Materials Innovations for Quantum Technology Acceleration: A Perspective.

A broad perspective of quantum technology state of the art is provided and critical stumbling blocks for quantum technology development are identified. Innovations in demonstrating and understanding electron entanglement phenomena using bulk and low-dimensional materials and structures are summarized. Correlated photon-pair generation via processes such as nonlinear optics is discussed. Application of qubits to current and future high-impact quantum technology development is presented. Approaches for realizing unique qubit features for large-scale encrypted communication, sensing, computing, and other technologies are still evolving; thus, materials innovation is crucially important. A perspective on materials modeling approaches for quantum technology acceleration that incorporate physics-based AI/ML, integrated with quantum metrology is discussed.

Electrical and Low Frequency Noise Characterization of Graphene Chemical Sensor Devices Having Different Geometries.

Chemiresistive graphene sensors are promising for chemical sensing applications due to their simple device structure, high sensitivity, potential for miniaturization, low-cost, and fast response. In this work, we investigate the effect of (1) ZnO nanoparticle functionalization and (2) engineered defects onto graphene sensing channel on device resistance and low frequency electrical noise. The engineered defects of interest include 2D patterns of squares, stars, and circles and 1D patterns of slots parallel and transverse to the applied electric potential. The goal of this work is to determine which devices are best suited for chemical sensing applications. We find that, relative to pristine graphene devices, nanoparticle functionalization leads to reduced contact resistance but increased sheet resistance. In addition, functionalization lowers 1/f current noise on all but the uniform mesa device and the two devices with graphene strips parallel to carrier transport. The strongest correlations between noise and engineering defects, where normalized noise amplitude as a function of frequency f is described by a model of AN/fγ, are that γ increases with graphene area and contact area but decreases with device total perimeter, including internal features. We did not find evidence of a correlation between the scalar amplitude, AN, and the device channel geometries. In general, for a given device area, the least noise was observed on the least-etched device. These results will lead to an understanding of what features are needed to obtain the optimal device resistance and how to reduce the 1/f noise which will lead to improved sensor performance.

Chemical gradients on graphene to drive droplet motion.

This work demonstrates the production of a well-controlled, chemical gradient on the surface of graphene. By inducing a gradient of oxygen functional groups, drops of water and dimethyl-methylphosphonate (a nerve agent simulant) are "pulled" in the direction of increasing oxygen content, while fluorine gradients "push" the droplet motion in the direction of decreasing fluorine content. The direction of motion is broadly attributed to increasing/decreasing hydrophilicity, which is correlated to high/low adhesion and binding energy. Such tunability in surface chemistry provides additional capabilities in device design for applications ranging from microfluidics to chemical sensing.

High-quality uniform dry transfer of graphene to polymers.

In this paper we demonstrate high-quality, uniform dry transfer of graphene grown by chemical vapor deposition on copper foil to polystyrene. The dry transfer exploits an azide linker molecule to establish a covalent bond to graphene and to generate greater graphene-polymer adhesion compared to that of the graphene-metal foil. Thus, this transfer approach provides a novel alternative route for graphene transfer, which allows for the metal foils to be reused.

Plasma-based surface modification of polystyrene microtiter plates for covalent immobilization of biomolecules.

In recent years, polymer surfaces have become increasingly popular for biomolecule attachment because of their relatively low cost and desirable bulk physicochemical characteristics. However, the chemical inertness of some polymer surfaces poses an obstacle to more expansive implementation of polymer materials in bioanalytical applications. We describe use of argon plasma to generate reactive hydroxyl moieties at the surface of polystyrene microtiter plates. The plates are then selectively functionalized with silanes and cross-linkers suitable for the covalent immobilization of biomolecules. This plasma-based method for microtiter plate functionalization was evaluated after each step by X-ray photoelectron spectroscopy, water contact angle analysis, atomic force microscopy, and bioimmobilization efficacy. We further demonstrate that the plasma treatment followed by silane derivatization supports direct, covalent immobilization of biomolecules on microtiter plates and thus overcomes challenging issues typically associated with simple physisorption. Importantly, biomolecules covalently immobilized onto microtiter plates using this plasma-based method retained functionality and demonstrated attachment efficiency comparable to commercial preactivated microtiter plates.

Surface composition, chemistry, and structure of polystyrene modified by electron-beam-generated plasma.

Polystyrene (PS) surfaces were treated by electron-beam-generated plasmas in argon/oxygen, argon/nitrogen, and argon/sulfur hexafluoride environments. The resulting modifications of the polymer surface energy, morphology, and chemical composition were analyzed by a suite of complementary analytical techniques: contact angle goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and reflection electron energy loss spectroscopy (REELS). The plasma treatments produced only minimal increases in the surface roughness while introducing the expected chemical modifications: oxygen-based after Ar/O(2) plasma, oxygen- and nitrogen-based after Ar/N(2) plasma, and fluorine-based after Ar/SF(6) plasma. Fluorinated PS surfaces became hydrophobic and did not significantly change their properties over time. In contrast, polymer treated in Ar/O(2) and Ar/N(2) plasmas initially became hydrophilic but underwent hydrophobic recovery after 28 days of aging. The aromatic carbon chemistry in the top 1 nm of these aged surfaces clearly indicated that the hydrophobic recovery was produced by reorientation/diffusion of undamaged aromatic polymer fragments from the bulk rather than by contamination. Nondestructive depth profiles of aged plasma-treated PS films were reconstructed from parallel angle-resolved XPS (ARXPS) measurements using a maximum-entropy algorithm. The salient features of reconstructed profiles were confirmed by sputter profiles obtained with 200 eV Ar ions. Both types of depth profiles showed that the electron-beam-generated plasma modifications are confined to the topmost 3-4 nm of the polymer surface, while valence band measurements and unsaturated carbon signatures in ARXPS and REELS data indicated that much of the PS structure was preserved below 9 nm.

Critical aspects of biointerface design and their impact on biosensor development.

The stable integration of a biological recognition element on a transducing substrate surface is the single most important step in the creation of a high-functioning sensor surface. The key factors affecting biotic and abiotic functionalities at the biointerface are both chemical and physical. Understanding the interactions between biomolecules and surfaces, and their emergent complexity, is critical for biointerface implementation for sensing applications. In this overview, we highlight materials and methods typically used for biosensor development. Particular emphasis has been given to the experimental evaluation of biointerfacial properties and functionality. Promising research directions for application of biointerfaces to biosensing are suggested.

Effect of physicochemical anomalies of soda-lime silicate slides on biomolecule immobilization.

Glass microscope slides are considered by many as the substrate of choice for microarray manufacturing due to their amenability to various surface chemistry modifications. The use of silanes to attach various functional groups onto glass slides has provided a versatile tool for the covalent immobilization of many diverse biomolecules of interest. We recently noted a dramatic reduction in biomolecule immobilization efficiency on standard microscope slides prepared using a well-characterized silanization method. A survey of commercial soda-lime slides yielded the surprising result that slides purchased prior to 2008 had superior immobilization efficiencies when compared to those purchased after 2008. Characterization of the slides by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM), revealed a significant correlation (R > 0.9) between magnesium content, surface roughness, and bioimmobilization efficiency. High performance slides had higher magnesium content and higher root-mean-square (rms) roughness (P < 0.005) than slides with lower bioimmobilization efficiencies. Although the exact mechanism of how magnesium content and surface roughness affect silane deposition has not yet been defined, we show that recent changes in the chemical and physical properties of commercial soda-lime slides affect the ability of these slides to be covalently modified.