IN-SITU TEM PLASMA CHIP NANOFABRICATION AND CHARACTERIZATION

A silicon-based microcell was fabricated with the potential for use in in-situ transmission electron microscopy (TEM) of materials under plasma processing. The microcell consisted of 50 nm-thick film of silicon nitride observation window with 60μm distance between two electrodes. E-beam scattering Mont Carlo simulation showed that the silicon nitride thin film would have very low scattering effect on TEM primary electron beam accelerated at 200 keV. Only 4.7% of primary electrons were scattered by silicon nitride thin film and the Ar gas (60 μm thick at 1 atm pressure) filling the space between silicon nitride films. Theoretical calculation also showed low absorption of high-energy e-beam electrons. Because the plasma cell needs to survive the high vacuum TEM chamber while holding 1 atm internal pressure, a finite element analysis was performed to find the maximum stress the low-stress silicon nitride thin film experienced under pressure. Considering the maximum burst stress of low-stress silicon nitride thin film, the simulation results showed that the 50 nm silicon nitride thin film can be used in TEM under 1 atm pressure as the observation window. Ex-situ plasma generation experiment demonstrated that air plasma can be ignited at DC voltage of 570. A Scanning electron microscopy (SEM) analysis showed that etching and deposition occurred during the plasma process and larger dendrites formed on the positive electrode.

Nanofabrication of Surface-Enhanced Raman Scattering Device by an Integrated Block-Copolymer and Nanoimprint Lithography Method

The integration of block-copolymers and nanoimprint lithography presents a novel and cost-effective approach to achieving nanoscale patterning capabilities. The authors demonstrate the fabrication of a surface-enhanced Raman scattering device using templates created by the block-copolymers nanoimprint lithography integrated method.

Nanofabrication towards biophotonics

This thesis explores methods for fabrication of nanohole arrays, and their integration into a benchtop system for use as sensors or anti-counterfeit labels. Chapter 1 gives an introduction to plasmonics and more specifically nanohole arrays and how they have potential as label free sensors compared to the current biosensors on the market. Various fabrication methods are explored, including Focused Ion Beam, Electron Beam Lithography, Nanoimprint lithography, Template stripping and Phase Shift Lithography. Focused Ion Beam was chosen to fabricate the nanohole arrays due to its suitability for rapid prototyping and it’s relatively low cost. In chapter 2 the fabrication of nanohole arrays using FIB is described, and the samples characterised. The fabricated nanohole arrays are tested as bulk refractive index sensors, before a bioassay using whole molecule human IgG antibodies and antigen is developed and performed on the senor. In chapter 3 the fabricated sensors are integrated into a custom built system, capable of real time, multiplexed detection of biomolecules. Here, scFv antibodies of two biomolecules relevant to the detection of pancreatic cancer (C1q and C3) are attached to the nanohole arrays, and detection of their complementary proteins is demonstrated both in buffer (10 nM detection of C1q Ag) and human serum. Chapter 4 explores arrays of anisotropic (elliptical) nanoholes and shows how the shape anisotropy induces polarisation sensitive transmission spectra, in both simulations and fabricated arrays. The potential use of such samples as visible and NIR tag for anti-counterfeiting applications is demonstrated. Finally, chapter 5 gives a summary of the work completed and discusses potential future work in this area.

Nanostructured Films Based on Carbon Nanotubes and Cobalt for the Electrocatalytic Reduction of H(2)O(2)

This paper presents the fabrication of a nanothick Co-modified film electrochemically synthesized on layer-by-layer (LbL) structures made with dendrimer polyamidoamine/carbon nanotubes (PAMAM/CNT), and its electrocatalytic properties toward H(2)O(2) reduction. Scanning electron microscopy indicated the formation of a homogeneous, 14 nm thick Co film. The porous nature of the PAMAM/CNT LbL film allowed the electrolyte access to the bottom of the electrode, generating a homogenous Co electrodeposit. In addition, the nanostructure based on Co-modified PAMAM/CNT LbL exhibited high electrocatalytic activity for H(2)O(2) reduction when compared to the Co-free PAMAM/CNT LbL film, which demonstrates the suitability of the system studied for biosensing. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3602200] All rights reserved.

