Positioning and joining of organic single-crystalline wires (original) (raw)
Related papers
Advanced Materials, 2013
Over the past decade, solid-state optical materials have been designed and synthesized at an ever diminishing size, owing to the rapid development of nanoscience and nanotechnology. Low-dimensional micro/nanostructures, mostly nanowires, have been proved to serve as effi cient optical waveguides above and below the wavelength range of visible light. [ 7 ] In these structures, photons could be confi ned and transported, with tunable parameters of intensity, polarization, phase, and so on. Thereby, such tiny optical structures could enable photon absorption, light amplifi cation, strong exciton-photon coupling, [ 8-10 ] and many other optical properties at nanometer range. Although modern state-of-the-art lithography techniques are capable of fabricating nanostructured features, chemically grown nanowires still possess unique advantages of being single-crystalline, relatively defect-free, atomically smooth surfaces, and being able to accommodate large lattice mismatches. Self-assembled crystalline micro/nanostructures from organic dye molecules are expected to play important roles in the next generation of miniaturized optoelectronics because of the excellent performance in both photonics and electronics. [ 11 ] Moreover, organic dye molecules, as a kind of active optical materials, show great potential for controlling light signals because they can benefi t from chemical versatility, structural processability, and excellent tunability in their optical properties. Among the organic crystals with various morphologies, 1D nanostructures have been specially highlighted as building blocks for miniaturized optoelectronic devices. [ 7 , 12 ] Several unique functional devices, such as lasers, [ 13 ] waveguides, [ 14 ] fi eld-effect transistors, [ 15 ] solar cells, [ 16 ] have been successfully fabricated with organic 1D crystalline materials. These singlecomponent systems provide ideal theoretical models to investigate the light-matter interactions in organic crystals, while the construction of multi-component structures is essential to achieve practical functions in photonic nanodevices. The complex systems could not only maintain the advantages of each component, but also exhibit novel performance from energy/ charge transfer, photon-plasmon coupling, exciton conversion, and so forth. Utilizing these, we can realize the overall control of photon parameters, such as intensity, wavelength, polarization, and phase, in optical systems towards the process of light signals. In this Progress Report, we introduce recent advances focused on the contrivable fabrication and optoelectronic property optimization of 1D organic composites towards distinct photonic devices. Here, we lay emphasis on the functionoriented material design, including the topological control of composition and geometry, the interactions among individual components in hybrid optical structures, and the relationships between material property and the device performance.
ACS nano, 2016
The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursor...
Advanced Materials, 2009
Organic conjugated compounds are envisaged as functional materials for fabricating devices able to drive low-cost, lowperformance consumer electronics. To reach this goal, however, a better understanding of their electrical behavior is needed. In this view, organic single crystals offer the interesting and unique opportunity to investigate the intrinsic electrical behavior of organic materials, excluding hopping phenomena due to grain boundaries and structural imperfections. Their structural asymmetry also allows the investigation of the correlation between their 3D order and their charge-transport characteristics. One useful investigation tool in this sense may be found in organic field-effect transistors (OFETs), which can provide precious information on the nature of the chargetransport phenomena in organic materials. Indeed, single-crystal organic transistors, where the active channel is a single crystal, exhibited up to now the best performances in terms of charge-carriers mobility, reaching time-of-flight (TOF)-measured values as high as 400 cm 2 V À1 s À1 , and FET-measured mobilities of several units, up to tens of cm 2 V À1 s À1 . In this light, macroscopic (millimeter-sized) self-standing crystals suitable for being manipulated and selectively deposited on any surface and in any position with respect to existing electrodes are very useful, and recent studies showed that macroscopic crystals of rubrene present 2D electrical anisotropy. For obtaining crystals suited for these investigations, vacuumbased methods are up to now the most exploited strategy. However, macroscopic organic crystals may be easily grown also from solution, permitting a considerable degree of control over the final crystal characteristics in terms of dimensions and of the developed crystallographic phase. The suitability of solution grown (SG) organic crystals for electronic studies has been recently confirmed by a report on dicyclohexyl-a-quaterthiophene single crystals. The crystals were grown from solution and used as active materials in FETs, demonstrating 2D electrical anisotropy even though in this case the studied crystals had dimensions in the micrometers domain, and an investigation of their electrical behavior in the third dimension was not presented.
