DOCSLIB.ORG

Sub-Second Quantum Cascade Laser Based Infrared Spectroscopic Ellipsometry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sub-Second Quantum Cascade Laser Based Infrared Spectroscopic Ellipsometry 3426 Vol. 44, No. 14 / 15 July 2019 / Optics Letters Letter Sub-second quantum cascade laser based infrared spectroscopic ellipsometry 1 1 2 3 ALEXANDER EBNER, ROBERT ZIMMERLEITER, CHRISTOPH COBET, KURT HINGERL, 1, 1 MARKUS BRANDSTETTER, * AND JAKOB KILGUS 1RECENDT—Research Center for Non-Destructive Testing GmbH, Science Park 2, Altenberger Str. 69, 4040 Linz, Austria 2Linz School of Education, Johannes Kepler Universität, Altenberger Str. 69, 4040, Linz, Austria 3Center for Surface and Nanoanalytics, Johannes Kepler Universität, Altenberger Str. 69, 4040, Linz, Austria *Corresponding author: [email protected] Received 1 May 2019; revised 5 June 2019; accepted 5 June 2019; posted 5 June 2019 (Doc. ID 366212); published 3 July 2019 Laser-based infrared spectroscopic ellipsometry (SE) is dem- By means of spectroscopic ellipsometry (SE), wavelength- onstrated for the first time, to the best of our knowledge, by dependent sample properties are probed. The spectral regions applying a tunable quantum cascade laser (QCL) as a mid- covered by SE span the ultra-violet (UV), visible (VIS) and in- infrared light source. The fast tunability of the employed frared (IR) spectral range. Whereas the UV and VIS regions are QCL, combined with phase-modulated polarization, sensitive to electronic states and excitons, in the IR molecular −1 enabled the acquisition of broadband (900–1204 cm ), vibrations, free-carrier and phonon absorptions are observed. In −1 high-resolution (1cm ) ellipsometry spectra in less contrast to free-carrier absorptions probed in the terahertz than 1 second. A comparison to a conventional Fourier- range [5], fundamental vibration modes occur in the finger- transform spectrometer-based IR ellipsometer resulted in print region, which is part of the mid-infrared (MIR) spectral an improved signal-to-noise ratio (SNR) by a factor of at least range. Therefore, SE in the MIR enables the determination of 290. The ellipsometry setup was finally applied for the real- both chemical composition and, in the case of anisotropy, spa- time monitoring of molecular reorientation during the tial orientation of the investigated structure. However, until re- stretching process of an anisotropic polypropylene film, cently, optical methods in the MIR range had to rely on thermal thereby illustrating the advantage of sub-second time reso- light sources. Such sources feature low brilliance—defined as lution. The developed method exceeds existing instrumenta- photon flux per solid angle and bandwidth—leading to long tion by its fast acquisition and high SNR, which could open integration times and to a significant loss of intensity after large up a set of new applications of SE such as ellipsometric inline path lengths or penetration depths. process monitoring and quality control. © 2019 Optical The advent of quantum cascade lasers (QCLs) eventually Society of America brought a unique, spectrally tunable, and high-brilliance MIR https://doi.org/10.1364/OL.44.003426 laser source. Thus, the advantages of lasers could be combined with the ability of broadband emission known from thermal Provided under the terms of the OSA Open Access Publishing Agreement light sources. QCLs are monochromatic sources, but offer a spectral tuning range up to several 100 cm−1 when realized The already well-established measurement technique ellipsom- in external cavity configuration (EC-QCL) [6]. Hence, spectro- etry gained an increasingly important role in various scientific scopic measurements without the need of any monochromator or interferometer became feasible [7]. In comparison to thermal and industrial disciplines resulting in numerous technological 4 and biomedical applications [1]. Ellipsometry is based on the MIR light sources, QCLs offer at least 10 times higher bril- determination of a polarization change due to light–matter in- liance. The