Molecular and carbon-based electronic systems

Transcription

1 Molecular and carbon-based electronic systems when Wednesday, 10h15-12h00 where seminar room 3.12, Physics Dpt, Klingelbergstrasse 82 credit 2KP debit attendance + 1 presentation VV lecture Nr web Michel Calame Empa, Dübendorf & Physics Dpt., Uni Basel michel.calame@empa.ch michel.calame@unibas.ch Thilo Glatzel Physics Dpt., Uni Basel thilo.glatzel@unibas.ch Vorlesung Uni Basel, FS2018 Assistant: Oliver Braun Empa, Dübendorf & Physics Dpt., Uni Basel oliver.braun@empa.ch oliver.braun@unibas.ch

2 Molecular and carbon-based electronic systems goals - provide background & fundamental aspects to anchor understanding - discuss hybrid devices/applications combining organic compounds with solid-state systems Tentative program fundamental aspects towards applications/ devices workshop Introduction. Carbon from 0D to 3D: fundamental properties Fundamental properties, part II Single molecule deposition and properties on surfaces Molecular junctions: formation mechanisms, transport basics Molecular junctions: basics & spectroscopy Insights in density functional theory for molecular junctions Molecule assemblies analysis and contacting on surfaces Graphene for molecular electronics Graphene oxide and applications Diamond: production, nano-diamond, NV vacancies tbc Sensing Mini-workshop: Talks by students (15 talk + 5 discussion)

3 workshop & preparing the talk: a few hints define topic, your main interest (Oliver will provide a list) pre-screening work, basic topic understanding to Oliver by March 30 th oliver.braun@unibas.ch, oliver.braun@empa.ch structure the document what do you need / have? What do you want to learn/convey? collect & select contents main message, refine contents key publications & data checked & available identify supporting information background knowledge, backup information, context, impact timing - review the above workflow and attribute a given time to each step - check back whether your prediction was appropriate help - ask for feedback/discuss with Oliver (topic, key papers, on what shall I focus) obviously if you are not interested/convinced yourself, neither will your audience/readership be

4 CONTEXT

5 outline electronics beyond Silicon - other possible pathways for electronics Carbon allotropes - discovery Carbon & molecular electronics - brief historical account - why molecules molecular junctions - how to contact nm-scale objects

6 the evolution of electronics transistor > 60 years old 1947, 24th December John Bardeen, Walter Brattain, William Schockley ATT Bell Labs first point contact transfer resistor Nobel 1956 Bell labs Bell labs

7 the evolution of electronics Bardeen, Brattain, Shockley 1947 today Building blocks (transistors) at nm scale Volume reduced by 10 12

8 the evolution of electronics planar geometry to 3D geometry fin-fets & gate all-around (GAA) improvement of substreshold swing, higher switching speed, lower operation Voltage M. Bohr, Intel

9 the evolution of electronics 14nm Intel 14nm node IBM, 2015 planar geometry to 3D geometry fin-fets & gate all-around (GAA) improvement of substreshold swing, higher switching speed, lower operation Voltage Major issues: power, leakage current, reproducibility since 2005, speed gate dielectric M. Bohr, Intel

10 electronics beyond Si? MRS Bulleting 2010 special issue Science 2010 special issue What technologies will extend silicon's reign as the preeminent material for electronics? What materials will ultimately supplant silicon? Charles Day, December 2013

11 electronics beyond Si? materials Oxides interfaces LaAlO3-SrTiO3 heterostructures Mannhardt et al., Science 2013 III V compound semic. transistors NW tunnel FETs Riel et al., MRS Bulletin 2014 Transition metal oxides charge, spin, orbital degrees of freedom for diversity of phases exploiting e-e correlation Takagi et al., Science 2013 Transition metal dichalcogenides & other 2D materials & stacked systems MoS 2, WS 2, Strano et al., Nat. Nano 2012; Hersam et al., Nat. Mater. 2017; N.Marzari et al., Nat. Nano 2018

