Tetramethylpentacene: Remarkable Absence of Steric Effect on Field Effect Mobility

Abstract

nanotube is observed and the lower side of the wall corresponds to the outside of the nanotube. The thickness of the wall is about 3.3 nm and it consists of many parallel graphene layers. Each layer, however, curves and wrinkles to some extent, indicating lower crystallinity of the present nanotubes than the ones prepared by other methods, such as arc discharge synthesis. It should be noted that this image does not exhibit any clear difference in crystallinity between pure carbon layers (upper half of the wall) and N-doped layers (the lower half). In the case of nanotubes from P-A CVD, their HRTEM images (not shown here) were found to be very similar to the image of Figure 4, and again there was no crystallinity difference between N-doped and undoped multiwalls.In conclusion, this study has demonstrated the fabrication of aligned carbon nanotubes with double coaxial structure of N-doped and undoped multiwalls. It can be determined whether the N-doped layer belongs to the inner or outer multiwalls by changing the sequence of the two-step CVD process. Moreover, the thickness of both the N-doped and pure carbon layers is controllable by changing each CVD period. The use of the AAO film as a template enables us for the first time to precisely control the nitrogen location in N-doped carbon nanotubes. Since nitrogen doping would enhance the electron-conducting properties of carbon nanotubes, the present carbon nanotubes may exhibit excellent performance as field electron emitters. The present technique opens up a novel route for the synthesis of heteroatom-doped carbon nanotubes with double coaxial structure and furthermore this will lead to the production of coaxial heterojunctions (pn, npn, or pnp) by stacking N-and B-doped layers. ExperimentalBy anodic oxidation of an aluminum plate, an AAO film with a channel diameter of 30 nm and a thickness of about 70 lm was prepared. Details are given elsewhere [13]. The resultant AAO film was placed on a quartz boat in a horizontal quartz reactor (inside diameter 55 mm). The reactor temperature was then increased to 800 C under N 2 flow. When the temperature reached 800 C, propylene gas (1.2 % in N 2 ) was passed through the reactor at a total flow rate of 1000 cm 3 (STP)/min. After the 2 h carbon deposition from propylene, the reactor was cooled down to room temperature and the carbon-coated AAO film taken out. In the second step, the carbon-coated film was placed in the reactor again and acetonitrile vapor (4.2 % in N 2 of 500 cm 3 (STP)/min) was allowed to flow over the film at 800 C. The vapor was generated by bubbling N 2 through acetonitrile liquid in a saturator kept at 0 C. This acetonitrile CVD was performed for 5 h. After this two-step sequential CVD process, the doubly coated AAO film was treated with 10 M NaOH solution at 150 C for 6 h to remove the alumina template, thereby liberating the nanotubes from the template AAO film.The carbon-coated AAO films and the corresponding carbon nanotubes were analyzed by X-ray photoelectron spectroscopy (XPS). The samples were...

Höhere Acene: vielseitige organische Halbleiter

“…2,3,9,10-Tetramethylpentacen (49) [277] kristallisiert in der für Acene typischen Fischgräten-Anordnung, und nach dem Aufdampfen liefert es Transistoren mit Lochbeweglichkeiten bis 0.3 cm 2 V À1 s À1 und einem An-AusStromverhältnis von 6 10 3 .…”

Syntheses and properties of copolymers containing indolocarbazole moiety in the side chain

“…[1][2][3][4][5][6][7] In particular, organic compounds that possess a p-conjugated system, such as pentacene and oligothiophene, have attracted much attention [8][9][10][11][12][13] because of their mechanical properties, low cost and variety of photonic properties obtained by chemical modification. Therefore, significant progress has been made in the study of p-conjugated organic compounds, which might be competitive with amorphous silicon in electronic and photonic devices.…”

High Mobility of Dithiophene-Tetrathiafulvalene Single-Crystal Organic Field Effect Transistors

“…3 These organic crystals were grown from the vapor phase in long and complex experiments. To progress in this field toward device applications, it is very important to search for new molecules that are able to act as organic semiconductors 4 and also to develop easy methods to grow single crystals or films. In this communication, we report on the clear observation of field effect hole mobility in single crystals of the organic semiconductor dithiophene-tetrathiafulvalene (DT-TTF, Figure 1a) grown by drop casting, a very simple method.…”