Mikheil Mebonia Ph D student at Ilia State

Mikheil Mebonia Ph. D student at Ilia State, RWTH Aachen Universities and Forschungszentrum Jülich. Advisors : Raphael Hermann (FZJ, University of Liege), Larissa Juschkin (FZJ, RWHT Aachen University ), Avtandil Tavkhelidze (Ilia State University) Electronic and thermoelectric properties of nanograiting layers presented at 6 -th Georgian-German School and Workshop in Basic Science (GGSWBS’ 14), July 2014, Tbilisi, Georgia

When it happens ? There will be two reflected waves. One reflected from the top of the indent and another from the bottom of the indent. If the depth a=λ/4 , where λ is electron de Broglie wavelength, two reflected waves will interfere destructively resulting in no reflected wave. Nanograting (NG) improves thermoelectric and electron emission properties when the grating pitch becomes comparable with the electron’s de Broglie wavelength

Density of state (DOS) of nanograting layer DOS in plane layer DOS in nanograting layer where, G (H, w, a)>1 is a geometry factor.

Geometry induced doping or G-doping Electron concentration n in the CB increases, which can be termed as geometryinduced electron doping or G-doping. There are no ionized impurities. G-doping is T-independent J. Simon, V. Protasenko, C. Lian, H. Xing and D. Jena, , Science 327, 60 -64 (2010). B. Yu, M. Zebarjadi, H. Wang, K. Lukas, H. Wang, D. Wang, C. Opeil, M. Dresselhaus, G. Chen, and Z. Ren, , Nano Lett. 12, 2077 (2012).

Process flow

Interference lithography • Large-area periodic structures • Large depth of focus • Requires a coherent light • Low cost – no complicated and expensive optics • Ultimate resolution (half-pitch) for the wavelength ~λ/4 EUV: l = 11 nm feature size: ~3 nm

Possible scheme for IL Lloyd mirror Resolution is limited by l/(sinq 1+sinq 2), max l/2. No mask needed. • Ultimate resolution (half-pitch) for the wavelength ~λ/4

EUV LABORATORY EXPOSURE TOOL Technical Specifications § § Cleanroom class 100 (ISO 3) environment § § § Accepts up to 100 mm wafer § Dose monitor for λ = 13. 5 nm Illumination scheme interference lithography Max. exposable area: 65 x 65 mm 2 Single field: 2 x 2 mm 2 EUV sensitive CCD camera High precision positioners on all axes (encoder resolution < 10 nm)

Gas Discharge Plasma Source for EUV Generation LABORATORY-SCALED EUV SOURCE Pinch Radius 100 µm Spectral Range and Technical Specifications f=j. XB § § § Radiance: L ~ 100 W/(mm 2 sr) @ λ = 10, 9 nm with 3, 2% bandwidth Electron/ion densities: n ~ 1017 cm− 3 Temperature of plasma: Te ~ 35 e. V Coherence length: lcoh ≈ 10 -25 µm Triggered source >> repetition rate: up to 1, 5 k. Hz I switch energy storage Power Supply

EXPERIMENTAL SET-UP EUV Laboratory Exposure Tool Capacitiv e Sensors Mask holder and Lithography Mask Wafer holder Loadlock EXPERIMENTAL SET EUV Laboratory Exposure Tool Lithography Chamber Dose Monitor EUV Source insid e CCD Camera

RIE facility in Physikzentrum Reactive Ion Etcher Sentech SI 591 1 M 2 (SF 6, CHF 3, CF 4, CH 4, H 2, N 2)

Review - Reactive Ion Etching q Evacuated chamber q Ionised gas q Etch gases flow in q Adsorbed electrons create voltage drop from ion cloud to wafer q Electrodes at top and bottom q Ions are accelerated towards wafer

Review - Reactive Ion Etching Ion energy Physical (sputtering) Ion-assisted Chemical pressure Different etching mechanisms in Reactive Ion Etching

We measure temperature and magnetic field dependence of • Resistivity • Thermal conductivity • Seebeck coefficient Use van der Pauw technique 4 pont method to measure resistivity

Conclusion * Make nanograiting on SOI wafer using XUV -IL * Do ion etching * Use CCMS to measure electrical and thermoelectric property * Use AFM (Atomic force microscopy), scanning electron microscope (SEM) and ellipsometrie to measure properties of structured SOI wafer * Different size of transmission mask to get less pitch size of structure

Thanks for your Attention!