Emmanuel Jacques

Epoxy Based Ink as Versatile Material for Inkjet-Printed Devices.

Drop on Demand inkjet printing is an attractive method for device fabrication. However, the reliability of the key printing steps is still challenging. This explains why versatile functional inks are needed. Epoxy based ink described in this study could solve this critical issue because it can be printed with low drawbacks (satellites droplets, long-lived filaments, etc.). Moreover, a wide concentration range of solute allows the fabrication of films from thin to high aspect ratio. Optimizing experimental parameters (temperature, overlap) and ink composition (single or cosolvent) is useful to tune the film profile. As a result, many shapes can be obtained such as donuts or hemispherical caps for a droplet and smooth or wavy shape for a thin film. This study demonstrates that epoxy based versatile ink can be used in numerous fields of applications (organic electronics, optics, sensors, MEMS, etc.). To prove this assertion, organic field effect transistors and light emitting films have been fabricated.

The structure–property relationship study of electron-deficient dihydroindeno[2,1-b]fluorene derivatives for n-type organic field effect transistors

A bridged syn triphenylene derivative, namely 5,7-dihydroindeno[2,1-b]fluorene, functionalized with dicyanovinylene units (2,1-b)-IF(C(CN)2)2 has been designed, synthesized and characterized. Its optical and electrochemical properties have been carefully studied through a combined experimental and theoretical approach and compared to those of three other structurally related dihydro[2,1-b]indenofluorene derivatives bearing methylenes, (2,1-b)-IF, carbonyls, (2,1-b)-IF(O)2, or both carbonyl and dicyanovinylene, (2,1-b)-IF(O)(C(CN)2) on the bridgeheads. (2,1-b)-IF(C(CN)2)2, which possesses a very low LUMO level, ca. −3.81 eV, has been successfully used as an active layer in n-channel OFETs using an epoxy based photoresist SU-8 as the gate insulator. (2,1-b)-IF(C(CN)2)2 based n-channel OFETs show promising properties such as a low threshold voltage functioning of 7.2 V (low gate–source and drain–source voltages), a high ratio between the on and the off currents (6.3 × 105), interesting subthreshold swing (SS = 2.16) and electron mobility (>10−3 cm2 V−1 s−1) and excellent stability under electrical stress. This electrical stability has allowed the incorporation of (2,1-b)-IF(C(CN)2)2 based n-channel OFETs in an integrated circuit. Thus, as a proof of concept, pseudo CMOS inverters made of n-type (2,1-b)-IF(C(CN)2)2-based OFETs have been fabricated and characterized highlighting the potential of this new family of materials.

An electron deficient dicyanovinylene-ladder-type pentaphenylene derivative for n-type organic field effect transistors

A bridged pentaphenylene derivative functionalized with dicyanovinylene units LPP([double bond, length as m-dash]C(CN)2)2 has been designed, synthesized and characterized. The optical and electrochemical properties have been carefully studied through a combined experimental and theoretical approach and compared with those of two pentaphenylene derivatives bearing methylenes (LPP) or carbonyl (LPP([double bond, length as m-dash]O)2) on the bridgeheads. LPP([double bond, length as m-dash]C(CN)2)2 which possesses a very low LUMO level, ca. −4.02 eV, has been successfully used as an active layer in n-channel OFETs using the epoxy based photoresist SU-8 as a gate insulator. LPP([double bond, length as m-dash]C(CN)2)2 based n-channel OFETs show low voltage functioning (low gate-source and drain-source voltages), high ratio between the on and the off currents (2 × 105), interesting subthreshold swing (S = 1) and excellent stability under electrical stress and in a nitrogen atmosphere. More importantly, we have also shown that LPP([double bond, length as m-dash]C(CN)2)2 based n-channel OFETs present an excellent environmental stability. This work is to the best of our knowledge the first report on bridged pentaphenylene-based semiconductors in n-type OFETs and highlights the potential of such type of material to provide air stable OFETs.

Electron-Rich 4-Substituted Spirobifluorenes: Toward a New Family of High Triplet Energy Host Materials for High-Efficiency Green and Sky Blue Phosphorescent OLEDs

We report herein a detailed structure-properties relationship study of the first examples of electron-rich 4-substituted spirobifluorenes for organic electronic applications, namely, 4-phenyl-N-carbazole-spirobifluorene (4-PhCz-SBF) and 4-(3,4,5-trimethoxyphenyl)-spirobifluorene (4-Ph(OMe)3-SBF). The incorporation of the electron-rich moieties in the ortho position of the biphenyl linkage (position C4) induces unique properties, very different from those previously described in the literature for this family of semiconductors. Both dyes can be readily synthesized, possess high triplet energies and excellent thermal stability, and their HOMO energy levels are highly increased compared to those of other 4-substituted SBFs. We also provide in this work the first rationalization of the peculiar fluorescence of 4-substituted SBFs. Finally, the present dyes have been successfully incorporated as host in green and blue phosphorescent organic light-emitting diodes with high performance either for the green (EQE of 20.2%) or the blue color (EQE of 9.6%). These performances are, to the best of our knowledge, among the highest reported to date for 4-substituted SBF derivatives.

