Spectroscopic analysis of copper oxide thin films and plasma produced by pulsed laser deposition

[EN] We use spectroscopic analysis to study plasma and copper thin films obtained by the Pulsed Laser Deposition tech-nique.The Optical Emission Spectroscopy (OES) was implemented to analyse of emission spectra of the copper plasma produced by the laser Nd:YAG of 1064 nm, which makes the ablation on the copper target. The thin film is growing over an amorphous substrate (glass) at room temperature, and the pressure is changed from 1.2 to 26.6 Pa. We obtained lines of neutral copper Cu I and copper ion, with a meaning difference in intensities, what is related with a greater probability of emission in the green and with the color observed in the plasma during the ablation. The spectroscopic analysis of the thin films is made with Raman; we observed peaks corresponding to the copper oxide. By AMF we could determine the grain size and roughness for the thin film at 20 Pa and at room temperature. The SEM analysis for different regions shows that the thin films are soft and smooth.[ES] Mediante análisis espectroscópico se estudia el plasma y las películas delgadas de cobre obtenidas por la técnica de Deposición de Láser Pulsado (PLD). Se utiliza la espectroscopía de emisión óptica, para analizar los espectros de emisión del plasma de cobre producidos con un láser Nd:YAG de 1064 nmque ablaciona el blanco de cobre. La película delgada crece sobre un sustrato amorfo (vidrio) a una temperatura ambiente y variando la presión del argón desde 1.2 Pa hasta 26.6 Pa. Se obtienen líneas de cobre neutro y de ion de cobre con una significativa diferencia en sus intensidades, lo que se relaciona con una mayor probabilidad de emisión en el verde y con el color del plasma observado durante la ablación. Se realiza análisis espectroscópico de las películas delgadas con Raman y se observan picos correspondientes óxido de cobre. Mediante AFM se determina el tamaño de grano (42.3 nm) y la rugosidad (de 1.2 nm) de las películas crecidas a 20 Pa y temperatura ambiente. El análisis SEM en diferentes regiones de la película delgada muestra que son suaves y lisas.Este trabajo fue posible gracias al apoyo por parte del GPLA.Peer Reviewe

Advances in Scanning Thermal Microscopy Measurements for Thin Films

One of the main challenges nowadays concerning nanostructured materials is the understanding of the heat transfer mechanisms, which are of the utmost relevance for many specific applications. There are different methods to characterize thermal conductivity at the nanoscale and in films, but in most cases, metrology, good resolution, fast time acquisition, and sample preparation are the issues. In this chapter, we will discuss one of the most fascinating techniques used for thermal characterization, the scanning thermal microscopy (SThM), which can provide simultaneously topographic and thermal information of the samples under study with nanometer resolution and with virtually no sample preparation needed. This method is based on using a nanothermometer, which can also be used as heater element, integrated into an atomic force microscope (AFM) cantilever. The chapter will start with a historical introduction of the technique, followed by the different kinds of probes and operation modes that can be used. Then, some of the equations and heating models used to extract the thermal conductivity from these measurements will be briefly discussed. Finally, different examples of actual measurements performed on films will be shown. Most of these results deal with thermoelectric thin films, where the thermal conductivity characterization is one of the most important parameters to optimize their performance for real applications

Análisis espectroscópico de un plasma de carbón producido por ablación láser

[EN] Spectroscopic analysis of plasma produced by laser ablation of coal samples using 1064 nm radiation pulses from a Q-switched Nd:YAG on different target under air ambient, was performed. The emission of molecular band systems such as C2 Swan System (d3Πg→a3Πu), the First Negative System N2 (Band head at 501,53 nm) and emission lines of the C I, C II, were investigated using the optical emission spectroscopy technique. The C2 molecular spectra (Swan band) were analyzed to determine vibrational temperature (0,62 eV); the density and electron temperature of the plasma have been evaluated using Stark broadening and the intensity of the nitrogen emission lines N II, the found values of 1,2 eV and 2,2 ×1018 cm-3 respectively.[ES] Se presenta un análisis espectroscópico en aire del plasma producido por la ablación de un láser infrarrojo Nd: YAG con λ = 1.064 nm sobre carbones provenientes de tres diferentes minas naturales (Santander, Norte de Santander y Cesar) en Colombia. El estudio de la emisión de los sistemas de bandas moleculares como Sistema Swan , primer Sistema Negativo N2 (alrededor de 501,53 nm) y diferentes líneas de emisión atómicas fueron investigados utilizando la técnica de espectroscopia de emisión óptica. Los espectros moleculares C2 (conocida como banda Swan) se analizaron para determinar la temperatura de vibración (0.62 eV). La temperatura de la densidad de electrones y del plasma han sido evaluadas utilizando el ensanchamiento Stark y la intensidad de las líneas de emisión de nitrógeno (N II). Se encontraron valores de 1,2 eV de temperatura electrónica y 1,82×1019 cm-3 de electrones densidad.Peer reviewe

Synthesis and characterization 3D Modulated and smooth TiO2 nanotubes for energy applications

Trabajo presentado en el International Conference on Hybrid and Organic Photovoltaics (HOPV16), celebrado en Swansea (Reino Unido), del 29 de junio al 1 de julio de 2016For more than a decade anodic TiO2 nanotubes layers (TNTL) have attracted the attention of many research groups, with more than 5000 publications in the 2009-14 period[1]. This interest bases on their optimal characteristics for different fields of applications ranging from biomaterials to water remediation and solar cells, and also due to their fast and easy synthesis processing. Pulsed galvanostatic anodization allows the modulation of the shape of TiO2 nanotubes resulting in a 3D nanostructure[2]. This 3D nanostructure can be tuned in order to control their optical properties[3][4]. In this contribution, we will present the obtained results on the synthesis and characterization of smooth TNTL and 3D modulated TNTL by potentiostatic and pulsed galvanostatic methods. The morphology (SEM), electrical and thermal properties by Kelvin probe and scanning thermal microscopy of the samples depending on their nanostructure will be discussed.This work was supported by the Marie Skłodowska-Curie Individual Fellowship 2015 grant 706094 “TONSOPS”.Peer reviewe

