In situ transmission electron microscopy studies enabled by microelectromechanical system technology
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We have designed and fabricated a standardized specimen holder that allows the operation of a microelectromechanical system (MEMS) device inside a transmission electron microscope (TEM). The details of the design and fabrication processes of the holder are presented. The sample loading mechanism is simple and allows reliable electrical contact to eight signal lines on the device. Using a MEMS-based, nanojoule calorimeter, we performed rapid-heating experiments on Bi nanoparticles to demonstrate the functionality of the holder. We show that the heat capacity can be measured simultaneously with TEM observations. The size-dependent melting of Bi nanoparticles was observed simultaneously by nanocalorimetry and selected area diffraction measurements. We believe this approach will open up new experimental pathways to researchers, combining the speed and resolution of transmission electron microscopy with the flexibility, precision, and compactness of MEMS-based sensors and actuators.
I. INTRODUCTION
There has been a growing tendency to use the transmission electron microscope (TEM) as a dynamic research tool to study atomic-scale mechanisms of complex materials processes. The main obstacle toward wider use of the technique is the limited space available in the objective lens pole-piece for incorporating an experimental laboratory. A new approach to in situ microscopy is to fabricate the experimental laboratory by employing micro- and nano-lithographic techniques and to use microelectromechanical systems to add functionality. This strategy for miniaturizing the laboratories makes judicious use of the available space and offers enhanced capabilities to stimulate and probe the system response compared with conventional approaches. Recent advances in microelectromechanical system (MEMS) fabrication allow for high-precision electrical, thermal, and mechanical manipulation of individual nanostructures, while simultaneously measuring their properties and
carrying out real-time, atomic-resolution imaging, electron diffraction, and spectroscopy. There are currently only a few functional devices, but they illustrate the potential of this approach.1,2 These experimental laboratories require a power source and must have the ability to return a control or measurement signal. This capability necessitates establishing a simple, reliable, and robust method for making the electrical connections between the experimental laboratory and the external controllers. This is different from conventional holders with electrical connections, as the connections are generally permanent and are not remade by the user. In this paper, we describe a methodology for creating up to eight electrical signals with an experimental laboratory on a standard holder base. To demonstrate the utility of the approach, we present data on the operation of a MEMS nanocalorimeter allowing in situ, rapid-heating experiments to investigate the dependence of the melting temperature on the size of bismuth nanoparticles while simultaneously observing the accompanying struc
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