NEW OPPORTUNITIES IN PHOTONICS APPLICATIONS : MICROPLASMA DEVICES AND ARRAYS FABRICATED IN SEMICONDUCTORS, CERAMIC AND POLYMER/METAL MULTILAYER STRUCTURES J. G. Eden
MICROPLASMAS: AT THE INTERSECTION OF OPTOELECTRONICS, MICROFABRICATION, AND PLASMA SCIENCE PLASMA SCIENCE New realm of discharge operation and characteristics MICROPLASMAS PHOTONICS MATERIALS SCIENCE, MICRO- AND NANOFABRICATION Broad array of applications
SUMMARY Glow discharges confined to mesoscopic dimensions ( < 10 ~ 100 µm) Microcavity volumes: nanoliters picoliters A variety of atomic and molecular emitters are available (VUV ~ IR) Can be operated continuously at gas pressures beyond one atmosphere at power loadings exceeding 100 kw/cm3 Leveraging MEMs and semiconductor processes for fabrication of devices and arrays Emphasis on processes amenable to mass production
GENERAL CONSIDERATIONS Macroscopic Annular Cathode Thin Film Structure d Disk Anode Discharge microcavity dimensions ( d ) on µm scale As d, surface area / volume : Importance of microcavity design
Semiconductor Devices
REPRESENTATIVE Si DEVICE STRUCTURES anode dielectric cathode Planar Si Electrode Inverted Pyramidal Electrode DRIE Electrode
SEMICONDUCTOR ARRAYS Inverted Square Pyramidal Cathode 400 Torr Ne 1200 Torr Ne
EMISSION UNIFORMITY: DC EXCITATION, ATOMIC AND MOLECULAR EMITTERS Ne Ar Ar/N2
LARGE ARRAYS FOR AC EXCITATION
200 200 ARRAY : 4 cm2 OF ACTIVE AREA
ARRAY INTENSITY CONTOUR 200 200 Arrays Uniformity : Better than 10 %
VOLTAGE-CURRENT CHARACTERISTICS : 200 200 ARRAY 800 200 x 200 10 kh z 5 0 0 T o rr 700 600 V o lta g e ( V p - p ) 700 900 600 500 400 15 20 25 C u rre n t (m A, R M S ) 30
1 5 khz 10 2 RMS RM S 10 10 15 10 10 0 1 10 10-1 0 10 10 0 10 1 10 2 10 T o t a l P o w e r C o n s u m p t io n ( W ) 7 0 0 T o rr N e -2 N o r m a liz e d P o w e r C o n s u m p t io n ( W - c m ) POWER CONSUMPTION 3 N u m b e r o f P ix e ls 10 4 10 5-2
A QUARTER MILLION PIXEL ARRAY : 25 cm2 OF ACTIVE AREA
500 500 ARRAY OPERATING in Ne 700 Torr Ne
500 500 ARRAY OPERATING in Ne 700 Torr Ne
PIXEL UNIFORMITY Attenuation with ND Filter
DRIE Si Devices (10 µm)2 Single (30 µm)2 10 X 11 arrays (30 µm)2 Single 900 Torr Ne
I-V Characteristics (10 µm)2 Si DRIE Device 330 700 T orr N e 800 900 325 1000 1100 V o l t a g e (V ) 320 315 310 10 µm Ni 305 Polyimide 300 200 µm SiO2 Si 295 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 C u rre n t ( µ A ) 2.0 2.2 2.4 2.6 2.8 3.0
Xe/O2 Microdischarges in 30 µm DRIE devices O2 10 mtorr
N Depletion Region Plasma Excitation of a Microdischarge with a Reverse-Biased PN Junction W P d = 300 µm, 180 V, 0.45 ma 200 Torr Neon
25 25 Pixel Array in Glass
Fresnel Arrays 400 Torr Ne Device Separation < Coherence Length
MICRODISCHARGE PHOTODETECTORS With Illumination 246.7V, 0.035 ma (50 234.3 V, 0.113 ma m)2 device, 500 Torr Neon
Photosensitivity Photosensitivity (A/W) 2 (100 µm) Device 500 Torr Ne λ = 780 nm 0 10 10-1 Active Plasma Device Entire Device Die 10-2 10-3 10-2 -1 10 0 10 1 10 Input Power (µw) 2 10 3 10
Spectral Response 4.0 DCD = 36 ma/cm Photosensitivity (A/W) DCD = 27 ma/cm DCD = 62 ma/cm 3.0 DCD = 58 ma/cm 2 2 2 2 2 (50 µm) Device, 800 Torr Ne 2.0 2 (100 µm) Device, 500 Torr Ne 1.0 0.0 400 500 600 700 800 Wavelength (nm) 900 1000 1100
Spectral Response Photosensitivity (A/W) 4.0 Scaled APD Response (100 µm)2, Active Plasma Device 2 (50 µm), Active Plasma Device 3.0 2.0 1.0 0.0 400 500 600 700 800 Wavelength (nm) 900 1000 1100
Band Diagram
Ceramic Devices
