Physical Properties and Functionalization of Low-Dimensional Materials

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1 Physical Properties and Functionalization of Low-Dimensional Materials Physics Department, University of Trieste Graduate School of Physics, XXVI cycle Supervisor: Co-supervisor: Prof. Alessandro BARALDI Dr. Silvano LIZZIT

2 Low-dimensional materials Fullerenes C-nanotubes Graphene Graphite 0-D 1-D 2-D 3-D Graphene - Published Items in Each Year (source: Scopus) 9500 on 1 November The 2010 Nobel Prize in Physics was awarded jointly to Andre Geim and Konstantin Novoselov for groundbreaking experiments regarding the twodimensional material graphene 0

3 2-dimensional atomic crystals Graphene (GR) hexagonal Boron Nitride (h-bn) Why h-bn and graphene are so interesting? superlatives thinnest imaginable materials thermal & chemical stability highest e - intrinsic mobility (GR) wide band gap insulator (h-bn) novel applications coatings, paint/ink, energy storage electronic devices / sensors h-bn as substrate for GR electronics S. Bae. et al., Nat. Nanotechnol. 5, 574 (2010) C.R. Dean et al., Nat. Nanotechnol. 5, 722 (2010) L. Britnell et al., Science 335, 947 (2012) L.A. Ponomarenko et al. Nat. Phys. 7, 958 (2011)

4 Challenges in large-scale production Mechanical exfoliation Chemical Vapor Deposition (CVD) 1 µm Liquid-phase exfoliation Synthesis on SiC 500 nm

5 Challenges in large-scale production Epitaxial growth on transition metals: Chemical Vapor Deposition (CVD) GR & h-bn GR Large scale Single layer High quality (GR) GR-metal interaction Conductive substrate

6 SuperESCA Elettra X-ray Photoelectron Spectroscopy (XPS) element specific and quantitative sensitive to chemical and structural environments surface sensitive High-energy resolution and fast-xps photon source hv e - energy analyzer sample

7 Challenges in large-scale production Epitaxial growth on transition metals: Chemical Vapor Deposition (CVD) GR & h-bn GR Large scale Single layer High quality (GR) GR-metal interaction Conductive substrate focus on: h-bn CVD parameters GR structural quality and electronic properties GR transfer necessary

8 h-bn growth on Ir(111) Standard high-t growth method: Borazine (B 3 N 3 H 6 ) 1000 K Why you need such a high T to crack borazine? atoms lateral mobility? h-bn structural quality grain boundaries are always there! h-bn/rh(111) W. M. Frenken et al. Phys. Rev. Lett. 104, (2010)

9 Epitaxial h-bn: rotational domains Pd(111): R30 + Azimuthally randomly oriented domains Rh(111) & Ru(0001): R180 misoriented islands Pt(111): R30 rotated domains (from B-Trichloroborazine (ClBNH) 3 )

10 Epitaxial h-bn: rotational domains Ni(111): R180 misoriented islands

11 h-bn growth on Ir(111) Looking for possible improvements different temperature? RT adsorption: dehydrogenated molecules & fragments intact molecules B adatoms on the surface Temperature Annealing from RT further molecular dissociation bulk diffusion of boron adatoms h-bn islands formation

12 h-bn growth on Ir(111): a novel CVD approach Growth procedure # 1: B 3 N 3 H K until saturation (XPS check) Growth procedure # 2: B 3 N 3 H 6 RT switch off B 3 N 3 H 6 flux annealing to 1270 K (4 K s -1 ) Temperature Temperature Temperature Temperature X 4 to ensure saturation (XPS check)

13 h-bn/ir(111): a novel CVD approach - XPS Ir 4f 7/2 No differences in XPS spectra between Growth # 1 and Growth # 2 B 1s N 1s

14 h-bn/ir(111): a novel CVD approach - XPD X-ray Photoelectron Diffraction: modulation of the photoemision intensity as a function of (Θ,Φ) local structure around the emitter element specific Boron 1s Nitrogen 1s Growth # 1 Growth # 2 Growth # 1 Growth # 2

15 h-bn/ir(111): (13x13)/(12x12) periodicity two possible domains 180 reversal

16 h-bn/ir(111): (13x13)/(12x12) periodicity two possible domains B 1s Growth # 2 Growth # 1

