Henry Alberto Méndez Pinzón

• Doctor rerum naturalium
• Professor (Associate) at Pontifical Xavierian University

Background: Amelogenesis imperfecta is a hereditary disorder affecting dental enamel. Among its phenotypes, Hypocalcified AI is characterized by mineral deficiency, leading to tissue wear and consequently dental sensitivity. Excessive fluoride intake (through drinking water, fluoride supplements, toothpaste, or by ingesting products such as pestici...

The multilayer structure is a well-studied architecture for electronic and optoelectronic applications and more recently in spintronic devices. In this work, we present the structural, morphological, topographical, and magnetic properties of GaSb/Mn multilayers deposited via DC magnetron sputtering at room temperature and 423 K. Raman measurements...

Traditionally, the vertical convective self-assembly method (VCSA) uses time-invariant temperature conditions to obtain high-quality colloidal crystal (CC) films, leaving unexplored possible effects due to temperature variations during the elaboration process. Here, the quality of colloidal crystal films grown by the VCSA method when applying tempe...

Objectives: The aim of this study was to assess the potential of a smear-layer removing agent (citric acid) vs. an accepted gutta-percha-softening agent (Xylol) as an alternative substance for removing the root canal filling materials, while investigating the potential for associated demineralization effects. Materials and Methods: Seventy healthy,...

Optical characterization of P3HT:PCBM (poly (3-hexylthiophene-2,5-diyl)): ([6,6]-phenyl C61 methyl ester of butyric acid) and PEDOT: PSS (layers of poly (3,4-ethylenedioxythiophene) thin films deposited using spin coating technique were studied using an effective medium approximation method (EMA). This method involves transmittance, reflectance and...

Here, it is reported an enhancement of the light-extraction efficiency in organic light emitting diodes (OLEDs) by growing a colloidal crystal (CC) matrix inside the luminescent layer of single bottom-emitting heterostructures. The CC matrix is obtained by self-assembly of Silica (SiO2) spheres during the spin-coating procedure used for the deposit...

Method for manufacturing a thin film consisting of a colloidal crystal infiltrated with the luminescent MDMO-PPV polymer made of silica (SiO2) spheres, having a face-centered-cubic system. Patent No.: US 9.859.497 B2

Ground-state integer charge transfer is commonly regarded as the basic mechanism of molecular electrical doping in both, conjugated polymers and oligomers. Here, we demonstrate that fundamentally different processes can occur in the two types of organic semiconductors instead. Using complementary experimental techniques supported by theory, we cont...

In order to determine the optimal conditions for the growth of high-quality 250 nm- SiO 2 colloidal crystals by the vertical convective self-assemble method, the Design of Experiments (DoE) methodology is applied. The influence of the evaporation temperature, the volume fraction, and the pH of the colloidal suspension is studied by means of an...

Molecular doping: The standard model for molecular p-doping of organic semiconductors (OSCs) assumes integer charge transfer between OSC and dopant. This is in contrast to an alternative model based on intermolecular complex formation instead. By systematically varying the acceptor strength it was possible to discriminate the two models. The latter...

The one-dimensional quantum Boltzmann equation in linear transport approximation was solved using the nonequilibrium Green's function method, and based on the lifetime approximation. As an example, the effect of interactions with electric fields were included, and the thermoelectric power coefficient (α) was evaluated, based on calculations of the...

Based on the solution of the quantum Boltzmann equation, in the linear transport approximation for an isotropic low-dimensional system, the thermoelectric power coefficient, Q, in a quantum well structure was determined. These calculations are based on variational methods, taking into account especial functions which include important parameters be...

Resumen Se fabricó y caracterizó eléctricamente (característica corriente-voltaje I-V) diodos emisores de luz basados en materiales orgánicos (Organic light emitting diodes OLEDs), mediante la técnica de spin coating. Estos dispositivos tienen el mérito de ser los primeros prototipos basados en polímeros orgánicos fabricados en el país. La emisión...

Resumen Películas delgadas de óxido de estaño dopado con indio (SnO 2 :In), material conocido como ITO por su sigla en inglés, fueron caracterizadas por medidas de resistividad eléctrica y movilidad Hall en el rango de temperaturas 14K-400K. Este material posee baja (~10-4 Ωcm), la cual se incrementa ligeramente con la temperatura, y una alta densi...

A Metal / Organic / Inorganic semiconductor heterostructure was built and characterized in situ under ultra-high vacuum conditions (UHV). The aim was to investigate the influence of a perylene-derivative organic thin film on the transport electronic properties of Schottky Ag / GaAs diodes. The device was studied using a combination of photoemission...

p> Objective: Fabrication and optical characterization of close-packed 225 nm SiO₂ -based colloidal crystals . Materials and methods: The vertical convective self-assembly method is used to grow high-quality 225 nm close-packed SiO₂-based colloidal crystals. An annealing process (550°C) is made in order to improve the mechanic...

Objective: Fabrication and optical characterization of close-packed 225 nm SiO2 -based colloidal crystals. Materials and methods: The vertical convective self-assembly method is used to grow high-quality 225 nm close-packed SiO2-based colloidal crystals. An annealing process (550°C) is made in order to improve the mechanical stability of the sample...