provided improvements in signal-to-noise ratio teraction at a sample [2]. This change in polarization can arise (SNR) and sensitivity enable new applications such as transmis- from various processes at the surface or inside the bulk leading sion measurements of liquid solutions beyond the limits of con- to a wide range of measurable sample parameters. As the ventional systems if the characteristic properties of EC-QCLs method relies on the measurement of intensity ratios of polari- are considered [8,9]. Furthermore, the fast tunability of several −1 zation components, including their phase difference, the com- 1000 cm ∕s leads to a major reduction of the acquisition plex refractive index can be obtained directly without any time per spectrum. reference measurements or performing a Kramers–Kronig The advantage of using a high-brilliance QCL for vibra- analysis. Thereby, unique information about the sample such tional circular dichroism measurements has already been shown as chemical composition, as well as dielectric and geometric by Lüdeke et al. [10]. Thereby, the efficiency of QCLs applied properties, can be obtained simultaneously. Additionally, ellips- to a polarization-modulating technique was demonstrated in ometry offers extraordinary sensitivity enabling sub-monolayer spectral regions that are difficult to study due to significant resolution, e.g., in epitaxial thin film growth [3,4]. water absorption. However, the potential high time resolution 0146-9592/19/143426-04 Journal © 2019 Optical Society of America Letter Vol. 44, No. 14 / 15 July 2019 / Optics Letters 3427 could not be exploited, as the application of a chopper (≤0.5cm−1) and precision (≤0.2cm−1), measurements with drastically reduces the available sampling rate. Compared to a spectral resolution below 1cm−1 were feasible. For polariza- dichroism measurements, ellipsometry turns out to be a more tion modulation a ZnSe photo-elastic modulator (PEM) oper- powerful method, as both phase shift and amplitude ratio— ating at 37 kHz (Hinds Instruments PEM-90) was used. The expressed by the ellipsometric parameters Δ and Ψ—are signal was detected with a thermoelectrically cooled mercury recorded simultaneously. Therefore, SE additionally covers di- cadmium telluride (MCT) detector (VIGO System PCI- chroism information and is not limited to anisotropic samples. 4TE-12). In order to split the detected signal into an AC as well The first application of ellipsometry using a QCL was presented as a DC part, a signal extraction unit consisting of a high- by mapping structured surfaces and molecular interactions in pass filter (10 kHz) and a low-pass filter (10 Hz or 2 kHz organic thin films at only two discrete wavelengths [11]. The depending on the acquisition speed) was implemented. For presented results demonstrate a promising outlook in terms of further signal processing, a digital lock-in amplifier (LIA) hyperspectral sample mapping ellipsometry. However, the po- (Anfatec Instruments eLockIn 204) offering multiple signal tential of realizable diffraction-limited spot sizes offered by outputs was used. Finally, the desired signals were recorded QCLs was not exploited, as only a spatial resolution in the by means of a 12 bit high-speed oscilloscope (Teledyne millimeter range was achieved. LeCroy HDO6104A). In our contribution, we present, to the best of our knowl- As indicated in Fig. 1, the vertically polarized QCL radiation edge, the first laser based SE measurements by recording con- −1 −1 was passed through a slightly tilted KBr window to prevent tinuous spectra (900–1204 cm ) with 1cm resolution in back reflections into the laser. In order to avoid interference Δ Ψ sub-second acquisition times (887 ms per , -spectrum). effects at the modulation frequency, the laser beam diameter In order to demonstrate the accuracy of the developed system, was reduced to about 0.6 mm by an aperture before the beam μ anisotropic polypropylene (PP) films of 6 m thickness have passed the 15° tilted PEM. Additionally, to sub-millimeter spot been measured in transmission at normal incidence