Conductance fluctuations in cobalt valence tautomer molecular thin films
The bistability and the conductivity changes associated with optical excitations in cobalt valence tautomer molecular thin films were investigated.
Phillips, Jared P.↗
Engineering topics
Cheng, Ruihua
Publications and source records attributed to Cheng, Ruihua.
Electronic structure of cobalt valence tautomeric molecules in different environments
A joint spectroscopy and ab initio study identifies electronic orbitals of valence tautomeric complexes on different semiconducting polymers, including a spin-polarized ligand-to-metal charge transfer state that spans the entire molecular plane.
Mishra, Esha↗
Perturbing the spin state and conduction of Fe (II) spin crossover complexes with TCNQ
In this study, we investigated modifications driven by 7,7,8,8-tetracyanoquinodimethane (TCNQ) to the spin state configuration of [Fe(3-bpp) 2 ](TCNQ) 2 co-crystal and both spin state and electric conductivity of [Fe{H 2 B(pz) 2 } 2 (bipy)] and TCNQ mixtures. The Fe 2+ site in the [Fe(3-bpp) 2 ](TCNQ) 2 co-crystal has a sizable orbital moment. During X-ray absorption measurements, the iron ion is partially excited to the high spin state and strong surface effects are indicated. Mixing TCNQ with the [Fe{H 2 B(pz) 2 } 2 (bipy)] spin crossover complex leads to a molecular combination with increased conductivity and drift carrier lifetimes. [Fe{H 2 B(pz) 2 } 2 (bipy)] thin films with TCNQ, grown using dimethylformamide (DMF), are to great extent locked mainly in the low spin (LS) state across a broad temperature range and exhibit drift carrier lifetimes approaching 0.5 s. When deposited onto a ferroelectric polyvinylidenefluoride-hexafluoropropylene thin film substrate, [Fe{H 2 B(pz) 2 } 2 (bipy)], shows enhanced transistor carrier mobility, likely associated with the increasing cationic character of [Fe{H 2 B(pz) 2 } 2 (bipy)] thin films with TCNQ.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Evidence of dynamical effects and critical field in a cobalt spin crossover complex
The [Co(SQ) 2 (4-CN-py) 2 ] complex exhibits dynamical effects over a wide range of temperature. Additionally, the orbital moment, determined by X-ray magnetic circular dichroism (XMCD) with decreasing applied magnetic field, indicates a nonzero critical field for net alignment of magnetic moments, an effect not seen with the spin moment of [Co(SQ) 2 (4-CN-py) 2 ].
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Magnetic Field Perturbations to a Soft X-ray-Activated Fe (II) Molecular Spin State Transition
The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft X-ray activation of the spin crossover transition for [Fe{H2B(pz)2}2(bipy)] molecular thin films is reduced in the presence of an applied magnetic field, as measured through X-ray absorption spectroscopy at various temperatures. The influence of a 1.8 T magnetic field is sufficient to cause deviations from the expected exponential spin state transition behavior which is measured in the field free case. We find that orbital moment diminishes with increasing temperature, relative to the spin moment in the vicinity of room temperature.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Nonvolatile Voltage Controlled Molecular Spin-State Switching for Memory Applications
Nonvolatile, molecular multiferroic devices have now been demonstrated, but it is worth giving some consideration to the issue of whether such devices could be a competitive alternative for solid-state nonvolatile memory. For the Fe (II) spin crossover complex [Fe{H2B(pz)2}2(bipy)], where pz = tris(pyrazol-1-yl)-borohydride and bipy = 2,2′-bipyridine, voltage-controlled isothermal changes in the electronic structure and spin state have been demonstrated and are accompanied by changes in conductance. Higher conductance is seen with [Fe{H2B(pz)2}2(bipy)] in the high spin state, while lower conductance occurs for the low spin state. Plausibly, there is the potential here for low-cost molecular solid-state memory because the essential molecular thin films are easily fabricated. However, successful device fabrication does not mean a device that has a practical value. Here, we discuss the progress and challenges yet facing the fabrication of molecular multiferroic devices, which could be considered competitive to silicon.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Probing the unpaired Fe spins across the spin crossover of a coordination polymer
For the spin crossover coordination polymer [Fe(L1)(bipy)] n (where L1 is a N 2 O 2 2− coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4′-bipyridine), there is compelling additional evidence of a spin state transition.
Ekanayaka, Thilini K.↗