Polymer-based organic light-emitting diodes (OLEDs) with the structure ITO / PEDOT:PSS / MDMO-PPV / Metal were prepared by spin coating. It is known that electroluminescence of these devices is strongly dependent on the material used as cathode and on the deposition parameters of the polymer electroluminescent layer MDMO-PPV. Objective. In this wor...

p>Polymer-based organic light-emitting diodes (OLEDs) with the structure ITO / PEDOT:PSS / MDMO-PPV / Metal were prepared by spin coating. It is known that electroluminescence of these devices is strongly dependent on the material used as cathode and on the deposition parameters of the polymer electroluminescent layer MDMO-PPV. Objective. In this w...

An hybrid metal/organic/inorganic semiconductor heterostructure was built under ultrahigh vacuum condi-tions UHV and characterized in situ. The aim was to investigate the influence of thin film layers of the organic material Dimethyl-3,4,9,10-perylenetetracarboxylic diimide DiMe-PTCDI on the electrical response of organic-modified Ag/ GaAs Schottky...

Thin films of indium oxide 200 nm thick and indium nitride 150 nm thick were produced by reactive sputtering deposition onto soda lime substrates. The Indium cathode was kept under vacuum attached to a high voltage dc. The InxOy films were obtained in argon-oxygen mixture with total pressure between 2 and 7 Pa, current density between 0.04 and 0.56...

In the present work a Metal / organic / inorganic semiconductor hybrid heterostructure (Ag / DiMe−PTCDI / GaAs) was built under UHV conditions and characterised in situ. The aim was to investigate the influence of the organic layer in the surface properties of GaAs(100) and in the electrical response of organic−modified Ag / GaAs Schottky diodes. T...

In the present work a Metal / organic / inorganic semiconductor hybrid heterostructure (Ag / DiMe−PTCDI / GaAs) was built under UHV conditions and characterised in situ. The aim was to investigate the influence of the organic layer in the surface properties of GaAs(100) and in the electrical response of organic−modified Ag / GaAs Schottky diodes. T...

Steady-state current–voltage (I–V) and impedance–voltage (Z–V) measurements were performed on in situ (UHV) prepared metal (Ag, Al)/Alq3/indium-tin oxide (ITO) devices after exposure to air. When increasing the positive bias on the top metal electrode to a relatively well-defined critical value, a transition from semiconducting to semi- or even ins...

Two types of Si/SiO2/pentacene organic field-effect transistors (OFET) with bottom Au-source (S) and – drain (D) electrodes were examined by charge transient spectroscopy (QTS), applying pulsed bias ΔUDS to the channel of an OFET with floating gate electrode. The transient charge Q (t ), flowing through the channel after the removal of the bias pul...

For a large number of organic disordered semiconductors the transport of electrons or holes via hopping is mediated by localized states in the band gap. An attempt is presented towards testing the widely met hopping transport model based on the assumption of a Gaussian density of states (DOS). An analysis of both isothermal and thermal charge trans...

The electric properties of a metal/organic/inorganic heterostructure were explored by current–voltage (I–V), feedback charge capacitance (C–V) and charge transient spectroscopy (QTS). Temperature dependent I–V characteristics from 100 K to 300 K were recorded while running the bias applied to the metallic electrode from negative to positive values....

The electronic properties of well ordered N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic dimide (DiMe-PTCDI) films prepared on sulfur passivated GaAs(001) substrates were studied by means of photoemission spectroscopy. From the photon energy dependence of normal emission spectra an intermolecular energy band dispersion of about 0.2 eV was determine...

The electronic properties of N,N'-dimethyl-3,4,9,10-perylene tetracarboxylic diimide (DiMePTCDI) films deposited on S-GaAs(100) surfaces are studied by ultraviolet photoelectron spectroscopy (UPS). The energy position of the highest occupied molecular orbital (HOMO) of clean DiMePTCDI films is found to be at 2.04 +/- 0.10 eV with respect to Fermi l...

Steady-state current-voltage (IV) characteristics of metal/organics/metal devices are modelled on the basis of thermionic emission into two back-to-back connected diodes separated by a series bulk resistance. It is shown that the analysis of the IV curves cannot be split in two independent branches corresponding to opposite polarities of the applie...

The adsorption of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,N -dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMe-PTCDI) on differently treated n-doped GaAs(100) surfaces was investigated using high-resolution photoemission spectroscopy. The chemical interaction between the molecules and the semiconductor substrate is found to...

The optical properties and the molecular orientation in thin films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and -dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMePTCDI) were studied by means of variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM), near edge x-ray absorption fine structure (NEXAFS) spe...

Two different organic molecules with similar structure, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,N 0 -dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMe-PTCDI), were used for the modification of Ag Schottky contacts on sulphur passivated GaAs(1 0 0) (S-GaAs). Such diodes were investigated recording in situ current–voltage (I–...

The energy position of the lowest u noccupied molecular orbital (LUMO) in 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) and dimethyl-3,4,9,10-perylenetetracarboxilic diimide (DiMe-PTCDI) was determined by investigating the energy level alignment at molecular semiconductor/GaAs(100) i nterfaces. Interface dipoles are found to form at the int...

SnO2 thin films doped with fluorine were studied through conductivity and Hall voltage measurements as a function of the temperature (between 100 K and 600 K). The experimental results were theorically reproduced using the electrical transport model proposed by Seto [1, 2] for polycrystalline semiconductors. It was found that the conductivity is st...

High transparent and conductive SnO₂ thin films deposited by spray pyrolysis using SnCl₂ as precursor solution and HF as source of the doping impurities were characterized through thermoelectric power, Hall voltage and conductivity measurements, in order to determine the influence of the F-content on the electrical transport p...