Topographical coloured plasmonic coins

The use of metal nanostructures for colourization has attracted a great deal of interest with the recent developments in plasmonics. However, the current top-down colourization methods based on plasmonic concepts are tedious and time consuming, and thus unviable for large-scale industrial applications. Here we show a bottom-up approach where, upon picosecond laser exposure, a full colour palette independent of viewing angle can be created on noble metals. We show that colours are related to a single laser processing parameter, the total accumulated fluence, which makes this process suitable for high throughput industrial applications. Statistical image analyses of the laser irradiated surfaces reveal various distributions of nanoparticle sizes which control colour. Quantitative comparisons between experiments and large-scale finite-difference time-domain computations, demonstrate that colours are produced by selective absorption phenomena in heterogeneous nanoclusters. Plasmonic cluster resonances are thus found to play the key role in colour formation.Comment: 9 pages, 5 figure

Creating new superconducting & semiconducting nanomaterials and investingating the effect of reduced dimensionality on their properties

The field of nanomaterials has continued to attract researchers to understand the fundamentals and to investigate potential applications in the fields of semiconductor physics, microfabrication, nanomedicine, surface sciences etc. One of the most critical aspects of the nanomaterials research is to establish synthetic protocols, which can address the underlying product requirements of reproducibility, homogenous morphology and controlled elemental composition. We have focused our research in exploring synthetic routes for the synthesis of superconducting and semiconducting nanomaterials and analyze their structure--property relationship through detailed characterizations. The first part of dissertation is focused on the synthesis of superconducting FeSe nanostructures using catalyst assisted chemical vapor deposition (CVD) technique. The effect of catalyst--FeSe interphase on the d spacing of the FeSe nanostructures has been analyzed, and the internal pressure effect on theTc has been investigated further through in depth characterizations. The emphasis of second part is on the development of a simple yet versatile protocol for the synthesis of vertically aligned nanorod arrays on conducting substrate by combining electron beam lithography technique with electrochemical deposition. The technique has been utilized to fabricate photovoltaic CdTe nanorod arrays on conducting substrate and further extended to devise CdS--CdTe nanorod arrays to create radial and lateral p--n junction assembly. Using photo--electrochemical analysis, it was observed that, the nanorod arrays yielded higher photo--electrochemical current compared to the thin film counterpart. The third part of dissertation describes the CVD protocol to synthesize multifunctional, dumbbell shaped Au--CoSe nanoparticles, which possess potential applications in \u27theronostic\u27 biological examinations --Abstract, page iv

Atomic and close-to-atomic scale manufacturing : status and challenges

Next-generation lithography techniques such as Extreme Ultraviolet Lithography have started to reach their physical limits and will not be able to meet the requirements of future Post-Moore Era Integrated Circuit chips that will be based on quantum, photonic, and DNA computing. These future chips and the next generation of quantum products will require sub-10nm and even atomic-scale functional features. Promising candidates for atomic and close-to-atomic scale manufacturing include well-established tip-based techniques such as Scanning Tunnelling Microscopy (STM) and Atomic Force Microscopy (AFM), however, they suffer from severely low throughput, although parallel tips have been suggested to increase the throughput. The integration of these techniques with others such as AFM in Scanning Electron Microscopy has created new hybrid techniques that have greatly enhanced the capabilities of the standalone process. On the other hand, higher throughput techniques like atomic layer etching (ALE) suffer from poor process control and defects despite being promising candidates due to the self-limiting nature of the processes. Studies into laser processing techniques are being investigated to test the feasibility of laser beam-based atomic scale precision manufacturing. Furthermore, the recent progress in quantum simulations has promoted the development of the optical tweezer towards atomic scale manufacturing

