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Phosphorus Based Ceramics for Positive Electrode Synthesis and Characterization

Journal of Modern Physics 2014年第15期5卷 1459-1466页

作者： diouma.kobor Abdou Kadri Diallo Modou Tine Laboratoire de Chimie et de Physique des Matériaux (LCPM) Département de Physique University Assane Seck of Ziguinchor Ziguinchor Senegal

Historically, the LiCoO2 is the most used as active material for battery positive electrode because of its great potential (3.7 - 4.2 V), its interesting specific capacity (150 mA·h·g-1) and its excellent life cycle [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003300390038003500370036003700340032000000 . However, its toxicity, the cobalt cost and its structural instability oriented research towards new materials more stable that can replace it. In another context, hybrid, electrical vehicles and communication (computers and mobile phones...) have increased the scientific and technological research for new materials capable of storing and return energy through a system called accumulator. And research has identified the phosphate olivine structure as the most prolific ceramic material for positive electrode. LiFePO4 is a promising cathode material for Lithium-ion batteries. It provides high thermal stability and is synthesized using low cost materials. Unfortunately LiFePO4 suffers from a low electrical conductivity, which is harmful to its electrochemical performance. Decreasing the particle size, coating the particles with carbon or doping with metal atoms can increase the conductivity of the material. In this paper, we present the synthesis, physico-chemical and electrical characterization of lithium and iron doped Al-phosphorrus-based ceramic. The NPK Fertiliser was used as Al and phosphorus precursors. The powder XRD spectrum shows a possible presence of LiFePO4 and Fe2(PO)3 in theheterostrcture. An important quantity of Al is found by EDX spectra which supposed that the most important based atom is Aluminum and not Phosphorus. This can explain the increase of the conductivity value 102 times more important than those found in the literature for LiFePO4.

关键词： Characterization X-Ray Diffraction EDX Ceramic Positive Electrode

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Determination of the Vibro-Rotational Constants, the Dipole Moment’s Function and the Intensities of the HTO’s ν1 (ν3 by Usual Convention) Band

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Journal of Modern Physics 2012年第12期3卷 1945-1957页

作者： Modou Tine diouma.kobor Ibrahima Sakho Laurent Coudert Laboratoire de Chimie et de Physique des Matériaux (LCPM) Université de Ziguinchor Ziguinchor Sénégal Laboratoire Inter-Universitaire des Systèmes Atmosphériques Créteil France

In the first part of this paper, an analysis of the high-resolution spectrum of the HTO molecule ν1(ν3) band, from 3630 to3950 cm–1, was undertaken. The rotational transition of this band was assigned using combination differences. Their wavenumbers were analyzed with a least squares fit program in order to obtain spectroscopic constants. A perturbed state has been evidenced. In the second part, with a view towards building a spectroscopic data base, a calculation of the dipolar momentum function was undertaken.

关键词： Infrared Spectrum Energy Level Rays Intensities Perturbation

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Electrical Instability in Pentacene Transistors with Mylar and PMMA/Mylar Gate Dielectrics Transferred by Lamination Process

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Journal of Applied Mathematics and Physics 2016年第7期4卷 1202-1209页

作者： Abdou Karim Diallo Abdoul Kadri Diallo diouma.kobor Marcel Pasquinelli Departement de Physique Appliquée Université de Gaston Berger Saint Louis Sénégal Laboratoire de Chimie et de Physique des Matériaux (LCPM) Université Assane Seck de Ziguinchor Ziguinchor Sénégal Aix Marseille Université Domaine Universitaire de Saint Jér&ocircme Marseille France

This study deals with electrical instability under bias stress in pentacene-based transistors with gate dielectrics deposited by a lamination process. Mylar film is laminated onto a polyethylene terephthalate (PET) substrate, on which aluminum (Al) gate is deposited, followed by evaporation of organic semiconductor and gold (Au) source/drain contacts in bottom gate top contact configuration (Device 1). In order to compare the influence of the semiconductor/dielectric interface, a second organic transistor (Device 2) which is different from the Device 1 by the deposition of an intermediate layer of polymethyl methacrylate (PMMA) onto the laminated Mylar dielectric and before evaporating pentacene layer is fabricated. The critical device parameters such as threshold voltage (VT), subthreshold slope (S), mobility (μ), onset voltage (Von) and Ion/Ioff ratio have been studied. The results showed that the recorded hysteresis depend on the pentacene morphology. Moreover, after bias stress application, the electrical parameters are highly modified for both devices according to the regimes in which the transistors are operating. In ON state regime, Device 1 showed a pronounced threshold voltage shift associated to charge trapping, while keeping the μ, Ioff current and S minimally affected. Regardless of whether Device 2 exhibited better electrical performances and stability in ON state, we observed a bias stress-induced increase of depletion current and subthreshold slope in subthreshold region, a sign of defect creation. Both devices showed onset voltage shift in opposite direction.

