1. High-Resolution Photoelectron Momentum Microscopy of Organic Charge-Transfer SaltsB8
Gerd Schönhense (Universität Mainz)
Charge localization in (DOEO)4[HgBr]4•TCE
Techniques
Achievements:
Temperature-dependent HAXPES crossing charge localization transition
Correlation between anisotropy parameter, XPS and HAXPES energy shifts and line redistribution
Goals and work program:
Full experimental characterization of band structure in wide temperature range by momentum microscopy
NEXAFS: Near-edge X-ray absorption fine structure EF
Absorption/Electron yield
N1s
hv = 400 eV π*
π*, σ*
K-edge
Near-edge
fine structure
(NEXAFS)
Beamline: WERA, ANKA, Karlsruhe
Energy range eV
Base vacuum mbar
Sample temperature K
Energy resolution 100 meV
B12
Chernenkaya et.al., SSP, accepted
Koplak et.al., EPJB, submitted
HAXPES
Beamline: MAX II, Lund, Sweden
Energy range eV
Base vacuum mbar
Sample temperature K
Energy resolution 28 meV
N → N*
∆ transport anisotropy parameter (R- R )/R
O XPS energy shifts
□ HAXPES peak intensities
HAXPES: Hard X-ray photoelectron spectroscopy
Beamline P09 Petra III, DESY
Photon energy eV
Base vacuum 2 · 10-8 mbar
Sample temperature is K
Energy resolution is 250 meV
Electronic structure of κ-(BEDT-TTF)2Cu[N(CN)2]Br
Achievements:
Pilot experiments on temperature-dependent NEXAFS and room temperature k-microscopy
hn=6 keV
First results
on -Br
TiSa (2PPE)
2h =6.6 eV
N → N - 1
Photoelectron momentum microscopy
@ 300 K
Bi2Te3
Goals and work program:
Temperature dependent NEXAFS crossing the glasslike transition
Band structure by momentum microscopy B2
Preliminary results
Beamline U125-2 SGM, BESSY
Photon energy eV
Base vacuum mbar
Sample temperature K
Energy resolution 60 meV, k-resolution Å-1
Data acquisition time: seconds - minutes
3D image detector (delay-line type)
Charge-transfer in thiophene-based thin films
B10
DTBDT
(HOMO ~ eV)
Achievements:
Experiments on room temperature NEXAFS on thin films of DTBDT donor in composition with TCNQ and F4-TCNQ acceptor show electron density redistribution on TCNQ molecule
IR analysis gives value of 0.22 eV for charge transfer in DTBDT-TCNQ system
Goals and work program:
NEXAFS on single crystals and comparison with thin films
+ F4-TCNQ TCNQ
(LUMO ~ eV) (LUMO ~ eV)
Staffing of the project from auxiliary support
Alisa Chernenkaya (Ph.D. student)
- NEXAFS and HAXPES measurements on (BEDT-TTF)2X and
(TMTTF)2X families
- Momentum microscopy on κ-(BEDT-TTF)2Cu[N(CN)2]Br
around the glasslike transition T = 77 K
N.N. (Ph.D. student)
Momentum microscopy on (TMTTF)2X family,
κ-d8-(BEDT-TTF)2Cu[N(CN)2]Br,
κ-(BEDT-TTF)2Cu[N(CN)2]Cl
Investigation of inhomogeneity in TTF-CA thin films in the
region of the neutral to ionic phase transition
Crystal structure of DTBDT-TCNQ charge-transfer compound B4
Transregional Collaborative Research Centre SFB/TR 49
Frankfurt / Kaiserslautern / Mainz