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Jesse, Stephen

Publications and source records attributed to Jesse, Stephen.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Electrochemical Strain Microscopy: Probing Electrochemical Transformations in Nanoscale Volumes

Electrochemical and electrocatalytic phenomena underpin a broad spectrum of energy, chemical, and information technologies. Examples range from electrocatalytic activation of oxygen reduction reactions in fuel cells, gas-solid reactions, and ionic transport in gas sensors and oxygen pumps, to a wide gamut of electrochemical and transport phenomena in primary and secondary batteries. Equally important is the role of ionic phenomena in information technologies, as exemplified by a recent wave of interest in memristive and electroresisitive information storage and logic devices. Finally, this article examines a new type of scanning probe microscopy (SPM), referred to as electrochemical strain microscopy (ESM), that can provide a better understanding of these complex phenomena.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Nanoscale Ferroelectricity in Crystalline γ-Glycine

Ferroelectrics are multifunctional materials that reversibly change their polari-zation under an electric fi eld. Recently, the search for new ferroelectrics has focused on organic and bio-organic materials, where polarization switching is used to record/retrieve information in the form of ferroelectric domains. This progress has opened a new avenue for data storage, molecular recognition, and new self-assembly routes. Crystalline glycine is the simplest amino acid and is widely used by living organisms to build proteins. Here, it is reported for the fi rst time that γ- glycine, which has been known to be piezoelectric since 1954, is also a ferroelectric , as evidenced by local electromechanical measurements and by the existence of as-grown and switchable ferroelectric domains in microcrystals grown from the solution. The experimental results are rationalized by molecular simulations that establish that the polarization vector in γ- glycine can be switched on the nanoscale level, opening a pathway to novel classes of bioelectronic logic and memory devices.

Chemistry↗
DOE OSTI2012

Nanoscale origins of nonlinear behavior in ferroic thin-films

The nonlinear response of a ferroic to an applied stimulus (e.g. electric field, mechanical stress) is a fundamental characteristic that underpins a number of technologically significant applications[1-3]. It is also the driving feature in numerous physical phenomena, such as interfacial motion[4,5], spin glasses[6], relaxors[7] and phase transitions[8]. In particular, nonlinearity associated with minor hysteresis loops is an extremely useful avenue to explore energy dissipation and losses in such systems. This knowledge is necessary for the design of future materials with enhanced low-field properties. Quantitatively, the macroscopic nonlinear response of ferroic systems at low to mid-range amplitudes of driving fields is given by the phenomenological Rayleigh law[9], first conceived in 1887 for magnetic materials. Yet, the applicability of the Rayleigh law at small length scales has not been extensively studied. Here, we show using a combination of scanning probe techniques and phase field modeling, that nanoscale response appears to follow a non-Rayleigh regime. However, through statistical analysis, we find that a distribution in the individual responses can lead to directly to Rayleigh-like behavior of the strain on a macroscale. The studies shed light on the nanoscale origins of nonlinear behavior in disordered ferroics.

ferroelectric↗
DOE OSTI2012

Banded Spherulitic Morphology in Blends of Poly(propylene fumarate) and Poly( -caprolactone) and Interaction with MC3T3-E1 Cells

The thermal properties, morphological development, crystallization behavior, and miscibility of semicrystalline PCL and its 25, 50, and 75 wt% blends with amorphous PPF in spin-coated thin films crystallized at various crystallization temperatures (T{sub c}) from 25 to 52 C are investigated. The surface roughness of PPF/PCL ({phi}{sub PCL} = 75%) films increases with increasing T{sub c} and consequently the adsorption of serum proteins is also increased. No significant variance is found in surface hydrophilicity or in mouse MC3T3-E1 cell attachment, spreading, and proliferation on PPF/PCL ({phi}{sub PCL} = 75%) films crystallized isothermally at 25, 37, and 45 C, because of low ridge height, nonuniformity in structures, and PPF surface segregation

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Local detection of activation energy for ionic transport in lithium cobalt oxide

Local activation energy for ionic diffusion is probed on the nanometer level in LiCoO{sub 2} thin films using variable temperature electrochemical strain microscopy (ESM). The high spatial resolution of ESM allows one to extract information about ionic activation energies on the level of individual grains and grain facets, thus bridging the lengths scales of atomistic calculations and traditional macroscopic experiments. A series of control experiments have been performed and possible signal generating mechanisms are discussed to explain the temperature-dependent ESM measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Probing surface and bulk electrochemical processes on the LaAlO3-SrTiO3 interface

Local electrochemical phenomena on the surfaces of LaAlO3-SrTiO3 heterostructure are explored using unipolar and bipolar dynamic electrochemical strain microscopy (D-ESM). The D-ESM suggests the presence of at least two distinct electrochemical processes, including fast reversible low-voltage process and slow high-voltage process. The latter process is associated with static surface deformations in the sub-nm regime. These behaviors are compared with Kelvin Probe Force Microscopy hysteresis data. The possible origins of observed phenomena are discussed and these studies suggest that charge-writing behavior in LAO-STO include strong surface/bulk electrochemical component and are more complicated than simple screening by surface adsorbates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Ionically-mediated electromechanical hysteresis in transition metal oxides

Electromechanical activity, remanent polarization states, and hysteresis loops in paraelectric TiO2 and SrTiO3 are observed. The coupling between the ionic dynamics and incipient ferroelectricity in these materials is analyzed using extended Ginsburg Landau Devonshire (GLD) theory. The possible origins of electromechanical coupling including ionic dynamics, surface-charge induced electrostriction, and ionically-induced ferroelectricity are identified. For the latter, the ionic contribution can change the sign of first order GLD expansion coefficient, rendering material effectively ferroelectric. These studies provide possible explanation for ferroelectric-like behavior in centrosymmetric transition metal oxides.