17 Challenges in large-scale production Epitaxial growth on transition metals: Chemical Vapor Deposition (CVD) GR & h-bn GR Large scale Single layer High quality (GR) GR-metal interaction Conductive substrate focus on: h-bn CVD parameters GR structural quality and electronic properties GR transfer necessary

18 Decoupling GR/Ir(111) by O 2 intercalation GR/Ir(111) GR/O/Ir(111) GR/Ir(111) Oxygen intercalation Oxygen deintercalation Synchrotron radiation spectroscopy: High-energy resolution and fast XPS SuperESCA Elettra (Trieste, Italy) Electronic band structure ARPES (Angle Resolved Photoemisson Spectroscopy) SGM-3 Astrid (Aarhus, Denmark)

19 GR/Ir(111) - O 2 intercalation Ir 2 Ir 1 GR/O/Ir(111) O 2 dose ~3x10 6 L p ~5x10-3 mbar C 1s Ir 4f 7/2 O 1s B S GR/Ir(111)

20 GR/Ir(111) - O 2 intercalation Ir 2 Ir 1 GR/O/Ir(111) C 1s intensity CONSTANT O 2 dose ~3x10 6 L p ~5x10-3 mbar C 1s Ir 4f 7/2 O 1s B S GR/Ir(111)

21 GR/O/Ir(111) ARPES measurements GR/Ir(111) GR/O/Ir(111) GR/Ir(111) GR/O/Ir(111) GR/Ir(111) Binding Energy (ev)

22 GR/O/Ir(111) Thermal stability O 1s C 1s Ir 4f 7/2 GR/O/Ir(111) TP-XPS GR/Ir(111)

23 GR/O/Ir(111) Thermal stability GR/O/Ir(111) TP-XPS GR/Ir(111)

24 GR/O/Ir(111) ARPES measurements GR/Ir(111) GR/O/Ir(111) GR/Ir(111) GR/Ir(111) GR/O/Ir(111) GR/Ir(111) Binding Energy (ev)

25 Challenges in large-scale production Epitaxial growth on transition metals: Chemical Vapor Deposition (CVD) GR & h-bn GR Large scale Single layer High quality (GR) GR-metal interaction Conductive substrate focus on: h-bn CVD parameters GR structural quality and electronic properties GR transfer necessary

26 GR/SiO 2 /Ir(111) High-energy resolution and fast XPS SuperESCA Elettra (Trieste, Italy) Surface resistance measurements Interdisciplinary Nanoscience Center (Aarhus, Denmark)

27 GR/SiO 2 /Ir(111) GR growth C2 C 1s C1 GR/Ru(0001) 1100 K C 2 H 4 flux time C 2 H 4 Exposure Ru3d 3/2

28 GR/SiO 2 /Ir(111) Si intercalation C1 Si2p Si2 Si1 C 1s GR/RuSi x Si dose C2 720 K Si evaporation C 1s C1 GR/Ru(0001)

29 GR/SiO 2 /Ir(111) O 2 intercalation T=640 K P(O 2 )=4x10-4 mbar O2 Surface resistance 1000 Ω Ru3 Ru4 B x 6 O ads O1s C1s Ru3d 5/2 Si2p Ru(0001) GR SiO nm 7x10 6 L x 3 7x10 6 L O1 7x10 6 L C1 C3 x 1.5 Ru1 B Ru2 SiO 2 Si2 Si1

30 Conclusions h-bn/ir(111) novel method to grow single-domain h-bn layers on TM F. Orlando et al., J. Phys. Chem. C 116, 157 (2012) F. Orlando et al. (submitted) GR/O/Ir(111) oxygen intercalation below a complete epitaxial GR layer heavily p-doped quasi free-standing GR with linear π-band dispersion R. Larciprete et al. ACS Nano 6, 9551 (2012) Highlighted in Nat. Mater. 12, 3 (2013) GR/SiO 2 /Ru(0001) novel method to insulate GR from the metal substrate with a thick SiO 2 insulating layer S. Lizzit et al. Nano Lett. 12, 4503 (2012) Highlighted in Nat. Nanotech. 7, 613 (2012)

31 On going research h-bn/ir(111) Nitrogen-doped GR Improving the control over the growth parameters of 2D materials GR/O/Ir(111) GR/O/Ru(0001) Tailoring the electronic properties of GR/metal interfaces GR/SiO 2 /Ru(0001) GR/ZrO 2 /Ir(111) GR/Al 2 O 3 Growing GR on insulating substrates