F. V. Di Girolamo

Very low bias stress in n-type organic single-crystal transistors

Bias stress effects in n-channel organic field-effect transistors (OFETs) are investigated using N,N′-bis(n-alkyl)-(1,7 and 1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide)s (PDIF-CN2) single-crystal devices with Cytop gate dielectric, both under vacuum and in ambient. We find that the amount of bias stress is very small as compared to all (p-channel) OFETs reported in the literature. Stressing the PDIF-CN2 devices by applying 80 V to the gate for up to a week results in a decrease of the source drain current of only ∼1% under vacuum and ∼10% in air. This remarkable stability of the devices leads to characteristic time constants τ, extracted by fitting the data with a stretched exponential—that are τ ∼ 2 × 109 s in air and τ ∼ 5 × 109 s in vacuum—approximately two orders of magnitude larger than the best values reported previously for p-channel OFETs.

Dermatofibrosarcoma protuberans: experience with 14 cases.

Dermatofibrosarcoma is a rare, low‐grade malignant skin tumour that can be considered the equivalent of malignant non‐cutaneous soft tissue fibrohistiocytoma. The high rate of recurrence of this tumour is correlated with poor surgical management because lesions, often smaller than 2 cm in diameter, may be confused with dermatofibroma or keloid.

Photoinduced long-term memory effects in n-type organic perylene transistors

In this paper, the photoexcitation response of high mobility n-type organic field-effect transistors is analyzed. White light exposure of N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8H) transistors is demonstrated to promote the occurrence of metastable conductance states with very long retention times, similar to what has been previously reported for p-type compounds. Even in the absence of a gate-source voltage VGS, the complete recovery of the initial electrical condition can take up to 20 days. However, the initial state restoring is electrically controllable by the application of a positive VGS. These effects suggest that PTCDI-C8H is an interesting n-type material for the development of light-sensitive organic circuitry.

Current distribution effects in organic sexithiophene field effect transistors investigated by lock-in thermography: Mobility evaluation issues

In this Letter, a lock-in thermography technique has been used to investigate the actual current distribution profile in the active channel region of organic field effect transistors. The high accuracy of the setup shows an evidence of nonuniformity in the current flow over the device area. The physical origin of this experimental occurrence is tentatively ascribed to a not uniform contact resistance distribution along the channel width or to inhomogeneities in the interface traps distribution. The subsequent implications on the carrier mobility evaluation are discussed too.

Bias stress instability in organic transistors investigated by ac admittance measurements

In this paper, the bias stress effect (BSE) in organic field-effect transistors has been analyzed by an alternative experimental approach based on ac admittance (Y=G+jωC) measurements. conductance (C) and capacitance (G) curves have been recorded as a function of frequency at different times of the bias stress experiments and simultaneously fitted through a transmission line circuit, able to separately model the conducting properties of the channel and contact regions. The determination of the time behavior of the model fitting parameters is assumed as the starting point for a quantitative analysis of the BSE occurrence. This experimental procedure clarifies that both channel resistance (Rch) and contact resistance (Rc) are largely affected by the BSE, while the channel capacitance (Cch), related to the charge accumulation sheet, and the contact capacitance (Cc) result almost unchanged.

Late onset Blueberry Muffin Syndrome following congenital rubella

The authors report a case of congenital rubella in a 7‐month‐old female infant presenting a Blueberry Muffin Rash. Blueberry Muffin Syndrome is a cutaneous manifestation characterized by widespread maculo papular lesions of a reddish‐blue or magenta colour, due to persistent dermal erythropoiesis in patients with congenital viral infections.

Surface doping in T6/PDI-8CN2 heterostructures investigated by transport and photoemission measurements

In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transistors by N,N′-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN2). We show that an accumulation heterojunction is formed at the interface between the organic semiconductors and that the consequent band bending in T6 caused by PDI-8CN2 deposition can be addressed as the cause of the surface doping in T6 transistors. Several evidences of this phenomenon have been furnished both by electrical transport and photoemission measurements, namely, the increase in the conductivity, the shift of the threshold voltage, and the shift of the T6 highest occupied molecular orbital peak towards higher binding energies.

Cell viability studies and operation in cellular culture medium of n-type organic field-effect transistors

The possibility of the fabrication of organic devices suitable to be applied in bio-sensing fields depends largely on the availability of organic compounds displaying robust electrical properties even in aqueous solutions and effective biocompatibility features. In this paper, we report about the good cellular biocompatibility and the electrical response stability in an ionic medium of n-type organic transistors based on the recently developed PDI-8CN2 oligomer. The biocompatibility has been tested by analyzing the adhesion and viability of two different cell lines, human epithelial HeLa cells and murine neuronal F11 cells, on PDI-8CN2 films grown by organic molecular beam deposition (OMBD) on SiO2 substrates. The effect of film thickness on cell attachment was also tested. Uncoated SiO2 substrates were used as control surfaces and sexithiophene (T6) as device testing control. Moreover, the possible toxicity of –CN groups of PDI-8CN2 was tested on HeLa cell cultures, using PDI-8 and T6 molecules as contro...