WDM technique.

• Past year, the feasibility of the goal was shown. 2009-2010 involved a process requiring higher yields for a multi-dimension ARRAY assembly.

• Design of the multi-s devices is based on GCSEL/DGR technology originally invented by the team (see image on the right).

• P-side grating couplers and N-side feedback grating monolithically integrated with the Broad Area laser diode were patterned using JEOL-9300FS electron beam lithography tool in GA tech facility.

• Table below shows the desired wavelengths matching grating period.

Recent Conference Presentations:1. Oleg V. Smolski, Viktor O. Smolski, Yigit O. Yilmaz, and Eric G. Johnson, “Vertically Stacked

Surface-Emitting Laser Diodes Array for High-Brightness Application,” CLEO, May 20102. Yigit O. Yilmaz, Viktor O. Smolski, Oleg V. Smolski and Eric G. Johnson, “Multi‐Wavelength

Blue Light Generation by Frequency Doubling,” in Integrated Photonics Research, Silicon and Nano Photonics (IPR) (2010)

3. Oleg V. Smolski, Viktor O. Smolski, Yigit O. Yilmaz, and Eric G. Johnson, “Modal Control of Broad Area Semiconductor Laser with Monolithically Integrated Feedback Gratings,” in Integrated Photonics Research, Silicon and Nano Photonics (IPR) (2010)

270nm‐periodicity outcoupling grating

220nm‐periodicity outcoupling grating

Feedback Littrow grating

Output beam

Schematic of a WL GCSEL w/DGR

DGR Section

1O’Daniel et al. Optics Lett. 31, 211 (2006)

Wafer inspection of the processed GCSEL/DGR emitters with active probing

(wafer is n-side up).

n‐contact

n‐GaAs

Emitting area (outcoupling grating  

on p‐side)

n‐contact

DGR area (Littrow grating  

on n‐side)

λ sw  (nm) d f  (nm)973.9 409.00975.1 407.75976.2 406.50977.3 405.25

Wavelength of Interest

Littrow Grating

SEM image of one of one of the Littrow Gratings

Oleg V. Smolski, Viktor O. Smolski, Yigit O. Yilmaz, and Eric G. Johnson, University of North Carolina, Charlotte, NC. Work performed at Georgia Tech Nanotechnology Research Center.

Hybrid Nanoplasmonic Photonic On-chip Sensors

Integrated nanoplasmonic photonic sensors are designed and implemented for on-chip sensing. The purpose of the novel integrated plasmonic photonic platform is to realize a lab-on-chip system for efficient light-matter interaction. This leads to a low-cost, highly sensitive, and portable sensing device for applications in point of care diagnostics in far reaching areas with limited resources, and also for chemical and environmental sensing. Different components of this sensing platform are fabricated using electron beam nanolithography, ICP etching, metal evaporation, and lift-off using the tools at GT-NRC. The device is fabricated on a Si wafer with layers of oxide, and nitride as the photonic component. The plasmonic component is implemented using gold nanoparticles.

Maysamreza Chamanzar and Ali Adibi, Georgia Institute of TechnologyFabrication performed at Georgia Tech Nanotechnology Research Center

Top scattering darkfield image of an array of plasmonicgold nanorods excited on a waveguide at resonance.Each nanorod can probe a few target molecules.

Scanning electron micrograph (SEM) of a SiN WG with a single gold nanorod

Gold nanorod

Fabrication of Grating Couplers and Planar Waveguides for Chemical Sensing of ExplosivesPaul Edmiston1, Janet Cobb-Sullivan2,4, Joel Keelor2, Adam Scofield3, David Gottfried4

College of Wooster1, Georgia Tech Research Institute2, Rensselaer Polytechnic Institute3, Georgia Institute of Technology4

SEM images of silicon template (left), imprinted resist (middle), and etched quartz (right).

Molecular imprinting scheme for chemical sensing of TNT

Optical waveguiding in a completed sensor.

Response of the sensor (BTB sensing film) to TNT (50 ml/min).

Nanoimprinting process for fabrication of grating couplers.