关键词： Organic Transistor Mylar Lamination Pentacene Bias Stress

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Mn Effect on Nonlinear and Structural Properties of <110>Oriented PZN-4.5PT Single Crystals

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Journal of Modern Physics 2012年第5期3卷 404-411页

作者： diouma.kobor Modou Tine Abdelowahed Hajjaji Laurent Lebrun Daniel Guyomar Ecole Nationale des Sciences Appliquées d’El Jadida Laboratoire de Chimie et de Physique des Matériaux (LCPM) Département de Physique Université de Ziguinchor Laboratoire Génie Electrique et Ferroélectricité Institut National des Sciences Appliquées de Lyon

Ferroelectric single crystals Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) are promising full materials for non resonant or large bandwidth transducers due to the large values of their piezoelectric properties (d ij , k ij ) and their low mechanical quality factor (Q ij ). Many studies on oriented PZN-4.5PT single crystals were carried out but it is very difficult to find research findings on oriented Mn doped PZN-PT. Thus, investigations were made using XRD, Raman and EPR characterization for oriented PZN-4.5PT grown through the Flux method. Mn doping effect on structural, dielectric, mechanical and piezoelectric properties with two values of Mn percentage (1 and 2 mol%) are also reported in this paper. Through the XRD study, the lattice parameters of doped PZN-PT crystals are slightly increased compared to the undoped one but the Mn didn’t change its structure. The room temperature dielectric permittivity along direction is about 1572 and 1626 (respectively 1% and 2% Mn doped crystals) which are much lower than that of the undoped PZN-4.5PT (2553). The remnant polarization and coercive field of oriented doped crystal measured at 1 KHz are respectively 30 μC/cm2 and 4.30 kV/cm (PZN-4.5PT), 32 μC/cm2 and 6.10 kV/cm (PZN-4.5PT + 1% Mn) and 28 μC/cm2 and 7.30 kV/cm (for the 2% Mn doped crystal). The mechanical quality factor Qm changed from 139 to 441 respectively for the pure and 1% Mn doped single crystals at room temperature while it decreases slightly to 336 for the 2 mol% Mn doped.

关键词： XRD Dielectric Piezoelectric EPR Raman Spectroscopy

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Optimization of 6,13Bis(triisopropylsilylethynyl)pentacene (TIPS-Pentacene) Organic Field Effect Transistor: Annealing Temperature and Solvent Effects

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Materials Sciences and Applications 2018年第11期9卷 900-912页

作者： Diallo Abdoul Kadri Diallo Abdou Karim Mané Seck kobor diouma Pasquinelli Marcel Laboratoire de Chimie et de Physique des Matériaux (LCPM) Assane Seck University Ziguinchor Senegal Gaston Berger University Department of Applied Physics Saint Louis Senegal OPTO-PV Group/Institut Matériaux Microélectronique Nanosciences de Provence (IM2NP) Marseille France

In this contribution, we report on the effect of solvents with different boiling points and annealing temperature on the performance of TIPS-pentacene transistors. Several solvents have been used for TIPS-pentacene thin film processing: toluene, chlorobenzene and tetrahy-drofuran. To study the influence of solvent and temperature;the electrical parameters of TIPS-pentacene field effect transistor were measured. The highest values of mobilities were 7.1 × 10-3 cm2·V-1·s-1, 4.5 × 10-3?cm2·V-1·s-1 and 1.43 × 10-3 cm2·V-1·s-1 respectively for TIPS-pentacene field effect transistor using chlorobenzene, toluene and tetrahydrofuran and annealed respectively at 120°C, 150°C and 120°C. We have correlated these electrical performances with AFM images in order to point out the role of morphological properties. It is found that the grain size, and roughness highly affect the electrical parameters.

