Francesca Ciccullo | University of Tübingen (original) (raw)

Uploads

Papers by Francesca Ciccullo

Research paper thumbnail of Electronic properties of the n-type PDI8-CN 2 organic semiconductor at the interface with SiO 2 : addressing the role of adsorbed water molecules by means of optical second-harmonic generation

New Journal of Physics, 2014

ABSTRACT We investigate the interfacial electronic properties of N,N’-bis(n-octyl)-(1,7&1... more ABSTRACT We investigate the interfacial electronic properties of N,N’-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) organic semiconductor films grown on silicon dioxide (SiO2) by polarization-resolved second harmonic generation optical spectroscopy. The analysis shows a non-uniform distribution of charge carriers in PDI8-CN2, whose spatial profile is affected by hydrophobic passivation of SiO2 surfaces by hexamethyldisilazane. An interpretation model strengthened by photoluminescence analysis is developed, based on the presence of the net charge localized at the SiO2 surface and on consequent charge redistribution in the organic semiconductor. Considerations are expounded suggesting a common and ‘universal’ mechanism for the bias stress effect in p-channel and n-channel organic field-effect transistors, related to proton migration toward SiO2 gate dielectrics.

Research paper thumbnail of Contact-free probing of interfacial charging and Debye-like charge screening in SiO$_2$/PDI8-CN$_2$ systems by optical second harmonic generation

Investigation of the interfacial electronic properties of N,N'-bis(n-octyl)-(1,7&1,6)-dicyano... more Investigation of the interfacial electronic properties of N,N'-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) organic semiconductor films grown on silicon dioxide is performed by polarization-resolved second harmonic generation optical spectroscopy, pointing out a spatial region where charge carriers distribution in the semiconductor lacks inversion symmetry. By developing a model for nonlinear susceptibility in the framework of Debye-Huckel screening theory, we show that the experimental findings can be interpreted as resulting from the presence of a net charge localized at the silicon dioxide, accompanied by a non-uniform charge distribution in the organic semiconductor. Photoluminescence analysis further reinforces this scenario. Reduction-oxidation reactions involving PDI8-CN2 and water molecules are invoked as physical origin of the localized charge. The work outlines a sensitive tool to probe the total charge localized at buried semiconductor/d...

Research paper thumbnail of Chemisorption, Morphology, and Structure of a n-Type Perylene Diimide Derivative at the Interface with Gold: Influence on Devices from Thin Films to Single Molecules

Chemistry - A European Journal, 2015

We have investigated thin films of a perylene diimide derivative with a cyano-functionalized core... more We have investigated thin films of a perylene diimide derivative with a cyano-functionalized core (PDI-8CN2) deposited on Au(111) single crystals from the monolayer to the multilayer regime. We found that PDI-8CN2 is chemisorbed on gold. The molecules experience a thickness-dependent reorientation, and a 2D growth mode with molecular stepped terraces is achieved adopting low deposition rates. The obtained results are discussed in terms of their impact on field effect devices, also clarifying why the use of substrate/contact treatments, decoupling PDI-8CN2 molecules from the substrate/contacts, is beneficial for such devices. Our results also suggest that perylene diimide derivatives with CN bay-functionalization are very promising candidates for single-molecule electronic devices.

Research paper thumbnail of Perylene diimides functionalized with N-thiadiazole substituents: Synthesis and electronic properties in OFET devices

Organic Electronics, 2012

Abstract Two new perylene diimide derivatives N, N′-bis (5-tridecyl-1, 3, 4-thiadiazol-2-yl) pery... more Abstract Two new perylene diimide derivatives N, N′-bis (5-tridecyl-1, 3, 4-thiadiazol-2-yl) perylene-3, 4, 9, 10-tetracarboxylic 3, 4: 9, 10-diimide (PDI-T1) and N, N′-bis [5-(1-hexyl) nonyl-1, 3, 4-thiadiazol-2-yl] perylene-3, 4, 9, 10-tetracarboxylic 3, 4: 9, 10-diimide (PDI-T2), achieved by functionalizing the basic perylene molecular core at imide nitrogen with 1, 3, 4-thiadiazole rings, have been synthesized. Both these compounds make possible the fabrication of n-type organic thin-film transistors able to work in air, even when bare SiO 2 ...

