Submicrometer spatial resolution

TOF-SIMS has been employed for the characterization of a wide range of materials, including metallic, salt, organometallic, organic, and polymeric substances, as well as for electronics, catalysts, and forensic samples. The ability to image molecular ions with submicrometer spatial resolution makes TOF-SIMS well suited to analysis of pharmaceuticals and biological cells, as well as for use in biotechnology and molecular electronics. 

Pugh, V.J., et al. (2003) Submicrometer spatial resolution of metal-enhanced fluorescence. Appl Spectrosc 57 1592-8. 

Nobumichi Tamura (left) obtained his Ph.D. in 1993 at the Institut National Polytechnique de Grenoble (INPG) for his work on the structure of quasicrystals and crystalline approximant phases. In 1998 he moved to Oak Ridge National Laboratory to contribute to the development of a new synchrotron-based X-ray microfocus technique capable of resolving strain and texture in thin films with submicrometer spatial resolution. He applied this technique in the field of microelectronics. He is currently staff scientist at the Lawrence Berkeley National Laboratory, where he leads the X-ray microdiffraction project at the Advanced Light Source. His research interest is presently focused on the study of mechanical properties of thin films at mesoscopic scale using synchrotron radiation. 

Multiple detection formats, including spectral, intensity, lifetime, polarization, quenching, energy transfer, time-resolved, and phase-resolved measurements. Imaging capability with submicrometer spatial resolution. two- and three-dimensional (with eonfoeal opties) sensitive visual detection. 

Surface analytical tools have increased in use as device dimensions have decreased into the near-surface realm. High spatial resolution and high analytical sensitivity are basic requirements for the characterization of impurities and defects in near and submicrometer devices. Electron, ion, and photon beam techniques are widely employed to characterize IC fabrication at each processing step and to analyze failures as they occur in processing as well as in the field. 

Through the addition of submicrometer-scale spatial resolution, SECM greatly increases the capacity of electrochemical techniques to characterize interfaces and measure local kinetics. In this way, it has proved useful for a broad range of interdisciplinary research. Various applications of SECM are discussed in this book, from studies of biological systems, to sensors, to probing reactions at the liquid/liquid interface. Although we did not intend to present even a brief survey of those diverse areas of research, each chapter... 

An AC voltage can be applied to the UME and a counter electrode (AC-SECM). The AC current response can be evaluated and it can provide information about local surface conductivity of the surface under investigation [123-125]. This setup has been applied to interrogate living cells [126]. Enhanced spatial resolution may be obtained by using a shear force-based distance control to operate the UME at submicrometer distance. 

In all modes of surface modification mentioned above, the spatial resolution is governed by the size of the SECM microprobe. With the commonly used micrometer-sized tips, fabricating submicrometer structures is difficult even... 

Fluorescent sensors in solution (chemosensors) and fiberoptic sensors. Fluorescence is a particularly important technique in this field because of its high sensitivity of detection down to a single molecule, subnanometer spatial resolution with submicrometer visualization and submillisecond temporal resolution. 

The reasons for the increase in the use of SPLS lie in its multidimensional character (spectral, lifetime, polarization, and other measurements) as well as in the need for a system that shows a large number of reactions and processes very efficiently. The advantages of SPLS include its sensitivity, low cost, ease in performance, versatility, and that it offers subnanometer spatial resolution with submicrometer visualization and submillisecond temporal resolution. 

Because there are more ex situ characterization techniques than this chapter could cover, here we only describe briefly the principles of some selected ex situ techniques. These characterization tools could provide average or collective chemical information, local chemical information with spatial resolution at micrometer and submicrometer ranges, and local structural information at nanometer and atomic scales for heterogeneous catalysts. Examples are selected that demonstrate the performances of these techniques, with a special focus on their applications in characterizing nanocatalysts for energy production and energy conversion. 

Figure 3 shows the measurement result of an application of the profile sensor at a microchannel flow obtained without traversing the sensor. Each point corresponds to a single tracer whose position and velocity were determined. A good agreement with the expected parabolic velocity profile of the laminar channel flow was achieved. The spatial resolution was approximately 3.5 xm (which is the standard deviation of the tracer position). It was limited by sensor properties and the size of the tracers, which was about 2 xra Using submicrometer tracers as well as improved sensor properties a spatial resolution in the nanometer range will be possible. 

The powerful combination of SECM with ITIES electrochemistry has enabled the spatially controlled deposition of metal particles, which is potentially extendable to nanoparticle (NP) deposition by using a nanotip. Eor instance, Ag particles were locally electrodeposited on a conductive substrate by employing a micropipet-supported ITIES tip in the egress IT mode (Eig. 9c). The spatial resolution of the tip-induced electrodeposition is controlled by the tip size and the tip-substrate distance. A shorter distance can be maintained by monitoring a shear force between the micropipet tip and the substrate to improve the spatial resolution. An even higher spatial resolution can be achievable by the shear-force-based control of a submicrometer-sized ITIES tip. ... 

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