Tupak García

Autonomous University of Mexico City (UACM), Mexico City, Mexico · Science and Technology

We report the fabrication of metal alloy Au–Pd nanoparticles on semiconductor thin film substrates (ZnO) by laser-induced dewetting. Employing a UV excimer laser, a single pulse was directed onto a three-layer film stack on a glass substrate: glass/ZnO/Au/Pd and glass/ZnO/Pd/Au. We simulated the temperature attained by the thin films enabling the p...

Optical microresonators based on Whispering Gallery Modes have been extensively investigated as unique tools for fundamental studies and as core components in several applications. Specifically, microbubbles resonators (MBR) made from glass capillaries combine high optical and mechanical Q-factors together with intrinsic microfluidics, and in this...

Gold nanoparticles (AuNPs) are used for different applications such as catalysis and biosensing. For numerous uses related to biosensing and therapy, AuNPs functionalization by thiols is required. The thiolation of AuNPs has been widely studied in nanoparticles synthesized by chemical approaches. However, studies of the thiolation of bare nanoparti...

Polymer-gold nanoparticle nanocomposites based on POSS polymer with a thiol group was obtained by laser ablation in liquids (LAL). Laser ablation of a gold target in a solution of ethanol and POSS-thiol produced high purity nanocomposites of POSS decorated with gold nanoparticles (Au NPs) in colloidal suspension. TEM characterization showed spheric...

Optical emission spectroscopy (OES) has been used as an in-situ method to monitor the film deposition carried out using a combination of two plasma-assisted techniques; pulsed laser deposition (PLD) and magnetron sputtering (MS). In this work, the plasmas produced during the PLD ablation of a gold target in an argon atmosphere and its simultaneous...

In this paper, we implement a Whispering Gallery mode microbubble resonator (MBR) as an optical transducer to detect the photoacoustic (PA) signal generated by plasmonic nanoparticles. We simulate a flow cytometry experiment by letting the nanoparticles run through the MBR during measurements and we estimate PA intensity by a Fourier analysis of th...

We present, for the first time, the use of graphene layers on the surface of transparent samples (glass) to improve laser-induced breakdown spectroscopy (LIBS) performance. Our results show that the presence of few-layer graphene allows the optical emission of glass to be observed at lower irradiance than conventional LIBS. This effect is discussed...

We implement a whispering-gallery-mode microbubble resonator (MBR) as a multifunctional component for all-optical photoacoustic inspection of materials in a platform combining microfluidic design and high sensitivity to spectral absorbance. In our setup, the MBR acts both as the acoustic transducer and as the vial for a sample causing the photoacou...

A hybrid technique that combines magnetron sputtering (MS) of zinc oxide and pulsed laser deposition (PLD) of gold was used to synthesize ZnO-Au composite thin films. Three different laser pulse fluence values of 4.5, 13.6 and 20.9 J cm⁻² were used. Films of ZnO and Au were deposited separately by MS and PLD respectively to compare the growth by th...

We report on the experimental and theoretical analysis of parametrical optomechanical oscillations in hollow spherical phoxonic whispering gallery mode resonators due to radiation pressure. The optically excited acoustic eigenmodes of the phoxonic cavity oscillate regeneratively leading to parametric oscillation instabilities.

We investigate the features of Au nanoparticles (NPs) formation by laser irradiation of thin films and its application in Nanoparticle Enhancement Laser Induced Breakdown Spectroscopy (NELIBS). Ns laser pulsed irradiation of Au thin films previously deposited on glass, allowed simultaneously the modification of the surface morphology of the metal f...

Au thin films with tens of nm in thickness deposited on glass substrates were irradiated with nanosecond UV (355 nm) laser pulses at atmospheric pressure and in vacuum conditions (∼600 and 10−5 Torr). We studied the effect of the laser fluence (200–400 mJ/cm2), thickness of the starting film (∼ 40–80 nm) and surrounding pressure on the partial abla...

We studied the effect of the repetition rate of laser pulses (RRLP) in the range from 1-10 Hz in the production of silver nanoparticles (Ag-NPs) by laser ablation in ethanol. Laser pulses with a duration of 7 ns, a wavelength of 1064 nm and an energy of 60 mJ were used to ablate a 99.99% pure silver target immersed in 10 ml of ethanol. Transmittanc...

This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon...

In this work, we study the effect of the substrate temperature (ST) during sputter-deposition as well as co-sputtering deposition on the fabrication of nanostructured Ni-Mn-Sn thin films. Sputtered films show Mn losses of around 10 at.% while the average grain size ( ) increased from 30 nm to 105 nm with the increasing of ST. Mn losses compensation...

Expanded use of fast photography is proposed to characterize laser ablation plasma plumes by the analysis of a set of photographs by means of appropriate mathematical algorithms. The laser ablation plasma plumes studied were generated by ablation of both a multicomponent target of the nominal composition Ni50Mn37Sn13 and a highly pure Cu target (Cu...

The present investigation was undertaken to investigate the effect of quenching rate on the microstructure of Ni50Mn50 − xSnx ribbon alloys and its influence on the martensitic starting phase-transition temperature MS. The study was performed on melt-spun ribbons of a ferromagnetic shape memory alloy (FSMA) of composition Ni50Mn37Sn13 produced by v...