关键词： Tips-Pentacene Transistor Solvent Annealing Temperature

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Dielectric and Ferroelectric Properties of PZN-4.5PT Nanoparticles Thin Films on Nanostructured Silicon Substrate for Ferrophotovoltaic and Energy Storage Application

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Journal of Modern Physics 2019年第6期10卷 613-623页

作者： Rémi Ndioukane Moussa Touré diouma.kobor Laurence Motte Jeanne Solard Laurent Lebrun Laboratoire de Chimie et de Physique des Matériaux (LCPM) University Assane Seck of Ziguinchor Ziguinchor Sénégal Laboratory for Vascular Translational Science (LVTS) University Paris 13 Paris France Centrale de Proximité en Nanotechnologies de Paris Nord Paris France Laboratoire Génie Electrique et Ferroélectricité Institut National des Sciences Appliquées de Lyon Villeurbanne France

The integration of ferroelectric materials as thin films has attracted considerable attention these last years thanks to their outstanding performances that allow considering new features for the realization of photovoltaic devices. Our study focuses on investigating structural, dielectric and ferroelectric properties of undoped and Mn doped PZN-4.5PT nanoparticles thin films on Silicon substrate. We fabricate very stable PZN-4.5PT nanoparticles thin films deposited on nanostructured silicon substrate with giant relative dielectric permittivity of 2.76 × 104 and 17.7 × 104 for respectively the undoped and Mn doped thin films. These values are very large compared to those found in single crystals and might be explained by the influence of the gel in which nanoparticles were dispersed. The SEM images show the crystallization of new hexagonal phases on the film surface probably coming from interaction between Si and the gel. The hysteresis loops permitted to determine the spontaneous polarization (Ps), remnant polarization (Pr) and coercive field Ec which are equal to 11.73 μC/cm2, 10.20 μC/cm2 and 20 V/cm, respectively for the undoped nanoparticles thin film and 22.22 μC/cm2, 19.32 μC/cm2 and 20 V/cm respectively for the Mn doped one. These values are high and correspond to the best ones found in literature compared to typical ferroelectric thin films.

关键词： PZN-PT Thin Film Ferroelectric Perovskite Nanoparticles Gel

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Fabrication and Characterization of PZN-4.5PT Inorganic Perovskites Nanoparticles Thin Films Deposited on P-Type Silicon Substrate

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Journal of Modern Physics 2018年第2期9卷 259-272页

作者： Rémi Ndioukane Moussa Touré diouma.kobor Laurence Motte Marcel Pasquinelli Jeanne Solard Laboratoire de Chimie et de Physique des Matériaux (LCPM) Université Assane Seck de Ziguinchor Ziguinchor Sénégal Laboratory for Vascular Translational Science (LVTS) Université Paris 13 Bobigny France Institutut Matériaux Microélectronique Nanosciences de Provence (IM2NP) Aix-Marseille Université Marseille France Centrale de Proximité en Nanotechnologies de Paris Nord Institut Universitaire de Technologie de Villetaneuse Paris France

This work involves an investigation of nanostructures, microelectronic properties and domain engineering of nanoparticles thin layers of Pb(Zn1/ 3Nb2/3)O3-PbTiO3 (PZN-PT) ferroelectric single crystals deposited on nanostructured silicon substrate. In this study, devices made from PZN-4.5PT nanoparticles thin films successfully deposited on silicon substrate have been studied and discussed. SEM images show the formation of local black circles and hexagonal shapes probably due to the nucleation of a new Si-gel component or phase induced by annealing. Micro Xray Fluorescence mapping shows that the high values of Si and B atoms (≅7 and 4 normalized unit respectively) can be explained by the fact that the substrate is p-type silicon. The most interesting result of optical measurements is the very good absorption for all the thin films in UV, Visible and NIR regions with values from 70% to 90% in UV, from 75% to 93% in Visible and NIR. Tauc plots present particularities (rarely encountered behavior) with different segments or absorption changes showing the presence of multiple band gaps coming from the heterogeneity of the thin films (nanowires, gel and nanoparticles). Their values are 1.9 and 2.8 eV for DKRN-Gel, 2.1 and 3.1 eV for DKRN-UD and 2.1 and 3.2 eV for DKRN-D) corresponding respectively to the band gap of nanowires and that of the gel while the last ones correspond to the undoped and doped nanoparticles (3.1 and 3.2 eV respectively).

关键词： Nanostructures Perovskite Nanoparticles Silicon Thin Layer Band Gap

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New Procedure to Obtain Specific and High Absorbent Silicon Nanotextures: Inverted Pyramids, Cubic Nano-Microholes, Spiroconical Nano-Microholes and Rhombohedral-Stared Nanosheet Bouquets (Nanobuckets)

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Journal of Modern Physics 2021年第9期12卷 1267-1280页

作者： Ndeye Coumba Y. Fall Moussa Touré Remi Ndioukane Abdoul Kadri Diallo diouma.kobor Marcel Pasquinelli Laboratoire de Chimie et de Physique des Matériaux (LCPM) Université Assane Seck de Ziguinchor Ziguinchor Senegal Aix Marseille Université Domaine Universitaire de Saint Jér&ocirc me Marseille France

