- Professor: solid state physics and semiconductoredit
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Abstract. Samples of p-type porous GaAs was obtained by electrochemical anodization of (100) oriented p-type GaAs. The formation of porous structure has been confirmed by Raman spectroscopy and scanning electron microscopy investigations.... more
Abstract. Samples of p-type porous GaAs was obtained by electrochemical anodization of (100) oriented p-type GaAs. The formation of porous structure has been confirmed by Raman spectroscopy and scanning electron microscopy investigations. The low-frequency Raman shift of the peaks conditioned by the main optical phonons was observed in the Raman spectra of the porous GaAs. Estimation of the size of nanocryslallites in porous GaAs both by Raman shift and scanning electron microscopy gives approximately the same values and was about 10-20 nm. Photoluminescence investigations of porous GaAs exhibit the presence of two infrared and one visible bands.
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A dysprosium oxide (Dy2O3) gate dielectric layer was deposited by electron beam deposition under ultra-vacuum onto p-GaAs (100) substrate. Morphological characterization was determined based on atomic force microscopy images. The x-ray... more
A dysprosium oxide (Dy2O3) gate dielectric layer was deposited by electron beam deposition under ultra-vacuum onto p-GaAs (100) substrate. Morphological characterization was determined based on atomic force microscopy images. The x-ray diffraction results indicate that the Dy2O3 oxide is polycrystalline. The interface properties of the (Au/Co)/Dy2O3/p-GaAs metal oxide semiconductor (MOS) capacitor was investigated by measuring the capacitance–voltage (C–V) and conductance–voltage (G/w–V) in the temperature and frequency ranges 80-500 K and 50 Hz to 1 MHz, respectively. Both the capacitance and conductance of the MOS capacitor are frequency- and temperature-dependent. The interface state density (Nss-V) distribution profile obtained from high-frequency–low-frequency (CHF–CLF) capacitance measurement indicates a peak in the depletion zone. In addition, the interface state density (Nss) value determined by the Hill-Coleman method of the (Au/Co)/Dy2O3/p-GaAs (MOS) capacitor was decreased with increasing temperature. The obtained results show that the interface states are important parameters that strongly influence the electric parameters of the studied MOS capacitor. The alternating current conductivity is strongly dependent on the applied frequency, voltage and temperature. The conductance against reciprocal temperature plots reveal a sequence of two activation energies of 20 meV and 86 meV at low and high temperature, respectively. Schottky emission and Fowler-Nordheim tunneling are the conduction mechanisms in the oxide layer, according to an investigation of leakage current characteristics.
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We present the optical properties of sulphide cadmium (CdS) deposited, by vacuum evaporation technique, on porous p-type GaAs substrates with different porosities and compared to that deposited on glass and nominal p-type GaAs substrates.... more
We present the optical properties of sulphide cadmium (CdS) deposited, by vacuum evaporation technique, on porous p-type GaAs substrates with different porosities and compared to that deposited on glass and nominal p-type GaAs substrates. The CdS layer deposited on glass substrate exhibit average transmittance about 62% in the visible region and very sharp absorption edge at 495 nm. The room
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... Actuators, B, 47 (1998), p. 43. [16] R. Mlika, H. Ben Ouada, R. Ben Chaabane, M. Gamoudi, G. Guillaud, N. Jaffrezic-Renault and R. Lamartine. Electrochem. Acta, 43-8 (1998), p. 841. [17]Hayley Lam., National Nanofabrication Users... more
... Actuators, B, 47 (1998), p. 43. [16] R. Mlika, H. Ben Ouada, R. Ben Chaabane, M. Gamoudi, G. Guillaud, N. Jaffrezic-Renault and R. Lamartine. Electrochem. Acta, 43-8 (1998), p. 841. [17]Hayley Lam., National Nanofabrication Users Network, UCSB Nanofabrication Facility.. ...