and were sizes, this configuration allows splitting the first transmitted compared with reference measurements done with a commer- beam from the ones experiencing multiple reflections in the cially available Fourier-transform infrared (FTIR) spectros- optical element of the PEM. The latter were then blocked copy-based rotating compensator ellipsometer. Furthermore, by a razor blade placed directly behind the PEM. After passing the enhanced noise performance of the presented setup com- the sample, the transmitted radiation was analyzed by four suc- pared to the conventional ellipsometer is shown. Finally, the cessively arranged wire grid polarizers before a ZnSe lens fo- spatial reorientation of molecules within a PP film due to cused the beam on the detector chip. The detected intensity an applied tensile force has been observed with the sequential I det was calculated by means of Jones matrices of the respective recording of multiple ellipsometry spectra. This realization of optical elements. In the given configuration with a PEM optical laser based SE measurements opens up new paths and oppor- axis and analyzer, each rotated 45° with respect to the initial tunities for future research in the MIR spectral range. polarization, this leads to The configuration of the developed QCL ellipsometer is illustrated in Fig. 1. The applied EC-QCL (DRS Daylight I det ∼ I 0 I 0J0 δ0 cos 2Ψ → I DC 900 cm−1 1204 cm−1 Solutions Hedgehog) is tunable from to 2I 0J1 δ0 sin 2Ψ sin Δ sin ωM t → I ω (1) (1000 cm−1∕s) while emitting a laser beam with a waist of 2I 0J2 δ0 cos 2Ψ cos 2ωM t → I 2ω, about 2.5 mm in the TEM00 spatial mode (linearly polarized >100:1). In the presented setup the laser was driven in con- after Jacobi–Anger expansion [12]. Here I 0 denotes the tinuous wave mode leading to an extremely narrow spectral intensity provided by the QCL, while δ0 and ωM refer to linewidth of just 3.3 × 10−3 cm−1 and a maximum emission the modulation amplitude and modulator circular frequency, power of 110 mW according to the manufacturer. Combined respectively. The Bessel functions arising due to the expansion −1 with high wavelength repeatability (≤0.1cm ), accuracy are given by J0, J1, and J2.
Load more

Recommended publications
  • Characterization of an Active Metasurface Using Terahertz Ellipsometry Nicholas Karl, Martin S
    Characterization of an active metasurface using terahertz ellipsometry Nicholas Karl, Martin S. Heimbeck, Henry O. Everitt, Hou-Tong Chen, Antoinette J. Taylor, Igal Brener, Alexander Benz, John L. Reno, Rajind Mendis, and Daniel M. Mittleman Citation: Appl. Phys. Lett. 111, 191101 (2017); View online: https://doi.org/10.1063/1.5004194 View Table of Contents: http://aip.scitation.org/toc/apl/111/19 Published by the American Institute of Physics APPLIED PHYSICS LETTERS 111, 191101 (2017) Characterization of an active metasurface using terahertz ellipsometry Nicholas Karl,1 Martin S. Heimbeck,2 Henry O. Everitt,2 Hou-Tong Chen,3 Antoinette J. Taylor,3 Igal Brener,4 Alexander Benz,4 John L. Reno,4 Rajind Mendis,1 and Daniel M. Mittleman1 1School of Engineering, Brown University, 184 Hope St., Providence, Rhode Island 02912, USA 2U.S. Army AMRDEC, Redstone Arsenal, Huntsville, Alabama 35808, USA 3Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 4Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA (Received 11 September 2017; accepted 19 October 2017; published online 6 November 2017) Switchable metasurfaces fabricated on a doped epi-layer have become an important platform for developing techniques to control terahertz (THz) radiation, as a DC bias can modulate the transmis- sion characteristics of the metasurface. To model and understand this performance in new device configurations accurately, a quantitative understanding of the bias-dependent surface characteristics is required. We perform THz variable angle spectroscopic ellipsometry on a switchable metasur- face as a function of DC bias. By comparing these data with numerical simulations, we extract a model for the response of the metasurface at any bias value.