Thermal conductivity measurements by scanning thermal microscopy of TiO2 nanotubes

Trabajo presentado en la 14th European Conference on Thermoelectrics (ECT2016), celebrada en Lisboa (Portugal), del 20 al 23 de septiembre de 2016The efficiency of thermoelectric (TE) materials through the figure of merit zT is linked to the thermal conductivity of the material. Although, evaluate the thermal conductivity of TE materials can be very challenging due to the micro/nanoscale interaction between the probe and the sample. Some of the current thermal methods have spatial resolution issues, which make the evaluation more difficult in the case of nanostructures materials [1]. However, the 3w-SThM (Scanning Thermal Microscopy) is a powerful technique for thermal measurements and using a commercial silicon nitride probe with palladium film is possible to achieve more than 100 nm of spatial resolution. In this work, the thermal conductivity measurements with this spatial resolution is very important to analyses anodic TiO2 nanotubes layers (TNTL), since the Magnéli phase titanium oxides exhibits interesting properties for TE applications [2]. The thermal behaviour of TNTL is determined with the SThM technique that can measure simultaneously, topographic and thermal images of the samples; electrical and morphological characterization of TiO2 nanotubes is also discussed.Peer reviewe

Correlation Between Optical, Morphological, and Compositional Properties of Aluminum Nitride Thin Films by Pulsed Laser Deposition

Aluminum nitride (AlN) thin films were grown in a N2 atmosphere onto a Si/Si3N4 substrate by pulsed laser ablation. We have varied the substrate temperature for the thin film growth, using X-ray reflectometry analysis, we have characterized the thickness and density of the thin layer and the interface roughness from the X-ray reflectivity profiles. Experimental data showed that the root-mean-square roughness was in the range of 0.3 nm. The X-ray photoelectron spectroscopy (XPS) was employed to characterize the chemical composition of the films. These measurements detected carbon and oxygen contamination at the surface. In the high-resolution XPS Al2p data, binding energies for Al-N and Al-O species were identified but no Al-Al species were present. In the N1s data, N-O species were not detected, but chemically bonded O was present in the films as Al-O species. Furthermore, the value of optical energy gap, Eg was ~5.3 (±0.1) eV. The composition varied with process conditions, and the nitrogen content decreased in AlN films processed above 500 °C.J.A.Pérez acknowledges Santander bank and your scholarship program “Young Professors and Researchers Latin America, Santander Universities” (Spain, 2015).Peer reviewe

3w SThM: Thermal Conductivity of TiO2 Nanotubes fi#12;lled with Polycarbonate

Trabajo presentado en el E-MRS Spring Meeting and Exhibit, celebrado en Estrasburgo (Francia), del 22 al 26 de mayo de 2017Peer reviewe

Thermal conductivity measurements of nanostructures by scanning thermal microscopy

Trabajo presentado en el 5th Thermal probe Workshop, celebrado en Zurich (Suiza), los días 28 y 29 de marzo de 2018Peer reviewe

Nanoscale heat transport analysis by scanning thermal microscopy: from calibration to high-resolution measurements

Scanning thermal microscopy (SThM) is a powerful technique for thermal characterization. However, one of the most challenging aspects of thermal characterization is obtaining quantitative information on thermal conductivity with nanoscale lateral resolution. We used this technique with the cross-point calibration method to obtain the thermal contact resistance, R, and thermal exchange radius, b, using thermo-resistive Pd/SiN probes. The cross-point curves correlate the dependence of R and b with the sample's thermal conductivity. We implemented a 3ω-SThM method in which reference samples with known thermal conductivity were used in the calibration and validation process to guarantee optimal working conditions. We achieved values of R = 0.94 × 10 ± 0.02 K W and b = 2.41 × 10 ± 0.02 m for samples with a low thermal conductivity (between 0.19 and 1.48 W m K). These results show a large improvement in spatial resolution over previously reported data for the Wollaston probes (where b ∼ 2.8 μm). Furthermore, the contact resistance with the Pd/SiN is ∼20× larger than reported for a Wollaston wire probe (with 0.45 × 10 K W). These thermal parameters were used to determine the unknown thermal conductivity of thermoelectric films of AgSe, AgSe, CuSe (smooth vs. rough surface), and BiTe, obtaining, in units of W m K, the values of 0.63 ± 0.07, 0.69 ± 0.15, 0.79 ± 0.03, 0.82 ± 0.04, and 0.93 ± 0.12, respectively. To the best of our knowledge, this is the first time these microfabricated probes have been calibrated using the cross-point method to perform quantitative thermal analysis with nanoscale resolution. Moreover, this work shows high-resolution thermal images of the V and V signals, which can offer relevant information on the material's heat dissipation.We want to acknowledge the MINECO project PID2020- 118430GB-100 for financial support. The authors acknowledge also the service from SEM for the MiNa Laboratory at IMN, and their funding CM (project SpaceTec, S2013/ICE2822), MINECO (Project CSIC13-4E-1794), and EU (FEDER, FSE)

Thermal conductivity reduction in Ordered Three-dimensional Bi2Te3 thermoelectric networks

Trabajo presentado en el Eurotherm Seminar 108: Nanoscale and Microscale Heat Transfer V, celebrado en Santorini (Grecia), del 26 al 30 de septiembre de 2016Peer reviewe