4 research outputs found
What Happens at the Interface between TTF and TCNQ Crystals (TTF = Tetrathiafulvalene and TCNQ = 7,7,8,8-Tetracyanoquinodimethane)?
The interface between tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) crystals was prepared by treating a TCNQ single crystal surface with TTF powder. Optical measurements and atomic force microscopy (AFM) observation of the interface indicated that not only are TTF–TCNQ nanocrystals formed at the interface, but also direct charge injection from TTF powder to the TCNQ single crystal surface may be responsible for the high conductivity of the interface
Fabrication of Conducting Thin Films on the Surfaces of 7,7,8,8-Tetracyanoquinodimethane Single-Component and Charge-Transfer Complex Single Crystals: Nucleation, Crystal Growth, Morphology, and Charge Transport
Electrically conducting TTF–TCNQ
thin films are fabricated
on various molecular crystals containing 7,7,8,8-tetracyanoquinodimethane
(TCNQ) by exposing a tetrathiafulvalene (TTF) vapor under ambient
conditions. To systematically investigate the properties of the films,
mixed-stack TCNQ charge-transfer (CT) complex crystals with nine kinds
of donors have been prepared as the substrates, and the morphology
change of the films on the surfaces at the initial stage of the TTF
vapor contact has been observed. When the substrate is a TCNQ single-component
crystal, randomly oriented TTF–TCNQ nanometer-size needle crystals
are grown by the reaction with a TTF vapor. However, when the substrate
is a TCNQ CT complex crystal, TTF–TCNQ crystals are grown with
alignment of their needle axis along the mixed-stack direction of
the substrate. The surface roughness, the size of the needle crystals,
and the degree of the dense packing of the needles have been found
to systematically depend on the strength of the CT interactions in
the substrate, and the sheet resistance also exhibits a systematic
change. The resistance drop is rapid and remarkable when the donor
of the substrate CT complex is weak. The difference in the morphology
and the properties is considered to arise from the difference in the
ease of nucleus formation and the rate of crystal growth of the TTF–TCNQ
nanocrystals
Fabrication of Conducting Thin Films on the Surfaces of 7,7,8,8-Tetracyanoquinodimethane Single-Component and Charge-Transfer Complex Single Crystals: Nucleation, Crystal Growth, Morphology, and Charge Transport
Electrically conducting TTF–TCNQ
thin films are fabricated
on various molecular crystals containing 7,7,8,8-tetracyanoquinodimethane
(TCNQ) by exposing a tetrathiafulvalene (TTF) vapor under ambient
conditions. To systematically investigate the properties of the films,
mixed-stack TCNQ charge-transfer (CT) complex crystals with nine kinds
of donors have been prepared as the substrates, and the morphology
change of the films on the surfaces at the initial stage of the TTF
vapor contact has been observed. When the substrate is a TCNQ single-component
crystal, randomly oriented TTF–TCNQ nanometer-size needle crystals
are grown by the reaction with a TTF vapor. However, when the substrate
is a TCNQ CT complex crystal, TTF–TCNQ crystals are grown with
alignment of their needle axis along the mixed-stack direction of
the substrate. The surface roughness, the size of the needle crystals,
and the degree of the dense packing of the needles have been found
to systematically depend on the strength of the CT interactions in
the substrate, and the sheet resistance also exhibits a systematic
change. The resistance drop is rapid and remarkable when the donor
of the substrate CT complex is weak. The difference in the morphology
and the properties is considered to arise from the difference in the
ease of nucleus formation and the rate of crystal growth of the TTF–TCNQ
nanocrystals
Charge Conduction Properties at the Contact Interface between (Phthalocyaninato)nickel(II) and Electron Acceptor Single Crystals
Single-component crystals of both
(phthalocyaninato)ÂnickelÂ(II)
(NiÂ(<i>Pc</i>)) and 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane
(F<sub>2</sub>TCNQ) are typical band insulators. However, the contact
interface between them demonstrates metal-like transport properties.
Although NiÂ(<i>Pc</i>) and F<sub>2</sub>TCNQ are an electron
donor and an acceptor, respectively, the combination of these two
components does not yield any charge transfer (CT) complex crystals.
Infrared spectra show that the highly conductive feature originates
from charge injection at the contact interface. The thermoelectric
power of the mixed powder reveals that the transport at the contact
interface is dominated by the holes in the NiÂ(<i>Pc</i>)
crystal