Bit-patterned perpendicular magnetic media

Transcription

1 Bit-patterned perpendicular magnetic media The project targets to employ E-beam lithography to pattern perpendicular anisotropy Co 80 Pt 20 films into nanopillar arrays as bit-patterned perpendicular magnetic media for next-generation recording media with ultra-high data storage capacity. The magnetic Co 80 Pt 20 thin films were deposited by sputtering, and negative resist HSQ was spin-coated on the top of Co 80 Pt 20 films for electron-beam lithography. The SEM images reveal that as density increase the nanopillar diameters get larger. These nanopillar arrays act as masks for ion miller etching. After etching, the magnetic properties of Co 80 Pt 20 nanopillar arrays were characterized by alternating gradient field magnetometer (AGM) and magnetooptical Kerr effect magnetometer (MOKE). Furthermore, magnetic force microscopy (MFM) was used to study the domain structure. Our results show that E-beam lithography provides a promising way to pattern perpendicular magnetic media. Zhenzhong Sun, Su Gupta and Dawen Li, MINT Center, The University of Alabama, Tuscaloosa, AL Work performed at Georgia Tech Nanotechnology Research Center

2 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 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. Wavelength of Interest Littrow Grating λ sw (nm) d f (nm) 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. 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 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) Schematic of a WL GCSEL w/dgr 270nm periodicity outcoupling grating Output beam Feedback Littrow grating 220nm periodicity outcoupling grating 1 O Daniel et al. Optics Lett. 31, 211 (2006) Wafer inspection of the processed GCSEL/DGR emitters with active probing (wafer is n-side up). Emitting area (outcoupling grating on p side) DGR area (Littrow grating on n side) n GaAs n contact n contact DGR Section

3 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. Gold nanorod Scanning electron micrograph (SEM) of a SiN WG with a single gold nanorod Top scattering darkfield image of an array of plasmonic gold nanorods excited on a waveguide at resonance. Each nanorod can probe a few target molecules. Maysamreza Chamanzar and Ali Adibi, Georgia Institute of Technology Fabrication performed at Georgia Tech Nanotechnology Research Center

4 Fabrication of Grating Couplers and Planar Waveguides for Chemical Sensing of Explosives Paul Edmiston 1, Janet Cobb-Sullivan 2,4, Joel Keelor 2, Adam Scofield 3, David Gottfried 4 College of Wooster 1, Georgia Tech Research Institute 2, Rensselaer Polytechnic Institute 3, Georgia Institute of Technology 4 Nanoimprinting process for fabrication of grating couplers. Molecular imprinting scheme for chemical sensing of TNT SEM images of silicon template (left), imprinted resist (middle), and etched quartz (right). Optical waveguiding in a completed sensor. Paul Edmiston, Janet Cobb-Sullivan, Joel Keelor, Adam Scofield, and David Gottfried of College of Wooster, Rensselaer Polytechnic Institute, and Georgia Tech Work performed at Georgia Tech Nanotechnology Research Center Response of the sensor (BTB sensing film) to TNT (50 ml/min).

5 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. Schematic plot of the laser chip Yunsong Zhao and Lin Zhu, Clemson University Work performed at Gerogia Tech's Institute for Electronics and Nanotechnology Centers SEM images at different fabrication phases. Last figure shows a completed laser device after die bonding and wire bonding.

6 Innovative Microwave and Terahertz Nanodetectors and Microgenerators Project The purpose of the project is to create a innovative antenna device working in microwave up to terahertz frequency range. This antenna is based on the ratchet effect phenomenon and can ensure two main capabilities: - detect a signal carried by microwave. Applications in telecommunication field are direct. For instance an audio signal could be carried at such high frequencies, - generate a voltage (or a current) by irradiating the ratchet cell using microwave. Applications in fast and miniaturized power generators field are opened. 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. Telecommunication application Ratchet cell 250 µm Microwave radiation carrying the audio signal 50 µm 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. Audio signal detected

7 Bottom-up Creation of Graphene Wire Arrays The purpose of the project was to demonstrate an alternative bottom-up method 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 Tech Work performed at Georgia Tech Microelectronics Research Center 3D rendering of trenches etched into SiC as seen by atomic force microscopy (AFM) 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 Band structure of the trench sidewalls measured using angle-resolved photoemission spectroscopy (ARPES) showing typical cone-like graphene band structure

8 Epitaxial Graphene Nanoribbon Transistors Graphene, an atomically thin sheet of carbon atoms, holds great promise as a future replacement material for silicon-based devices. The goal of this research is to investigate how epitaxial graphene, produced on silicon carbide substrates, behaves at the nanoscale, as such small feature sizes are necessary for future device scaling. We have investigated the mobility degradation in graphene nanoribbons (GNRs) as a function of line width, and found that improvements in both lithographically patterned line edge roughness and the substrate morphology are necessary to maintain high levels of conduction. In addition, we have demonstrated the first electrical measurements of p-type epitaxial GNRs, obtained by the simple thermal annealing of the electron-beam resist HSQ. 5 µm A scanning electron microscope image of 10 parallel 20-nm GNRs. As-fabricated An atomic force microscope image of monolayer epitaxial graphene on silicon carbide. 300 nm 3-Day 3-Day Anneal Anneal Sarah E. Bryan, Yinxiao Yang, Kevin Brenner, Raghu Murali, and James D. Meindl Work performed at Georgia Tech Nanotechnology Research Center I-V data of GNRs showing a change from strong n-type doping to p-type doping via thermal annealing.