reSolution_LNT_No1_en - Leica Microsystems

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INDUSTRY A Word on Cathodoluminescence Cathy Johnson, Nanotechnology Division, Leider Lane, Buffalo Grove, IL Cathodoluminescence microanalysis is an emerging technique that is fast gaining popularity in the world of materials science. CL is a light emission phenomena resulting from the electron beam excitation of a luminescent material. As electronic transitions occur between the conduction and valence bands, CL photons are generated and detected. Electronic transitions due to defect levels within the band gap, particularly in the case of semiconductors and devices, can also infl uence CL data. Data acquisition results in a mapping of the optical activity for a specimen. Cathy Johnson, Leica Microsystems CL data can indicate defects such as imperfections or impurities within the microstructure of a material phase. These defects can have an effect on the material’s optical, electrical and mechanical properties. Utilizing the high resolution capability of a SEM or STEM, a spectrum can be acquired at each point location (i.e. hyperspectral imaging). As such, it serves as an important spectroscopy and imaging technique in the characterization of materials. Image resolution is dependent on instrument confi guration, experimental parameters and specimen interaction, but can range from < 10 nanometers to the micron level. The fi rst MAS Cathodoluminescence Topical Conference was hosted October 24-28, 2011 by the National Institute of Standards and Technology (NIST) in Gaithersburg, MD. This conference was sponsored by the Microbeam Analysis Society (MAS), and was co-sponsored by the Australian Microbeam Analysis Society (AMAS). The four day program included a pre-conference tutorial targeted for the CL novice on October 24 th . The remaining three days included a combination of technical presentations, hands-on laboratory demonstrations and a contributed poster session. Presentation topics included: CL theory, data quantifi cation, advances in instrumentation, analysis and databases. Applications in geological, semiconductor and nanomaterial disciplines including sample preparation and Correlative CL in conjunction with complementary techniques such as EBIC and EBSD were also addressed. Instruments rel related to this sample preparation: Leica EM TXP Target Surfacing System Leica EM TIC 3X Ion Beam Slope Cutter Leica EM RES101 Ion Milling System Contact Cathy Johnson Leica Microsystems Nanotechnology Division 1700 Leider Lane Buffalo Grove, IL 60089 Cathy.Johnson@leica-microsystems.com Panchromatic cathodoluminescence image of cassiterite mineral (SnO 2 ) Image Credits Scott Wight 1 , Ed Vicenzi 2 , Doug Meier 1 , and Kurt Benkstein 1 1 National Institute of Standards and Technology 2 Smithsonian Institution Source: Smithsonial National Mineral Collection, Preparation: Cut and polished with the Leica EM TXP Data Collection: FEI Company QuantaTM 200F SEM with Gatan, MonoCL4 Elite System
Atomic Force Microscopy Study of a Stretched Impact Copolymer INDUSTRY Dalia G. Yablon, Jean Grabowski, and Andy H. Tsou, Exxon Mobil Research and Engineering, Clinton, New Jersey, USA. Abstract Atomic force microscopy (AFM) is a powerful tool in the suite of nanoscale characterization techniques that provides a variety of information including topography, mechanical properties, and electrical properties with nanoscale lateral and sub-nanometer vertical resolution. Cryoultramicrotomy is an essential tool for effective polymer sample preparation for atomic force microscopy (AFM) in order to get rid of the polymer skin from processing and to ensure a smooth surface for analysis. We present an AFM study of the effect of tensile stress on a cryotomed impact copolymer (ICP), a multicomponent material typically used in automotive and appliance applications where a balance of stiffness and toughness is needed to investigate material deformation and interface adhesion as a function of tensile stress. Article The fi eld of atomic force microscopy (AFM), which was invented in the mid 1980’s, has revolutionized our capabilities to explore and understand nanoscale phenomena by allowing unprecedented characterization of surface and interface reactions and molecular and sub-molecular structures. Especially with commercial instruments available for widespread academic and industrial research beginning in the early 1990’s, the atomic force microscope (AFM) has become a main tool in the suite of techniques available for characterization, and is included in most characterization facilities alongside optical and electron microscopes. AFM now can routinely provide ~10nm lateral resolution and angstrom vertical resolution on a variety of surfaces and in fl exible environments including ambient and in situ fl uid imaging and is routinely used to provide a wealth of information including topography, mechanical properties, electrical and magnetic properties on a variety of materials ranging from biological cells to semiconductors to polymers. The heart of the AFM measurements lies in the precisely monitored interaction between a very sharp tip (~10nm in diameter) mounted on a cantilever (typically 100’s of microns long, tens of microns wide and a few microns thick) and the surface of interest via optical detection. Through this tip-sample interaction, multiple surface properties can be probed on the nanoscale, including nanomechanical properties of polymeric materials. Specifi cally, an AFM mode called tapping mode or amplitude modulation mode is employed to image polymeric surfaces where the cantilever is oscillated at a resonance frequency and thus gently “taps” along the surface through intermittent contact, resolving features in the material based on its mechanical properties such as stiffness and other viscoelastic properties. Sample preparation of polymeric samples via ultracryomicrotomy for AFM analysis is critical for two reasons. First, a smooth surface is essential for effective AFM analysis as the maximum vertical range on AFM is typically less than 5 um. This is also means that if there are features that are taller than 5 um (or whatever the specifi cation on the particular AFM instrument), that surface will not be able to be imaged. Second, many polymer materials come in a processed form where the material has either been injection molded or compression molded and thus forms a rough skin on the surface that is not representative of the bulk material and needs to be removed. Cryomicrotomy is able to remove the surface skin and provide a smooth surface (all at cold temperatures below Tg of the polymer, which is essential, otherwise the surface features of interest will not be resolved). The Leica EM UC6 system provides convenient AFM attachments where samples can be cryofaced in conjunction with the Leica EM FC6 and directly transferred to the AFM for convenient analysis without removing the specimen, ensuring a smooth fl at surface for AFM imaging. We show here AFM data examining the rubber/matrix interface of a commercially important material, a polypropylene based impact copolymer. The interface of the two components in this material is examined by inserting a cryotomed dogbone of the impact copolymer material into an AFM tensile stage (NanoRack Asylum Research). Dalia G. Yablon NANOTECHNOLOGY 17
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