Nanoscience and Nanotechnology Commons^™

Dreams Of Molecular Beams: Indium Gallium Arsenide Tensile-Strained Quantum Dots And Advances Towards Dynamic Quantum Dots (Moleculare Radiorum Somnia: Indii Gallii Arsenicus Tensa Quanta Puncta Et Ad Dinamicae Quantae Puntae Progressus), Kevin Daniel Vallejo

Boise State University Theses and Dissertations

Through the operation of a molecular beam epitaxy (MBE) machine, I worked on developing the homoepitaxy of high quality InAs with a (111)A crystallographic orientation. By tuning substrate temperature, we obtained a transition from a 2D island growth mode to step- ow growth. Optimized MBE parameters (substrate temperature = 500 °C, growth rate = 0.12 ML/s and V/III ratio ⩾ 40) lead to growth of extremely smooth InAs(111)A films, free from hillocks and other 3D surface imperfections. We see a correlation between InAs surface smoothness and optical quality, as measured by photoluminescence spectroscopy. This work establishes InAs(111)A as a platform …

Tensile-Strained Germanium Quantum Dots Grown On Indium Aluminum Arsenide (111)A And (110) By Molecular Beam Epitaxy, Kathryn Eva Sautter

Boise State University Theses and Dissertations

Molecular beam epitaxy (MBE) enables the growth of semiconductor nanostructures known as tensile-strained quantum dots (TSQDs). The highly tunable nature of TSQD properties means that they are of interest for a wide variety of applications including for infrared (IR) lasers and light-emitting diodes (LEDs), improved tunnel junction efficiency in multijunction solar cell technology, quantum key encryption, and entangled photon emission. In this project, I focus on one of the most technologically important materials, germanium (Ge). Ge has a high gain coefficient, high electron mobility, and low band gap: all excellent properties for optoelectronic applications. Until recently, these technological advantages were …

Mxenes As Flow Electrodes For Capacitive Deionization Of Wastewater, Naqsh E. Mansoor

Boise State University Theses and Dissertations

The energy-water nexus poses an integrated research challenge, while opening up an opportunity space for the development of energy efficient technologies for water remediation. Capacitive Deionization (CDI) is an upcoming reclamation technology that uses a small applied voltage applied across electrodes to electrophoretically remove dissolved ionic impurities from wastewater streams. Similar to a supercapacitor, the ions are stored in the electric double layer of the electrodes. Reversing the polarity of applied voltage enables recovery of the removed ionic impurities, allowing for recycling and reuse. Simultaneous materials recovery and water reclamation makes CDI energy efficient and resource conservative, with potential to …

Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In_0.52Al_0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we …

In Silico Sequence Optimization For The Reproducible Generation Of Dna Structures, Michael D. Tobiason

Boise State University Theses and Dissertations

Biologically, deoxyribonucleic acid (DNA) molecules have been used for information storage for more than 3 billion years. Today, modern synthesis tools have made it possible to use synthetic DNA molecules as a material for engineering nanoscale structures. These self-assembling structures are capable of both resolutions as fine as 4 angstroms and executing programed dynamic behavior. Numerous approaches for creating structures from DNA have been proposed and validated, however it remains commonplace for engineered systems to exhibit unexpected behaviors such as low formation yields, poor performance, or total failure. It is plausible that at least some of these behaviors arise due …

Additive Manufacturing Of High Performance Flexible Thermoelectric Generators Using Nanoparticle Inks, Tony Valayil Varghese

Boise State University Theses and Dissertations

Flexible thermoelectric devices are attractive power sources for the growing demand of flexible electronics and sensors. Thermoelectric generators have an advantage due to no moving parts, silent operation and constant power production with a thermal gradient.

Conventional thermoelectric devices are rigid and fabricated using complex and relatively costly manufacturing processes, presenting a barrier to increase the market share of this technology. To overcome such barriers, this work focuses on developing near ambient-temperature flexible thermoelectric generators using relatively low-cost additive manufacturing processes. A screen printable ink was developed for transforming nanoparticle ink into high-performance flexible thermoelectric generators with a peak thermoelectric …

Improving The Selectivity And Reducing The Leakage Of Dna Strand Displacement Systems, Shohei Kotani

Boise State University Theses and Dissertations

Because of the elegance of Watson-Crick base pairing and the programmability of toehold-mediated strand displacement, DNA is a model material for designing, building, and testing molecular assemblies. DNA assemblies are categorized as structural when they are at thermodynamic equilibrium and dynamic when they are not. Through programmed perturbations, metastable assemblies perform physical, chemical, and computational work. When integrated into a diagnostic package, disease-specific nucleic acid sequences can be identified, amplified, and analyzed via standard DNA nanotechnology rules. In order for these rules to make an impact, two critical challenges in the field have been undertaken in this dissertation. First, the …

