Microscope mode

One of the primary goals of current research in the area of tribology is to understand how it is that the kinetic energy of a sliding object is converted into internal energy. These dissipation mechanisms detennine the rate of energy flow from macroscopic motion into the microscopic modes of the system. Numerous mechanisms can be... 

Scanning Auger Electron Spectroscopy (SAM) and SIMS (in microprobe or microscope modes). SAM is the most widespread technique, but generally is considered to be of lesser sensitivity than SIMS, at least for spatial resolutions (defined by primary beam diameter d) of approximately 0.1 im. However, with a field emission electron source, SAM can achieve sensitivities tanging from 0.3% at. to 3% at. for Pranging from 1000 A to 300 A, respectively, which is competitive with the best ion microprobes. Even with competitive sensitivity, though, SAM can be very problematic for insulators and electron-sensitive materials. 

Another large instrument with emphasis on high transmission at high resolution for isotopic measurements in geological applications is the IMS 1270 [60]. This instrument is similar in design to the IMS-3f and other Cameca f-series instruments but is much larger. It operates in either microprobe or microscope mode. Four auxiliary detector assemblies, containing an electron multiplier or Faraday cup plus the central beam primary detector, provide simultaneous detection of five isotopes. 

The most commonly used technique for sintering studies of model catalysts, TEM, has two variations (1) a macroscopic mode in which the sample is examined before and after various treatments without attempting to examine the exact same collection of crystallites or (2) a microscopic mode in which the same area of the sanqile is examined befne and after thermal treatments. Examples of TEM micrographs of fresh and oxygen-sintered model Pt/alumina taken in the macroscopic mode are shown in Figure 1, while same area microgr hs for a fresh and... 

Operation of a SIMS instrument resembles both that of an isotope ratio mass spectrometer and an electron microscope. Most SIMS instruments include an optical microscope so that the sample can be directly viewed during analysis, which allows for accurate positioning of the area of interest on the sample. Data can be in the standard mode used for other types of mass spectrometers in which ions are produced and the mass spectrum is analyzed by scanning or peak-hopping. This mode is sometimes called the microprobe mode in SIMS. Another application for SIMS is the acquisition of ion-images. This mode is called the microscope mode because the SIMS is operated as an ion microscope. 

This means that the lateral resolution can be better than the diffraction limit of the chosen laser wavelength. It has been shown that a lateral resolution a factor of 3 below the diffraction limit is possible in infrared MALDI microscope mode imaging [16]. 

Generally, SIMS instruments are operated in two modes microscope mode and microprobe mode. A defocused primary ion beam ( 5—300 pm) is used for investigating a large surface in the microscope mode. The secondary ions are then transmitted to the mass spectrometer and generally detected by imaging. In the microprobe mode, a focused primary ion beam (< 10 pm) is used to investigate a small portion of the surface and detected usually in an electron multiplier. 

The major area of application for solids and liquids is chemical fingerprinting and the identification of unknown compounds. For solids, Raman is also used for phase identification, following amorphous/crystalline transitions, measurement of stress and strain, and, in the microscope mode, the detection and analysis of defects, including particles during wafer processing. 

A CAMECA IMS-3f magnetic sector SIMS instrument, capable of producing isotopic (elemental) images with 500-nm spatial resolution in the ion microscope mode, was used in this study. A 5.5 keV primary ion beam of (approximately 100 nA beam current with a spot size of 60 xm in diameter) was used in this study. The primary ion beam was raster scanned over a 250 xm region. A 60- xm contrast aperture was used for imaging positive secondary ion images. 

Figure 3. The topography of a particular area of the carbon-black-polymer composite surface, as imaged in Ae tapping mode atomic force microscope mode of the scanning probe microscope. (Reproduced with permission from ref 4. Copyright 1995 American Physical Society.)...

Fig. 4.29 Poly crystal vanadium with a low sulfur content (less than 0.02 %) has been imaged to detect sulfur at grain boundaries. Sulfur in the upper left image is segregated at the grain boundaries while a potential interference of O2 at mass 32 is not segregated in the image in the lower left. (Cameca IMS 5f, microscope mode, 150 pm image field)...

AlAs/GaAs. Sample preparation and laser melting techniques are found in reference [62], Images of Al, Ga, Si, and O were sequentially recorded with a resistive anode encoder as the sample was depth profiled with Cs" and positive secondary ions in a Cameca IMS 5f in the microscope mode of operation. Two-dimensional cross sections of the Al, Ga, Si, and O images from a 60 pm rectangular slice centered around the 4 pm laser stripe were then computer generated and are shown in Fig. 4.30a. Depth profiles of Al, Ga, and O from selected 4 pm areas were also generated in the non laser-striped area in Fig. 4.30b and in the laser-striped area in Fig. 4.30c. Samples similar to the one in Fig. 4.30 have been analyzed with TEM, SEM, and electron dispersive X-ray spectroscopy (EDS) in addition to SIMS for full characterization [62]. 

Images in all three dimensions can be constructed by stacking the spatial images collected at every depth. Imaging can be carried out via either the microprobe or the microscope modes (both are discussed in Section 5.3.2.2). When carried out using the microprobe mode, an ultimate spatial resolution approaching 10 to 20 nm is possible (McPhail et al. 2010), although 50 nm and above is more common. This spatial resolution is, however, heavily dependent on primary ion spot size, and hence the primary ion current. When carried ont in the microscope mode, the spatial resolution is fixed at 1 pm irrespective of the primaiy ion spot size/cnrrent. Note Improved detection limits also allow for improved spatial resolntion. 

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