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In the present work we have investigated the initial stage of InAs layer grown on porous GaAs (π-GaAs) substrate by using reflection high-energy electron diffraction (RHEED) and low temperature photoluminescence (PL). RHEED measurements... more
In the present work we have investigated the initial stage of InAs layer grown on porous GaAs (π-GaAs) substrate by using reflection high-energy electron diffraction (RHEED) and low temperature photoluminescence (PL). RHEED measurements show that the 2D–3D growth mode transition appears after a deposition of 4.2 atomic monolayer (ML) of InAs, which is higher than that deposited on nominal GaAs
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Abstract We report on experimental and theoretical study of current-voltage characteristics of C/Si-doped GaAs tunnel diode. For the investigation of the experimental data, we take into account the band-gap narrowing (BGN) effect due to... more
Abstract We report on experimental and theoretical study of current-voltage characteristics of C/Si-doped GaAs tunnel diode. For the investigation of the experimental data, we take into account the band-gap narrowing (BGN) effect due to heavily-doped sides of the tunnel diode. The BGN of the n- and p-sides of tunnel diode was measured by photoluminescence spectroscopy. The comparison between theoretical results and experimental data reveals that BGN effect enhances tunneling currents and hence should be considered to identify more accurately the different transport mechanisms in the junction. For C/Si-doped GaAs tunnel diode, we found that direct tunneling is the dominant transport mechanism at low voltages. At higher voltages, this mechanism is replaced by the rate-controlling tunneling via gap states in the forbidden gap.
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Abstract The dielectric properties of Al/Dy2O3/porous Si heterostructure were investigated in the temperature range 270–420 K by capacitance and conductance-frequency measurements. The G (f) characteristics were well described by the... more
Abstract The dielectric properties of Al/Dy2O3/porous Si heterostructure were investigated in the temperature range 270–420 K by capacitance and conductance-frequency measurements. The G (f) characteristics were well described by the modified law GAC = A1 fS1 + A2 fS2, and the results showed frequency dependent and evidence of two different behaviors in ac conductance. It was found that the Dy2O3 film exhibited a thermally activated conductance, i.e., G (T) = G0 exp (Ea/kBT), over a considerable temperature range. Activation energy is deduced from the variation of conductance with temperature using the Arrhenius relationship. The Arrhenius plot shows two activation energies revealing the presence of two distinct trap states in the chosen temperature range. The effect of temperature on series resistance (Rs) and interface state density (Nss) were investigated. Further, in order to gain an insight into the electric nature of the elaborated structure, the Cole-Cole diagrams are also investigated at different temperatures. Impedance analysis on the structure help to understand the contributions of electrical conductivity and interfacial polarization so, the Al/Dy2O3/porous Si heterostructure is accurately modeled as a two parallel elements (RC) network placed in series.
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The electrical properties of CaMn0.6Fe0.4O2.8 perovskite sample have been investigated, using complex impedance analysis in 102–5.22 × 106 Hz frequency range with varying temperature from 293 to 348 K. SEM micrograph shows that the sample... more
The electrical properties of CaMn0.6Fe0.4O2.8 perovskite sample have been investigated, using complex impedance analysis in 102–5.22 × 106 Hz frequency range with varying temperature from 293 to 348 K. SEM micrograph shows that the sample exhibits well-developed grains with average particle size of about 320 nm. Rietveld analysis of XRD pattern shows that sample crystallizes in the orthorhombic structure with Pnma space group. The total conductance curves of the sample are found to obey Jonscher power law G(ω) = GDC +Aωn with an increase of frequency exponent (n) as temperature increases. The activation energy deduced from the analysis of the conductance is about 0.19 eV. The imaginary part (Z″) of the impedance is characterized by the appearance of peak which shifts to higher frequencies with the increase of temperature. Such behavior shows the existence of a relaxation process in our system. The impedance study using Nyquist representation revealed the appearance of semicircular arcs and an equivalent circuit, R1 + (R2//C), has been proposed to explain the impedance results.
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Abstract This paper describes the electrical and dielectric characteristics for the first time of the high-k Dy 2 O 3 oxide film deposited on the porous GaAs substrate by electron beam deposition under ultra vacuum. Morphological... more
Abstract This paper describes the electrical and dielectric characteristics for the first time of the high-k Dy 2 O 3 oxide film deposited on the porous GaAs substrate by electron beam deposition under ultra vacuum. Morphological characterization is investigated by atomic force microscopy (AFM). The electrical and dielectric properties of Co/Au/Dy 2 O 3 /n-porous GaAs structure were studied in the temperature range of 80–500 K. The conductance and capacitance measurements were performed as a function of bias voltage and frequency. The dielectric constant (e′), dielectric loss (e″) and dielectric loss tangent (tanδ) of the structure are obtained from capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. These parameters are found to be strong functions of temperature and bias voltage. In the forward bias region, C–V plots show a negative capacitance (NC) behavior, e′–V plots for each temperature value take negative values as well. Such negative values of C correspond to the maximum of the conductance (G/ω). The negative capacitance values appear abnormal when compared to the conventional behavior of ideal Schottky barrier diode (SBD) and metal–oxide–semiconductor (MOS) structures. The following behavior of the C and e′ in the forward bias region has been explained with the minority-carrier injection and relaxation theory. From DC conductance study, electronic conduction is found to be dominated by thermally activated hopping at high temperature. Activation energy is deduced from the variation of conductance with temperature. The Nyquist plots exhibited single semi-circular arcs which were well fitted to an equivalent circuit.