MULTISTAGE, MONOLITHIC CERAMIC MICRODISCHARGE DEVICE d anode pad anode cathode anode cathode ceramic layer cathode pad Pre-fired Fired
PLANAR ARRAY ELECTRODE GEOMETRY Electrode spacing is ~100 µm Parallel plate annular electrode design yields more electrode area Better device stability Longer lifetime Reduced field enhancement Individually-ballasted pixels Fabrication by screen printing
300 Torr Xe
LINEAR ARRAY CW or Pulsed Excitation Bore: 80 X 360 µm2 Active Length ~1 cm
600 Torr Ne
Intensity Gain at 460.3 nm: Xe+ 600 500 400 300 200 100 0 2500 2000 1500 1000 500 0 5000 4000 3000 2000 1000 0 300 V 500 V 800 V 440 450 460 470 Wavelength (nm) 480 490
Nanoporous Dielectrics for Microcavity Devices Pore diameter: tens~hundreds of nm
Multilayer Al/Al2O3 Microplasma Array 100 µm V Al2O3 Al 200 µm
3 3 Array Operating in Ne and Ar/N2 700 Torr Ne 500 Torr Ar/N2 (3%)
Flexible Device and Arrays
Thin Film Self-Ballasted Microdischarge Arrays d = 100 µm Dielectric Anode V 30 ~ 40 µm Cathode Layer (Ni) Dielectric Conducting Substrate Resistive Layer
d = 100 µm, 500 Torr Ne 20 mm 148.2V DC, 15 ma
13 ~ 30 µm DEVICES Metal/Polymer Structure 30 µm dia. Microdischarge Device 30 µm 30 µm ND filter
Devices Approaching Cellular Dimensions 900 Torr Neon
Flexible Large Arrays ~ 100 µm dia. 500 Torr Ne
SEALED LARGE ARRAY: 66 66 ARRAY in 3 cm2 OF ACTIVE AREA 100 µm dia. Pixels 760 Torr Ne 10 khz AC, 800 Vp-p
ADDRESSABLE FLEXIBLE ARRAY
AIR DISCHARGE DEVICES Ni / BN / Ni d = 100 µm, DC 450 V, 4 ma
MICRODISCHARGE ARRAY ASSISTED IGNITION OF A HIGH PRESSURE DISCHARGE
3.0 Ar d=400 µm 2.5 Vs (kv) 2.0 L=3.5 cm 1.5 Microdischarge Array 1.0 OFF I = 1 ma 1.5 ma 2 ma 3 ma L=1.0 cm 0.5 0.0 0 50 100 150 200 Pressure (Torr) 250 300 350
Microdischarge Device with Carbon Nanotubes Ni screen anode BN (~70 µm) Ni cathode (50 µm) 200 µm CNT Type I CNT 25 µm 200 µm Type II Si 2nd cathode SEM Image of Microcavity in Type I
Microdischarge Device with CNTs Type I Before Operation 400 Torr Ne
140 I-V Characteristics 2 0 0 T o rr N e Type I 300 400 130 500 600 125 120 115 N i / B N ( 7 0 µm ) / N i 110 145 0.0 4 0.0 8 140 0.1 2 0.1 6 0.2 0 0.2 4 0.2 8 C u rre n t (m A ) 135 2 0 0 T o rr N e 128 300 130 1 0 0 T o rr N e 400 200 500 600 125 0.0 2 0.0 4 0.0 6 0.0 8 0.1 0 0.1 2 0.1 4 0.1 6 0.1 8 C u rre n t (m A ) Type II Without CNTs D e v ic e V o lt a g e ( V ) D e v ic e V o lt a g e ( V ) 150 D e v ic e V o lt a g e ( V ) 135 124 300 400 500 120 600 116 112 108 0.0 5 0.1 0 0.1 5 0.2 0 C u rre n t (m A ) 0.2 5 0.3 0
Efficiency vs. Ignition Voltage 9.6 W it h o u t C N T s 9.2 260 S ta rtin g V o lta g e (V ) R e la tiv e R a d ia tiv e E ffic ie n c y 270 8.8 8.4 8.0 7.6 T yp e I W ith o u t C N T s T yp e I T y p e II 250 240 230 220 210 200 7.2 200 300 400 P Ne 500 600 190 100 200 300 (T o rr) Efficiency improved up to ~9 % Ignition voltage reduced by ~18% 400 P Ne 500 (T o rr) 600 700
APPLICATIONS Microdischarges
WHERE DO WE GO FROM HERE? d < 10 µm < 1 µm Full Implementation of Nanotechnology d λ : QED Effects Optical Integration of Emitters With Waveguides, Micro-Reactors Operation at Extremely High Pressures ( > 5 atm) : Clusters, New Regime of Molecular Excitation
RESEARCH TEAM UNIVERSITY OF ILLINOIS S. J. Park N. P. Ostrom K.-F. Chen C. J. Wagner K. S. Kim K. Kunze M. Leach ANVIK CORPORATION M. Zemel M. Klosner K. Jain EWING TECHNOLOGY ASSOCIATES J. J. Ewing P. von Allmen (now at NASA, JPL) D. L. Wilcox F. Zenhausern M. Oliver D. Sadler C. Jensen MOTOROLA LABORATORIES (TEMPE, AZ) CAVITON C. Herring D. Kellner CAMBRIDGE, UK K.-H. Park