Synthesis and characterization of plasmonic nanostructures with controlled geometry for photonic applications

The purpose of the present thesis is the study of the interaction of plasmonic and pre-plasmonic nanostructures with an emitter in close proximity. The investigation was carried out following different approaches but always with the aim of inserting the experimental results in the frame- work of new or existing theoretical models in order to better understand the photophysical nature of the interaction. To this aim in the framework of this thesis different nanoarchitectures have been synthesised and coupled to Er-doped silica layers. The choice of Erbium as emitting source was driven by the great technological importance of this rare earth in photonics and optoelectronics, connected to the characteristic emission at 1540 nm that matches the window of minimum transmission loss for silica. For this reason the first step of the research activity was devoted to the optimization of the Erbium photoluminescent properties in silica. When an emitter is placed near an interface, its optical properties will be modified. To describe this variation different contributions have to be taken into account: the variation of the local density of state due to the reflection from the interface, the coupling of the emitted radiation with propagating surface plasmons on the metal-dielectric interface and the dissipation in the overlayer. All these aspects have been studied in detail for different overlayer materials demonstrating that the strong control of the excited state lifetime of the emitter can be obtained by tailoring the dielectric properties of the overlayer and the separation distance from the interface. Nanostructuring the overlayer offers further opportunities for changing the optical properties of a nearby emitter. Among different plasmonic nanostructures, nanohole arrays (NHAs) can represent the ideal candidate for this purpose due to their extraordinary optical transmission (EOT): at specific frequencies determined by the hole periodicity, the light transmitted through the NHA is orders of magnitude higher than the one predicted with the classical diffraction theory. When the EOT peak was tailored with the emission wavelength of the emitter strong plasmonic coupling was demonstrated, leading to lifetime shortening with almost no dissipation in the overlayer. The improvement of the optical performances of an emitter can be obtained not only acting on the decay from the excited state but also increasing the excitation efficiency. For this purpose, an interesting possibility that has been explored is the sensitization by of ultra-small molecular-like metal nanoclurters (NCs) produced by ion implantation. Noble metal NCs can indeed efficiently absorb light through broad-band interband transitions and transfer energy to a nearby emitter, acting as efficient nanoantennae for excitation of the emitter. Such interaction leads to the increase of the effective excitation cross-section by several orders of magnitude. Finally, all the obtained results allowed the development of predictive models that can be used in the design of novel devices for different photonic application

Acceleration and Deceleration in the Internationalization Process of the Firm

By adopting a processual and dynamic view on internationalization, we develop the concepts of acceleration and deceleration, providing analytical tools to enhance our understanding of the non-linearity and multidimensionality of internationalization. We argue that acceleration and deceleration are embedded in the internationalization process and are a consequence of the firm’s capability to absorb and integrate acquired knowledge, and to find and exploit opportunities. In addition, we advance the idea that changes in speed are further influenced by how the firm integrates and coordinates the resources it has deployed within and across various internationalization dimensions. Thus, it emerges that the overall evolution of commitment to internationalization is more complex than received theories tend to present; therefore, empirical studies should aim to include a wide set of international activities and processes embedded in time

Export channel choice for SMEs: a cognitive perspective

Despite decades of research on SME export channel choice, we know little about the role played by managerial mindsets. Managerial mindsets are the cognitive mental models managers rely on for processing and evaluating information and making decisions. In this paper, we develop and test the notion that, in addition to the influence of transaction cost factors, the global mindset of top managers has a significant impact on the export channels that SMEs use. We also suggest that this relation is sensitive to the level of political instability in the target market since such instability increases risk and uncertainty. A multinomial regression analysis was used to analyze the responses of a sample of 208 Chinese SMEs. The results provide support for our ideas. In this way, we contribute to a better understanding of how managerial thinking can influence the strategic choices that are made and the boundary conditions that exist when SMEs expand abroad.</p

Examining the two-dimensional perceived marketplace influence and the role of financial incentives by SEM and ANN

In recent years, research on sustainable consumption has been particularly relevant, highlighting the importance of the collective over the individual to reduce pollution. This study focuses on the study of the perceived marketplace influence (PMI) concept in its organizational and consumer dimensions, together with the financial incentives that exist in the adoption of electric cars and their effect on green customer engagement. A sample of 382 potential buyers of electric vehicles was obtained. A new hybrid analytical approach was taken structural equation modelling and artificial neural network. The research found the most significant variables affecting purchase intention were financial incentives, followed by PMI Organization and finally PMI Consumer. The results of artificial neural network analysis confirmed all the findings of the structural equation modelling, although the importance of each PMI dimension is different for each technique used. The conclusions point to new business opportunities that can be exploited by companies selling this green technology.Funding for open access charge: Universidad de Granada / CBU