Kim, Yunseok↗
DOE OSTI2012

Controlling magnetoelectric coupling by nanoscale phase transformation instrain engineered bismuth ferrite

The magnetoelectric coupling in multiferroic materials is promising for a wide range of applications, yet manipulating magnetic ordering by electric field proves elusive to obtain and difficult to control. In this paper, we explore the prospect of controlling magnetic ordering in misfit strained bismuth ferrite (BiFeO3, BFO) films, combining theoretical analysis, numerical simulations, and experimental characterizations. Electric field induced transformation from a tetragonal phase to a distorted rhombohedral one in strain engineered BFO films has been identified by thermodynamic analysis, and realized by scanning probe microscopy (SPM) experiment. By breaking the rotational symmetry of a tip-induced electric field as suggested by phase field simulation, the morphology of distorted rhombohedral variants has been delicately controlled and regulated. Such capabilities enable nanoscale control of magnetoelectric coupling in strain engineered BFO films that is difficult to achieve otherwise, as demonstrated by phase field simulations.

42 ENGINEERING↗
DOE OSTI2012

Half-harmonic Kelvin probe force microscopy with transfer function correction

An approach for surface potential imaging based on half-harmonic band excitation (BE) in Kelvin probe force microscopy is demonstrated. Using linear and half-harmonic BE enables quantitative correction of the cantilever transfer function. Half-harmonic band excitation Kelvin probe force microscopy (HBE KPFM) thus allows quantitative separation of surface potential and topographic contributions to the signal, obviating the primary sources of topographic cross-talk. HBE KPFM imaging and voltage spectroscopy methods are illustrated for several model systems.

Guo, Senli↗
DOE OSTI2012

Dynamic piezoresponse force microscopy: Spatially resolved probing of polarization dynamics in time and voltage domains

An approach for probing dynamic phenomena during hysteresis loop measurements in piezoresponse force microscopy (PFM) is developed. Dynamic PFM (D-PFM) necessitates development of 5-dimensional (5D) data acquisition protocols and associated methods for analysis and visualization of multidimensional data. Using a combination of multivariate statistical analysis and phenomenological fitting, we explore dynamic behavior during polarization switching in model ferroelectric films with dense ferroelastic domain structures and in ferroelectric capacitors. In polydomain films, multivariate analysis of the switching data suggests that ferroelectric and ferroelastic components can be decoupled and time dynamics can be explored. In capacitors, a strong correlation between polarization dynamics and microstructure is observed. The future potential of D-PFM for probing time-dependent hysteretic phenomena in ferroelectrics and ionic systems is discussed.

Dynamic piezoresponse force microscopy↗
DOE OSTI2012

Open-loop Band excitation Kelvin Probe Force Microscopy

A multidimensional scanning probe microscopy approach for quantitative, cross-talk free mapping of surface electrostatic properties is demonstrated. Open-loop band excitation Kelvin probe force microscopy (OL BE KPFM) probes the full response-frequency-potential surface at each pixel at standard imaging rates. The subsequent analysis reconstructs work function, tip surface capacitance gradient and resonant frequency maps, obviating feedback-related artifacts. OL BE KPFM imaging is demonstrated for several materials systems with topographic, potential and combined contrast. This approach combines the features of both frequency and amplitude KPFM and allows complete decoupling of topographic and voltage contributions to the KPFM signal.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

The partially reversible formation of Li-metal particles on a solid Li electrolyte: applications toward nanobatteries

The feasibility of large-scale implementation of Li-air batteries (LABs) hinges on understanding the thermodynamic and kinetic factors that control charge-discharge rates, efficiency and life times. Here, the kinetics of bias-induced reactions is explored locally on the surface of Li-ion conductive glass ceramics, a preferred electrolyte for LABs, using direct current-voltage and strain spectroscopies. Above a critical bias, particle growth kinetics were found to be linear in both the bias and time domains. Partial reversibility was observed for Li particles as evidenced by the presence of anodic peaks following the Li{sup +} reduction, as well an associated reduction in particle height. The degree of reversibility was highest for the smallest particles formed. These observations thus suggest the possibility of producing nanobatteries with an active anode volume of the order of 0.1 al.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Ferroelectric Domain Scaling and Switching in Ultrathin BiFeO3 Films Deposited on Vicinal Substrates

We report on electrically switchable polarization and ferroelectric domain scaling over a thickness range of 5-100 nm in BiFeO{sub 3} films deposited on [110] vicinal substrates. The BiFeO{sub 3} films of variable thickness were deposited with SrRuO{sub 3} bottom layer using the pulsed laser deposition technique. The domains are engineered into preferentially oriented patterns due to substrate vicinality along the [110] direction. The domain width scales closely with the square root of film thickness, in agreement with the Landau-Lifschitz-Kittel (LLK) law. Switching spectroscopy piezo-response force microscopy provides clear evidence for the ferroelectric switching behavior in all the films.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