a.n.andriotis [email protected] andriot [email protected] theoretical condensed matter...
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http://esperia.iesl.forth.gr/~andriot
Theoretical Condensed Matter Physics and Materials Research
Heraklion, 28 March 2006
Theoretical Condensed Matter Physics and Materials Research
New and SmartMaterials
Clusters
NanotubesNanowires
DiluteMagnetic Semicond.
Fullerenes
Materials of current and intense technological and basic research interest.
Applications (indicatively):- New (magnetic) materials- Sensors- Nano-electronics- Energy (Hydrogen) storage- Catalysis - Medical applications
Theoretical Condensed Matter Physics and Materials Research
New and SmartMaterials
Clusters
NanotubesNanowires
DiluteMagnetic Semicond.
Fullerenes
Grain Magnetic Materials for Advanced Magnetic
Storage Devices
s-p Magnetismin Carbon-based Materials
Magnetism in non-traditionalInorganic Materials
Nano-electronics
ACTIVITIES
Grain Magnetic Materials for Advanced Magnetic Storage Devices; (grains of diameter 2-10nm)
• Enhancing the magnetism of transition metal grains
(Our contribution : Structural- and T-effects on electronic and magnetic properties)
• Fe-Co grains break the Super-para-magnetic limit
• ‘AMMARE’-GROWTH PROJECT (Coordinated by IESL ; terminated successfully 31st Dec. 2004; budget 2,322,800 Euros; 73.17 % EU-funding)
Co-Pt clusters (2 nm) (Lyon)
Co clusters on Au(111) (STM) (Strasbourg)
Grain Magnetic Materials
Conclusion : Binary grains (2-10 nm in diameter)
made of 3d-Transition Metals can enhance their magnetic moments by exploiting effects of magnetic anisotropy and rehybridization processes; template assistance may help to this direction.
• A.N.Andriotis et al, PRL 93, 026402 (2004); JCP 120, 11901 (2004); JCP
119, 7498 (2003), PR B68, 125407 (2003); PR B72, 104417 (2005)
Transition-Metal ClustersT=0 and collinear approximation
Magnetic Moments of Ni-clustersFe-Co clusters : Magnetic Enhancement
Co induces structural changes to Fe Clusters. These lead to rehybridization of MOs and re-determination of d-band filling.
From : M.B.Knickelbeim,JCP, 116, 9703 (2002)
Transition-Metal ClustersNon-zero-T and non-collinear approximation
CURRENT WORK
TT=400 500 600 K
Ni43 and Ni201
Theoretical Condensed Matter Physics and Materials Research
New and SmartMaterials
Clusters
NanotubesNanowires
DiluteMagnetic Semicond.
Fullerenes
Grain Magnetic Materials for Advanced Magnetic
Storage Devices
s-p Magnetismin Carbon-based Materials
Magnetism in non-traditionalInorganic Materials
Nano-electronics
s-p type ferromagnetism in C-based materials A.N.Andriotis et al, PRL 90, 026801 (03)
• 2D-Rh-C60-polymer
• The defect model appears as a generic model for magnetism in systems with only s-p electrons
Interplay between Nitrogen impurities and vacancies in C60s
Spin density Charge density
Interplay between Nitrogen impurities and vacancies in SWCNs
Spin-density Charge density
Theoretical Condensed Matter Physics and Materials Research
New and SmartMaterials
Clusters
NanotubesNanowires
DiluteMagnetic Semicond.
Fullerenes
Grain Magnetic Materials for Advanced Magnetic
Storage Devices
s-p Magnetismin Carbon-based Materials
Magnetism in non-traditionalInorganic Materials
Nano-electronics
s-p type ferromagnetism in non-traditional inorganic materials
A.N.Andriotis et al, Condens.Matter 17, L35 (05)
• The defect model appears as a generic model for magnetism in non-traditional inorganic materials
• NEW CLASS of magnetic Materials
• FUTURE WORK : Exploit this new magnetism for fabricating new materials
• Zn(TM)O • Ti (TM) O2• Ca(Vac)O • Hexaborides• Dilute magnetic
semiconductors
s-p type ferromagnetism in non-traditional inorganic materials
A.N.Andriotis et al, Condens.Matter 17, L35 (05),PRL 87, 066802 (01)
• Generalized McConnell model : Vacancies behave as donors while the 2+2 cycloaddition bonds behave as acceptors
• 500 downloads during 2005
(Editor’s aknowledgment)
Theoretical Condensed Matter Physics and Materials Research
New and SmartMaterials
Clusters
NanotubesNanowires
DiluteMagnetic Semicond.