Research paper thumbnail of Investigation on bias stress effects in n-type PDI8-CN2 thin-film transistors

Organic Electronics, 2012

Abstract In this contribution, we investigate the bias stress phenomenon in n-type PDI8-CN 2 thin... more Abstract In this contribution, we investigate the bias stress phenomenon in n-type PDI8-CN 2 thin-film transistors fabricated by evaporation on both bare and hexamethyldisyloxane (HMDS)-treated SiO 2 gate dielectrics. Since the morphological properties of PDI8-CN 2 films are poorly influenced by the SiO 2 treatment, all the differences observed in the DC electrical response and the bias stress performances of these devices can be mainly ascribed to the interface chemistry between the dielectric and the semiconductor. In long- ...

Research paper thumbnail of Photoluminescence dynamics in strontium titanate

Journal of Luminescence, 2009

ABSTRACT The recombination dynamics of electron–hole pairs of pure and n-doped strontium titanate... more ABSTRACT The recombination dynamics of electron–hole pairs of pure and n-doped strontium titanate (STO) bulk samples after an intense UV laser-pulse excitation has been investigated by collecting and analyzing the frequency- and time-resolved photoluminescence (PL) signal, as a function of the sample temperature. The observed PL decay is in the nanosecond time-scale and it shows a peculiar mixed kinetics. In particular, two decay channels are clearly singled-out: the faster one has a decay-time that is markedly dependent on the photo-excited carrier density and it is well described as a bimolecular recombination process, while the second slower channel shows an excitation-independent rate and follows an unimolecular law. The PL spectra show a considerable variation with temperature, with a previously unreported, pronounced difference between pure and doped samples emerging at high temperatures. A first discussion of the possible underlying mechanisms is attempted.

Research paper thumbnail of High mobility n-type organic thin-film transistors deposited at room temperature by supersonic molecular beam deposition

Applied Physics Letters, 2014

ABSTRACT In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylene... more ABSTRACT In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylenediimide (PDIF-CN2) organic thin-film transistors by Supersonic Molecular Beam Deposition. The devices exhibit mobility up to 0.2 cm2/V s even if the substrate is kept at room temperature during the organic film growth, exceeding by three orders of magnitude the electrical performance of those grown at the same temperature by conventional Organic Molecular Beam Deposition. The possibility to get high-mobility n-type transistors avoiding thermal treatments during or after the deposition could significantly extend the number of substrates suitable to the fabrication of flexible high-performance complementary circuits by using this compound.

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

Applied Physics Letters, 2012

In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transisto... more In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transistors by N,N'-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN 2 ). 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-8CN 2 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 HOMO peak towards higher binding energies.

Research paper thumbnail of Electronic properties of the n-type PDI8-CN 2 organic semiconductor at the interface with SiO 2 : addressing the role of adsorbed water molecules by means of optical second-harmonic generation

New Journal of Physics, 2014

ABSTRACT We investigate the interfacial electronic properties of N,N’-bis(n-octyl)-(1,7&1... more ABSTRACT We investigate the interfacial electronic properties of N,N’-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) organic semiconductor films grown on silicon dioxide (SiO2) by polarization-resolved second harmonic generation optical spectroscopy. The analysis shows a non-uniform distribution of charge carriers in PDI8-CN2, whose spatial profile is affected by hydrophobic passivation of SiO2 surfaces by hexamethyldisilazane. An interpretation model strengthened by photoluminescence analysis is developed, based on the presence of the net charge localized at the SiO2 surface and on consequent charge redistribution in the organic semiconductor. Considerations are expounded suggesting a common and ‘universal’ mechanism for the bias stress effect in p-channel and n-channel organic field-effect transistors, related to proton migration toward SiO2 gate dielectrics.

Research paper thumbnail of Contact-free probing of interfacial charging and Debye-like charge screening in SiO$_2$/PDI8-CN$_2$ systems by optical second harmonic generation

Investigation of the interfacial electronic properties of N,N'-bis(n-octyl)-(1,7&1,6)-dicyano... more Investigation of the interfacial electronic properties of N,N'-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) organic semiconductor films grown on silicon dioxide is performed by polarization-resolved second harmonic generation optical spectroscopy, pointing out a spatial region where charge carriers distribution in the semiconductor lacks inversion symmetry. By developing a model for nonlinear susceptibility in the framework of Debye-Huckel screening theory, we show that the experimental findings can be interpreted as resulting from the presence of a net charge localized at the silicon dioxide, accompanied by a non-uniform charge distribution in the organic semiconductor. Photoluminescence analysis further reinforces this scenario. Reduction-oxidation reactions involving PDI8-CN2 and water molecules are invoked as physical origin of the localized charge. The work outlines a sensitive tool to probe the total charge localized at buried semiconductor/d...

