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BSA 12-11: Sample Holder with Optical Features

BNL Reference Number: BSA 12-11

Patent Status: U.S. Patent Number 8,497,487 was issued on July 30, 2013

Summary
TCP Technology
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Multimodal optical nanoprobe being mounted in a transmission electron microscope.

BNL has developed a multimodal optical nanoprobe (MON): a scanning/transmission electron microscope (S/TEM) sample stage integrated with optical excitation and transport measurement capabilities, compatible with various commercial electron microscopy systems. This in-situ specimen holder enables the simultaneous measurement of optical, electrical, and mechanical properties of samples inside any S/TEM without compromising the microscope's performance. To our knowledge it provides the only means currently available for the simultaneous in-situ correlation of optical, spectroscopic, electronic, and structural properties of complex materials and devices at length scales ranging from hundreds of micrometers to fractions of a nanometer. Examples of mutually compatible measurements include atomic imaging, nanoprobe electron diffraction to identify local phase inhomogeneity, and spectroscopy using electron induced characteristic X-ray and electron energy-loss signals to identify local chemical composition and bonding states. Of particular technological importance is the ability to investigate the site or location-specific properties of engineered material interfaces such as the p-n junctions of photovoltaic structures. In this article we describe the design and the functioning of the component parts of the system, as well as its possible applications.

Description

The MON body has within it two channels that pass all the way to the sample module from the external optics module. These channels are used as optical pathways, each several mm in diameter. Each channel can pass light either as a narrow, free space laser beam or via an optical fiber threaded through. Depending on the choice, the part of the body external to the vacuum can be terminated with either an optical window for free laser beams or with a polytetrafluoroethylene (PTFE) vacuum feed-through for the optical fiber. In addition to mechanical interfaces for external optics, there are several electrical connectors built into this part of the body external to the TEM column. There are a total of 6 electrical connectors available; two are reserved for a scanning tunneling microscope (STM)/nanoprobe (one for the STM tip and one for the sample) and the remaining four connectors are available for additional in-situ electrical measurements of the sample.

Benefits

In-situ electron microscopy provides a "live" view of a material or device under study at various length scales. For example, by heating or cooling a sample one can study structural change at the atomic scale to understand the driving forces and mechanisms of phase transitions. By applying electric and magnetic fields on a ferroelectric or magnetic architecture in operation, one can directly observe how electric and magnetic domains switch, how anions and cations shift their positions, and how spins change their configuration across a domain wall, aiding the development of better electromagnetic devices. In the study of photovoltaic devices and junctions, a major challenge is to directly correlate light-induced electric currents with local structural inhomogeneities and dynamics. The MON offers such a capability allowing evaluation of the performance of individual p-n junctions and improving optoelectronic efficiency.

Applications and Industries

It is expected that the materials of greatest interest for examination with this device are optically active samples such as quantum dots, cathodoluminescent and electroluminescent materials, nanowires, photovoltaics, complex oxides, and other optoelectronic systems in which structural, electronic, optical, and mechanical properties are intertwined. Examples include optoelectronic behavior of photovoltaic junctions, failure analysis of semiconductor devices, strain effects on optoelectronic properties, and near-field scanning optical microscopy (NSOM). It is also an ideal system for time resolved microscopy and spectroscopies, using a synchronized pulsed laser to excite the sample in TEM.

Journal Publication
Have Questions?

For more information about this technology, contact Poornima Upadhya, (631) 344-4711.