Nanostructure of Thin Films Grown by Deposition of Isotropically Distributed Gaseous Particles

: Presentación en la conferencia “12th International Conference on Plasma Surface Engineering”Peer reviewe

Growth of SiO2 Thin Films by Plasma-Assisted Reactive Magnetron Sputtering under the Impingement of Positive and Negative Ions

Presentación en la VII Reunión Bienal del Grupo Especializado de Física de Estado SólidoPeer reviewe

Surface chemistry and germination improvement of Quinoa seeds subjected to plasma activation

Plasma treatment is recognized as a suitable technology to improve germination efficiency of numerous seeds. In this work Quinoa seeds have been subjected to air plasma treatments both at atmospheric and low pressure and improvements found in germination rate and percentage of success. Seed water uptake by exposure to water vapor, although slightly greater for plasma treated seeds, did not justify the observed germination improvement. To identify other possible factors contributing to germination, the chemical changes experienced by outer parts of the seed upon plasma exposure have been investigated by X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM-EDX). XPS revealed that the outer layers of the Quinoa plasma treated seeds were highly oxidized and appeared enriched in potassium ions and adsorbed nitrate species. Simultaneously, SEM-EDX showed that the enrichment in potassium and other mineral elements extended to the seed pericarp and closer zones. The disappearance from the surface of both potassium ions and nitrate species upon exposure of the plasma treated seeds to water vapor is proposed as a factor favoring germination. The use of XPS to study chemical changes at seed surfaces induced by plasma treatments is deemed very important to unravel the mechanisms contributing to germination improvement

Kinetic Energy-induced Growth Regimes of Nanocolumnar Ti Thin Films Deposited by Evaporation and Magnetron Sputtering

We experimentally analyze different growth regimes of Ti thin films associated to the existence of kinetic energy-induced relaxation mechanisms in the material's network when operating at oblique geometries. For this purpose, we have deposited different films by evaporation and magnetron sputtering under similar geometrical arrangements and at low temperatures. With the help of a well-established growth model we have found three different growth regimes: (i) low energy deposition, exemplified by the evaporation technique, carried out by species with typical energies in the thermal range, where the morphology and density of the film can be explained by solely considering surface shadowing processes, (ii) magnetron sputtering under weak plasma conditions, where the film growth is mediated by surface shadowing mechanisms and kinetic-energy-induced relaxation processes, and (iii) magnetron sputtering under intense plasma conditions, where the film growth is highly influenced by the plasma, and whose morphology is defined by nanocolumns with similar tilt than evaporated films, but with much higher density. The existence of these three regimes explains the variety of morphologies of nanocolumnar Ti thin films grown at oblique angles under similar conditions in the literature.EU-FEDER and MINECO-AEI 201560E055EU-FEDER and MINECO-AEI MAT2014-59772-C2-1-PEU-FEDER and MINECO-AEI MAT2016-79866-REU-FEDER and MINECO-AEI MAT2015-69035-REDCUniversity of Seville V and VI PPIT-U

Influence of plasma-generated negative oxygen ion impingement on magnetron sputtered amorphous SiO2 thin films during growth at low temperatures

Growth of amorphous SiO2 thin films deposited by reactive magnetron sputtering at low temperatures has been studied under different oxygen partial pressure conditions. Film microstructures varied from coalescent vertical column-like to homogeneous compact microstructures, possessing all similar refractive indexes. A discussion on the process responsible for the different microstructures is carried out focusing on the influence of (i) the surface shadowing mechanism, (ii) the positive ion impingement on the film, and (iii) the negative ion impingement. We conclude that only the trend followed by the latter and, in particular, the impingement of O- ions with kinetic energies between 20 and 200 eV, agrees with the resulting microstructural changes. Overall, it is also demonstrated that there are two main microstructuring regimes in the growth of amorphous SiO2 thin films by magnetron sputtering at low temperatures, controlled by the amount of O2 in the deposition reactor, which stem from the competition between surface shadowing and ion-induced adatom surface mobilityMinisterio de Innovación español-MAT 2007-65764Ministerio de Innovación español (CONSOLIDER INGENIO 2010)-CSD2008-00023Junta de Andalucía-TEP2275, TEP5283, P07-FQM-03298 y P10-FQM-690

Nanocolumnar growth of thin films deposited at oblique angles: Beyond the tangent rule

The growth of nanostructured physical vapor deposited thin films at oblique angles is becoming a hot topic for the development of a large variety of applications. Up to now, empirical relations, such as the so-called tangent rule, have been uncritically applied to account for the development of the nanostructure of these thin films even when they do not accurately reproduce most experimental results. In the present paper, the growth of thin films at oblique angles is analyzed under the premises of a recently proposed surface trapping mechanism. The authors demonstrate that this process mediates the effective shadowing area and determines the relation between the incident angle of the deposition flux and the tilt angle of the columnar thin film nanostructures. The analysis of experimental data for a large variety of materials obtained in our laboratory and taken from the literature supports the existence of a connection between the surface trapping efficiency and the metallic character of the deposited materials. The implications of these predictive conclusions for the development of new applications based on oblique angle deposited thin films are discussed. © 2014 American Vacuum Society.Peer Reviewe

Growth of nanocolumnar thin films on patterned substrates at oblique angles

The influence of one dimensional substrate patterns on the nanocolumnar growth of thin films deposited by magnetron sputtering at oblique angles is theoretically and experimentally studied. A well‐established growth model has been used to study the interplay between the substrate topography and the thin film morphology. A critical thickness has been defined, below which the columnar growth is modulated by the substrate topography, while for thicknesses above, the impact of substrate features is progressively lost in two stages; first columns grown on taller features take over neighboring ones, and later the film morphology evolves independently of substrate features. These results have been experimentally tested by analyzing the nanocolumnar growth of SiO2 thin films on ion‐induced patterned substrates.University of Seville: V PPIUSUniversity of Seville: VI PPIT-USEuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2013-40852-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2016- 79866-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2015-69035-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2015-69035-REDCEuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2017-85089-C2-1- RComunidad Autónoma de Madrid S2013/MIT-3029Comunidad Autónoma de Madrid IND2017/IND766