Superconductivity suppression and peak resistivity enhancement for thin crystals of κ‐(BEDT‐TTF) 2 Cu(SCN) 2

Thick (100–130µm) crystals of κ ‐(BEDT‐TTF) 2 Cu(SCN) 2 show maximum of ρ ( T ) dependence at 100 K (2.5–2.8 times larger than their resistivity at 298 K) and reproducible T c (onset) at 10.4 K. Thin (2–5 µm) crystals attached to a SiO 2 wafer demonstrated profound enhancement of peak resistivity near 100 K (up to 3000 times greater than their room temperature resistivity). Further, superconductivity is absent in the thin films. We argue that these effects are due to ‘negative pressure’ (about −2.5 kbar at 100 K) caused by the large difference in the thermal expansion coefficients of SiO 2 and κ ‐(BEDT‐TTF) 2 Cu(SCN) 2 .Thin single crystal on Au patterned Si/SiO 2 wafer.