Paul Edmiston, Janet Cobb-Sullivan, Joel Keelor, Adam Scofield, and David Gottfried of College of Wooster, Rensselaer Polytechnic Institute, and Georgia TechWork performed at Georgia Tech Nanotechnology Research Center

On-chip coherently combined angled grating broad-area laser

The on-chip coherently combined angled grating broad-area laser is aimed to provide high power and high brightness light output. The laser structure is built on angled grating broad-area lasers which are coherently combined monolithically by a 2D coupling region. The observed interference patterns of two output ports confirm the coherent combination in our laser design. The whole laser chip is fabricated in GT IEN Centers. The gratings are defined by an advanced JEOL 9300 EBL system and then transferred to an InP-based MQW wafer by dry etching.

Yunsong Zhao and Lin Zhu, Clemson UniversityWork performed at Gerogia Tech's Institute for Electronics and Nanotechnology Centers

Schematic plot of the laser chip

SEM images at different fabrication phases. Last figure shows a completed laser device after die bonding and wire bonding.

Innovative Microwave and Terahertz Nanodetectors and Microgenerators Project

The purpose of the project is to create ainnovative antenna device working in microwaveup to terahertz frequency range. This antenna isbased on the ratchet effect phenomenon andcan ensure two main capabilities:- detect a signal carried by microwave.Applications in telecommunication field aredirect. For instance an audio signal could becarried at such high frequencies,- generate a voltage (or a current) by irradiatingthe ratchet cell using microwave. Applications infast and miniaturized power generators field areopened.

This project is a France / US partnership supported by the PUF / FACE program.

Devin Brown and Jean-Claude Portal respectively from Georgia Institute of Technology, Atlanta, USA and CNRS/LNCMI-INSA, Grenoble France.

Georgia Tech SEM picture of the “ratchet cell” : : semicircle antidots in an hexagonal symetry are etched in a semiconductor heterostructure.

The antidot radius and period are respectively:r = 120 nm,a = 600 nm.

250 µm50 µm

Microwave radiation carrying the audio signal

Ratchet cell

Audio signal detected

Telecommunication application

Bottom-up Creation of Graphene Wire Arrays

The purpose of the project was to demonstrate an alternative bottom-upmethod to creating graphene wires capable of creating smaller features with better electronic conduction than is currently possible with top-down shaping of the graphene through a lithographically-defined etch mask. Electron beam lithography is used to define a series of rectangular apertures in silicon carbide (SiC) that are then etched into trenches using a plasma. In the lab, these features are heated to about 1500C, where the silicon preferentially evaporates from the sides of the trenches, with the remaining carbon-rich layer spontaneously forming graphene. We have so far used this technique to demonstrate 10nm-wide graphene strips spaced 100nm apart over a 1.5mm x 1.5mm area.

Jeremy Hicks and Edward H. Conrad in collaboration with the Epitaxial Graphene group, Georgia TechWork performed at Georgia Tech Microelectronics Research Center

3D rendering of trenches etched into SiC as seen by atomic force microscopy (AFM)

Band structure of the trench sidewalls measured using angle-resolved photoemission spectroscopy (ARPES) showing typical cone-like graphene band structure

Zoomed-in electrostatic force microscopy (EFM) image, with bright areas denoting graphene confined to the trench sidewalls. Dark areas are either the trenches or the plateaus between trenches

Epitaxial Graphene Nanoribbon Transistors

Graphene, an atomically thin sheet of carbonatoms, holds great promise as a futurereplacement material for silicon-baseddevices. The goal of this research is toinvestigate how epitaxial graphene,produced on silicon carbide substrates,behaves at the nanoscale, as such smallfeature sizes are necessary for future devicescaling. We have investigated the mobilitydegradation in graphene nanoribbons(GNRs) as a function of line width, and foundthat improvements in both lithographicallypatterned line edge roughness and thesubstrate morphology are necessary tomaintain high levels of conduction. Inaddition, we have demonstrated the firstelectrical measurements of p-type epitaxialGNRs, obtained by the simple thermalannealing of the electron-beam resist HSQ.

Sarah E. Bryan, Yinxiao Yang, Kevin Brenner, Raghu Murali, and James D. MeindlWork performed at Georgia Tech Nanotechnology Research Center

An atomic force microscope image of monolayer epitaxial graphene on silicon carbide.

5 µm

3-Day AnnealAs-fabricated

300 nm

I-V data of GNRs showing a change from strong n-type doping to p-type doping via thermal annealing.

A scanning electron microscope image of 10 parallel 20-nm GNRs.

3-Day Anneal