    [Show full text]
  • Optical Characterization of Ultra-Thin Films of Azo-Dye-Doped Polymers Using Ellipsometry and Surface Plasmon Resonance Spectroscopy
    hv photonics Article Optical Characterization of Ultra-Thin Films of Azo-Dye-Doped Polymers Using Ellipsometry and Surface Plasmon Resonance Spectroscopy Najat Andam 1,2 , Siham Refki 2, Hidekazu Ishitobi 3,4, Yasushi Inouye 3,4 and Zouheir Sekkat 1,2,4,* 1 Department of Chemistry, Faculty of Sciences, Mohammed V University, Rabat BP 1014, Morocco; [email protected] 2 Optics and Photonics Center, Moroccan Foundation for Advanced Science, Innovation and Research, Rabat BP 10100, Morocco; [email protected] 3 Frontiers Biosciences, Osaka University, Osaka 565-0871, Japan; [email protected] (H.I.); [email protected] (Y.I.) 4 Department of Applied Physics, Osaka University, Osaka 565-0871, Japan * Correspondence: [email protected] Abstract: The determination of optical constants (i.e., real and imaginary parts of the complex refractive index (nc) and thickness (d)) of ultrathin films is often required in photonics. It may be done by using, for example, surface plasmon resonance (SPR) spectroscopy combined with either profilometry or atomic force microscopy (AFM). SPR yields the optical thickness (i.e., the product of nc and d) of the film, while profilometry and AFM yield its thickness, thereby allowing for the separate determination of nc and d. In this paper, we use SPR and profilometry to determine the complex refractive index of very thin (i.e., 58 nm) films of dye-doped polymers at different dye/polymer concentrations (a feature which constitutes the originality of this work), and we compare the SPR results with those obtained by using spectroscopic ellipsometry measurements performed on the Citation: Andam, N.; Refki, S.; Ishitobi, H.; Inouye, Y.; Sekkat, Z.
    [Show full text]
  • Use of Spectroscopic Ellipsometry and Modeling in Determining Composition and Thickness of Barium Strontium Titanate Thin-Films
    Use of Spectroscopic Ellipsometry and Modeling in Determining Composition and Thickness of Barium Strontium Titanate Thin-Films A Thesis Submitted to the Faculty of Drexel University by Dominic G. Bruzzese III in partial fulfillment of the requirements for the degree of MS in Materials Science and Engineering June 2010 c Copyright June 2010 Dominic G. Bruzzese III. All Rights Reserved. Acknowledgements I would like to acknowledge the guidance and motivation I received from my advi- sor Dr. Jonathan Spanier not just during my thesis but for my entire stay at Drexel University. Eric Gallo for his help as my graduate student mentor and always making himself available to help me with everything from performing an experiment to ana- lyzing some result, he has been an immeasurable resource. Keith Fahnestock and the Natural Polymers and Photonics Group under the direction of Dr. Caroline Schauer for allowing the use of their ellipsometer, without which this work would not have been possible. I would like to thank everyone in the MesoMaterials Laboratory, espe- cially Stephen Nonenmann, Stephanie Johnson, Guannan Chen, Christopher Hawley, Brian Beatty, Joan Burger, and Andrew Akbasheu for help with experiments, as well as Oren Leffer and Terrence McGuckin for enlightening discussions. Claire Weiss and Dr. Pamir Alpay at the University of Connecticut have both contributed much to the the field and I am grateful for their work; also Claire produced the MOSD samples on which much of the characterization and modeling was done. Dr. Melanie Cole and the Army Research Office and Dr. Marc Ulrich for funding the project under W911NF-08-0124 and W911NF-08-0067.
