Introducing dusty plasma particle growth of nanospherical titanium dioxide

In dusty plasma environments, the spontaneous growth of nanoparticles from reactive gases has been extensively studied for over three decades, primarily focusing on hydrocarbons and silicate particles. Here, we introduce the growth of titanium dioxide, a wide band gap semiconductor, as dusty plasma nanoparticles. The resultant particles exhibited a spherical morphology and reached a maximum homogeneous radius of 230 $\pm$ 17 nm after an elapsed time of 70 seconds. The particle grew linearly and the growth displayed a cyclic behavior; that is, upon reaching their maximum radius, the largest particles fell out of the plasma, and a new growth cycle immediately followed. The particles were collected after being grown for different amounts of time and imaged using scanning electron microscopy. Further characterization was carried out using energy dispersive X-ray spectroscopy, X-ray diffraction and Raman spectroscopy to elucidate the chemical composition and crystalline properties of the maximally sized particles. Initially, the as-grown particles after 70 seconds exhibited an amorphous structure. However, annealing treatments at temperatures of 400 $^\circ$C and 800 $^\circ$C induced crystallization, yielding anatase and rutile phases, respectively. Notably, annealing at 600 $^\circ$C resulted in a mixed phase of anatase and rutile. These findings open new avenues for a rapid and controlled growth technique of titanium dioxide as dusty plasma.Comment: 8 pages, 5 figure

Functional Single-Walled Carbon Nanotubes and Nanoengineered Networks for Organic- and Perovskite-Solar-Cell Applications.

Carbon nanotubes have a variety of remarkable electronic and mechanical properties that, in principle, lend them to promising optoelectronic applications. However, the field has been plagued by heterogeneity in the distributions of synthesized tubes and uncontrolled bundling, both of which have prevented nanotubes from reaching their full potential. Here, a variety of recently demonstrated solution-processing avenues is presented, which may combat these challenges through manipulation of nanoscale structures. Recent advances in polymer-wrapping of single-walled carbon nanotubes (SWNTs) are shown, along with how the resulting nanostructures can selectively disperse tubes while also exploiting the favorable properties of the polymer, such as light-harvesting ability. New methods to controllably form nanoengineered SWNT networks with controlled nanotube placement are discussed. These nanoengineered networks decrease bundling, lower the percolation threshold, and enable a strong enhancement in charge conductivity compared to random networks, making them potentially attractive for optoelectronic applications. Finally, SWNT applications, to date, in organic and perovskite photovoltaics are reviewed, and insights as to how the aforementioned recent advancements can lead to improved device performance provided

Challenges and recent advancements of functionalization of two-dimensional nanostructured molybdenum trioxide and dichalcogenides

Atomically-thin two-dimensional (2D) semiconductors are the thinnest functional semiconducting materials available today. Among them, both molybdenum trioxide and chalcogenides (MT&Ds) represent key components within the family of the different 2D semiconductors for various electronic, optoelectronic and electrochemical applications due to their unique electronic, optical, mechanical and electrochemical properties. However, despite great progress in research dedicated to the development and fabrication of 2D MT&Ds observed within the last decade, there are significant challenges affected their charge transport behavior, fabrication on a large scale as well as high dependence of the carrier mobility on thickness. In this article, we review the recent progress on the carrier mobility engineering of 2D MT&Ds and elaborate devised strategies dedicated to the optimization of MT&Ds properties. Specifically, the latest physical and chemical methods towards the surface functionalization and optimization of the major factors influencing the extrinsic transport at the electrode-2D semiconductor interface are discusse

Laser-controlled synthesis and manipulation of carbon nanotubes

This document presents novel laser-based strategies for controlled synthesis, manipulation, and fabrication of carbon nanotubes (CNTs) and CNT-based devices. CNTs are fascinating materials with extraordinary optical and electrical properties that make them potential candidates for a number of applications. However, integration of CNTs into functional devices is a great challenge in conventional CNT growth techniques. Additionally, applications of CNTs in electronic and optoelectronic devices are limited by variations in their types, chiralities and diameters. During the course of my dissertation project, the main objective of my research has been focused on self-integration of CNTs into functional devices and controlling the structural, electrical and optical properties of CNTs with laser-based strategies. Self-aligned growth and integration of CNTs across the contact electrodes were successfully achieved via optical field enhancement at the tips of silver nanoantennas resulting in selective heating and activation of catalyst nanoparticles for CNT growth. CNT-integrated plasmonic nanoantenna arrays were fabricated for infrared bolometers. We showed that strong concentration of optical fields and the small volume of CNTs in the gaps of the nanoantenna arrays resulted in an enhanced light-CNT interaction and hence improved photoresponse of the bolometers. Due to the inability to selectively synthesize CNTs of a given electronic type, both semiconducting and metallic CNTs exist in the CNT-based devices. Since most electronic and optoelectronic devices depend on semiconducting behavior, the presence of metallic CNTs hinders CNT device development. We presented a method to selectively remove metallic CNTs from the CNT mixtures by coupling a laser beam from an optical parametric oscillator (OPO) into their free electrons to selectively heat and burn the metallic CNTs. Furthermore, electronic and optical properties of semiconductive single-walled carbon nanotubes (SWNTs) were successfully manipulated through the modulation of their diameters in a laser-assisted chemical vapor deposition (LCVD) process. Due to inverse relationship between the diameter and bandgap of semiconducting-SWNTs, modulation of their diameter resulted in unique optical and electronic behaviors. Finally, a laser-based single-step approach was developed for synthesis of CNT/silicon core/shell structures. This was achieved through laser-induced melting and evaporation of CNT-deposited Si substrates using a continuous wavelength CO 2 laser

Laser-Assisted Surface Defects and Pore Reduction of Additive Manufactured Titanium Parts

Laser surface treatment of additively manufactured parts has attracted considerable interest in the past few years due to its flexibility, operation speed, and capability for polishing complex surfaces as compared to conventional mechanical based methods. This study presents the role of laser surface processing in minimizing the surface roughness and pores that have detrimental effects on the fatigue behavior of additively manufactured specimens. This study is performed by a precise laser melting and recrystallization process to close the pores within 70 μm of the surface in order to enhance the fatigue life of these specimens. A continuous-wave fiber laser is employed to investigate the effect of various processing parameters for controlled laser surface treatments in this study.Mechanical Engineerin

Controlled growth of carbon nanotubes on electrodes under different bias polarity

Carbon nanotubes (CNTs) of different alignments, such as surface-bounded and vertically aligned arrays, enable applications in different fields. In this study, controlled growth of CNTs with different alignments was achieved by electrically biasing catalyzed electrodes with different polarities in a laser-assisted chemical vapor deposition process. CNT growth was suggested to be guided by the movement of electrically charged catalyst-nanoparticles under the influence of an external electric field. This discovery provides a convenient approach to control the alignment of CNT arrays for different applications