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In this paper, we investigate the structural and photoluminescence properties of aqueous solution-processed ZnO/GaAs and ZnO/porous GaAs films.
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Abstract The paper considers control of an autonomous under-water vehicle (AUV) with a reduced number of actua-tors. A nonlinear model describing both the dynamics and the kinematics of an AUV is studied. A continu-ous periodic... more
Abstract The paper considers control of an autonomous under-water vehicle (AUV) with a reduced number of actua-tors. A nonlinear model describing both the dynamics and the kinematics of an AUV is studied. A continu-ous periodic time-varying feedback law is presented. It is ...
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ABSTRACT This paper addresses the problem of stabilizing and trajectory tracking control of a remotely operated vehicle (ROV-Observer) in the vertical plane. The underwater vehicle is not actuated in the pitch direction and cannot be... more
ABSTRACT This paper addresses the problem of stabilizing and trajectory tracking control of a remotely operated vehicle (ROV-Observer) in the vertical plane. The underwater vehicle is not actuated in the pitch direction and cannot be locally asymptotically stabilized by continuous feedbacks which are functions of the state only. In the present note, exponential convergence is obtained by considering time-varying feedbacks which are only continuous. Furthermore, using the backstepping technique and the tracking error dynamics, the system states are stabilized by forcing the tracking errors to an arbitrarily small neighborhood of zero.
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A particular structure of a four rotors mini-flying robot where two rotors are directional (X4 bidirectional rotors) is presented in this paper. The two internal degree of freedom leads to a transformation between the equivalent system of... more
A particular structure of a four rotors mini-flying robot where two rotors are directional (X4 bidirectional rotors) is presented in this paper. The two internal degree of freedom leads to a transformation between the equivalent system of the control-inputs and the rotor force-inputs which is not a diffeomorphism. This makes our system different from that of the classical flyer robot
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The tracking control problem of a parallel robot including the electrical actuator dynamics is addressed in the task space. For the electrically-actuated robots, we design a nonlinear control law for armature input voltages. The control... more
The tracking control problem of a parallel robot including the electrical actuator dynamics is addressed in the task space. For the electrically-actuated robots, we design a nonlinear control law for armature input voltages. The control technique consists of a cartesian tracking control and a force convergent control. The model obtained is in standard form to allow the application of singular
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ABSTRACT The aim of CISA'09 is to present the latest research and application results emerging from new research and technological developments of complex systems and intelligent machines acting on known or unknown, virtual or... more
ABSTRACT The aim of CISA'09 is to present the latest research and application results emerging from new research and technological developments of complex systems and intelligent machines acting on known or unknown, virtual or real, environments in an autonomous way or in cooperation with humans. This field requires skills in automation and control, perception of the environment, human-computer interfaces, mechanics and design, simulation, etc. It also aims at encouraging scientific cooperation between North and South and promoting scientific exchanges through a durable event.
ABSTRACT The effects of inserting a thin gold (Au) layer between the indium tin oxide (ITO) electrode and the poly [2-methoxy-5-(2-ethylhexyl-oxy)-p-phenylenevinylene] (MEH-PPV) organic material on the electrical properties of a... more
ABSTRACT The effects of inserting a thin gold (Au) layer between the indium tin oxide (ITO) electrode and the poly [2-methoxy-5-(2-ethylhexyl-oxy)-p-phenylenevinylene] (MEH-PPV) organic material on the electrical properties of a ITO/MEH-PPV/Al device are investigated through current–voltage I(V) characteristics and surface morphology analysis. The atomic force microscopy (AFM) surface roughness analysis indicates that a uniform and smoother surface is formed when the ITO is covered by the Au interlayer. The modified device with ITO/Au anode shows improved current density-voltage characteristics as compared with the device with ITO bare as anode. Diode parameters such as ideality factor, barrier height, series resistance and Shunt resistance are calculated using Schottky model corrected from the series and Shunt resistances. In the presence of the Au interlayer, the junction resistance across the ITO/MEH-PPV interface is significantly reduced, leading to an improvement in hole injection. The conduction mechanisms for both structures are also investigated and several parameters are extracted. The main factors contributing to such improvements induced by the thin gold buffer layer are discussed.