    [Show full text]
  • Ellipsometry
    AALBORG UNIVERSITY Institute of Physics and Nanotechnology Pontoppidanstræde 103 - 9220 Aalborg Øst - Telephone 96 35 92 15 TITLE: Ellipsometry SYNOPSIS: This project concerns measurement of the re- fractive index of various materials and mea- PROJECT PERIOD: surement of the thickness of thin films on sili- September 1st - December 21st 2004 con substrates by use of ellipsometry. The el- lipsometer used in the experiments is the SE 850 photometric rotating analyzer ellipsome- ter from Sentech. THEME: After an introduction to ellipsometry and a Detection of Nanostructures problem description, the subjects of polar- ization and essential ellipsometry theory are covered. PROJECT GROUP: The index of refraction for silicon, alu- 116 minum, copper and silver are modelled us- ing the Drude-Lorentz harmonic oscillator model and afterwards measured by ellipsom- etry. The results based on the measurements GROUP MEMBERS: show a tendency towards, but are not ade- Jesper Jung quately close to, the table values. The mate- Jakob Bork rials are therefore modelled with a thin layer of oxide, and the refractive indexes are com- Tobias Holmgaard puted. This model yields good results for the Niels Anker Kortbek refractive index of silicon and copper. For aluminum the result is improved whereas the result for silver is not. SUPERVISOR: The thickness of a thin film of SiO2 on a sub- strate of silicon is measured by use of ellip- Kjeld Pedersen sometry. The result is 22.9 nm which deviates from the provided information by 6.5 %. The thickness of two thick (multiple wave- NUMBERS PRINTED: 7 lengths) thin polymer films are measured. The polymer films have been spin coated on REPORT PAGE NUMBER: 70 substrates of silicon and the uniformities of the surfaces are investigated.
    [Show full text]
  • A Dissertation Entitled Spectroscopic Ellipsometry Studies of Thin Film Si
    A Dissertation entitled Spectroscopic Ellipsometry Studies of Thin Film Si:H Materials in Photovoltaic Applications from Infrared to Ultraviolet by Laxmi Karki Gautam Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics _________________________________________ Dr. Nikolas J. Podraza, Committee Chair _________________________________________ Dr. Robert W. Collins, Committee Member _________________________________________ Dr. Randall Ellingson, Committee Member _________________________________________ Dr. Song Cheng, Committee Member _________________________________________ Dr. Rashmi Jha, Committee Member _________________________________________ Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo May, 2016 Copyright 2016, Laxmi Karki Gautam This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Spectroscopic Ellipsometry Studies of Thin Film Si:H Materials in Photovoltaic Applications from Infrared to Ultraviolet by Laxmi Karki Gautam Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics The University of Toledo May 2016 Optimization of thin film photovoltaics (PV) relies on the capability for characterizing the optoelectronic and structural properties of each layer in the device over large areas and correlating these properties with device performance. This work builds heavily upon that done previously by us, our collaborators, and other researchers. It provides the next step in data analyses, particularly that involving study of films in device configurations maintaining the utmost sensitivity within those same device structures. In this Dissertation, the component layers of thin film hydrogenated silicon (Si:H) solar cells on rigid substrate materials have been studied by real time spectroscopic ellipsometry (RTSE) and ex situ spectroscopic ellipsometry (SE).
    [Show full text]
  • 1. Introduction & Theory
    1. Introduction & Theory Neha Singh October 2010 Course Overview Day 1: Day 2: Introduction and Theory Genosc Layer Transparent Films Absorbing Films Microstructure – EMA If time permits: – Surface roughness Non-idealities – Grading (Simple and Ultra thin films function-based ITO) Uniqueness test – Thickness non-uniformity UV Absorption Review – Point-by-point fit Actual Samples © 2010, All Rights Reserved 2 Introduction & Theory Light Materials (optical constants) Interaction between light and materials Ellipsometry Measurements Data Analysis © 2010, All Rights Reserved 3 Light Electromagnetic Plane Wave From Maxwell’s equations we can describe a plane wave ⎛ 2π ⎞ E(z,t) = E0 sin⎜ − (z − vt) + ξ ⎟ ⎝ λ ⎠ Amplitude Amplitude arbitraryarbitrary phase phase X Wavelength Wavelength VelocityVelocity λ Electric field E(z,t) Y Z Direction Magnetic field, B(z,t) of propagation © 2010, All Rights Reserved 4 Intensity and Polarization Intensity = “Size” of Electric field. I ∝ E 2 Polarization = “Shape” of Electric field travel. Different Size Y •Y E More Intense Less (Intensity) Intense E Same Shape! X (Polarization) •X © 2010, All Rights Reserved 5 What is Polarization? Describes how Electric Field travels through space and time. X wave1 Y E wave2 Z © 2010, All Rights Reserved 6 Describing Polarized Light Jones Vector Stokes Vector Describe polarized light Describe any light beam with amplitude & phase. as vector of intensity ⎡S ⎤ ⎡ E2 + E2 ⎤ iϕx 0 x0 y0 ⎡Ex ⎤ ⎡E0xe ⎤ ⎢ ⎥ ⎢ 2 2 ⎥ = S1 ⎢ Ex0 −Ey0 ⎥ ⎢ ⎥ ⎢ iϕy ⎥ ⎢ ⎥ = E E e ⎢ ⎥ ⎢ ⎥ ⎣ y ⎦ ⎣⎢ 0y ⎦⎥ S2 2Ex0Ey0 cosΔ ⎢ ⎥ ⎢ ⎥ ⎣S3 ⎦ ⎣⎢2Ex0Ey0 sinΔ⎦⎥ © 2010, All Rights Reserved 7 Light-Material Interaction velocity & c wavelength vary v = in different n materials n = 1 •n = 2 Frequency remains constant v υ = λ © 2010, All Rights Reserved What are Optical Constants n , k Describe how materials and light interact.