A nanopore-based stochastic detection method: Single molecule characterisation of nanoparticles using ()- hemolysin

Dissertation presented to obtain the Ph.D degree in Chemistry.

Improving silicon probe performance through layer-by-layer coating

Fully comprehending brain function, as the scale of neural networks, will only be possi-ble with the development of tools by micro and nanofabrication. Regarding specifically silicon microelectrodes arrays, a significant improvement in long-term performance of these implants is essential. This project aims to create a silicon microelectrode coating that provides high-quality electrical recordings, while limiting the inflammatory response of chronic implants. To this purpose, a combined chitosan and gold nanoparticles coating was produced allied with electrodes modification by electrodeposition with PEDOT/PSS in order to reduce the im-pedance at 1kHz. Using a dip-coating mechanism, the silicon probe was coated and then charac-terized both morphologically and electrochemically, with focus on the stability of post-surgery performance in anesthetized rodents. Since not only the inflammatory response analysis is vital, the electrodes recording degradation over time was also studied. The produced film presented a thickness of approximately 50 μm that led to an increase of impedance of less than 20 kΩ in average. On a 3 week chronic implant, the impedance in-crease on the coated probe was of 641 kΩ, compared with 2.4 MΩ obtained for the uncoated probe. The inflammatory response was also significantly reduced due to the biocompatible film as proved by histological tests.