Kinetic Control Of Nucleic Acid Strand Displacement Reactions, Xiaoping Olson

Boise State University Theses and Dissertations

Nucleic acids are information-dense, programmable polymers that can be engineered into primers, probes, molecular motors, and signal amplification circuits for computation, diagnostic, and therapeutic purposes. Signal amplification circuits increase the signal-to-noise ratio of target nucleic acids in the absence of enzymes and thermal cycling. Amplification is made possible via toehold mediated strand displacement – a process where one nucleic acid strand binds to a nucleation site on a complementary helix, which then displaces one of the two strands in a nucleic acid complex. When compared to polymerase chain reactions (PCR), the sensitivity and stability of toehold-mediated strand displacement reactions suffer …

Analog Spiking Neuromorphic Circuits And Systems For Brain- And Nanotechnology-Inspired Cognitive Computing, Xinyu Wu

Boise State University Theses and Dissertations

Human society is now facing grand challenges to satisfy the growing demand for computing power, at the same time, sustain energy consumption. By the end of CMOS technology scaling, innovations are required to tackle the challenges in a radically different way. Inspired by the emerging understanding of the computing occurring in a brain and nanotechnology-enabled biological plausible synaptic plasticity, neuromorphic computing architectures are being investigated. Such a neuromorphic chip that combines CMOS analog spiking neurons and nanoscale resistive random-access memory (RRAM) using as electronics synapses can provide massive neural network parallelism, high density and online learning capability, and hence, paves …

Design, Synthesis, And Characterization Of Nanoscale Optical Devices Using Dna Directed Self-Assembly, William Peter Klein

Boise State University Theses and Dissertations

Near-field energy transfer has great potential for use in nanoscale communications, biosensing, and light harvesting photonic devices. However, the light collecting and energy transferring efficiency of current devices is poor, resulting in few commercially available applications. Current human-made light harvesting devices lack the benefits of natural selection. Natural systems are typically highly optimized and highly efficient. For example, transfer efficiency in photosynthesis is greater than 90%.

In this work, two classes of optical devices were designed, synthesized, and characterized: Plasmonic waveguides and FRET-based photonic devices. In the case of plasmonic waveguides, a multi-scaffold DNA origami synthesis method was developed to …

Electrical Characterization Of Gold Functionalized Dna Origami Nanotubes, Christopher Vinhtroung Buu

Boise State University Theses and Dissertations

Conductivity types (i.e., insulator, semiconductor, and conductor) can be tuned by varying the size of metallic nanoparticles. DNA origami, a molecular self-assembly technique, has promise to programmatically self-assemble nanoparticles (NPs) with nanometer precision. The work presented here demonstrates the programmatic self-assembly of AuNPs on DNA origami nanotubes (NTs). DNA origami NTs were also functionalized with positively charged Au clusters. DNA origami NTs, both bare and functionalized with Au, were electrically characterized using DC current-voltage (DC-IV) measurements. The measurements showed that bare, undecorated DNA NTs behaved as an insulator, whereas linear, ohmic conductivity was observed for Au enhanced Au decorated NTs. …

Moving Forward With Citizen Deliberation: Lessons And Inspiration From The National Citizens' Technology Forum, Jason Delborne, Jen Schneider

Jen Schneider

In his article on the National Citizens' Technology Forum (NCTF) in this chapter, Cobb notes that the NCTF was essentially a decendant of the "consensus conference," a form of political engagement that originated in Denmark and then traveled elsewhere. Sponsored by the Danish Parliament, the Danish Board of Technology was tasked with involving groups of citizens in making informed policy recommendations related to science and technology: these policy recommendations were and are considered by lawmakers in forming science policy. Cobb and others have noted that the consensus conference and related forms of public engagement have garnered significant academic interest in …

Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones

Paul J. Simmonds

In addition to quantized conductance plateaus at integer multiples of 2e²/h, the differential conductance G=dI/dV shows plateaus at 0.25(2e²/h) and 0.75(2e²/h) under applied source-drain bias in In_0.75Ga_0.25As quantum wires defined by insulated split gates. This observation is consistent with a spin-gap model for the 0.7 structure. Using a tilted magnetic field to induce Landau level crossings, the g factor was measured to be ~9 by the coincidence method. This material, with a mobility of 1.8×10⁵ cm …

Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes

Paul J. Simmonds

Two-dimensional electron gases (2DEGs) were formed in undoped In_0.75Al_0.25As / In_0.75Ga_0.25As / In_0.75Al_0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm²/V s and n = 1.36 × 10¹¹ cm⁻² at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a significantly thinner InAlAs …

Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields

Paul J. Simmonds

Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In_0.53Ga_0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10^-6 ns^-1. This corresponds to an internal efficiency of 6.3%.

Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie

Paul J. Simmonds

The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In_0.53Ga_0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10⁻⁶ ns⁻¹ for 1310 nm photons.

Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie

Paul J. Simmonds

The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In_0.524Al_0.476As. InAs QDs both buried in, and on top of, In_0.524Al_0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of almost 700 nm. Increasing growth …