12 electronics beyond Si: "hot" materials Si GaAs amorphous oxide semiconductor (IGZO) Hersam et al., Nat. Mater. (2017)

13 electronics beyond Si: "hot" materials Marzari et al., Nat. Nano. (2018)

14 electronics beyond Si? materials Oxides interfaces Transition metal oxides charge, spin, orbital degrees of freedom for diversity of phases exploiting e-e correlation Transition metal dichalcogenides (2D) MoS 2, WS 2, Strano et al., Nat. Nano 2012 LaAlO3-SrTiO3 heterostructures Mannhardt et al., Science 2013 III V compound semic. transistors NW tunnel FETs Riel et al., MRS Bulletin 2014 Takagi et al., Science 2013 Organic & inorganic materials with elastomeric substrates Stretchable electronics Rodgers et al., Science 2013

15 carbon-based materials

16 "nano-carbons" # publications/year on nanocarbons M.S. Dresselhaus Data extracted from Science Citation Index searching for the words fullerene, nanotube, and graphene NB: nanoribbons

17 carbon wiki

18 outline electronics beyond Silicon - other possible pathways for electronics Carbon allotropes - discovery Carbon & molecular electronics - brief historical account - why molecules molecular junctions - how to contact nm-scale objects

19 carbon-based materials sp 2 allotropes of carbon 2D 3D 2D OD 1D 3D Nobel lectures, Geim & Novoselov, 2010

20 carbon allotropes discovery

21 im Elektronenmikroskop Bleistift

22 im Elektronenmikroskop Bleistift

23 im Elektronenmikroskop Bleistift

24 im Elektronenmikroskop Bleistift

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30 im Elektronenmikroskop Bleistift

31 im Elektronenmikroskop Bleistift

32 fullerenes fullerenes C60, C70,... Buckminster Fuller dome, Montreal, 1967 NB. 1st detection of C60, C70 in space: Cami et al., Science 2010 R.S. Smalley, Nobel lecture, 1996 Nobel.se

33 carbon allotropes discovery Research - PhD program Teaching bachelor & master Tech. transfer Public outreach H.G. Güntherodt ( 2014) & Harry W. Kroto ( 2016) in Basel for the 10 th Anniversary celebration of the NCCR Nanoscale Science

34 carbon allotropes discovery 2012 Kavli Prize in Nanoscience M. Dresselhaus "for her pioneering contributions to the study of phonons, electron-phonon interactions, and thermal transport in nanostructures" M.S. Dresselhaus, Cargèse, 2014

35 carbon nanotubes Single-wall or multi-wall Metallic or semiconducting Diameter: nm Length: < 100 mm S. Iijima, 1991,

36 carbon nanotubes structure (wrapping vector) armchair (n,n) (11,0) zig-zag (n,0) or (0,n) chiral (n,m) with n m (0,7) (11,7) armchair (n,n)=(9,9) n-m = 3*i: n-m <> 3*i: metallic semiconducting

37 carbon allotropes discovery Nobel.se

38 Graphene: scotch tape 2.0µm J. Trbovic and H. Aurich 970nm

39 graphene discovery

40 carbon-based materials and devices graphene : the missing 2D system in carbon allotropes 1947 Graphene first studied as a limiting case for theoretical work on graphite by Phillip Wallace 1966 First attempts to grow multilayer graphite Hess W M and Ban L L also Karu A E and Beer M 1984 Massless charge carriers in graphene pointed out theoretically by Gordon Walter Semenoff, David P. DeVincenzo and Eugene J. Mele 1987 Name graphene first mentioned by S. Mouras and co-workers 2004 Graphene isolated in free form by Andre Geim and Kostya Novoselov 2004 Observation of graphene s ambipolar field effect by Geim & Novoselov 2005 Anomalous quantum hall effect detected showing massless nature of charge carriers in graphene Geim, Novoselov and Kim, Zhang 2006 Quantum Hall effect seen at room temperature by Novoselov et. al first detection of a single molecule adsorption event by Schedin et. al Measurements of extremely high carrier mobility by Bolotin et. al Nobel prize in physics to Geim & Novoselov from