Organische Mikro- und Nanodrähte auf Basis von Perylendiimiden

Diese Arbeit thematisiert die optimierte Darstellung von organischen Mikro- und Nanodrähten, Untersuchungen bezüglich deren molekularen Aufbaus und die anwendungsorientierte Charakterisierung der Eigenschaften. Mikro- und Nanodrähte haben in den letzten Jahren im Zuge der Miniaturisierung von Technologien an weitreichendem Interesse gewonnen. Solche eindimensionalen Strukturen, deren Durchmesser im Bereich weniger zehn Nanometer bis zu einigen wenigen Mikrometern liegt, sind Gegenstand intensiver Forschung. Neben anorganischen Ausgangssubstanzen zur Erzeugung von Mikro- und Nanodrähten haben organische Funktionsmaterialien aufgrund ihrer einfachen und kostengünstigen Verarbeitbarkeit sowie ihrer interessanten elektrischen und optischen Eigenschaften an Bedeutung gewonnen. Eine wichtige Materialklasse ist in diesem Zusammenhang die Verbindungsklasse der n-halbleitenden Perylentetracarbonsäurediimide (kurz Perylendiimide). Dem erfolgreichen Einsatz von eindimensionalen Strukturen als miniaturisierte Bausteine geht die optimierte und kontrollierte Herstellung voraus. Im Rahmen der Doktorarbeit wurde die neue Methode der Drahterzeugung „Trocknen unter Lösungsmittelatmosphäre“ entwickelt, welche auf Selbstassemblierung der Substanzmoleküle aus Lösung basiert und unter dem Einfluss von Lösungsmitteldampf direkt auf einem vorgegebenen Substrat stattfindet. Im Gegensatz zu literaturbekannten Methoden ist kein Transfer der Drähte aus einem Reaktionsgefäß nötig und damit verbundene Beschädigungen der Strukturen werden vermieden. Während herkömmliche Methoden in einer unkontrolliert großen Menge von ineinander verwundenen Drähten resultieren, erlaubt die substratbasierte Technik die Bildung voneinander separierter Einzelfasern und somit beispielsweise den Einsatz in Einzelstrukturbauteilen. Die erhaltenen Fasern sind morphologisch sehr gleichmäßig und weisen bei Längen von bis zu 5 mm bemerkenswert hohe Aspektverhältnisse von über 10000 auf. Darüber hinaus kann durch das direkte Drahtwachstum auf dem Substrat über den Einsatz von vorstrukturierten Oberflächen und Wachstumsmasken gerichtetes, lokal beschränktes Drahtwachstum erzielt werden und damit aktive Kontrolle auf Richtung und Wachstumsbereich der makroskopisch nicht handhabbaren Objekte ausgeübt werden. Um das Drahtwachstum auch hinsichtlich der Materialauswahl, d. h. der eingesetzten Ausgangsmaterialien zur Drahterzeugung und somit der resultierenden Eigenschaften der gebildeten Strukturen aktiv kontrollieren zu können, wird der Einfluss unterschiedlicher Parameter auf die Morphologie der Selbstassemblierungsprodukte am Beispiel unterschiedlicher Derivate betrachtet. So stellt sich zum einen die Art der eingesetzten Lösungsmittel in flüssiger und gasförmiger Phase beim Trocknen unter Lösungsmittelatmosphäre als wichtiger Faktor heraus. Beide Lösungsmittel dienen als Interaktionspartner für die Moleküle des funktionellen Drahtmaterials im Selbstassemblierungsprozess. Spezifische Wechselwirkungen zwischen Perylendiimid-Molekülen untereinander und mit Lösungsmittel-Molekülen bestimmen dabei die äußere Form der erhaltenen Strukturen. Ein weiterer wichtiger Faktor ist die Molekülstruktur des verwendeten funktionellen Perylendiimids. Es wird der Einfluss einer Bay-Substitution bzw. einer unsymmetrischen Imid-Substitution auf die Morphologie der erhaltenen Strukturen herausgestellt. Für das detaillierte Verständnis des Zusammenhanges zwischen Molekülstruktur und nötigen Wachstumsbedingungen für die Bildung von eindimensionalen Strukturen zum einen, aber auch die resultierenden Eigenschaften der erhaltenen Aggregationsprodukte zum anderen, sind Informationen über den molekularen Aufbau von großer Bedeutung. Im Rahmen der Doktorarbeit konnte ein molekular hoch geordneter, kristalliner Aufbau der Drähte nachgewiesen werden. Durch Kombination unterschiedlicher Messmethoden ist es gelungen, die molekulare Anordnung in Strukturen aus einem Spirobifluoren-substituierten Derivat in Form einer verkippten Molekülstapelung entlang der Drahtlängsrichtung zu bestimmen. Um mögliche Anwendungsbereiche der erzeugten Drähte aufzuzeigen, wurden diese hinsichtlich ihrer elektrischen und optischen Eigenschaften analysiert. Neben dem potentiellen Einsatz im Bereich von Filteranwendungen und Sensoren, sind vor allem die halbleitenden und optisch wellenleitenden Eigenschaften hervorzuheben. Es konnten organische Transistoren auf der Basis von Einzeldrähten mit im Vergleich zu Dünnschichtbauteilen erhöhten Ladungsträgerbeweglichkeiten präpariert werden. Darüber hinaus wurden die erzeugten eindimensionalen Strukturen als aktive optische Wellenleiter charakterisiert. Die im Rahmen der Dissertation erarbeiteten Kenntnisse bezüglich der Bildung von eindimensionalen Strukturen durch Selbstassemblierung, des Drahtaufbaus und erster anwendungsorientierter Charakterisierung stellen eine Basis zur Weiterentwicklung solcher miniaturisierter Bausteine für unterschiedlichste Anwendungen dar. Die neu entwickelte Methode des Trocknens unter Lösungsmittelatmosphäre ist nicht auf den Einsatz von Perylendiimiden beschränkt, sondern kann auf andere Substanzklassen ausgeweitet werden. Dies eröffnet breite Möglichkeiten der Materialauswahl und somit der Einsatzmöglichkeiten der erhaltenen Strukturen.

