Dose influence on the PMMA e-resist for the development of high-aspect ratio and reproducible sub-micrometric structures by electron beam lithography

In this work, a statistical process control method is presented showing the accuracy and the reliability obtained with of PMMA E-resist AR-P 672, using an Elphy Quantum Electron Beam Lithography module integrated on a FE-SEM Zeiss Auriga instrument. Reproducible nanostructures with an high aspect ratio between e-resist thickness and width of written geometric structure are shown. Detailed investigation of geometry features are investigated with dimension in the range of 200nm to 1-m. The adopted method will show how tuning the Area Dose factor and the PMMA thickness it was possible to determine the correct and reproducible parameters that allows to obtain well defined electron-beam features with a 4:1 aspect ratio. Such high aspect ratio opens the possibility to realize an electron-beam lithography lift-off process by using a standard e-beam resist. © 2016 Author(s)

Analysis and synthesis of plasmonic devices and metamaterials at optical and terahertz frequencies

Fabrication technologies have played a major role ever since the ‘60s to the rapid growth of information processing, and to the information revolution we are living today; in the electronic industry, by scaling down the size of devices, it has been possible to improve performance, functionality and reliability, all while reducing cost and increasing the production volume of the devices. Industrial success has given more impetus to further research microfabrication and nanofabrication [1 - 3], which has not only propelled more success, but has also opened to scientists and engineers a new array of physical phenomena to study and apply [4]. Over the last decades, the same fabrication apparatus and approach have allowed significant development in the field of optics, plasmonics, metamaterials, microfluidics and even mechanics [5 - 7]; those are still being extensively researched, sometimes in conjunction, for key applications such as: creation of novel materials, increase in volume of computation and communication, precise medical operations, and sensors for chemistry, biology and telecommunication [8 - 10]. As an example, we can take the plasmonics, where the discovering of a subwavelength confinements [11], coupled to the research of new nano-metamaterials [12, 13], has contributed to different families of the nanodevices with unprecedented functionalities, such as subwavelength waveguides [14, 15], optical nanoantennas [16 – 18], superlenses [19, 20], optical invisibility cloaks [21, 22], hyperlenses [23, 24], planar magnifying hyperlens and light concentrators [25, 26]. In this thesis, I present my research activity as a PhD student which encompasses various projects. My main objective has been the analysis and synthesis of plasmonic filters based on metamaterials; I have also worked on a waveguiding systems and gratings-sensors supporting long range surface plasmon polaritons. The activities were focused mainly on optical frequencies, but some devices worked on THz regime. In the first part of my PhD, I have studied devices working in plasmonic optical frequencies. In order to perform the analysis and design, I have used numerical instruments such as the finite-difference time-domain method (FDTD) included in the software Lumerical FDTD; with the aim to have a numerical comparison for the Lumerical’s results I have also used the Finite Element Method (FEM) present in the Comsol Multyphisics software. The post-processing of the simulation’s results were performed by using Matlab. I could use these tools in the S.B.A.I. (Basic and Applied Sciences for Engineering at Sapienza University of Rome) department and in the LabCEm2 laboratory of the D.I.E.T. (Department of Information Engineering, Electronics and Telecommunications at Sapienza University of Rome). To complete and then expand the analysis performed with numerical instruments in the second part of my PhD I have worked on the fabrication of the devices. With the gradual reduction of the devices’ dimension, various challenges have been encountered: as can be seen in later chapters, while research on nano-optics and metamaterials may be mature from an analytical and numerical point of view, there are still many challenges on the actual fabrication of the devices, because of non-ideality of geometrical shapes, materials and chemical composition; sometimes, even the characterization poses as a limiting factor. Thus, a good part of the activities has been the study of compromises between feasibility and performance of the devices: study on the fabrication tolerances and optimum fabrication dosages. As already told, I have used the same fabrication approach of microelectronics field, which is defined “top down”: externally controlled tools are used to depose, etch, and shape materials (litography) into the desired shape. In contrast, the bottom-up approach the devices are fabricated by using the auto-assembly of molecular components through their chemical bonds; these methods are widely used today to manufacture a large variety of useful chemicals such as pharmaceuticals or commercial polymers. Therefore, I created a nanofabrication procedure following the top-down approach and by using the classics microelectronic processes and techniques: Spin Coating followed by Hot plate for the deposition of polymer materials; Vacuum Evaporator and Sputtering for the deposition of metals and Electron Beam Lithography to imprint the desired geometry to the devices in nano-fabrication; while, for imprint geometry in micro-fabrication field, I used the standard UV-Lithography. I have performed the processes described above in collaboration with the CNR-IMM (Institute for Microelectronics and Microsystem) of Rome and I could use the FESEM Zeiss Auriga system who is kept in the Sapienza’s C.N.I.S. (Centro di Ricerca per le Nanotecnologie Applicate all’Ingegneria) laboratory in order to perform the EBL technique. The characterization of the manufactured samples are finally carried out in collaboration with the CNR-Nanotech institute of nanotechnology and Univesity of Palermo