Patterning organic single-crystal transistor arrays
Nature, 2006
Field-effect transistors made of organic single crystals are ideal for studying the charge transport characteristics of organic semiconductor materials 1 . Their outstanding device performance 2-8 , relative to that of transistors made of organic thin films, makes them also attractive candidates for electronic applications such as active matrix displays and sensor arrays. These applications require minimal cross-talk between neighbouring devices. In the case of thin film systems, simple patterning of the active semiconductor layer 9,10 minimizes cross-talk. But when using organic single crystals, the only approach currently available for creating arrays of separate devices is manual selection and placing of individual crystals-a process prohibitive for producing devices at high density and with reasonable throughput. In contrast, inorganic crystals have been grown in extended arrays , and efficient and large-area fabrication of silicon crystalline islands with high mobilities for electronic applications has been reported 14,15 . Here we describe a method for effectively fabricating large arrays of single crystals of a wide range of organic semiconductor materials directly onto transistor source-drain electrodes. We find that film domains of octadecyltriethoxysilane microcontact-printed onto either clean Si/SiO 2 surfaces or flexible plastic provide control over the nucleation of vapour-grown organic single crystals. This allows us to fabricate large arrays of high-performance organic single-crystal field-effect transistors with mobilities as high as 2.4 cm 2 V 21 s 21 and on/off ratios greater than 10 7 , and devices on flexible substrates that retain their performance after significant bending. These results suggest that our fabrication approach constitutes a promising step that might ultimately allow us to utilize high-performance organic single-crystal field-effect transistors for large-area electronics applications. illustrates the single-crystal patterning process (see Methods for a detailed description). First, thick octadecyltriethoxysilane (OTS) films (average thickness ,13 6 2 nm, measured by ellipsometry) are printed by microcontact printing onto a clean SiO 2 /Si substrate, using a polydimethylsiloxane (PDMS) stamp with a relief structure in the desired pattern. We note that although the results discussed here mainly relate to structures grown on arrays of micrometre-sized OTS squares, it is straightforward to create more-complex OTS film patterns for single-crystal nucleation ( . After film deposition, crystals are grown using a vapour transport method 16 applicable to a broad range of materials, including high-mobility p-type materials such as rubrene, pentacene and tetracene, and n-type materials such as C 60 , fluorinated copper phthalocyanine (F 16 CuPc) and tetracyanoquinodimethane (TCNQ) . We find that sublimation of the organic material and crystal growth are accomplished in as little as five minutes for pentacene and as much as two hours for C 60 , and that crystal nucleation is restricted to OTS-stamped regions and not observed on the SiO 2 background. The crystals show strong birefringence in optical micrographs recorded under cross-polarized light ( ), confirming their crystalline nature. We also observe intense and narrow diffraction peaks in the X-ray diffraction patterns of pentacene, rubrene and C 60 single crystals, which are indicative of a high degree of crystallinity .
Colloquium: Electronic transport in single-crystal organic transistors
Reviews of Modern Physics, 2006
Small-molecule organic semiconductors, together with polymers, form the basis for the emerging field of organic electronics. Despite the rapid technological progress in this area, our understanding of fundamental electronic properties of these materials remains limited. Recently developed organic field-effect transistors ͑OFETs͒ based on single crystals of small-molecule organic materials are characterized by an unprecedented quality and reproducibility. These devices provide a unique tool to study the fundamentals of polaronic transport on organic surfaces and to explore the limits of OFET performance. This Colloquium focuses on the intrinsic, not limited by static disorder, charge transport in single-crystal OFETs and on the nature of defects on surfaces of organic crystals. In the conclusion, an outline of the outstanding problems that are now becoming within experimental reach owing to the development of single-crystal OFETs is presented.