Fluorescence Lifetime Microscopy Facility

Fluorescence lifetime microscopy is a very versatile tool due to its capability for investigating organic, bio-organic, and condensed matter systems at nanoscale. In biology, it is often uses as a "molecular ruler" since the fluorescence lifetime of a fluorophore can chance dramatically when surrounding molecules shift their positions by even a few angstroms. This allows for very sensitive measurements of the distances between proteins. In condensed matter systems, fluoresecence lifetime measurements are used to investigate nanoscale-sized semiconductors whose fluorescence properties are being utilized in such diverse applications as biological tagging and quantum computing. This custom-designed fluorescence lifetime facility incorporates a femtosecond pulsed Ti:sapphire laser, inverted microscope, and detectors for the investigation of these and many other critical studies at the nanoscale.

E-Beam Metrology Laboratory

Electron Beam Lithography (EBL) utilizes the fact that certain chemicals change their properties when irradiated with electrons just as a photographic film does when irradiated with light. The electron beam is generated in a Scanning Electron Microscope which normally is set up to provide an image of an object by rastering with a well focused beam of electrons over it. Collecting electrons that are scattered or emanated from that object for each raster point provides an image. With computer control of the position of the electron beam it is possible to write arbitrary structures onto a surface. The steps to produce a structure by EBL are: The sample is covered with a thin layer of PMMA, then the desired structure is exposed with a certain dose of electrons. The exposed PMMA changes its solubility towards certain chemicals. This can be used to produce a trench in the thin layer. If one wants to produce a metallic structure, a thin metal film is evaporated onto the sample and, after dissolving the unexposed PMMA with its cover (lift-off), the desired metallic nanostructure remains on the substrate.

Scanning Electron Microscope

The Scanning Electron Microscope (SEM) is an incredible tool for seeing the unseen worlds of microspace. Conventional light microscopes use a series of glass lenses to bend light waves and create a magnified image. The Scanning Electron Microscope creates the magnified images by using electrons instead of light waves. The SEM shows very detailed 30dimensional images at much higher magnifications than is possible with a light microscope.

Transmission Electron Microscope Laboratory

The Transmission Electron Microscope (TEM) is an indispensable tool in materials research. Operating on the basic principles of the light microscope, the TEM takes advantage of the much shorter wavelengths of electron beams vs. light beams, providing resolving powers on the order of 0.2 nm, rather than 200 nm for the light microscope.

Nanofabrication Class 100 Clean Room

This Class 100 Clean Room is designed as a device fabrication facility. Researchers are provided with the equipment and environment needed to design and fabricate many different types of devices. All Nanoscience Institute Members, as well as all of the NRL community, are provided the opportunity to use this facility.

Dip-Pen Nanolithography

Dip-Pen Nanolithography (DPN) uses a scanning probe microscope in contact mode to deposit a layer of molecules on a substrate. A Thermo-microscopes (TM) CP-Research Atomic Force Microscope (AFM) with nanolithography software provided by TM is used for this application. These features are drawn on the surface much as a picture is created using a fountain pen. However, in this case, the lines drawn with the AFM are as small as 10 nanometers wide, as long as 100 micrometers, and can range between 0.5 nanometers to several nanometers thick. Because of the integrated use of the AFM, DPN is capable of reproducibly placing features within 50 nanometers of photo-lithographically produced features, as well as those produced by nanolithography. The inks used for DPN can be a variety of materials including DNA, proteins, polymer, dendrimers, metal salts, and a variety of small molecules. Additionally, this method has been shown useful with both metal and dielectric substrates.

Focused Ion Beam

The Focused Ion Beam (FIB) system is similar to that of the Scanning Electron Microscope, the major difference being the use of a gallium ion (GA+) beam instead of an electron beam. The ion beam is generated in a liquid-metal ion source (LMIS), and the application of a strong electric field causes emission of positively charged ions from a liquid gallium cone, which is formed on the top of a tungsten rod. The beam energy is typically 30 or 50 keV with a beam current in the range of 1 to 20 nA, and the best image resolution that can be obtained is approximately 5 to 7 nm.

The beam is raster-scanned over the sample, which is mounted in a vacuum chamber at pressured of around 10-7mbar. Secondary electrons emitted from its surface are used to generate an image of the surface. The energetic ions can remove atoms from the surface, allowing the system to ion mill very small (~10 nm) features.

Multiprobe STM Instrument Lab

Scanning tunneling microscopy/spectroscopy (STM/S) enables the surface topography, chemical reactivity, and electronic structure of conductive substrates to be observed with atomic-scale resolution.

Atomic Force Microscope

The atomic force microscope is one of about two dozen types of scanned-proximity probe microscopes. All of these microscopes work by measuring a local property—such as height, optical absorption, or magnetism—with a probe or "tip" placed very close to the sample. The small probe-sample separation (on the order of the instrument's resolution) makes it possible to take measurements over a small area. To acquire an image, the microscope raster-scans the probe over the sample while measuring the local property in question. The resulting image resembles an image on a television screen in that both consist of many rows or lines of information placed one above the other. Unlike traditional microscopes, scanned-probe systems do not use lenses, so the size of the probe, rather than diffraction effects, determine their resolution.