Phase transitions and structural and magnetic properties of rapidly solidified Ni50Mn38Sn12 alloy ribbons have been studied. Ribbon samples crystallize as a single-phase, ten-layered modulated (10M) monoclinic martensite with a columnar-grain microstructure and a magnetic transition temperature of 308 K. By decreasing the temperature, martensite un...

The kinetic arrest of martensitic transformation (MT) has been observed in as-solidified Ni52.2Mn34.3In13.5 melt spun ribbons. The main characteristics of this unusual field-induced magneto-structural phenomenon have been determined through a dc magnetization study. The sample studied was fabricated by rapid solidification using the melt spinning t...

Continuous and pulsed electromagnetic radiation was used to detect the self-accommodation mechanism on a polycrystalline Cu–13.83 wt.%Al–2.34 wt.%Ni shape memory alloy. Rectangular samples of this alloy were mechanically polished to observe the austenite and martensite phases. The samples were cooled in liquid nitrogen prior to the experiments to o...

In this work two colliding laser-induced plasmas (LIP) on Cu and C were studied by means of time resolved emission spectroscopy and fast photography. The experiments were performed using two opposing parallel targets of Cu and C in vacuum, ablated with two synchronized ns lasers. The results showed an increased emission intensity from copper ions C...

A Cu–Al 11.2 wt.%-Be 0.6 wt.% shape memory alloy was subjected to a uniaxial tension test using an MTS load frame with an attached optical microscope. Digital images of the sample's surface were acquired using white light and He–Ne laser illumination. The obtained images were associated to the engineering stress–strain behavior, which was calculate...

Thin films were grown by pulsed laser deposition, PLD, on Si (100) substrates by the ablation of a sintered ceramic SrFe12O19 target with and without the presence of a nonhomogeneous magnetic field of μ0H=0.4T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd–Fe–B permanent...

Pulsed laser deposition technique (PLD) has had a widespread use during the last years, but there is not a full understanding of the different processes involved in this technique. In the present paper a study of the ablation process of a BaTiO3 target and its deposition as a thin film is shown. Two interesting results were observed. First, an inve...

Pulsed laser depositions of PLZT thin films were performed using an Nd:YAG (1064nm) laser. The growths took place in vacuum or in an oxygen background. Room temperature and 500°C were the used substrate temperatures. The X-ray diffraction analysis revealed a preferential crystallographic orientation in the films grown at room temperature in vacuum....

Thin films of SrFe 12 O 19 , BaFe 12 O 19 , Pb 0.76 La 0.16-0.08 Zr 0.53 Ti 0.47 O 3 and Sr 0.3 Ba 0.7 Nb 2 O 6 were grown on monocrystalline silicon substrates by pulsed laser deposition using a 20-ns Nd : YAG laser (1064 nm). The deposited thin films were analyzed by X-ray diffraction in the grazing incidence configuration. The analysis showed ev...

Thin films of substoichiometric silicon oxides (SiOx, 0 < x < 2) were obtained using a pulsed laser deposition technique under vacuum. The irradiated targets were prepared by mixing pure SiO2 and silicon powders and pressing them into cylindrical targets of different compositions. The samples were subjected to two distinct thermal treatments and th...

Textured strontium ferrite thin films has been grown at room temperature using a Nd:YAG laser. The spectroscopic study of the produced plasma revealed that the expansion velocities of the species are of the order of 106 cm/s, which could explain the obtained texture. The stoichiometric analysis shows a small oxygen reduction in the films due to the...

PZT thin films were deposited by laser ablation at high vacuum and at room temperature. After that, some of the samples were annealed at air in the temperature range 450 degree(s)C - 550 degree(s)C. The samples were characterized by XPS and X-ray diffraction. A decrease in the oxygen composition of the as-deposited sample was observed. In the as-de...

Polycrystalline SrFe12O19 thin films were deposited on Si (100) substrates by PLD using a Nd-YAG laser ((lambda) equals 1064 nm). During the deposition process substrates were kept at room temperature. As-deposited films were annealed in air at temperatures between 600 degree(s)C and 840 degree(s)C. Samples were characterized by AES, ESCA, SEM, AFM...

The research projects at the Laser Technology Laboratory of Havana University are devoted to Nd:YAG lasers development and to the implementation of new laser applications in different fields. Relative to the lasers research the objective is the development of compact, light and relative low-cost lasers. This development is based on a vertical integ...

The evaluation of different routes to prepare polycrystalline thin films based on hexagonal ferrites is of considerable interest due to the excellent properties of these materials as high density magnetic recording media. In particular, the metal-organic decomposition and the pulsed laser ablation deposition have been used for us to grow high coerc...

Polycrystalline BaFe12O19 thin films were deposited on Si substrates by pulsed laser ablation using a Nd-YAG laser system. Samples were investigated by means of Auger electron spectroscopy, scanning electron microscopy and vibrating sample magnetometry. Nanocrystalline particles of barium hexaferrite formed after annealing of as-deposited films at...

Tin oxide (SnO2) thin films were prepare by pulsed laser deposition on glass substrates. An electric field (positive or negative) between target and substrate was applied. Structural, optical, compositional and morphological characterization of the films was made by different analytical techniques. The influence of electric field on the growth para...