Co-editor of 2 Journals: EP-JAP and "ISRN Materials Science"

Transcription

1 Maria LOSURDO NIM_NIL Laurea cum laude in hemistry from University of Bari, Italy Joint PhD from Ecole Polytechnique (Palaiseau-France) and University of Bari, Italy in Materials Science. Senior Scientist in the Institute of Inorganic Methodologies and of Plasmas at National ouncil of Reserach (NR), and an Adjunct Professor at the Department of Electrical and omputer Engineering of the Duke University at Durham, N-US. o-editor of 2 Journals: EP-JAP and "ISRN Materials Science" Specialist in VD growth of materials and ellipsometry She approached graphene by her expertise in VD growth and plasma processing of Si.; she is co-author of a US patent on Metal-aided graphenization of Si

2 raphene in Large Area Fabrication of 3D Negative Index Materials by NanoImprint Lithography Maria Losurdo and iovanni Bruno Location, 09/09/2009 Page 1 Brussels, March 21-22, 2011

3 Outline NIMNIL onsortium NIMNIL Objective in the NIMNIL context Processing/Structuring of raphene exfoliation Si graphenization VD Real-Time Monitoring and ontrolling raphene growth Summary/Outlook Page 2 Location, 09/09/2009 Page 2

4 onsortium Structuring raphene Real Time Monitoring haracterisation onclusions onsortium Duration: 3 years Starting date: Page 3 oordinator: Profactor mbh; Iris Bergmair iris.bergmair@profactor.at Location, 09/09/2009 Page 3

5 onsortium Project NIM= Negative Index Materials Design of NIMs New structure designs for NIMs New material raphene Fabrication of NIMs NIL as fabrication method Deposition & Structuring of raphene Large area NIMs 3D NIMs haracterisation of NIMs Optical properties of raphene and its structures Ellipsometry, Raman, AFM/SEM Transmission, reflection, phase measurements Demonstration of NIMs 3D NIM prism Structuring raphene Real Time Monitoring haracterisation onclusions Page 4 Location, 09/09/2009 Page 4

6 onsortium Structuring raphene Real Time Monitoring haracterisation onclusions Main activities relate to: Original concepts for using graphene Structuring graphene Fabrication of graphene haracterisation of graphene Page 5 Location, 09/09/2009 Page 5

7 onsortium Structuring raphene Real Time Monitoring haracterisation onclusions [Science, 328, (2010) p.582] 1 In the Visible: Medium composite consisting of single- or few-layer graphene on nanostructured metal films graphene Silver metamaterial structure raphene has potential to cover the range Visible-infrared-terahertz by 2 approaches 2 In the Infrared and Terahertz: Electroptical Modulation Page 6 Location, 09/09/2009 Page 6

8 enhancement hange of Transmission with raphene Ag plasmon peak PSI 2 mx2 m 5 mx5 m onsortium Structuring raphene Real Time Monitoring haracterisation onclusions raphene in a Photonic Metamaterial: Approach-1 IR: raphene on old graphene Silver fishnet Visible: raphene on Silver Silver gratings 1 Plasma Passivation of Ag + 2 Transfer of graphene ontop raphene limits/inhibits silver oxidation As deposited gratings AgO Ag 40 raphene enhances resonance Ag as-grown after passivation 14.0 After processing 13.5 Ag 35 Wavelength (nm) raphene modifies the transmission spectrum of such a metamaterial leading to an increase of transmission exceeding 250%. [N. Papasimakis et al. OPTIS EXPRESS 18, 8353 (2010)] oxidized cleaned 1h 1day 3day 5day TIME of AIR EXPOSURE Photon Energy (ev) Page 7 Location, 09/09/2009 Page 7

9 onsortium raphene in Metamaterials: Approach-2 Mold raphene is nanostructured to achieve ontrolled Size and Shape layers using NIL and an O 2 plasma Structuring raphene Real Time Monitoring haracterisation onclusions Resist raphene (a) 100 m raphene (b) 100 µm raphene (c) The height of structures is 2 nm raphene (d) a) exfoliated graphene is placed on the substrate. b) resist is patterned on the graphene by nanoimprint lithography c) an O 2 plasma etching of graphene takes place on the area without mask d) a graphene pattern is obtained after removing the resist raphene Swiss ross structures. Linewidth is 20 nm. Layer height is 500 pm raphene Fishnet structures. Line width is 70 nm Page 8 Location, 09/09/2009 Page 8