Fullerenes
Grain Magnetic Materials for Advanced Magnetic
Storage Devices
s-p Magnetismin Carbon-based Materials
Magnetism in non-traditionalInorganic Materials
Nano-electronics
Nanotubes (NTs)
• Structural and electronic properties of NTs (Carbon-, Si-,SiC-, BN-based)
Future applications in NTs made of other materials (e.g., SiO2, VO2 ) for spintronics applications
• Transport properties of NTs
• Functionalized NTs• Hydrogen storage (FUTURE)
Nano-electronics
PRL cover-pageIssue : Vol. 87, No.66 Aug. 2001
Nano-electronics
Major achievements (predictions)• Rectification and switching properties of
branched Carbon Nanotubes• Stability of Si-nanotubes by
encapulation of transition metals
• A.N.Andriotis et al, PRL 87, 066802 (2001); PR B65, 165416 (2002); PRL 91, 145501 (2003); PR B69, 115322 (2004).
Nano-electronicsSWCN in contact with metal leads Si-NT stabilized by a Ni-chain
Branched SWCNs I-V curves for branched SWCNs
Y-SWCN : Ballistic SwitchingBandaru et al Nature Materials 4, 663 (2205)
Andriotis and Menon (2006)
Y-SWCN : Ballistic SwitchingBandaru et al Nature Materials 4, 663 (2205)
Andriotis and Menon (2006)
Si-nanowires(submitted 2005) Transition from Direct to
Indirect Gap at 4.5-5.3 nm
tetrahedral
fcc-34
sc-46
polycrystalline
Tetrahedral grown Along <111> direction; D=1-5 nm
Methods employed
• Orthogonal and Non-orthogonal TBMD - M.Menon and K.R.Subbaswamy, PRB 50, 11577 (1994) - A.N.Andriotis and M.Menon PRB 57, 10069 (1998)
• Surface Green’s Function Matching (SGFM) method
- S.Datta in “Electronic Transport in Mesoscopic Systems”, (1995) - A.N.Andriotis and M.Menon, JCP 115, 2737 (2001)
• Transfer Hamiltonian Approach (THA) method
- J. Bardeen, PRL, 6, 57 (1961) - A.N.Andriotis, M.Menon and D.Srivastava, JCP 117, 2836 (2002)
• Ab initio methods (Gaussian 98)
Publications 2000-2005JOURNAL 2000 2001 2002 2003 2004 2005 Total
PRL 1 1 2 1 1 6PRB 2 2 1 2 2 2 11
NanoL 1 1 2APL 1 1 1 1 4
CPL 1 1 2
JCP 1 1 2 1 5
JPCM 1 1
NJP 1 1 2
EPL
Other 1
1
1
1
2
Total 5 6 4 9 5 7 36
Collaborators
• Prof. Madhu Menon (Univ. of Kentucky, Lexington, KY)• Dr. R. Michael Sheetz (Univ. of Kentucky, Lexington,
KY)• Prof. Leonid Chernozatonskii (Institute of
Biochemical Physics, Russian Academy of Sciences, Moscow)
• Dr. Deepak Srivastava, NASA Ames, USA• Dr. Inna Ponomareva, Russian Academy of Sciences,
Moscow, Russian Federation• Dr. G. Froudakis, Chemistry Dpt., Univ. of Crete• Mr. G. Mpourmpakis, Chemistry Dpt., Univ. of Crete• Mr. Z. Fthenakis, IESL, FORTH, Crete