    [Show full text]
  • Optical Properties of Teflon AF Amorphous Fluoropolymers
    J. Micro/Nanolith. MEMS MOEMS 7͑3͒, 033010 ͑Jul–Sep 2008͒ Optical properties of Teflon® AF amorphous fluoropolymers MinK.Yang Abstract. The optical properties of three grades of Teflon® AF— Roger H. French AF1300, AF1601, and AF2400—were investigated using a J.A. Woollam DuPont Co. Central Research VUV-VASE spectroscopic ellipsometry system. The refractive indices for Experimental Station each grade were obtained from multiple measurements with different film Wilmington, Delaware 19880-0400 thicknesses on Si substrates. The absorbances of Teflon® AF films were E-mail: [email protected] determined by measuring the transmission intensity of Teflon® AF films on CaF2 substrates. In addition to the refractive index and absorbance per cm ͑base 10͒, the extinction coefficient ͑k͒, and absorption coefficient Edward W. Tokarsky ͑␣͒ per cm ͑base e͒, Urbach parameters of absorption edge position and DuPont Fluoropolymer Solutions edge width, and two-pole Sellmeier parameters were determined for the Chestnut Run Plaza three grades of Teflon® AF. We found that the optical properties of the Wilmington, Delaware 19880-0713 three grades of Teflon® AF varied systematically with the AF TFE/PDD composition. The indices of refraction, extinction coefficient ͑k͒, absorp- tion coefficient ͑␣͒, and absorbance ͑A͒ increased, as did the TFE con- tent, while the PDD content decreased. In addition, the Urbach edge position moved to a longer wavelength, and the Urbach edge width became wider. © 2008 Society of Photo-Optical Instrumentation Engineers. ͓DOI: 10.1117/1.2965541͔ Subject terms: fluoropolymer; absorbance absorption coefficient; VUV ellipsometry. Paper 07086R received Oct. 24, 2007; revised manuscript received May 16, 2008; accepted for publication Jun.
    [Show full text]
  • Ellipsometry for Csige Metrology
    Ellipsometry for cSiGe Metrology Saiqa Farhat, Srinivasan Rangarajan, Timothy J. Dawei Hu, Ming Dai Mcardle, Michael Steigerwalt Films Metrology Division 300mm East Fishkill KLA Tencor Corp. IBM Corp San Jose, CA Hopewell Jn, NY, USA Abstract— In this paper we report the effectiveness of sensitive to the refractive index and thickness of the films in optical ellipsometry in measuring thickness and Germanium % the stack. Next, the elliptically polarized light will pass through of channel SiGe on SOI substrate used in advanced node high the analyzer and become linear polarized light again. Finally, performance semiconductor devices. the detector will receive the linear polarized light signal. The value tanΨ and cosΔ are extracted as a function of wavelength. Keywords—cSiGe, Ellipsometry, Thickness, Ge These are called the measured spectra. Concentration, metrology. I. INTRODUCTION Optical metrology of film thickness is the “work-horse” technique in semiconductor fabrication for control of a wide variety of processes. The tools and their technology are well established, providing low cost of ownership (COO) to manufacturers by giving fast and reliable feedback to their processes. In this study we demonstrate the successful implementation of optical metrology for cSiGe process control replacing a X-ray diffraction technique. The performance of SiGe channel in devices is dependent on film thickness and %Ge. X-ray diffraction (XRD) technique measures the change Figure 1: SE measurement optics schematic in lattice spacing of the strained silicon which is well correlated with %Ge in the film [1]. The technique is slow and new, posing challenges in manufacturing. Optical metrology on the other hand is a model based technique relying on the ability to B.
