Rechargeable, all-solid-state Li ion batteries (LIBs) with high specific capacity and small footprint are highly desirable to power an emerging class of miniature, autonomous microsystems that operate without a hardwire for power or communications. A variety of three-dimensional (3D) LIB architectures that maximize areal energy density has been proposed to address this need. The success of all of these designs depends on an ultrathin, conformal electrolyte layer to electrically isolate the anode and cathode while allowing Li ions to pass through. However, we find that a substantial reduction in the electrolyte thickness, into the nanometer regime, can lead to rapid self-discharge of the battery even when the electrolyte layer is conformal and pinhole free. We demonstrate this by fabricating individual, solid-state nanowire core-multishell LIBs (NWLIBs) and cycling these inside a transmission electron microscope. For nanobatteries with the thinnest electrolyte, ≈110 nm, we observe rapid self-discharge, along with void formation at the electrode/electrolyte interface, indicating electrical and chemical breakdown. With electrolyte thickness increased to 180 nm, the self-discharge rate is reduced substantially, and the NWLIBs maintain a potential above 2 V for over 2 h. Analysis of the nanobatteries' electrical characteristics reveals space-charge limited electronic conduction, which effectively shorts the anode and cathode electrodes directly through the electrolyte. Our study illustrates that, at these nanoscale dimensions, the increased electric field can lead to large electronic current in the electrolyte, effectively shorting the battery. The scaling of this phenomenon provides useful guidelines for the future design of 3D LIBs.

We report direct observation of controlled and reversible switching of magnetic domains using static (dc) electric fields applied in situ during Lorentz microscopy. The switching is realized through electromechanical coupling in thin film Fe(0.7)Ga(0.3)/BaTiO(3) bilayer structures mechanically released from the growth substrate. The domain wall motion is observed dynamically, allowing the direct association of local magnetic ordering throughout a range of applied electric fields. During application of approximately 7-11 MV/m electric fields to the piezoelectric BaTiO(3) film, local magnetic domains rearrange in the ferromagnetic Fe(0.7)Ga(0.3) layer due to the transfer of strain from the BaTiO(3) film. A simulation based on micromagnetic modeling shows a magnetostrictive anisotropy of 25 kPa induced in the Fe(0.7)Ga(0.3) due to the strain. This electric-field-dependent uniaxial anisotropy is proposed as a possible mechanism to control the coercive field during operation of an integrated magnetoelectric memory node.

Minimizing Joule heating remains an important goal in the design of electronic devices. The prevailing model of Joule heating relies on a simple semiclassical picture in which electrons collide with the atoms of a conductor, generating heat locally and only in regions of non-zero current density, and this model has been supported by most experiments. Recently, however, it has been predicted that electric currents in graphene and carbon nanotubes can couple to the vibrational modes of a neighbouring material, heating it remotely. Here, we use in situ electron thermal microscopy to detect the remote Joule heating of a silicon nitride substrate by a single multiwalled carbon nanotube. At least 84% of the electrical power supplied to the nanotube is dissipated directly into the substrate, rather than in the nanotube itself. Although it has different physical origins, this phenomenon is reminiscent of induction heating or microwave dielectric heating. Such an ability to dissipate waste energy remotely could lead to improved thermal management in electronic devices.

The high intensity of light emitted in In x Ga 1Àx N/GaN heterostructures has been generally attributed to the formation of indium-rich clusters in In x Ga 1Àx N quantum wells (QWs). However, there is significant disagreement about the existence of such clusters in as-grown In x Ga 1Àx N QWs. We employ atomically resolved C S-corrected scanning transmission electron microscopy and electron energy loss spectroscopy at 120 kV-which we demonstrate to be below the knock-on displacement threshold-and show that indium clustering is not present in as-grown In 0.22 Ga 0.78 N QWs. This artifact-free, atomically resolved method can be employed for investigating compositional variations in other In x Ga 1Àx N/GaN heterostructures. V

We present real-time, nanoscale temperature mapping using a transmission electron microscope and standard phase transitions in metal islands. Islands are deposited on the reverse side of commercially available silicon nitride membranes, while local thermal gradients are produced by Joule heating in a thin wire on the front side of the membrane. Change in contrast due to the liquid-solid transition in the islands allows the mapping of absolute temperature, as above or below the transition temperature, over the entire field-of-view. Experiments demonstrate nanoscale (<100 nm) resolution and video-rate (>30 thermal-images per second) speed, supported by combined electrical and thermal modeling. This provides a generic and adaptable platform for nanoscale thermal characterization independent of strong probe coupling and optical effects.

The ability to tune the thermal resistance of carbon nanotube mechanical supports from insulating to conducting could permit the next generation of thermal management devices. Here, we demonstrate fabrication techniques for carbon nanotube supports that realize either weak or strong thermal coupling, selectively. Direct imaging by in-situ electron thermal microscopy shows that the thermal contact resistance of a nanotube weakly-coupled to its support is greater than 250 K·m/W and that this value can be reduced to

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The interactions of electrical current and materials structure are of fundamental importance to the future of nanoscale systems. Subtle changes in nanostructure can induce marked changes in the electrical transport properties, and an electrical current can, in turn, induce its own changes in a system. These correlations between nanostructure and electrical transport are most important and complex as device sizes approach the nanoscale, and, unfortunately, this is the very realm where traditional techniques for observing device dynamics fail.Traditionally, the dynamics of electrical and mechanical devices are studied by video-rate light microscopy techniques. These imaging techniques are limited by the wavelength of light and are thus ineffective on nanoscale systems. Although there are a few key instruments, like the STM and AFM, that have enabled the early development of nanosystems, they provide only a limited view, due to a slow imaging speed. Transmission electron microscopy (TEM) is a natural candidate for extending a larger class of studies into the nanoscale realm, but conventionally TEM studies of devices have focused only on uncovering the materials' structure before or after device operation. At the University of Maryland, we are building up a research program dedicated to studying the structure and performance of nanoscale devices during device operation. In comparison with scanned-probe microscopies, TEM images can be acquired a thousand times faster, at video rates. This means that, practically speaking, an experimenter can accomplish in about a day the same scope of experiments on a nanoscale device that would require a year's worth of study using a scanned probe technique, such as STM or AFM.There are two key tools that make this area of research possible. The first is a nano-manipulation stage. This is essentially just an STM that can be operated inside a TEM [1]. It allows electrical probing and deformation of nanomaterials during microscopic investigations [2][3][4][5]. Using this, it is possible to fabricate devices in-situ and observe their operation at the same time. The second tool is a reliable multi-contact electrical measurement specimen holder. We have developed the techniques for performing reliable lithography (both photolithography and electron-beam lithography) on commercially available silicon nitride membranes. Devices fabricated on these substrates can be investigated in any TEM specimen holder during the fabrication process and then can be transferred to the electrical measurement holder for in-situ observations of the device operation.These capabilities enable a wide variety of new research areas. We have already used this approach for the fabrication of ultra-fast nanoscale heating strips (~10µs response time). These heating strips also generate very strong temperature gradients that may be used for imaging how material's structure evolves in a strong gradient, for imaging the non-equilibrium structure of a material in response to very fast temperature changes, or for performin...