Patterning and detailed study of human hNT astrocytes on parylene-C/silicon dioxide substrates to the single cell level

It is estimated that the adult human brain contains 100 billion neurons with 5–10 times as many astrocytes. Although it has been generally considered that the astrocyte is a simple supportive cell to the neuron, recent research has revealed new functionality of the astrocyte in the form of information transfer to neurons of the brain. In our previous work we developed a protocol to pattern the hNT neuron (derived from the human teratocarcinoma cell line (hNT)) on parylene-C/SiO2 substrates. In this work, we report how we have managed to pattern hNT astrocytes, on parylene-C/SiO2 substrates to single cell resolution. This article disseminates the nanofabrication and cell culturing steps necessary for the patterning of such cells. In addition, it reports the necessary strip lengths and strip width dimensions of parylene-C that encourage high degrees of cellular coverage and single cell isolation for this cell type. The significance in patterning the hNT astrocyte on silicon chip is that it will help enable single cell and network studies into the undiscovered functionality of this interesting cell, thus, contributing to closer pathological studies of the human brain.

First human hNT neurons patterned on parylene-C/silicon dioxide substrates: Combining an accessible cell line and robust patterning technology for the study of the pathological adult human brain

In this communication, we describe a new method which has enabled the first patterning of human neurons (derived from the human teratocarcinoma cell line (hNT)) on parylene-C/silicon dioxide substrates. We reveal the details of the nanofabrication processes, cell differentiation and culturing protocols necessary to successfully pattern hNT neurons which are each key aspects of this new method. The benefits in patterning human neurons on silicon chip using an accessible cell line and robust patterning technology are of widespread value. Thus, using a combined technology such as this will facilitate the detailed study of the pathological human brain at both the single cell and network level.

First human hNT astrocytes patterned to single cell resolution on parylene-C/Silicon dioxide substrates

In our previous work we developed a successful protocol to pattern the human hNT neuron (derived from the human teratocarcinoma cell line (hNT)) on parylene-C/SiO2 substrates. This communication, reports how we have successfully managed to pattern the supportive cell to the neuron, the hNT astrocyte, on such substrates. Here we disseminate the nanofabrication, cell differentiation and cell culturing protocols necessary to successfully pattern the first human hNT astrocytes to single cell resolution on parylene-C/SiO2 substrates. This is performed for varying parylene strip widths providing excellent contrast to the SiO2 substrate and elegant single cell isolation at 10μm strip widths. The breakthrough in patterning human cells on a silicon chip has widespread implications and is valuable as a platform technology as it enables a detailed study of the human brain at the cellular and network level.

Directed self-assembly of quantum structures by nanomechanical stamping using probe tips

We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs( 100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed.

Upconversion luminescence in Er3+ doped and Er3+/Yb3+ codoped zirconia and hafnia nanocrystals excited at 980 nm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tailored SERS substrates obtained with cathodic arc plasma ion implantation of gold nanoparticles into a polymer matrix

This manuscript reports on the fabrication of plasmonic substrates using cathodic arc plasma ion implantation, in addition to their performance as SERS substrates. The technique allows for the incorporation of a wide layer of metallic nanoparticles into a polymer matrix, such as PMMA. The ability to pattern different structures using the PMMA matrix is one of the main advantages of the fabrication method. This opens up new possibilities for obtaining tailored substrates with enhanced performance for SERS and other surface-enhanced spectroscopies, as well as for exploring the basic physics of patterned metal nanostructures. The architecture of the SERS-active substrate was varied using three adsorption strategies for incorporating a laser dye (rhodamine): alongside the nanoparticles into the polymer matrix, during the polymer cure and within nanoholes lithographed on the polymer. As a proof-of-concept, we obtained the SERS spectra of rhodamine for the three types of substrates. The hypothesis of incorporation of rhodamine molecules into the polymer matrix during the cathodic arc plasma ion implantation was supported by FDTD (Finite-Difference Time-Domain) simulations. In the case of arrays of nanoholes, rhodamine molecules could be adsorbed directly on the gold surface, then yielding a well-resolved SERS spectrum for a small amount of analyte owing to the short-range interactions and the large longitudinal field component inside the nanoholes. The results shown here demonstrate that the approach based on ion implantation can be adapted to produce reproducible tailored substrates for SERS and other surface-enhanced spectroscopies.