This LDRD program was directed towards the development of a portable micro-nuclear magnetic resonance ({micro}-NMR) spectrometer for the detection of bioagents via induced amplification of solvent relaxation based on superparamagnetic nanoparticles. The first component of this research was the fabrication and testing of two different micro-coil ({micro}-coil) platforms: namely a planar spiral NMR {micro}-coil and a cylindrical solenoid NMR {micro}-coil. These fabrication techniques are described along with the testing of the NMR performance for the individual coils. The NMR relaxivity for a series of water soluble FeMn oxide nanoparticles was also determined to explore the influence of the nanoparticle size on the observed NMR relaxation properties. In addition, The use of commercially produced superparamagnetic iron oxide nanoparticles (SPIONs) for amplification via NMR based relaxation mechanisms was also demonstrated, with the lower detection limit in number of SPIONs per nanoliter (nL) being determined.
Nanostructured materials are the basis for emerging technologies, such as MEMS, NEMS, sensors, and flexible electronics, that will dominate near term advances in nanotechnology. These technologies are often based on devices containing layers of nanoscale polymer, ceramic and metallic films and stretchable interconnects creating surfaces and interfaces with properties and responses that differ dramatically from bulk counterparts. The differing properties can induce high interlaminar stresses that lead to wrinkling, delamination, and buckling in compression [1,2], and film fracture and decohesion in tension. [3] However, the relationships between composition, structure and properties, and especially adhesion and fracture, are not well-defined at the nanoscale. These relationships are critical to assuring performance and reliability of nanostructured materials and devices. They are also critical for building materials science based predictive models of structure and behavior.
The ''Design and Manufacturing of Complex Optics'' LDRD sought to develop new advanced methods for the design and manufacturing of very complex optical systems. The project team developed methods for including manufacturability into optical designs and also researched extensions of manufacturing techniques to meet the challenging needs of aspherical, 3D, multi-level lenslet arrays on non-planar surfaces. In order to confirm the applicability of the developed techniques, the team chose the Dragonfly Eye optic as a testbed. This optic has arrays of aspherical micro-lenslets on both the exterior and the interior of a 4mm diameter hemispherical shell. Manufacturing of the dragonfly eye required new methods of plunge milling aspherical optics and the development of a method to create the milling tools using focused ion beam milling. The team showed the ability to create aspherical concave milling tools which will have great significance to the optical industry. A prototype dragonfly eye exterior was created during the research, and the methods of including manufacturability in the optical design process were shown to be successful as well.
We investigate evolving surface morphology during focused ion beam bombardment of C and determine its effects on sputter yield over a large range of ion dose (10{sup 17}-10{sup 19} ions/cm{sup 2}) and incidence angles ({Theta} = 0-80{sup o}). Carbon bombarded by 20 keV Ga{sup +} either retains a smooth sputtered surface or develops one of two rough surface morphologies (sinusoidal ripples or steps/terraces) depending on the angle of ion incidence. For conditions that lead to smooth sputter-eroded surfaces there is no change in yield with ion dose after erosion of the solid commences. However, for all conditions that lead to surface roughening we observe coarsening of morphology with increased ion dose and a concomitant decrease in yield. A decrease in yield occurs as surface ripples increase wavelength and, for large {Theta}, as step/terrace morphologies evolve. The yield also decreases with dose as rippled surfaces transition to have steps and terraces at {Theta} = 75{sup o}. Similar trends of decreasing yield are found for H{sub 2}O-assisted focused ion beam milling. The effects of changing surface morphology on yield are explained by the varying incidence angles exposed to the high-energy beam.
We have conducted an extensive study of the evolution of surface morphology of single crystal diamond surfaces during sputtering by 20 keV Ga{sup +} and Ga{sup +} + H{sub 2}O. We observe the formation of well-ordered ripples on the surface for angles of incidence between 40 and 70{sup o}. We have also measured sputter yields as a function of angle of incidence, and ripple wavelength and amplitude dependence on angle of incidence and ion fluence. Smooth surface morphology is observed for <40{sup o}, and a transition to a step-and-terrace structure is observed for >70{sup o}. The formation and evolution of well-ordered surface ripples is well characterized by the model of Bradley and Harper, where sputter-induced roughening is balanced by surface transport smoothing. Smoothing is consistent with an ion-induced viscous relaxation mechanism. Ripple amplitude saturates at high ion fluence, confirming the effect of nonlinear processes. Differences between Ga{sup +} and Ga{sup +} + H{sub 2}O in ripple wavelength, amplitude, and time to saturation of amplitude are consistent with the increased sputter yield observed for Ga{sup +} + H{sub 2}O. For angle of incidence <40{sup o}, an ion bombardment-induced 'atomic drift' mechanism for surface smoothing may be responsible for suppression of ripple formation. For Ga{sup +} + H{sub 2}O, we observe anomalous formation of very large amplitude and wavelength, poorly ordered surface ridges for angle of incidence near 40{sup o}. Finally, we observe that ripple initiation on smooth surfaces can take place by initial stochastic roughening followed by evolution of increasingly well-ordered ripples.
