Showing papers on "Pentacene published in 1997"
TL;DR: In this article, photolithographically defined organic thin-film transistors (OTFTs) with improved field-effect mobility and sub-threshold slope were fabricated using two layers of pentacene deposited at different substrate temperatures.
Abstract: Using two layers of pentacene deposited at different substrate temperatures as the active material, we have fabricated photolithographically defined organic thin-film transistors (OTFTs) with improved field-effect mobility and subthreshold slope. These devices use photolithographically defined gold source and drain electrodes and octadecyltrichlorosilane-treated silicon dioxide gate dielectric. The devices have field-effect mobility as large as 1.5 cm/sup 2//V-s, on/off current ratio larger than 10/sup 8/, near zero threshold voltage, and subthreshold slope less than 1.6 V per decade. To our knowledge, this is the largest field-effect mobility and smallest subthreshold slope yet reported for any organic transistor, and the first time both of these important characteristics have been obtained for a single device.
915 citations
TL;DR: Pentacene-based organic thin-film transistors (TFT's) with field effect mobility as large as 0.7 cm/sup 2/V/spl middot/s and on/off current ratio larger than 10/sup 8/ have been fabricated as mentioned in this paper.
Abstract: Pentacene-based organic thin-film transistors (TFT's) with field-effect mobility as large as 0.7 cm/sup 2//V/spl middot/s and on/off current ratio larger than 10/sup 8/ have been fabricated. Pentacene films deposited by evaporation at elevated temperature at low-to-moderate deposition rates have a high degree of molecular ordering with micrometer-sized and larger dendritic grains. Such films yield TFT's with large mobility. Films deposited at low temperature or by flash evaporation have small grains and poor molecular ordering and yield TFT's with low mobility.
754 citations
TL;DR: In this article, the authors present results on metal-insulator-semiconductor field effect transistors using conjugated organic semiconductors which can be processed from solution.
605 citations
TL;DR: In this paper, the authors show that the large sub-threshold slope typically observed is not an intrinsic property of the organic semiconducting material and that devices with sub-reshold slope similar to amorphous silicon devices are possible.
Abstract: Organic thin-film transistors using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active electronic material have shown mobility as large as 0.7 cm/sup 2//V-s and on/off current ratio larger than 10/sup 8/; both values are comparable to hydrogenated amorphous silicon devices. On the other hand, these and most other organic TFT's have an undesirably large subthreshold slope. We show here that the large subthreshold slope typically observed is not an intrinsic property of the organic semiconducting material and that devices with subthreshold slope similar to amorphous silicon devices are possible.
520 citations
TL;DR: The field effect mobility of these TFTs ranges from 10−2'cm2/V's for p-4P to 10−1'cm 2/V's for P-6P with on/off current ratio from 105 to 106 as mentioned in this paper.
Abstract: Organic thin film transistors (TFTs) have been fabricated using thermally evaporated films of the oligophenyls p-quaterphenyl (p-4P), p-quinquephenyl (p-5P), and p-sexiphenyl (p-6P). The field-effect mobility of these TFTs ranges from 10−2 cm2/V s for p-4P to 10−1 cm2/V s for p-6P with on/off current ratio from 105 to 106. These values are comparable to those achieved using the more widely studied organic semiconductors alpha-sexithienyl (α-6T) and pentacene. X-ray diffraction reveals a high degree of molecular ordering, believed to be important for obtaining high field-effect mobility in organic TFTs.
140 citations
07 Dec 1997
TL;DR: In this article, an integrated voltage inverter with voltage gain large enough to be useful for the fabrication of electronic circuits has been fabricated using the fused-ring small-molecule aromatic hydrocarbon pentacene as the active material.
Abstract: Organic thin film transistors and simple electronic circuits have been fabricated using the fused-ring small-molecule aromatic hydrocarbon pentacene as the active material. Carrier field-effect mobilities greater than 0.2 cm/sup 2//V-s were obtained for thin film transistors fabricated on glass using low-temperature ion-beam deposited silicon dioxide as the gate dielectric and thermally evaporated pentacene as the active material. Using similar transistors, integrated voltage inverters with voltage gain large enough to be useful for the fabrication of electronic circuits have been fabricated.
49 citations
23 Jun 1997
TL;DR: In this article, the authors reported pentacene-based organic thin film transistors (TFTs) with field-effect mobility and on/off current ratio comparable to hydrogenated amorphous silicon devices.
Abstract: We recently reported pentacene-based organic thin film transistors (TFTs) with field-effect mobility and on/off current ratio comparable to hydrogenated amorphous silicon devices. However, these devices had large threshold voltage (typically >+20 V; that is, the devices are on at zero gate bias) and large subthreshold slope (typically >5 V/decade), which makes application in low-voltage circuits problematic. We have now fabricated pentacene-based TFTs with field-effect mobility as large as 1.5 cm/sup 2//V-s, low threshold voltage, and subthreshold slope as low as 1.6 V/decade.
