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‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4 n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K x picene, five benzene rings). Its superconducting transition temperatures ( T c ’s) were 7 and 18 K. Recently, we found a new superconducting K x picene phase with a T c as high as 14 K, so we now know that K x picene possesses multiple superconducting phases. Besides K x picene, we discovered new superconductors such as Rb x picene and Ca x picene. A most serious problem is that the shielding fraction is ⩽15% for K x picene and Rb x picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T c that is clearly observed in some phases of aromatic hydrocarbon superconductors, suggesting behavior not explained by the standard BCS picture of superconductivity. In this article, we describe the present status of this research field, and discuss its future prospects. [ABSTRACT FROM AUTHOR]

Field-effect transistors (FETs) were fabricated with a thin film of 3,10-ditetradecylpicene, picene-(C14H29)2, formed using either a thermal deposition or a deposition from solution (solution process). All FETs showed p-channel normally-off characteristics. The field-effect mobility, μ, in a picene-(C14H29)2 thin-film FET with PbZr0.52Ti0.48O3 (PZT) gate dielectric reached ∼21 cm2 V-1 s-1, which is the highest μ value recorded for organic thin-film FETs; the average μ value (<μ>) evaluated from twelve FET devices was 14(4) cm2 V-1 s-1. The <μ> values for picene-(C14H29)2 thin-film FETs with other gate dielectrics such as SiO2, Ta2O2, ZrO2 and HfO2 were greater than 5 cm2 V-1 s-1, and the lowest absolute threshold voltage, ∣Vth∣, (5.2 V) was recorded with a PZT gate dielectric; the average ∣Vth∣ for PZT gate dielectric is 7(1) V. The solution-processed picene-(C14H29)2 FET was also fabricated with an SiO2 gate dielectric, yielding μ =3.4× 10-2 cm2 V-1 s-1. These results verify the effectiveness of picene-(C14H29)2 for electronics applications. [ABSTRACT FROM AUTHOR]

We report the observation of zero resistivity (p) in a hydrocarbon superconductor, and describe the temperature dependence of p in metal-doped hydrocarbons. The resistivity of K-doped picene (Kx picene) has been recorded from pellet samples in a four-terminal measurement mode. A drop in p is observed below 7 K for K3.1 picene and below 11 K for K3.5picene, which clearly displays zero resistivity. The resistivity drop at 7 K is consistent with the superconducting critical temperature (Tc) obtained from the magnetic susceptibility of the 7 K phase of K3picene, while the drop at 11 K is inconsistent with the Tc's of both the 7 and 18 K phases of K3 picene reported previously. The temperature dependence of p for both samples exhibits granular-metal-like behavior in the normal state. [ABSTRACT FROM AUTHOR]

Abstract: Thin film transistors (TFTs) with ionic liquid gate dielectrics, [1-ethyl-3-methylimidazolium][bis(trifluoromethanesulfonyl)imide] (emim[TFSI]) and [1-butyl-3-methylimidazolium][hexafluorophosphate] (bmim[PF6]), are fabricated with thin films of one dimensional (1D) hydrocarbon, [7]phenacene. P-channel characteristics are observed for [7]phenacene TFTs with both ionic liquids by use of platinum electrode. The field-effect mobility μ for [7]phenacene TFT with bmim[PF6] was recorded to be 0.28cm2 V−1 s−1. The value of absolute threshold voltage, |V TH|, was less than 2.5V, showing low-voltage operation. The accumulation of hole in the [7]phenacene TFTs with ionic liquids was confirmed from the voltage or time dependence of capacitance in metal–insulator-semiconductor structure, which shows that these TFTs operate electrochemically and the carriers are accumulated in the whole of [7]phenacene thin films. [Copyright &y& Elsevier]