Adhesion is an important factor in controlling properties and performance of thin film devices. It is a critical factor in hybrid microcircuits with multilayer films and dissimilar metal interconnects where diffusion of copper from leads during processing and environmental effects during service can modify the adhesion strength of the gold conductive films. Previous work using gold and gold-copper alloy films to simulate different stages of processing and service showed that copper in solution improved film adhesion. More importantly, it took a combination of stressed overlayers and nanoindentation to trigger interfacial fracture of the gold-copper alloy films. The improvement in performance scaled directly with an increase in film strength. However, during two years air exposure telephone cord buckles formed at the gold-copper alloy film edges, grew slowing across the film surface, and eventually covered the sample. Formation of these buckles shows that a significant degradation in interfacial fracture strength had occurred in these films. We characterized the size and shape of the blisters that formed during nanoindentation of the as-deposited films and in the films following aging. These measurements were then combined with mechanics-based models to determine residual stresses and interfacial fracture energies. This analysis shows that air aging decreased the mode I interfacial fracture energy for the gold-copper alloy film from 3.2 J/m{sup 2} to 1.5 J/m{sup 2}. A similar decrease in fracture energy has been observed for many systems exposed to hydrogen from processing and environmental exposure, including copper films, beryllium films, steels and iron- and nickel-based superalloys. This paper describes the effect of environment on resistance of gold-copper alloy film systems to premature interfacial failure, and by comparison with previous studies shows it can be attributed to hydrogen embrittlement.
Recent world events have underscored the need for a satellite based persistent global surveillance capability. To be useful, the satellite must be able to continuously monitor objects the size of a person anywhere on the globe and do so at a low cost. One way to satisfy these requirements involves a constellation of satellites in low earth orbit capable of resolving a spot on the order of 20 cm. To reduce cost of deployment, such a system must be dramatically lighter than a traditional satellite surveillance system with a high spatial resolution. The key to meeting this requirement is a lightweight optics system with a deformable primary and secondary mirrors and an adaptive optic subsystem correction of wavefront distortion. This proposal is concerned with development of MEMS micromirrors for correction of aberrations in the primary mirror and improvement of image quality, thus reducing the optical requirements on the deployable mirrors. To meet this challenge, MEMS micromirrors must meet stringent criteria on their performance in terms of flatness, roughness and resolution of position. Using Sandia's SUMMIT foundry which provides the world's most sophisticated surface MEMS technology as well as novel designs optimized by finite element analysis will meet severe requirements on mirror travel range and accuracy.
We have researched several new focused ion beam (FIB) micro-fabrication techniques that offer control of feature shape and the ability to accurately define features onto nonplanar substrates. These FIB-based processes are considered useful for prototyping, reverse engineering, and small-lot manufacturing. Ion beam-based techniques have been developed for defining features in miniature, nonplanar substrates. We demonstrate helices in cylindrical substrates having diameters from 100 {micro}m to 3 mm. Ion beam lathe processes sputter-define 10-{micro}m wide features in cylindrical substrates and tubes. For larger substrates, we combine focused ion beam milling with ultra-precision lathe turning techniques to accurately define 25-100 {micro}m features over many meters of path length. In several cases, we combine the feature defining capability of focused ion beam bombardment with additive techniques such as evaporation, sputter deposition and electroplating in order to build geometrically-complex, functionally-simple devices. Damascene methods that fabricate bound, metal microcoils have been developed for cylindrical substrates. Effects of focused ion milling on surface morphology are also highlighted in a study of ion-milled diamond.
Many microfabrication techniques are being developed for applications in microelectronics, microsensors, and micro-optics. Since the advent of microcomponents, designers have been forced to modify their designs to include limitations of current technology, such as the inability to make three-dimensional structures and the need for piece-part assembly. Many groups have successfully transferred a wide variety of patterns to both two-dimensional and three-dimensional substrates using microcontact printing. Microcontact printing is a technique in which a self-assembled monolayer (SAM) is patterned onto a substrate by transfer printing. The patterned layer can act as an etch resist or a foundation upon which to build new types of microstructures. We created a gold pattern with features as small as 1.2 {micro}m using microcontact printing and subsequent processing. This approach looks promising for constructing single-level structures such as microelectrode arrays and sensors. It can be a viable technique for creating three-dimensional structures such as microcoils and microsprings if the right equipment is available to achieve proper alignment, and if a means is available to connect the final parts to other components in subsequent assembly operations. Microcontact printing provides a wide variety of new opportunities in the fabrication of microcomponents, and increases the options of designers.
