Brookhaven’s Sample Holder with Optical Features

Brookhaven’s Sample Holder with Optical Features

Dept. of Energy

Multimodal optical nanoprobe being mounted in a transmission electron microscope (Photo credit: Brookhaven National Laboratory).

Laboratory: Brookhaven National Laboratory (BNL)

Technology: Sample Holder with Optical Features

Opportunity: This patented technology is available for licensing.

Details: Brookhaven National Laboratory (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 its ability to investigate the site or location-specific properties of engineered material interfaces such as the p-n junctions of photovoltaic structures. This article describes the design and functioning of the component parts of the system, as well as its possible applications.

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 a polytetrafluoroethylene (PTFE) vacuum feed-through for the optical fiber. In addition to mechanical interfaces for external optics, several electrical connectors are built into this part of the body external to the TEM column. Six electrical connectors are 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 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, it is a major challenge to directly correlate light-induced electric currents with local structural inhomogeneities and dynamics. The MON offers such a capability, allowing the performance of individual p-n junctions to be evaluated and optoelectronic efficiency to be improved.

Applications: 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 spectroscopy, using a synchronized pulsed laser to excite the sample in TEM.

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

To view the original technology listing on BNL’s website, visit