D.B. Zhu

Electrical Switching and Memory Phenomena in Electrodeposited [TBA]x [Ni(DMID)2] Thin Films

Abstract This paper reports reproducible bistable electrical switching and memory phenomena observed in a lamellar structure with an amorphous film of [TBA]x[Ni(DMID)2] between Pt and Al electrodes where the [TBA]x[Ni(DMID)2] is electrically deposited on a Pt substrate with galvanostatic conditions (TBA = tetrabutylammonium, DMID = 1,3-dithiole-2-one-4,5-dithiolate).The switching effect is insensitive to air, moisture, light, and the polarity of the applied potentials. The device is stable over a long period of time and has a lifetime of roughly 20 switching cycles. The current-voltage characteristics reveal an abrupt increase in impedance from 300Ω to about 100 kΩ at a field strength of about 2400 V/cm for a 10 μm film sample. Switching with high-power dissipation yields a high-impedance memory state which can be erased by the application of high voltage in either direction. The character of the switching from a low to a high impedance state in this organic charge transfer complex is in contrast to the o...

New organic conductors based on bis(1,1-dicyanoethylene-2,2-dithiolato)transition metal, M(ct)2

Abstract To prepare a series of bis(1,1-dicyanoethylene-2,2-dithiolato)transition metal complexes, M(ct) 2 is described. The conducting molecular crystals based on a variety of organic donors and M(ct) 2 were synthesized by electrochemical oxidation. The crystal structures were determined by x-ray diffraction. The electrical properties and the results of X.P.S. are reported.

X-ray photoelectron spectra and electrical properties of new metal complexes of [M(DMID)2][TAA]x

Abstract X-ray photoelectron spectroscopy (XPS) spectra of a series of metal complexes of the DMID ligand [M(DMID) 2 ][TAA] x . (DMID=1,3- dithiole-2-one-4,5-dithiolate, MNi, Cu, Zn; TAA = tetraalkylammonium, such as tetrabutylammonium (TBA), tetraethylammonium (TEA), and tetramethylammonium (TMA); X = integer or non-integer) were studied by comparing with other metal bisdithiolene complexes. The XPS results show that in the metal-DMID complexes the formal oxidation states of the central chelating metal ion are in the valence states of 3+ with the extra negative charge residing essentially on the ligands, especially on the sulfur atoms, and the electron density on the sulfur atoms is higher than that in the electron-rich organic donor molecule tetrathiafulvalene (TTF). Electrical properties of these complexes were investigated by conductivity and cyclic voltammetric measurements. Furthermore, the effects of the central metal atoms, counter cations and ligands on the electrical properties and XPS shifts are discussed.

Preparation and properties of a new organic conductor (BEDT-TTF)4Cu(C2O4)2

Abstract Organic single crystals of (BEDT-TTF) 4 Cu(C 2 O 4 ) 2 have been prepared and their properties studied. The conductivity at room temperature is 55 S/cm. The temperature dependence of resistivity has been measured.

Physical and structural properties of a new organic conductor (BEDT-TTF)4Cu(C2O4)2

Abstract The crystal structure of a novel quasi three-dimensional organic conductor (BEDT-TTF) 4 Cu(C 2 O 4 ) 2 (BEDT-TTF: bis(ethylenedithio)-tetrathiafulvalene) is determined by X-ray analysis. Each temperature dependence of resistivity and ESR intensity exhibits anomalies at about 260, 160 and 65 K. The anomaly observed at 65 K is ascribed to metal-insulator transition; the energy gap is 15 meV. The transition at 260 K can be considered to be a kind of metal-metal transition related to the lattice distortion of the complex.

Characterization of a new asymmetrically substituted metal-free phthalocyanine

Abstract The present publication is devoted to the characterization of a new asymmetrically substituted metal-free phthalocyanine. After chemical modification by attaching donor-acceptor substituents to its peripheral ring, the phthalocyanine derivative becomes a polarized molecule, and shows dipole moment of 3.8 D in benzene. Comparision with symmetrical tetra- t -butylphthalocyanine (BuPc), the oxidation peak potential of nitro-tri- t -butylphthalocyanine (NtBuPc) is 0.08 volt higher than that of BuPc as a result of electron-withdrawing nitro group. Thermogravimetry analysis indicates that the initial decomposition temperature of NtBuPc is as high as 389 °C, exhibiting good thermal stability.

Preparation and electronic properties of Schottky devices utilizing an asymmetrically substituted metal-free phthalocyanine Langmuir-Blodgett film as barrier layers

Abstract Langmuir-Blodgett films of an asymmetrically substituted phthalocyanine, nitro-tri- t -butylphthalocyanine (NtBuPc) were fabricated with a Z-type deposition model. An Al/NtBuPc L-B film/ITO cell was prepared and its electronic properties were investigated. The cell showed a rectifying effect with a rectification ratio of 10 at ± 2.0 V. The ideality factors were 1.3 in the low voltage region and 3.1 in the high voltage region. respectively. The origin of the rectifying properties for such a cell is discussed.

The synthesis, structures and physical properties of new forms of (BEDT-TTF)2I3

Abstract The crystals of BEDT-TTF complexes have various structural modifications. Thus, we consider that BEDT-TTF complexes with polyhalide anions are particularly suited to study and reveal the relationship between their crystal structures and physical properties. We have obtained several new forms of (BEDT-TTF)2IX. The crystal growth was carried out by diffusion of BEDT-TTF and TBA I5 in suitable organic solvent (e.g. THF. CH2Cl2). The structures and physical properties of the new crystal forms of (BEDT-TTF)2I3 will be reported.

New results on molecular inorganic and organic conductors

Abstract New results obtained at Toulouse and through national and international collaboration are reported and concern (i) the preparation of new molecular conductors derived from metal complexes of 1,2-dithiolate ligands, (ii) the preparation of new donors, (iii) attempts to prepare charge transfer complexes of C60, (iv) the suppression of an insulating state in (BETS)2FeCl4 by applying a magnetic field, and (v) the study of mixed valence bis-TTF compounds exhibiting intervalence transitions.

Four New ET- and TTM-TTF-Based CT Salts with Cu-Containing Binuclear Polyhalide Complex Anions: Synthesis, Properties, and Structure

Abstract Four new CT salts with Cu-containing binuclear polyhalide complex anions ET3Cu2Br x (x ∼ 5) (A), ET3Cu2CI4 (B), (TTM-TTF) Cu2Br4.72 (C), and (TTM-TTF), Cu2Cl6 (D) [ET = BEDT-TTF = bisethylenedithio-tetrathiafulvalene, TTM-TTF = tetrathiomethyl-tetrathiafulvalene are prepared and the degree of charge transfer as well as the valence states of the Cu atom in the four CT salts are discussed based on the analysis of X-ray photoelectron spectroscopy. The conductivity of the four charge-transfer salts A, B, C, and D at room temperature and their temperature dependence from room temperature down to 77 K along the crystal growth direction are reported. A behaves metallic down to about 250 K, then turns to a semi-conductor; B is an organic metal down to liquid nitrogen temperature; C shows a semi-conducting behavior down to about 230 K, then turns to an insulator and D is an insulator. The crystal structures of C and D are determined. In crystal C, both donors and acceptors occupy symmetry centers in the c...