The effects of H{sub 2}O vapor introduced during focused ion beam (FIB) milling of diamond(100) are examined. In particular, we determine the yield, surface morphology, and microstructural damage that results from FIB sputtering and H{sub 2}O-assisted FIB milling processes. Experiments involving 20 keV Ga{sup +} bombardment to doses {approx}10{sup 18} ions/cm{sup 2} are conducted at a number of fixed ion incidence angles, {theta}. For each {theta} selected, H{sub 2}O-assisted ion milling shows an increased material removal rate compared with FIB sputtering (no gas assist). The amount by which the yield is enhanced depends on the angle of incidence with the largest difference occurring at {theta} = 75{sup o}. Experiments that vary pixel dwell time from 3 {micro}s to 20 ms while maintaining a fixed H{sub 2}O gas pressure demonstrate the additional effect of beam scan rate on yield for gas-assisted processes. Different surface morphologies develop during ion bombardment depending on the angle of ion incidence and the presence/absence of H{sub 2}O. In general, a single mode of ripples having a wave vector aligned with the projection of the ion beam vector forms for {theta} as high as 70{sup o}. H{sub 2}O affects this morphology by lowering the ripple onset angle and decreasing the ripple wavelength. At high angles of incidence ({theta} > 70{sup o}) a step/terrace morphology is observed. H{sub 2}O-assisted milling at {theta} > 70{sup o} results in a smoother stepped surface compared with FIB sputtering. Transmission electron microscopy shows that the amorphized thickness is reduced by 20% when using H{sub 2}O-assisted FIB milling.
A test method, the Tensile Brazil Nut Sandwich (TBNS) specimen, was developed to measure mixed-mode interfacial toughness of bonded materials. Interfacial toughness measured by this technique is compared to the interfacial toughness of thin film adhesive coatings using a nanoindentation technique. The interfacial toughness of solvent-cast and melt-spun adhesive thin films is compared and found to be similar. Finally, the Johnson-Kendall-Roberts (JKR) technique is used to evaluate the cleanliness of aluminum substrates.
This document summarizes research of reactively deposited metal hydride thin films and their properties. Reactive deposition processes are of interest, because desired stoichiometric phases are created in a one-step process. In general, this allows for better control of film stress compared with two-step processes that react hydrogen with pre-deposited metal films. Films grown by reactive methods potentially have improved mechanical integrity, performance and aging characteristics. The two reactive deposition techniques described in this report are reactive sputter deposition and reactive deposition involving electron-beam evaporation. Erbium hydride thin films are the main focus of this work. ErH{sub x} films are grown by ion beam sputtering erbium in the presence of hydrogen. Substrates include a Al{sub 2}O{sub 3} {l_brace}0001{r_brace}, a Al{sub 2}O{sub 3} {l_brace}1120{r_brace}, Si{l_brace}001{r_brace} having a native oxide, and polycrystalline molybdenum substrates. Scandium dideuteride films are also studied. ScD{sub x} is grown by evaporating scandium in the presence of molecular deuterium. Substrates used for scandium deuteride growth include single crystal sapphire and molybdenum-alumina cermet. Ultra-high vacuum methods are employed in all experiments to ensure the growth of high purity films, because both erbium and scandium have a strong affinity for oxygen. Film microstructure, phase, composition and stress are evaluated using a number of thin film and surface analytical techniques. In particular, we present evidence for a new erbium hydride phase, cubic erbium trihydride. This phase develops in films having a large in-plane compressive stress independent of substrate material. Erbium hydride thin films form with a strong <111> out-of-plane texture on all substrate materials. A moderate in-plane texture is also found; this crystallographic alignment forms as a result of the substrate/target geometry and not epitaxy. Multi-beam optical sensors (MOSS) are used for in-situ analysis of erbium hydride and scandium hydride film stress. These instruments probe the evolution of film stress during all stages of deposition and cooldown. Erbium hydride thin film stress is investigated for different growth conditions including temperature and sputter gas, and properties such as thermal expansion coefficient are measured. The in-situ stress measurement technique is further developed to make it suitable for manufacturing systems. New features added to this technique include the ability to monitor multiple substrates during a single deposition and a rapidly switched, tiltable mirror that accounts for small differences in sample alignment on a platen.