Polarization-maintaining reflection-mode THz time-domain spectroscopy of a polyimide based ultra-thin narrow-band metamaterial absorber

This paper reports the design, the microfabrication and the experimental characterization of an ultra-thin narrow-band metamaterial absorber at terahertz frequencies. The metamaterial device is composed of a highly flexible polyimide spacer included between a top electric ring resonator with a four-fold rotational symmetry and a bottom ground plane that avoids misalignment problems. Its performance has been experimentally demonstrated by a custom polarization-maintaining reflection-mode terahertz time-domain spectroscopy system properly designed in order to reach a collimated configuration of the terahertz beam. The dependence of the spectral characteristics of this metamaterial absorber has been evaluated on the azimuthal angle under oblique incidence. The obtained absorbance levels are comprised between 67% and 74% at 1.092 THz and the polarization insensitivity has been verified in transverse electric polarization. This offers potential prospects in terahertz imaging, in terahertz stealth technology, in substance identification, and in non-planar applications. The proposed compact experimental set-up can be applied to investigate arbitrary polarization-sensitive terahertz devices under oblique incidence, allowing for a wide reproducibility of the measurements

An interdisciplinary approach to the nanomanipulation of SiO2 nanoparticles. Design, fabricationand feasibility

Although some recent developments in nanotechnology made the prospects of a direct mechanical manipulation of micro- or nano-objects quite realistic, there are still several concerns and difficulties that affect such an endeavor. This is probably due to the large base of knowledge that is necessary to approach the problem of handling a nano-object by means of a nano- or micro-device. Therefore, any progress in this field is possible only by means of an integrated and interdisciplinary approach, which takes into account different aspects of the phenomenon. During the actual pioneering phase, there is a certain convenience in handling nano-objects that: (a) have peculiar known characteristics; (b) are easily recognizable, and (c) are interesting to the scientific community. This paper presents the interdisciplinary activities that were necessary to set up an experiment where specifically synthesized SiO2 particles came in contact with the tips of specifically-designed and -fabricated nanomanipulators. SiO2 mesoporous nanoparticles (KCC-1), having a peculiar dendritic structure, have been selected as a suitable nano-object because of the possibility to easily modulate their morphology. The expected contact force has been also calculated by means of Finite Element Analysis (FEA) electro-mechanical simulations

Analysis of Early Events during the First Year of Tyrosine Kinase Inhibitor Therapy in Patients with Chronic Phase - Chronic Myeloid Leukemia: A "Campus CML" Study

Tyrosine kinase inhibitors (TKIs) revolutionized treatment of chronic myeloid leukemia (CML). However, the rst months of therapy are crucial, as optimal response is dened as the achievement of molecular milestones at 3, 6 and 12 months (mo.) and as many toxicities, also causing a TKI switch, are more frequent in the 1st yea

An Approach to the Extreme Miniaturization of Rotary Comb Drives

The evolution of microelectronic technologies is giving constant impulse to advanced micro-scaled systems which perform complex operations. In fact, the actual micro and nano Electro-Mechanical Systems (MEMS/NEMS) easily integrate information-gathering and decision-making electronics together with all sorts of sensors and actuators. Mechanical manipulation can be obtained through microactuators, taking advantage of magnetostrictive, thermal, piezoelectric or electrostatic forces. Electrostatic actuation, more precisely the comb-drive approach, is often employed due to its high versatility and low power consumption. Moreover, the device design and fabrication process flow can be simplified by compliant mechanisms, avoiding complex elements and unorthodox materials. A nano-scaled rotary comb drive is herein introduced and obtained using NEMS technology, with an innovative design which takes advantages of the compliant mechanism characteristics. A theoretical and numerical study is also introduced to inspect the electro-mechanical behavior of the device and to describe a new technological procedure for its fabrication

Numerical evaluation of irradiation diagram by plasmonic gratings and slit apertures

We describe a fast method to evaluate the far-field profile of a generic planar disposition of plasmonic gratings and slit apertures, based on the ideal decomposition of the structure into a linear array of distinct scattering elements and provided an accurate description of their plasmonic and radiating behaviors. This approach allows for a fast calculation of the irradiation diagram, and has general validity for any kind of surface defects and for multiple set of gratings and slit apertures

Nems-technology based nanogripper for mechanic manipulation in space exploration missions

We present the first prototype of a new concept grasping device whose overall size has been reduced as much as permitted by a new NEMS-based fabrication procedure. The fabrication processes used are compatible with rigid or flexible substrates and the materials employed are biocompatible and chemically inert. The jaws lumen size is adequate to the mechanical manipulation of micro- and sub-microscaled objects and organic matter like bacteria. The proposed device represents a promising solution for pick-transport-place operation and biological experiments for future space exploration missions