41 graphene: why it may have taken so long fluctuations "kill" a 2D crystal Finally, we remark on the strict 2D nature of graphene from a structural viewpoint. The existence of finite 2D flakes of graphene with crystalline order at finite temperature Landau & does Lifschitz, not instatistical any wayphysics, violate the Hohenberg-Mermin-Wagner-Coleman theorem 3 rd ed.,1980, whichpart rules I, 137 out& the 138, breaking pp of a continuous symmetry in two dimensions. This is because the theorem only asserts a slow power law decay of the crystalline (i.e., positional order) correlation with distance, and hence, very large flat 2D crystalline flakes of graphene (or for that matter of any material) are manifestly allowed by this theorem. In fact, a 2D Wigner crystal, i.e., a 2D hexagonal classical crystal of electrons in a very low-density limit, was experimentally observed more than 30 years ago (Grimes and Adams, 1979) on the surface of liquid 4He (where the electrons were bound by their image force). A simple back of the envelope calculation shows that the size of the graphene flake has to be unphysically large for this theorem to have any effect on its crystalline nature (Thompson-Flagg et al., 2009). There is nothing mysterious or remarkable about having finite 2D crystals with quasi-long-range positional order at finite temperatures, which is what we have in 2D graphene flakes. Castro-Neto et al., Rev. Mod. Phys 2011 "According to the so-called Mermin Wagner theorem 1, longwavelength fluctuations destroy the long-range order of 2D the ripples of graphene crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled 2. These fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes meaning that a 2D membrane can exist but will exhibit strong height fluctuations." Katsnelson et al., Nature Mat. (2007)

42 graphene 0.14nm 0.12nm Mechanically strong: composite materials A 1m 2 "hamac" weighting 0.77mg could support a 4kg load nobelprize.org Flexible conductor may replace ITO High charge mobility: electrical applications

43 reminder: energy bands semimetals: small overlap between valence and conduction bands Energy gaps Si ~ 1.12 ev Ge ~ 0.66 ev GaAs ~ 1.43 ev NB: kt (RT) ~25meV

44 graphene electronic structure C: 1s 2 2s 2 2p 2 1 extra electron / p orbital half-filled p band Kane, Princeton

45 graphene electronic structure Graphene honeycomb lattice with the two triangular sublattices blue sublattice A yellow sublattice B Graphene Brillouin zone in momentum space Graphene bandstructure Valence band filled, fermi energy at E=0 for neutral graphene Zero band-gap semiconductor Two non-equivalent valleys, K and K pseudo-spin Castro Neto et al., Rev. Mod. Phys. 2009; Das Sarma et al., Rev. Mod. Phys 2011

46 graphene electronic structure Low-energy excitations: massless, chiral Dirac Fermions At the Fermi energy the spectra are linear, hence the electrons are here massless. Normal materials Normal (free electrons), particles with mass: Massless particles, photons Graphene: where v F, Fermi velocity is c/300 Dirac electrons in graphene mimic the physics of quant. electrodynamics for massless Fermions Relativistic effects can be seen in graphene Castro Neto et al., Rev. Mod. Phys. 2009; Das Sarma et al., Rev. Mod. Phys 2011

47 graphene roadmap A. Ferrari, et al. 2011, 2015

48 graphene roadmap graphene-flagship.eu/

49 graphene roadmap graphene-flagship.eu/

50 adding a gap: graphene ribbons structure graphene surface (edges) states: two types of edges Dresselhaus, Cargèse, 2014

51 other 2D systems for electronics Dresselhaus, Cargèse, 2014

52 other 2D systems Transition Metal Dichalcogenides (TMDs) Chhowalla et al., Nat. Chem. (2013); Dresselhaus, Cargèse, 2014

53 other 2D systems Chhowalla et al., Nat. Chem. (2013)

54 other 2D systems Chhowalla et al., Nat. Chem. (2013)

55 other 2D systems Martel, Szkopek, Cargèse, 2014