10 onsortium Structuring raphene Real Time Monitoring haracterisation onclusions ontrolled Etching of raphene raphene ratings on Nickel and opper by VD structured using NIL and an O 2 plasma VD- on Ni VD- on u Magnification x. Line width is 1.5 µm Wavenumber (cm-1) Wavenumber (cm-1) Page 9 Location, 09/09/2009 Page 9

11 TEMPERATURE ( ) leaning & Annealing of substrate H 2 flow raphene growth ooling down H 2 flow onsortium Synthesis Routes to raphene in NIMNIL 1 Exfoliation of raphite Real Time Monitoring haracterisation Structuring raphene onclusions 2 Si Decomposition 3 VD on Polycrystalline&foils Nickel and opper 100 m 100 µm D 24cm Wavenumber (cm-1) I /I = cm -1 FWHM=39cm -1 1 H 4 in H4 out 2 3 H 4 + H 2 /Ar graphene T 900, P<4 Torr 1587cm -1 FWHM=31cm Wavenumber (cm -1 ) TIME Page 10 Location, 09/09/2009 Page 10

12 onsortium Real Time Monitoring haracterisation raphene VD: Implementation of rowth Process Structuring raphene onclusions Peculiarities of our VD growth processes: Integration of a Remote Plasma Source Integration of in-situ Real Time Monitoring by Ellipsometry hallenging goal: To growth graphene of large scale with uniform thickness How to achieve this? We have uniquely developed a Real-Time raphene Metrology Page 11 Location, 09/09/2009 Page 11

13 onsortium Real Time Monitoring raphene on opper Foil by VD Impact of opper foil impurities haracterisation Since the growth was first demonstrated on opper foil, there is a tendency to use the same foil: Impurities affect not only quality but also the catalytic decomposition of H4 and therefore the thickness (Single or bi-layer) Structuring raphene onclusions D Bi-L grown on 99.5%u (800 50min) Wavenumber (cm-1) No growth of bilayer even after 120min The dopants or impurities could effectively enhance the catalytic activity of the u surface Kinetic factors, such as the surface reaction rate, play a critical role on the uniformity of thickness of VD graphene layers by limiting the deposition of carbon atoms on u surface. The higher the impurities (e.g. u 99.8%), the faster surface reaction rate, the lower the thickness uniformity. [Z. Luo et al. Adv. Funct. Mater. 2011, 21, ] Page 12 Location, 09/09/2009 Page 12

14 Intensity (cnt/sec) Intensity (cnt/sec) Intensity (cnt/sec) onsortium Structuring raphene raphene by VD on opper Films Impact of rowth temperature Real Time Monitoring T=1000 T=1100 haracterisation onclusions Residual u T=1200 graphene FWHM= 50cm D raphe FWHM= ne on 60cm -1 u/sio 2/Si D I /I =0.6 FWHM= 33cm Raman Shift (cm -1 ) Raman Shift (cm -1 ) Single Loretnzian peak mark of monolayer graphene Raman Shift (cm -1 ) Three regimes of temperature have been identified that can be exploited for improving processes 500 Page 13 Location, 09/09/2009 Page 13

15 300 mx300 m onsortium Real Time Monitoring haracterisation raphene by VD on opper T>1200 Structuring raphene onclusions raphene directly on SiO 2 and Al 2 O 3 (residual copper-white strips can be removed by 5min Hl etching) Taking benefit of u dewetting (T melting =1084 ), graphene can be obtained on any substrate avoiding the tedious etching/transferring/pmma steps Substrate engineering Page 14 Location, 09/09/2009 Page 14