Research paper thumbnail of Chemisorption, Morphology, and Structure of a n-Type Perylene Diimide Derivative at the Interface with Gold: Influence on Devices from Thin Films to Single Molecules

Chemistry - A European Journal, 2015

We have investigated thin films of a perylene diimide derivative with a cyano-functionalized core... more We have investigated thin films of a perylene diimide derivative with a cyano-functionalized core (PDI-8CN2) deposited on Au(111) single crystals from the monolayer to the multilayer regime. We found that PDI-8CN2 is chemisorbed on gold. The molecules experience a thickness-dependent reorientation, and a 2D growth mode with molecular stepped terraces is achieved adopting low deposition rates. The obtained results are discussed in terms of their impact on field effect devices, also clarifying why the use of substrate/contact treatments, decoupling PDI-8CN2 molecules from the substrate/contacts, is beneficial for such devices. Our results also suggest that perylene diimide derivatives with CN bay-functionalization are very promising candidates for single-molecule electronic devices.

Research paper thumbnail of Perylene diimides functionalized with N-thiadiazole substituents: Synthesis and electronic properties in OFET devices

Organic Electronics, 2012

Abstract Two new perylene diimide derivatives N, N′-bis (5-tridecyl-1, 3, 4-thiadiazol-2-yl) pery... more Abstract Two new perylene diimide derivatives N, N′-bis (5-tridecyl-1, 3, 4-thiadiazol-2-yl) perylene-3, 4, 9, 10-tetracarboxylic 3, 4: 9, 10-diimide (PDI-T1) and N, N′-bis [5-(1-hexyl) nonyl-1, 3, 4-thiadiazol-2-yl] perylene-3, 4, 9, 10-tetracarboxylic 3, 4: 9, 10-diimide (PDI-T2), achieved by functionalizing the basic perylene molecular core at imide nitrogen with 1, 3, 4-thiadiazole rings, have been synthesized. Both these compounds make possible the fabrication of n-type organic thin-film transistors able to work in air, even when bare SiO 2 ...

Research paper thumbnail of Investigation on bias stress effects in n-type PDI8-CN2 thin-film transistors

Organic Electronics, 2012

Abstract In this contribution, we investigate the bias stress phenomenon in n-type PDI8-CN 2 thin... more Abstract In this contribution, we investigate the bias stress phenomenon in n-type PDI8-CN 2 thin-film transistors fabricated by evaporation on both bare and hexamethyldisyloxane (HMDS)-treated SiO 2 gate dielectrics. Since the morphological properties of PDI8-CN 2 films are poorly influenced by the SiO 2 treatment, all the differences observed in the DC electrical response and the bias stress performances of these devices can be mainly ascribed to the interface chemistry between the dielectric and the semiconductor. In long- ...

Research paper thumbnail of Photoluminescence dynamics in strontium titanate

Journal of Luminescence, 2009

ABSTRACT The recombination dynamics of electron–hole pairs of pure and n-doped strontium titanate... more ABSTRACT The recombination dynamics of electron–hole pairs of pure and n-doped strontium titanate (STO) bulk samples after an intense UV laser-pulse excitation has been investigated by collecting and analyzing the frequency- and time-resolved photoluminescence (PL) signal, as a function of the sample temperature. The observed PL decay is in the nanosecond time-scale and it shows a peculiar mixed kinetics. In particular, two decay channels are clearly singled-out: the faster one has a decay-time that is markedly dependent on the photo-excited carrier density and it is well described as a bimolecular recombination process, while the second slower channel shows an excitation-independent rate and follows an unimolecular law. The PL spectra show a considerable variation with temperature, with a previously unreported, pronounced difference between pure and doped samples emerging at high temperatures. A first discussion of the possible underlying mechanisms is attempted.

Research paper thumbnail of High mobility n-type organic thin-film transistors deposited at room temperature by supersonic molecular beam deposition

Applied Physics Letters, 2014

ABSTRACT In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylene... more ABSTRACT In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylenediimide (PDIF-CN2) organic thin-film transistors by Supersonic Molecular Beam Deposition. The devices exhibit mobility up to 0.2 cm2/V s even if the substrate is kept at room temperature during the organic film growth, exceeding by three orders of magnitude the electrical performance of those grown at the same temperature by conventional Organic Molecular Beam Deposition. The possibility to get high-mobility n-type transistors avoiding thermal treatments during or after the deposition could significantly extend the number of substrates suitable to the fabrication of flexible high-performance complementary circuits by using this compound.

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

Applied Physics Letters, 2012

In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transisto... more In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transistors by N,N'-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN 2 ). 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-8CN 2 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 HOMO peak towards higher binding energies.