    [Show full text]
  • Infrared Spectroscopy and Ellipsometry of Magnetic Metamaterials
    Invited Paper Infrared spectroscopy and ellipsometry of magnetic metamaterials W.J. Padilla1, Ta Jen Yen2, N. Fang2, D.C. Vier3, David R. Smith4, J.B. Pendry5, X. Zhang2, D.N. Basov3 1Los Alamos National Laboratory, MS K764 MST-10, Los Alamos, NM 87545. 2Department of Mechanical and Aerospace Engineering, University of California at Los Angeles, 420 Westwood Plaza, Los Angeles, CA 90095. 3Department of Physics, University of California San Diego, La Jolla, California 92093-0319. 4Department of Electrical & Computer Engineering, Durham, NC 27708-0291. 5Condensed Matter Theory Group, Blackett Laboratory, Imperial College, London SW7 2AZ, UK. ABSTRACT We present S and P polarized measurements of artificial bianisotropic magnetic metamaterials with resonant behavior at infrared frequencies. These metamaterials consist of an array of micron sized (~40µm) copper rings fabricated upon a quartz substrate. Simulation of the reflectance is obtained through a combination of electromagnetic eigenmode simulation and Jones matrix analysis, and we find excellent agreement with the experimental data. It is shown that although the artificial magnetic materials do indeed exhibit a magnetic response, care must be taken to avoid an undesirable electric dipole resonance, due to lack of reflection symmetry in one orientation. The effects of bianisotropy on negative index are detailed and shown to be beneficial for certain configurations of the material parameters. Keywords: THz, meta material, left handed, negative index, bianisotropy, chiral, ellipsometry 1. INTRODUCTION Recently the field of electromagnetism has seen significant excitement and rapid growth, due the discovery of left- handed metamaterials.i These artificially constructed materials are capable of achieving simultaneous values of negative electric (ε<0) and negative magnetic (µ<0) response, a feat that is difficult or impossible to achieve with naturally occurring materials.
    [Show full text]
  • 1 Narrowband Metamaterial Absorber for Terahertz Secure Labeling
    Narrowband Metamaterial Absorber for Terahertz Secure Labeling Magued Nasr *a, Jonathan T. Richard *d, Scott A. Skirlo *b, Martin S. Heimbeck c, John D. Joannopoulos,b Marin Soljacic b, Henry O. Everitt c†, Lawrence Domash a * Equal contributors a Triton Systems Inc., 200 Turnpike Rd #2, Chelmsford, MA 01824 b Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 c U.S. Army Aviation and Missile RD&E Center, Redstone Arsenal, AL 35898 d IERUS Technologies, 2904 Westcorp Blvd Suite 210, Huntsville, AL 35805 † Corresponding author: [email protected] Abstract Flexible metamaterial films, fabricated by photolithography on a thin copper-backed polyimide substrate, are used to mark or barcode objects securely. The films are characterized by continuous wave terahertz spectroscopic ellipsometry and visualized by a scanning confocal imager coupled to a vector network analyzer that constructed a terahertz spectral hypercube. These films exhibit a strong, narrowband, polarization- and angle-insensitive absorption at wavelengths near one millimeter. Consequently, the films are nearly indistinguishable at visible or infrared wavelengths and may be easily observed by terahertz imaging only at the resonance frequency of the film. 1 Introduction Terahertz radiation in the long wavelength 1 - 3 mm band penetrates dry dielectrics such as plastics, concrete, and fabric while being strongly absorbed by water and water vapor. This combination of characteristics may be exploited for numerous applications including short-range communications and radar, collision avoidance radar, non-destructive testing of materials and structures, security imaging, medical diagnosis, and spectroscopy.[1,2,3] Materials with interesting terahertz properties also play a role in numerous security applications due to their limited range and high bandwidth.