AI/ML Algorithms and Applications in VLSI Design and Technology

An evident challenge ahead for the integrated circuit (IC) industry in the nanometer regime is the investigation and development of methods that can reduce the design complexity ensuing from growing process variations and curtail the turnaround time of chip manufacturing. Conventional methodologies employed for such tasks are largely manual; thus, time-consuming and resource-intensive. In contrast, the unique learning strategies of artificial intelligence (AI) provide numerous exciting automated approaches for handling complex and data-intensive tasks in very-large-scale integration (VLSI) design and testing. Employing AI and machine learning (ML) algorithms in VLSI design and manufacturing reduces the time and effort for understanding and processing the data within and across different abstraction levels via automated learning algorithms. It, in turn, improves the IC yield and reduces the manufacturing turnaround time. This paper thoroughly reviews the AI/ML automated approaches introduced in the past towards VLSI design and manufacturing. Moreover, we discuss the scope of AI/ML applications in the future at various abstraction levels to revolutionize the field of VLSI design, aiming for high-speed, highly intelligent, and efficient implementations

Memristives Schaltverhalten in selbst-assemblierten Nanopartikel-Systemen

In this work, the self-assembly of functional nanoparticle composites towards integration into future three-dimensional electronic circuitry was investigated. Using complementary surface-functionalization of metal and semiconductor nanoparticles, self-assembly of heterogeneous nanoparticle agglomerates in dispersion and the formation of nanoparticle arrays on oxide surfaces was shown. Electrical characterization of these systems yielded pronounced non-volatile bipolar memristive switching and threshold switching behavior, respectively.In dieser Arbeit wurde die Selbstassemblierung funktionaler Nanopartikelsysteme in Richtung der Integration in zukünftig dreidimensionale elektronische Schaltkreise untersucht. Durch komplementäre Oberflächenfunktionalisierung von Metall- und Halbleiternanopartikeln wurde die Selbstassemblierung von heterogenen Nanopartikel-Agglomeraten in Lösung und die regelmäßige Anordnung von Nanopartikeln auf Oxidoberflächen gezeigt. Die elektrische Charakterisierung dieser Systeme zeigte jeweils ausgeprägtes nicht-volatiles, bipolares memristives Schaltverhalten und Schwellspannungs-Schaltverhalten

Magnetic field directed self-assembly of gold Pickering emulsion for preparing patterned film.

Patterning plays a vital in role in sensor-based devices like surface-enhanced Raman spectroscopy (SERS), surface-enhanced infrared absorption (SEIRA), radio frequency (RF) antennas and many others. The linear array spacing and width of gold strips has been shown to increase the local intensity through near-field coupling with diffracted electromagnetic waves. This rise in local charge boosts vibrational energies of molecules in close-surface contact or proximity, resulting in increased IR absorption. The strip-like or any other types of patterns are efficiently achieved through top-down nanofabrication processes like atomic-force-deposition, nanoimprinting, UV-Lithography etc., which involve high capital cost, complex processing and occasionally low throughput. This research was therefore undertaken with the aim of reducing the process complexities and improving scalability, by applying a magnetic and spin coating directed self-assembly (MSCDS) to prepare optically sensitive dipole-dipole chain-like ordered arrays of the gold nanoparticle Pickering ferrofluid in polyvinyl alcohol (PVA) emulsion, in the form of a thin film on glass and silicon substrate. Previously-conducted MSCDS processes lacked the control over the dimensions of the prepared patterns. Here, the static magnetic field approach was taken to modify the MSCDS process to overcome the limitation of pattern dimension control, providing tuneability for optical applications. Quantitative image analysis of the patterned thin film allowed for the measurement of pattern geometrical dimension (chain length-CL, chain gap-CG and chain thickness-CT), which was then correlated with processing parameters such as magnetic field configurations (single, compound and concentric), spinning speeds and viscosities of Pickering emulsion. Upon optimization, spectroscopical characterisation was performed on prepared patterned thin film to demonstrate the capability of the modified MSDS process in enhancing the molecular detection at low concentrations. The UV-vis spectra of the patterns demonstrated the impact of CT and CG on the degree of gold-iron oxide nanoscale interactions leading to tuneability of absorption bands between 390-700nm. The coupling of the increased optical sensitivity through enhanced charge transfer dynamics with the mid-infra-red range grating order (CT+CG) resulted in an amplification in vibrational band excitation of molecular bonds. For example, SEIRA measurements of thin film patterns showed a vibrational signal enhancement in asymmetric vibration of -CH2 (2920cm-1) bonds of PVA by 40%, as CT increased by 178% from 1.2μm at probing 45 degree grazing angle. Furthermore, the magneto-optical SERS phenomenon - involving local polarization of gold nanoparticles through the neighbouring magnetised iron oxide nanoparticle in the presence of external magnetic field - was exploited to reveal the varying degree of enhancement in peaks related to Rhodamine 6G (R6G) coated on thin film nanostructure, which was dependent on magnetized CT/CG morphology; especially the C-C-C ring (671 cm-1), for which the Raman peak increased by 12,000% when magnetized by a 43mT field. In summary, the modified MSCDC process is cheap with an expandable throughput rate ( > 0.1 m2/h) and flexible designs, offering both nanoscale and microscale tuneability of pattern dimensions. Even with higher defectivity (~14%) in comparison to the nanoimprinting method, this method can potentially be used to create repetitive array-like structure. Furthermore, the use of iron oxide reduces the cost without sacrificing the optical performance and thus contributes to the optical tuneability of the thin film nanostructure, thereby making the entire product a potential absorbing antenna and microfluidics thin film for biomolecule detection

