Preparation of metal mixed plastic superconductors: Electrical properties of tin-antimony thin films on plastic substrates

Abstract

Metal mixed polymers are a cheap and effective way to produce flexible metals and superconductors. As part of an on-going effort to learn how to tune the properties of these systems with ion implantation, we present a study of the electrical properties of these systems prior to metal-mixing. We show that the electrical properties of tin-antimony thin films are remarkably robust to variations in the substrate morphology. We demonstrate that the optical absorbance of the films at a fixed wavelength provides a reliable and reproducible characterization of the relative film thickness. We find that as the film thickness is reduced, the superconducting transition in the unimplanted thin films is broadened, but the onset of the transition remains at ∼3.7 K, the transition temperature of bulk Sn. This is in marked contrast to the behavior of metal mixed films, which suggests that the metal mixing process has a significant effect of the physics of the superconducting state beyond that achieved by reducing the film thickness alone.

Competition between superconductivity and weak localization in metal-mixed ion-implanted polymers

“…That said, we expect the coupling to be dependent on the nature of the carbonized polymer matrix created by the ion beam, 28 which fills the space between the grains, as well as the size distribution and morphology of the grains themselves. However, on the weight of evidence presented here and in our earlier work, 13,15 it is clear that this material system is granular.…”

“…The first is the preimplant metal thickness because it provides the easiest control over the conductivity, even though this can be a slightly difficult parameter to control with precision. 15 The second is the implant temperature, which we believe provides some control over the disorder of the resulting film, as we will show in the next section. A more extensive study of the role of the fabrication and ion-implantation parameters in determining the sample conductivity will be the subject of a separate, forthcoming paper.…”

“…[13][14][15] To summarize briefly, we commence with cleaned PEEK substrates onto which a thin film of 19:1 Sn:Sb alloy was deposited by thermal evaporation. For the metal-mixed samples, ion implantation was then performed using a 0.37 A cm −2 , 50 keV N + ion beam that illuminated a circular area 14 mm in diameter to a dose of 10 16 ions/ cm 2 .…”

“…It is perhaps dangerous to suppose that the magnetoresistance peaks in our unimplanted films have the same origin as that in -͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 without much more solid physical evidence, given the important physical differences between the two materials systems. 13,15,34 However, the commonalities in the data are tantalizing, and further studies of this phenomenon in both systems are certainly called for.…”

A Tunable Metal–Organic Resistance Thermometer

“…Although the conductivity can be controlled by the pre-implant metal thickness, we have recently shown that doing so gives inhomogeneous films with anisotropic electrical properties as the metal thickness and resulting conductivity are reduced. [14,15] Herein, we demonstrate that a much more effective route to achieving tunability in metal-mixed polymers is to harness the same sputtering process that limits the conductivity when using a metal ion beam to implant native polymer films. [10] Metal mixing with a heavier element ion beam enhances the sputtering, allowing one to start with a thicker metal layer, and achieve more uniform and precise control over the metal content and the resulting film's electrical properties.…”