Conformal Electronics Wrapped Around Daily Life Objects Using an Original Method: Water Transfer Printing

The water transfer printing method is used to transfer patterned films on random three-dimensional objects. This industrially viable technology has been demonstrated to intimately wrap metallic and polymeric films around different materials. This method avoids the use of rigid substrate during the transfer step. Patterns can be transferred to objects without folds even when holed, addressing a challenging issue in the field of conformal electronics. This technique allows high film bending properties to be reached. This promising method enables us to integrate large-area films onto daily life objects. A bent capacitive touchpad is fabricated showing the potential applications of this technology.

Electrical behavior of MIS devices based on Si nanoclusters embedded in SiOxNy and SiO2 films

We examined and compared the electrical properties of silica (SiO2) and silicon oxynitride (SiOxNy) layers embedding silicon nanoclusters (Sinc) integrated in metal-insulator-semiconductor (MIS) devices. The technique used for the deposition of such layers is the reactive magnetron sputtering of a pure SiO2 target under a mixture of hydrogen/argon plasma in which nitrogen is incorporated in the case of SiOxNylayer. Al/SiOxNy-Sinc/p-Si and Al/SiO2-Sinc/p-Si devices were fabricated and electrically characterized. Results showed a high rectification ratio (>104) for the SiOxNy-based device and a resistive behavior when nitrogen was not incorporating (SiO2-based device). For rectifier devices, the ideality factor depends on the SiOxNylayer thickness. The conduction mechanisms of both MIS diode structures were studied by analyzing thermal and bias dependences of the carriers transport in relation with the nitrogen content.

Polycrystalline Silicon Nanowires Synthesis Compatible With CMOS Technology for Integrated Gas Sensing Applications

Polysilicon nanowires are synthesized following a classical top-down approach using conventional UV lithography technique fully compatible with the existing silicon complementary metal-oxide-semiconductor technology. N- and P-type in situ doping of these nanowires is controlled over a large range of doping levels and the electrical properties of these nanowires are analyzed. The results show that resistivity dependence with the doping level is both related to the nanowire size-dependent structural quality and doping specie. Charged gas species (ammonia) sensitivity of these nanowires has also been studied. In addition, the feasibility of N- and P-channel polysilicon nanowire transistors is demonstrated.

Direct Integration of Red-NIR Emissive Ceramic-like AnM6Xi8Xa6 Metal Cluster Salts in Organic Copolymers Using Supramolecular Interactions

Hybrid nanomaterials made of inorganic nanocomponents dispersed in an organic host raise an increasing interest as low-cost solution-processable functional materials. However, preventing phase segregation while allowing a high inorganic doping content remains a major challenge, and usual methods require a functionalization step prior integration. Herein, we report a new approach to design such nanocomposite in which ceramic-like metallic nanocluster compounds are embedded at 10 wt % in organic copolymers, without any functionalization. Dispersion homogeneity and stability are ensured by weak interactions occurring between the copolymer lateral chains and the nanocluster compound. Hybrids could be ink-jet printed and casted on a blue LED. This proof-of-concept device emits in the red-NIR area and generates singlet oxygen, O2 (1 Δg), of particular interest for lights, display, sensors or photodynamic based therapy applications.

MOSFET on Thin Si Diaphragm as Pressure Sensor

This paper presents original designs of pressure sensor combining thin membrane micro-technology with a simple MOSFET (Metal Oxide Silicon Field Effect Transistor) detection. The proposed microelectronic process (fig. 1) is quite simple and could lead to the development of low pressure sensor. The sensor designs are based on square and cross shaped P-channel MOSFET directly integrated on the diaphragm. Electrical characterization of the FET-sensor shows wide drift of the characteristics in response to mechanical strain on the membrane. The shift importance is shown to depend on the different designs used to fabricate the FET-sensors.

High rectifying behavior in Al/Si nanocrystal-embedded SiOxNy/p-Si heterojunctions

We examine the electrical properties of MIS devices made of Al/Si nanocrystal-SiOxNy/p Si. The J V characteristics of the devices present a high rectifying behavior. Temperature measurements show that the forward current is thermally activated following the thermal diffusion model of carriers. At low reverse bias, the current is governed by thermal emission amplified by Poole-Frenkel effect of carriers from defects located in the silicon nanocrystals/SiOxNy interfaces, whereas tunnel conduction in silicon oxynitride matrix dominates at high reverse bias. Devices exhibit a rectification ratio >104 for the current measured at V=  1V. Study reveals that thermal annealing in forming gas (H2/N2) improves electrical properties of the devices due to the passivation of defects.