EXPLORING THE STRUCTURE AND PROPERTIES OF NANOMATERIALS USING ADVANCED ELECTRON MICROSCOPY TECHNIQUES

Nowadays people are relying on all kinds of electronic devices in their daily life. All these devices are getting smaller and lighter with longer battery life due to the improvement of nanotechnology and materials sciences. Electron microscopy (EM) plays a vital role in the evolution of materials characterization which shapes the technology in today’s life. In electron microscopy, electron beam is used as the illumination source instead of visible light used in traditional optical microscopy, the wavelength of an electron is about 105 times shorter than visible light. By taking this advantage, the resolving power and magnification are greatly improved which gives us the ability to understand the morphology and the structure of smaller materials. Besides high resolution and high magnifications, the electron-matter interactions in electron microscopy are also very interesting and provide useful information. Typically, there are three types of post electron-matter interaction electrons, and they are: secondary electrons, backscattered electrons and transmitted electrons. Different signals are carried out with these electron-matter interactions, the most common techniques including electron dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED). In this dissertation, I will discuss how electron microscopy techniques approach complicated nanostructures, such as MnSb2Se4 nanorods to reveal the composition, structure, surfactant controlled size, and relative magnetic properties. Other important features such as mapping localized surface plasmon resonance (LSPR) using EELS and newly developed liquid cell scanning mode transmission electron microscopy (STEM) in situ observation are also presented

Layered architecture for quantum computing

We develop a layered quantum computer architecture, which is a systematic framework for tackling the individual challenges of developing a quantum computer while constructing a cohesive device design. We discuss many of the prominent techniques for implementing circuit-model quantum computing and introduce several new methods, with an emphasis on employing surface code quantum error correction. In doing so, we propose a new quantum computer architecture based on optical control of quantum dots. The timescales of physical hardware operations and logical, error-corrected quantum gates differ by several orders of magnitude. By dividing functionality into layers, we can design and analyze subsystems independently, demonstrating the value of our layered architectural approach. Using this concrete hardware platform, we provide resource analysis for executing fault-tolerant quantum algorithms for integer factoring and quantum simulation, finding that the quantum dot architecture we study could solve such problems on the timescale of days.Comment: 27 pages, 20 figure

Electron Beam Processing of Materials

This Special Issue reprint presents articles from researchers working on materials processing via electron beams as well as on their characterization, properties, and applications. The articles presented cover various topics, including metal melting and welding, additive manufacturing, electron beam irradiation, electron beam lithography, process modeling, etc