The metal/organic interface in cobalt/vinylidene fluoride heterostructures

Abstract

Organic-based electronic devices are rapidly increasing in popularity, making it essential to understand and characterize the interface between organic materials and metallic electrodes. This work reports on the characterization of the interface between thin films of an emerging organic ferroelectric, vinylidene fluoride (VDF) oligomer, and Co, an important high Curie temperature ferromagnet. Using a wide battery of experimental techniques, it is shown that VDF oligomer thin films as thin as 15 nm can halt, or prevent, Co oxidization in atmospheric conditions, a necessary condition for device applications. Selectivity of magnetic properties, such as remanent magnetization, is enabled by the clarification of the time scale of Co oxidation, a topic on which there are many conflicting reports. Furthermore, this work shows evidence of chemical bonding at the interface between VDF oligomer and Co, a result with important implications for organic spintronic devices. These results establish the suitability of VDF oligomer for organic-based electronic devices.

Interfacial and Permeating Modification Effect of n-type Non-fullerene Acceptors toward High-Performance Perovskite Solar Cells

“…Such changes could be related to the higher oxidation state induced by Coulombic interaction between the ion cores in the PVSK and photoemitted electrons. The new Pb–F and Pb–S binding could have resulted due to additional interactions. ,− What is more, the binding energies of CO in the Y6 polymer, PCBM, and PVSK/PCBM + Y6 interface are 530.8, 531.6, and 531.7 eV, respectively, which can be observed by the significant up-shift in the O 1s spectrum. This indicates a higher oxidation state and could originate from new Pb–O binding with the same mechanism of the S 2p peak.…”

Ferroelectricity and the phase transition in large area evaporated vinylidene fluoride oligomer thin films

“…A conductive Pt-Ir coated PFM tip (Bruker model SCM-PIC-V2) with a nominal spring constant of 0.1 N/m was used for reading and writing ferroelectric domains. The soft organic films are bound by weak van der Waals forces, 1,23 necessitating the relatively soft PFM tip to ensure that there are no topographical changes in the surface of the soft film during PFM measurements without compromising the piezoresponse signal. An ac voltage at a frequency of 45 kHz is applied between the tip and sample during domain reading/mapping.…”

“…However, the VDF oligomer holds a crucial advantage over the polymer: VDF oligomer thin films can be deposited in vacuum. Unlike PVDF, which is commonly deposited in ambient conditions using Langmuir-Blodgett deposition 21 or spin coating, 22 vacuum deposition of the VDF oligomer preserves the cleanliness of the interface between the organic and adjacent layers, 23 an essential need for spintronics and other devices. Our earlier work [23][24][25] has established the conditions for optimal growth via thermal evaporation, investigated the physical properties of these thermally evaporated VDF oligomer thin films, and established that these thin films both protect and are chemically inert with an underlying metal thin film, thereby preserving the interface.…”