The stress of scandium dideuteride, ScD{sub 2}, thin films is investigated during each stage of vacuum processing including metal deposition via evaporation, reaction and cooldown. ScD{sub 2} films with thin Cr underlayers are fabricated on three different substrate materials: molybdenum-alumina cermet, single crystal sapphire and quartz. In all experiments, the evaporated Cr and Sc metal is relatively stress-free. However, reaction of scandium metal with deuterium at elevated temperature to form a stoichiometric dideuteride phase leads to a large compressive in-plane film stress. Compression during hydriding results from an increased atomic density compared with the as-deposited metal film. After reaction with deuterium, samples are cooled to ambient temperature, and a tensile stress develops due to mismatched coefficients of thermal expansion (CTE) of the substrate-film couple. The residual film stress and the propensity for films to crack during cooldown depends principally on the substrate material when using identical process parameters. Films deposited onto quartz substrates show evidence of stress relief during cooldown due to a large CTE misfit; this is correlated with crack nucleation and propagation within films. All ScD{sub 2} layers remain in a state of tension when cooled to 30 C. An in-situ, laser-based, wafer curvature sensor is designed and implemented for studies of ScD{sub 2} film stress during processing. This instrument uses a two-dimensional array of laser beams to noninvasively monitor stress during sample rotation and with samples stationary. Film stress is monitored by scattering light off the backside of substrates, i.e., side opposite of the deposition flux.
Meso-scale manufacturing processes are bridging the gap between silicon-based MEMS processes and conventional miniature machining. These processes can fabricate two and three-dimensional parts having micron size features in traditional materials such as stainless steels, rare earth magnets, ceramics, and glass. Meso-scale processes that are currently available include, focused ion beam sputtering, micro-milling, micro-turning, excimer laser ablation, femtosecond laser ablation, and micro electro discharge machining. These meso-scale processes employ subtractive machining technologies (i.e., material removal), unlike LIGA, which is an additive meso-scale process. Meso-scale processes have different material capabilities and machining performance specifications. Machining performance specifications of interest include minimum feature size, feature tolerance, feature location accuracy, surface finish, and material removal rate. Sandia National Laboratories is developing meso-scale mechanical components and actuators which require meso-scale parts fabricated in a variety of materials. Subtractive meso-scale manufacturing processes expand the functionality of meso-scale components and complement silicon based MEMS and LIGA technologies.
This paper presents techniques for fabricating microscopic, curvilinear features in a variety of workpiece materials. Micro-grooving and micro-threading tools having cutting widths as small as 13 {micro}m are made by focused ion beam sputtering and used for ultra-precision machining. Tool fabrication involves directing a 20 keV gallium beam at polished cylindrical punches made of cobalt M42 high-speed steel or C2 tungsten carbide to create a number of critically aligned facets. Sputtering produces rake facets of desired angle and cutting edges having radii of curvature equal to 0.4 {micro}m. Clearance for minimizing frictional drag of a tool results from a particular ion beam/target geometry that accounts for the sputter yield dependence on incidence angle. It is believed that geometrically specific cutting tools of this dimension have not been made previously. Numerically controlled, ultra-precision machining with micro-grooving tools results in a close match between tool width and feature size. Microtools are used to machine 13 {micro}m wide, 4 {micro}m deep, helical grooves in polymethyl methacrylate and 6061 Al cylindrical workplaces. Micro-grooving tools are also used to fabricate sinusoidal cross-section features in planar metal samples.
Meso-scale manufacturing processes are bridging the gap between silicon-based MEMS processes and conventional miniature machining. These processes can fabricate two and three-dimensional parts having micron size features in traditional materials such as stainless steels, rare earth magnets, ceramics, and glass. Meso-scale processes that are currently available include, focused ion beam sputtering, micro-milling, micro-turning, excimer laser ablation, femto-second laser ablation, and micro electro discharge machining. These meso-scale processes employ subtractive machining technologies (i.e., material removal), unlike LIGA, which is an additive meso-scale process. Meso-scale processes have different material capabilities and machining performance specifications. Machining performance specifications of interest include minimum feature size, feature tolerance, feature location accuracy, surface finish, and material removal rate. Sandia National Laboratories is developing meso-scale electro-mechanical components, which require meso-scale parts that move relative to one another. The meso-scale parts fabricated by subtractive meso-scale manufacturing processes have unique tribology issues because of the variety of materials and the surface conditions produced by the different meso-scale manufacturing processes.