    [Show full text]
  • SOLID STATE PHYSICS PART II Optical Properties of Solids
    SOLID STATE PHYSICS PART II Optical Properties of Solids M. S. Dresselhaus 1 Contents 1 Review of Fundamental Relations for Optical Phenomena 1 1.1 Introductory Remarks on Optical Probes . 1 1.2 The Complex dielectric function and the complex optical conductivity . 2 1.3 Relation of Complex Dielectric Function to Observables . 4 1.4 Units for Frequency Measurements . 7 2 Drude Theory{Free Carrier Contribution to the Optical Properties 8 2.1 The Free Carrier Contribution . 8 2.2 Low Frequency Response: !¿ 1 . 10 ¿ 2.3 High Frequency Response; !¿ 1 . 11 À 2.4 The Plasma Frequency . 11 3 Interband Transitions 15 3.1 The Interband Transition Process . 15 3.1.1 Insulators . 19 3.1.2 Semiconductors . 19 3.1.3 Metals . 19 3.2 Form of the Hamiltonian in an Electromagnetic Field . 20 3.3 Relation between Momentum Matrix Elements and the E®ective Mass . 21 3.4 Spin-Orbit Interaction in Solids . 23 4 The Joint Density of States and Critical Points 27 4.1 The Joint Density of States . 27 4.2 Critical Points . 30 5 Absorption of Light in Solids 36 5.1 The Absorption Coe±cient . 36 5.2 Free Carrier Absorption in Semiconductors . 37 5.3 Free Carrier Absorption in Metals . 38 5.4 Direct Interband Transitions . 41 5.4.1 Temperature Dependence of Eg . 46 5.4.2 Dependence of Absorption Edge on Fermi Energy . 46 5.4.3 Dependence of Absorption Edge on Applied Electric Field . 47 5.5 Conservation of Crystal Momentum in Direct Optical Transitions . 47 5.6 Indirect Interband Transitions .
    [Show full text]
  • Metrology Standards for Semiconductor Manufacturing Yu Guan and Marco Tortonese VLSI Standards, Inc., 3087 North First Street, San Jose, CA 95134, USA
    Metrology Standards for Semiconductor Manufacturing Yu Guan and Marco Tortonese VLSI Standards, Inc., 3087 North First Street, San Jose, CA 95134, USA Abstract made traceable to SI units because this gives us the guarantee that the results from any metrology In semiconductor manufacturing, the performance of instruments in any places that have been calibrated with metrology equipment directly impacts yield. Fabs and such standards are matched. For instance, it is desirable equipment suppliers depend on calibration standards to that dimensional standards are made traceable to the SI ensure that their metrology results are within tolerances unit of length. Actually, most calibration standards used and to maintain their ISO [1] and QS [2] quality in semiconductor fabrications (e.g. CD, film thickness, certifications. This task becomes more challenging as the step height, and particle size) are dimensional. It is, device features shrink and tolerances become tighter, to however, usually not straightforward to establish the extent of their physical limits in many cases. As the traceability for these quantities because the chain of industry keeps finding ways to meet the demanding comparison involved can be complex and the equipment metrology requirements, calibration standards have been required is not commonly available. In order to help the developed and enhanced for all essential measurements, industry obtain and maintain traceable standards, some i.e. critical dimensions, thin films, surface topography, governmental standard organizations, such as the overlay, doping, and defect inspections. This paper National Institute of Standards and Technology (NIST) provides an overview of such standards and in the US, have made available master standards that are demonstrates how they are certified and tested to be traceable to SI units, known as Standard Reference traceable to the International System (SI) unit of length Materials (SRMs).
    [Show full text]