Here, we propose a new vacuum deposition process with an ionic liquid, and demonstrate that the singlecrystal phase of pentacene, which is thermodynamically the most stable phase of its polymorphs, can be easily grown through this process. In this process, pentacene was deposited at a temperature above 363 K directly into an ionic-liquid droplet that had been prepared on a substrate beforehand, and nucleated in the ionic-liquid droplet to form many plate-shape crystals in the single-crystal phase. Even though our process time was just 100 min, the crystal quality of pentacene singlecrystal phase, the maximum size of which was as large as 300 μm, was almost equivalent to that obtained by the conventional solution growth process. The ionic-liquid assisted vacuum deposition, therefore, will become one of the alternative processes for the growth of organic single crystals in vacuum.' ASSOCIATED CONTENT b S Supporting Information. Figure S1, Table S1, and detail of XRD measurement. This material is available free of charge via the Internet at http://pubs.acs.org.

We propose a new approach to nanoscience and technology for ionic liquids (ILs): molecular beam deposition of IL in ultrahigh vacuum by using a continuous wave infrared (CW-IR) laser deposition technique. This approach has made it possible to prepare a variety of "nano-IL" with the given composition on the substrate: a nanodroplet, on one hand, the volume of which goes down to 1 aL and, on the other hand, an ultrathin film with a thickness to several 100 nm or less. The result of fractional distillation of a binary mixture of ILs, investigated by nuclear magnetic resonance as well as electrospray ionization time-of-flight mass spectrometry, indicates that this deposition process is based on the thermal evaporation of ILs, and thus this process also can be used as a new purification method of ILs in vacuum. Furthermore, the fabrication of binary mixture droplets of two ILs on the substrate by alternating deposition of two ILs was demonstrated; the homogeneity of the composition was confirmed even for one single droplet by high-spatial-resolution Raman spectroscopy.

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