The present work relates to a process for silicon surface texturing for preparing large-area, silicon nanotextures on silicon substrates at ambient temperature by assisted chemical etching. A novel strategy comprises of two fundamental steps (metal-assisted chemical etching (MACE) and solution post-treatment) of using the silver catalyst to obtain specific nano- or micro-textures. The strategy is based on metal-induced (Ag) local oxidation and dissolution of a silicon substrate in three different concentrations of aqueous fluoride solution with the post-treatment solution. The etching technique is dependent on the etching time and concentration of aqueous fluoride solution. Therefore, detailed scanning electron microscopy observations reveal specifics shapes as inverted pyramids, cubic nano-microholes, spiroconical nano-microholes and rhombohedral-stared nanosheet bouquets (called Nanobukets), obtained for the first time on a (100) silicon surface by this new variant of the MACE method named Double Etching Method (DEM). Silicon nanostructures are used in many nanotechnology applications such as nano-microelectronics, optoelectronics or biomedical applications. UV-Visible spectrometry measurements carried out made it possible to obtain the lowest reflectance and highest absorbance values who are 3% and 97%, respectively for the rhomboedral-stared nanosheet bouquets on (100) crystalline silicon substrates in the UV-visible-NIR wavelength range from 300 to 1200 nm.

关键词： Silicon Nanotextures New Procedure Etching Reflectance Absorption

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Influence of Temperature and Pentacene Thickness on the Electrical Parameters in Top Gate Organic Thin Film Transistor

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Advances in Materials Physics and Chemistry 2017年第3期7卷 85-98页

作者： Abdoul Kadri Diallo El Hadji Babacar Ly Diene Ndiaye diouma.kobor Marcel Pasquinelli Abdou Karim Diallo Laboratoire de Chimie et de Physique des Materiaux(LCPM) Universite Assane Seck de ZiguinchorZiguinchorSenegal Departement de physique appliquee Universite de Gaston BergerSaint LouisSenegal Aix Marseille Universite Domaine Universitaire de Saint JeromeMarseilleFrance

In this contribution, we report on the effect of pentacene thickness and temperature on the performance of top gate transistors. We first investigated the temperature dependence of the transport properties in the temperature range of 258 K - 353 K. The electrical characteristics showed that the threshold voltage (VT) and the onset voltage (Von) remain unchanged. However, the subthreshold current (Ioff), the on-current (Ion) and the field effect mobility (μ) are highly affected with a slight deterioration of subthreshold slope. We observed Arrhenius-like behavior suggesting a thermally activated mobility with an activation energy EA = 68 meV. Moreover the dependence of the charge carrier mobility on the organic semiconductor thickness has also been studied. The mobility decreased as the pentacene thickness increases whereas the threshold voltage and Ioff current remain minimally affected. In order to understand the transport properties and in view to put in light morphology peculiarities of pentacene, AFM images were performed. It turns out that the pentacene grain sizes are smaller and disorganized as the film thickness increases, and charge carriers are more prone to be trapped, leading to decrease the field effect mobility and the Ion current. The devices were also tested under bias stress and the transistors with low thicknesses exhibited a relatively good electrical stability compared to those with high pentacene thicknesses. This work points out the influence of temperature, semiconductor thickness and bias stress effect on the device performance and stability of transistor using top gate configuration.

关键词： Pentacene Organic Transistor Top Gate Thin Film Transistor Bias Stress Parylene

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Dielectric and Mechanical Nonlinear Behavior of Mn Doped PMN-35PT Ceramics

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Journal of Modern Physics 2010年第4期1卷 211-216页

作者： diouma.kobor Abdelowahed Hajjaji Jose E. Garcia Rafel Perez Alfons Albareda Laurent Lebrun Daniel Guyomar 不详

This paper presents an investigation on dielectric and mechanical nonlinear properties in Mn-doped PMN-35PT ceramics. The structural study of the ceramics verifies that the 1% mol Mn doped PMN-35PT is a pure perovskite phase with a tetragonal symmetry. SEM micrograph shows the same microstructural mor- phology of an undoped ceramic. From the EPR spectra, it has been concluded that the major part of Mn is present in Mn2+ rather than in Mn4+ form. The addition of Mn2+ ions acts on the dielectric, piezoelectric and mechanical properties by decreasing the relative dielectric permittivity (3800 to 2074), the dielectric losses (0.60 to 0.53), the piezoelectric coefficient d33 (650 to 403 pC/N), and increasing the mechanical quality fac- tor Qm (78 to 317). It was found that in Mn2+ doped ceramics the dielectric response can not be described by Rayleigh law. This result can be understood taking into account that reversible motion of the domain wall is a relevant contribution to response of this material.

关键词： Piezoelectrics Ceramics Nonlinearity Dielectric properties Mechanical Properties PMN-PT

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