Ron Manginell

Hand-Held Miniature Chemical Analysis System (μChemlab) for Detection of Trace Concentrations of Gas Phase Analytes

A miniature, integrated chemical laboratory (μChemLab) is being developed that utilizes microfabrication to provide faster response, smaller size, lower power operation, and an ability to utilize multiple analysis channels for enhanced versatility and chemical discrimination. Improved sensitivity and selectivity are achieved with three cascaded components: (1) a sample collector/concentrator, (2) a gas chromatographic (GC) separator, and (3) a chemically selective surface acoustic wave (SAW) array detector. Prototypes of all three components have been developed and demonstrated both individually and when integrated on a novel electrical and fluidic printed circuit board. A hand-held autonomous system containing two analysis channels and all supporting electronics and user interfaces is currently being assembled and tested.

A silicon metal-oxide-semiconductor electron spin-orbit qubit

The silicon metal-oxide-semiconductor (MOS) material system is a technologically important implementation of spin-based quantum information processing. However, the MOS interface is imperfect leading to concerns about 1/f trap noise and variability in the electron g-factor due to spin–orbit (SO) effects. Here we advantageously use interface–SO coupling for a critical control axis in a double-quantum-dot singlet–triplet qubit. The magnetic field-orientation dependence of the g-factors is consistent with Rashba and Dresselhaus interface–SO contributions. The resulting all-electrical, two-axis control is also used to probe the MOS interface noise. The measured inhomogeneous dephasing time,

Characterization of thin GaAs films grown on nanostructured silicon substrates

T_{{\mathrm{2m}}}^ \star

Investigation of optical absorption in thin-film Si/Ge solar cells

T2m⋆, of 1.6 μs is consistent with 99.95% 28Si enrichment. Furthermore, when tuned to be sensitive to exchange fluctuations, a quasi-static charge noise detuning variance of 2 μeV is observed, competitive with low-noise reports in other semiconductor qubits. This work, therefore, demonstrates that the MOS interface inherently provides properties for two-axis qubit control, while not increasing noise relative to other material choices.As the performance of silicon-based qubits has improved, there has been increasing focus on developing designs that are compatible with industrial processes. Here, Jock et al. exploit spin-orbit coupling to demonstrate full, all-electrical control of a metal-oxide-semiconductor electron spin qubit.Ryan M. Jock, ∗ N. Tobias Jacobson, Patrick Harvey-Collard, 3 Andrew M. Mounce, Vanita Srinivasa, Dan R. Ward, John Anderson, Ron Manginell, Joel R. Wendt, Martin Rudolph, Tammy Pluym, John King Gamble, Andrew D. Baczewski, Wayne M. Witzel, and Malcolm S. Carroll † Sandia National Laboratories, Albuquerque, NM 87185, USA Center for Computing Research, Sandia National Laboratories, Albuquerque, NM 87185, USA Département de physique et Institut quantique, Université de Sherbrooke, 2500 boul. de l’Université, Sherbrooke, QC, J1K 2R1, Canada

Absorption enhancement in thin-film silicon solar cells in SOI configuration using physical and geometrical optics

Sandia National Laboratories has developed both gas and liquid phase chemical analysis systems. An autonomous hand-held system has been fabricated and demonstrated for sensitive and selective detection of gas phase chemical warfare agents. Recent efforts have focused on maturing this technology and extending its application to other analytical needs. We have now fabricated an on-chip packed gas chromatography column and demonstrated its ability to separate gases such as methane, ethane, ethylene, and acetylene. We have also demonstrated the use of a thermally isolated membrane to rapidly modify and pyrolize fatty acids to form volatile fatty acid methyl esters (FAMEs). This new tool is useful in analyzing biological samples. Finally, we have used rapid temperature ramping of our on-chip open tubular columns to enable separation of low volatility analytes such as explosives and FAMEs. These new capabilities significantly extend the applicability of Sandia’s µChemLab™ technology.

Miniature microwave frequency standard with trapped 171 Yb

Compound semiconductor multi-junction solar cells are limited to small sizes (4-inch diameters) and are expensive due to starting wafer costs such as Ge and GaAs. High-quality GaAs films grown on Si substrates addresses many of these challenges. GaAs growth on high aspect ratio Si nanostructures has been investigated. High aspect ratio nanostructures can serve as templates for defect reduction as well as sacrificial layers. Thin (∼ 5 µm) films of GaAs have been grown on a wide range of Si nanostructures using MBE and MOCVD methods. Both methods demonstrate effectiveness of defect density reduction with nanostructured surfaces. With MBE method, a high density of whisker growth is observed. With MOCVD growth, whisker-free relatively smooth surfaces have been produced. PL signal is also stronger with lower full width at half maximum from the MOCVD grown films. Spectral transmission measurements exhibit GaAs band edge consistent with crystalline GaAs substrates. A systematic effort aimed at growth optimization on nanostructured Si surfaces is expected to lead to defect density reduction in 103/cm2 range.

An investigation of three-dimensional texturing in silicon solar cells for enhanced optical absorption

In Si solar cells, the cost of the Si wafer itself accounts for over 50 % of energy conversion; therefore, economic use of Si contributes significantly towards lowering cost. Thin-film (∼ 25 µm) crystalline Si (c-Si) solar cells films are ideally-suited for low-cost photovoltaics. These thin-film c-Si solar cells are manufactured through a wide range of industrial processes including epitaxial growth, smart-cut, and layer transfer. In these devices, weak optical absorption of Si fundamentally limits performance. Historically, several surface texturing mechanisms have evolved to enhance optical absorption in solar cells. Most of geometrical-optics based texturing mechanisms require etched features comparable to thin-film thickness. As a result, randomly-created subwavelength structures are finding increasing applications for reducing surface reflection as well as enhancing near IR absorption. We report on diffractive and physical optics mechanisms in enhancing absorption in thin Si films. Randomly-created subwavelength diffractive structures as well periodically-patterned deeply-etched subwavelength structures have been demonstrated to be highly effective in reducing reflection and creating broadband absorption using scattering and physical optics mechanisms.

Towards an Integrated Microneedle Total Analysis Chip for Protein Detection

Thin-film, high efficiency crystalline Si solar cells promise significant cost savings in contrast with conventional substrate solar cells. These savings are achieved through reduced Si usage assuming highly (∼ 20–30%) efficient thin film Si solar cells can be manufactured. A necessary condition for high efficiency solar cells in thin-film configurations is complete optical absorption of sunlight. However, due to its indirect bandgap, Si has inherently weak absorption in near IR region so thicker films are required to accommodate longer path lengths. Even incorporation of scattering mechanisms (geometrical, diffractive, and physical) is not enough to achieve complete absorption in Si thin-films. We propose thin-film crystalline Si/Ge solar cell configuration in which the top surface comprises of thin Si film and the bottom surface of thin Ge film. This heterojunction solar cell combines the best attributes of both materials with strong Si absorption in the visible followed by absorption in Ge through most of the near IR region. The absorption spectrum ranges from 300 nm to 1600 nm in this solar cell with only two thin film layers. This approach has not been investigated extensively in past due to technical challenges associated with growth of high-quality Ge layers on Si. We have demonstrated growth of very high quality SixGe1−x and Ge films on nanostructured Si substrates, thus, identifying a promising pathway in addressing the fundamental problem of pseudomorphic growth of Ge on Si, a necessary condition for high efficiency heterojunction Si/Ge thin-film solar cells. Preliminary optical measurements on Si/Ge films exhibit strong absorption dependence on growth quality.