16 onsortium raphene on Polycrystalline Nickel [A. Reina et al. Nano Lett., 9,1, 2009] Real Time Monitoring State-of-the-art [A.Reina et al, Nanotechnology 21 (2010) ] haracterisation [A.J. Pollard et al. J. Phys. hem., 113, 2009, 16565] Structuring raphene onclusions FWHM=50cm -1 On Single crystal Ni(111) On poly-ni Typically growth on polycrystalline Ni results in a non-homogeneous mixture of few-layers graphene NR-IMIP We are able to achieve on polycrystalline Ni results similar to what obrained on single crystalline Ni Page 15 Location, 09/09/2009 Page 15

17 Intensity (cnt/ sec) Intensity (cnt/ sec) onsortium raphene by VD on Nickel Real Time Monitoring Progress Beyond the State-of-the-art haracterisation Structuring raphene onclusions (we started from here-heterogeneous) We can get this-more homogeneous I /I 2.1 I /I = cm I /I cm -1 31cm cm cm -1 39cm Raman Shift (cm -1 ) Wavenumber (cm -1 ) Raman Shift (cm -1 ) Non homogeneity mainly depends on pre-treatment of Ni, H 4 /H 2 ratio and deposition time Noteworthy, absence of the D peak indicative of defects Page 16 Location, 09/09/2009 Page 16

18 onsortium raphene transferred from Ni to SiO 2 Progress Beyond the State-of-the-art Starting from typical non-homogeneous Real Time Monitoring haracterisation Structuring raphene onclusions I /I = cm cm -1 39cm -1 D 30cm Wavenumber (cm -1 ) 700 mx700 m 1593cm -1 I /I = cm -1 D 43cm Wavenumber (cm -1 ) Improvement is achieved by enhancement of catalysts substrate treatments Page 17 Location, 09/09/2009 Page 17

19 Real Time Monitoring of VD process < 1 > <K> <k> onsortium A Ni ref Ni ref B A B Ni substrate crystallization Time (s) B Time (s) Page 18 D D Real Time Monitoring 5 mx5 m D A < 1 > Time (s) H 4 in H 4 in H 4 in H 4 in H 4 off H 4 off H 4 off H 4 off rowth kinetics Time (s) haracterisation cooling raphene deposition mx100 m Structuring raphene Wavenumber (cm -1 ) D I /I Wavenumber (cm -1 ) Location, 09/09/2009 Page 18 onclusions I /I 3 39cm -1 I /I 0.9 We have set a correlation between In-situ Real-Time Ellipsometry and Ex-situ Raman mapping that allows us to monitor and control the whole VD process from substrate preparation to graphene thickness and quality 51cm -1 80cm -1

20 onsortium Hydrogen in VD raphene Real Time Monitoring haracterisation Structuring raphene IR Reflection spectra run at BESSY Synchrotron Intrinsic Hydrogen is the main difference between VD and exfoliated graphene onclusions When the angle of incidence is increased the -H stretching band increases. This suggests that the -H bonds are out-of-plane Page 19 Location, 09/09/2009 Page 19

21 onsortium Real Time Monitoring haracterisation Roadmap for Progress in raphene Synthesis Structuring raphene onclusions The electron mobility within the graphene is effected by the substrate. finding better substrates for future graphene devices in order to reduce the effects of charged impurity scattering and remote interfacial phonon scattering Substrate Engineering There are still many chemical routes to synthesis of graphene and a lot of room for improving the exploited ones. Finding technological solution to optimize processes hallenging the growth of large area graphene with controlled thickness Real Time Monitoring vs Parametric Trials Page 20 Location, 09/09/2009 Page 20

22 We will be pleased to take any question/curiosity oordinator: Iris Bergmair Nanoimprint Lithography of NIMs Rados ajic Exfoliation and characterisation of graphene Maria Losurdo, iovanni Bruno Synthesis and haracterisation of Large area raphene ostas Soukoulis Simulation of Different Design of NIMs Kurt Hingerl Modelling Optical properties in the IR and UV-VIS Karsten Hinrichs, Tom Oates Ellipsometry measurements in the IR and UV-VIS Ingolf Reischel, Lars Dick Master Fabrication Hakan Atasoy, S. Herrndorf Resists for Nanoimprint Litography Markus Oppel,. Helgert, Nanoimprint Litography stamps Lars Reissmann, Michael Arens Ellipsometry, Plasma Etching Page 21 Location, 09/09/2009 Page 21