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ABSTRACT The nonlinear planar dynamic model of an underactuated autonomous airship and its position/orientation control are addressed, for moderate-amplitude sinusoidal perturbation in three directions. The dynamic model, even if it is... more
ABSTRACT The nonlinear planar dynamic model of an underactuated autonomous airship and its position/orientation control are addressed, for moderate-amplitude sinusoidal perturbation in three directions. The dynamic model, even if it is reduced into a plan, it presents some strong coupling terms due to the non coincidence of buoyancy and gravity centers and the presence of added masses while two control acting on the airship model. A nonlinear control law is proposed that guaranteed the convergence of the airship in the neighborhood of a desired point in presence of perturbations. Numerical results are presented to show the effectiveness of the proposed nonlinear control law.
Aerial robotics has been known for several years as a considerable passion of private manufacturers as well as research laboratories. This interest is justified by the recent technological projections which make possible the design of... more
Aerial robotics has been known for several years as a considerable passion of private manufacturers as well as research laboratories. This interest is justified by the recent technological projections which make possible the design of powerful systems endowed with real capacities of autonomous navigation, at non-prohibitive cost. Today, the principal limitations which the researchers meet are related on one hand
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The work describes an automatically on-line Self-Tunable Fuzzy Inference System (STFIS) of a mini-flying called XSF drone. A Fuzzy controller based on an on-line optimization of a zero order Takagi-Sugeno fuzzy inference system (FIS) by a... more
The work describes an automatically on-line Self-Tunable Fuzzy Inference System (STFIS) of a mini-flying called XSF drone. A Fuzzy controller based on an on-line optimization of a zero order Takagi-Sugeno fuzzy inference system (FIS) by a back propagation-like algorithm is successfully applied. It is used to minimize a cost function that is made up of a quadratic error term and
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In this paper we present a particular architecture of parallel robots which has six-degrees-of-freedom (6-DOF) with only three limbs. The particular properties of the geometric and kinematic models with respect to that of a classical... more
In this paper we present a particular architecture of parallel robots which has six-degrees-of-freedom (6-DOF) with only three limbs. The particular properties of the geometric and kinematic models with respect to that of a classical parallel robot are presented. We show that inverse problems have an analytical solution. However, to solve the direct problems, an efficient numerical procedure which needs
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This paper proposes an adaptive control using the integrated longitudinal and lateral dynamics models of automated vehicles. Dynamics are described by a nonlinear nonholonomic model. We show that the dynamics of the DC-actuated vehicle is... more
This paper proposes an adaptive control using the integrated longitudinal and lateral dynamics models of automated vehicles. Dynamics are described by a nonlinear nonholonomic model. We show that the dynamics of the DC-actuated vehicle is asymptotically stable, with well updated dynamic parameters
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We present in this paper the stabilization (tracking) with motion planning of the six independent configurations of a mini unmanned areal vehicle equipped with four streamlined rotors. Naturally, the yaw-dynamic can be stabilized without... more
We present in this paper the stabilization (tracking) with motion planning of the six independent configurations of a mini unmanned areal vehicle equipped with four streamlined rotors. Naturally, the yaw-dynamic can be stabilized without difficulties and independently of other motions. The remaining dynamics are linearly approximated around a small roll and pitch angles. It will be shown that the system
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ABSTRACT The study of automated guided vehicle behavior when moving on a plane occupies practically a central place in the automobile theory. While an automated vehicle travels at a relatively low speed, controlling it with only a... more
ABSTRACT The study of automated guided vehicle behavior when moving on a plane occupies practically a central place in the automobile theory. While an automated vehicle travels at a relatively low speed, controlling it with only a kinematics model may work. However, as automated vehicles are designed to travel at higher speeds, dynamics modelling becomes important. For the studies concerning the automated vehicle modeling and control we can refer to [5], [6], [8], and [14]; they deal only with some simplified low-order linear models. These models are too simple for studying the integrated longitudinal and lateral dynamics. Works such as [9] and [13] highlight the contribution of the internal variables such as the rotation angles and velocities of the wheels into the dynamics model. The exponential stabilization of some equilibria of automated vehicles was subject of our work in [1].