Biometric m-payment systems: A multi-analytical approach to determining use intention

Although mobile payment systems offer countless advantages, they do present certain drawbacks, mainly associated with security and privacy concerns. The inclusion of biometric authentication technologies seeks to minimise such drawbacks. The aim of this article is to examine the effect of key antecedents of the Unified Theory of Acceptance and Use of Technology 2 (UTAUT2) and perceived risk on the intention to use a mobile payment system featuring biometric identification. A new hybrid analytical approach is taken. A sample of more than 2500 smartphone users was obtained through an online panel-based survey. Two techniques were used: first, structural equation modelling (PLS-SEM) was conducted to determine which variables had a significant influence on the adoption of the mobile payment system, and second, an artificial neural network (ANN) model was used, taking a deep learning approach, to rank the relative influence of significant predictors of use intention obtained via PLS-SEM. The study found that the most significant variables affecting use intention were performance expectancy, effort expectancy, facilitating conditions, hedonic motivation and risk. In contrast, subjective norms, price value and habit were found to be weak predictors of use intention. The results of the ANN analysis confirmed almost all SEM findings but yielded a slightly different order of influence among the least significant predictors. A review of the extant scientific literature revealed a paucity of published studies dealing with the adoption and use of mobile payment systems featuring biometric identification. The conclusions and managerial implications point to new business opportunities that can be exploited by firms through the use of this technology

Affordable Loss in Entrepreneurial Internationalisation: A Focus on Finnish Biotechnology Firms

This paper develops the concept of affordable loss in the context of decision-making in entrepreneurial internationalisation and offers both an in-depth conceptual analysis and practical application in the biotechnology sector. Based on our findings, affordable loss seems to be connected to short-term, operative decisions, but is less applicable for long-term, strategic decisions. Furthermore, the use of the affordable loss principle appears to be more common in decisions involving a single decision-maker than in shared decision-making. However, we also challenge the premise of effectuation theory, as affordable loss and expected reward do not seem to present alternative elements when viewing decision-making in the context of entrepreneurial internationalisation. Instead, they are used in parallel, indicating that making a single decision may include the use of both causation and effectuation-based logic

Quasi-BIC Modes in All-Dielectric Slotted Nanoantennas for Enhanced Er3+ Emission

In the quest for new and increasingly efficient photon sources, the engineering of the photonic environment at the subwavelength scale is fundamental for controlling the properties of quantum emitters. A high refractive index particle can be exploited to enhance the optical properties of nearby emitters without decreasing their quantum efficiency, but the relatively modest Q-factors (Q ∼ 5–10) limit the local density of optical states (LDOS) amplification achievable. On the other hand, ultrahigh Q-factors (up to Q ∼ 109) have been reported for quasi-BIC modes in all-dielectric nanostructures. In the present work, we demonstrate that the combination of quasi-BIC modes with high spectral confinement and nanogaps with spacial confinement in silicon slotted nanoantennas lead to a significant boosting of the electromagnetic LDOS in the optically active region of the nanoantenna array. We observe an enhancement of up to 3 orders of magnitude in the photoluminescence intensity and 2 orders of magnitude in the decay rate of the Er3+ emission at room temperature and telecom wavelengths. Moreover, the nanoantenna directivity is increased, proving that strong beaming effects can be obtained when the emitted radiation couples to the high Q-factor modes. Finally, via tuning the nanoanntenna aspect ratio, a selective control of the Er3+ electric and magnetic radiative transitions can be obtained, keeping the quantum efficiency almost unitary

Co3O4 Nanopetals on Si as Photoanodes for the Oxidation of Organics

Cobalt oxide nanopetals were grown on silicon electrodes by heat-treating metallic cobalt films deposited by DC magnetron sputtering. We show that cobalt oxide, with this peculiar nanostructure, is active towards the photo-electrochemical oxidation of water as well as of organic molecules, and that its electrochemical properties are directly linked to the structure of its surface. The formation of Co3O4 nanopetals, induced by oxidizing annealing at 300 \ub0C, considerably improves the performance of the material with respect to simple cobalt oxide films. Photocurrent measurements and electrochemical impedance are used to explain the behavior of the different structures and to highlight their potential application in water remediation technologies