17 citations
TL;DR: In this article, the precursor-route pentacene thin film transistor characteristics are presented and the device temperature dependance is reported and the results discussed in terms of a distribution of mobilities.
16 citations
TL;DR: In this article, the crystal structure of an endoperoxide of tetrabenzo[de,hi,op,st]pentacene (TBPA-O2) was determined by X-ray crystallography.
14 citations
TL;DR: Pulsed-laser deposition (PLD) constitutes a novel and highly promising but at present ill-characterized recent addition to available fabrication techniques as discussed by the authors, and it is shown that PLD is capable of achieving significant improvements in device characteristics, whilst simultaneously allowing films to be deposited at least 100 times faster than TE.
Abstract: Organic thin films are of increasing interest as active media in thin-film electronic devices. Pulsed-laser deposition (PLD) constitutes a novel and highly promising but at present ill-characterized recent addition to available fabrication techniques. In this paper, we report very promising measurements on PLD films of pentacene, comparing them with the characteristics of their more conventional counterparts obtained by thermal evaporation (TE). It is shown that PLD is capable of achieving significant improvements in device characteristics, whilst simultaneously allowing films to be deposited at least 100 times faster than TE. Surface morphology analysis by atomic force microscopy and scanning electron microscopy suggests that the enhanced properties are associated with appreciably improved molecular ordering. PLD thin-film transistors (TFTs) deposited onto room-temperature substrates exhibit a field-effect mobility μ FE of 3 x 10 -2 cm 2 V -1 s -1 , a 0.25V threshold voltage, and an on-to-off current ratio of more than 1400. In contrast, TE devices prepared under otherwise identical conditions exhibit a μ FE of only about 10 -4 cm 2 V -1 s -1 , a 0.8 V threshold voltage and an on-to-off ratio of 240. The mobility values for the PLD TFTs are already the highest reported for undoped pentacene devices and are sufficient to make the material viable for prototype active circuits. Moreover, our most recent experiments have established that raising the substrate temperature during PLD deposition to 473 K yields a dramatic reduction in the surface roughness of films, to a value of 0.4 nm, which is comparable with the dimensions of the pentacene molecule! This is accompanied by further improvements in electrical conductivity, offering exciting possibilities for devices of even higher performance.
10 citations
TL;DR: In this article, the static susceptibility of the new molecular compound potassium doped pentacene was measured for the first time together with electron spin resonance (ESR) spectra in the dilution temperature region 4.2-0.02 K.
Abstract: Static susceptibility of the new molecular compound potassium doped pentacene was measured for the first time together with electron spin resonance (ESR) spectra in the dilution temperature region 4.2–0.02 K. Interesting thermal hysteresis and magnetic field dependence were observed in both the ESR spectra and static susceptibility indicating that an unusual kind of magnetic transition is taking place in this system. The present result is consistent with the previous observation of an antiferromagnetic-like transition in ESR data around 0.2 K.
TL;DR: In this paper, the authors studied the properties of polycrystalline C60 and Pentacene films grown on W(110) and Pt(111) and found asymmetries up to 50% in the region of the σ-electrons.
TL;DR: In this article, an anomalous temperature dependence of the g shift and line width was observed, with a change of behavior around 240 K, while no abrupt change in the spin susceptibility or static susceptibility was observed around 240K.
Abstract: Doping of iodine to pentacene (PEN) has been previously reported to cause a drastic transformation from an insulator to a conductor, with conductivity increasing 1010 times to 150 S cm−1 at room temperature. ESR was measured at 9.3 GHz and 7.7 MHz over a wide temperature region from 300 to 0.05 K. An anomalous temperature dependence of the g shift was observed, with the g shift and line width showing a change of behavior around 240 K , while no abrupt change in the spin susceptibility or static susceptibility was observed around 240 K. The particular temperature dependence of the conductivity previously observed was attributed to be not due to a transition from a semiconductor to a metal, but it was indicated that relaxation is governed by Elliott's mechanism, with the orbital scattering time having a minimum at 240 K.
TL;DR: In this article, the crystal structure of an endoperoxide of tetrabenzo[de,hi,op,st]pentacene (TBPA-O2) was determined by X-ray crystallography.
Abstract: The crystal structure of an endoperoxide of tetrabenzo[de,hi,op,st]pentacene (TBPA-O2) was determined by X-ray crystallography. The unusually long OO and CO bonds were rationalized by the characteristic molecular structure of TBPA-O2. The photochromic behavior between TBPA-O2 and TBPA was discussed based on the enthalpy difference between TBPA-O2 and TBPA + O2 and the thermodynamic parameters of the extrusion reaction of oxygen from TBPA-O2.
TL;DR: In this article, the optically detected coherent transient response of a single chromophore molecule in an organic matrix is analyzed using a model in which N-independent random telegraph processes produce fluctuations of the resonant spin transition frequency.