FIELD ION MICROSCOPE AND IMAGING ATOM-PROBE INVESTIGATIONS OF OXIDE FORMATION ON W AND Ir FIELD EMITTERS

1989 ◽  
Vol 50 (C8) ◽  
pp. C8-297-C8-302 ◽  
Author(s):  
G. L. KELLOGG
Author(s):  
Brian Ralph ◽  
A.R. Waugh ◽  
S.A. Hill ◽  
M.J. Southon ◽  
M.P. Thomas

This brief review attempts to summarize the main uses to which the atom-probe field-ion microscope and its variants have been put in the examination of materials. No attempt is made to produce a comprehensive list of all the studies made to date, rather the type of application is illustrated from recent studies.The original form of the field-ion microscope was really limited to the acquisition of geometrical and crystallographic information on the fine scale distribution of defects and phases (e.g. 1). Even in these early applications, the study proved considerably more fruitful when other microstructural techniques, such as transmission electron microscopy, were applied in parallel. The advent of the atom-probe (AP) and imaging atom-probe (IAP) instruments allowed precise microchemical information to be obtained and these instruments have now been used for a number of detailed investigations of materials. In the main, these have divided into (I) studies of surface process and films (e.g. 2) and (II) investigations of phase distributions and segregation in the bulk (e.g. 3).


The measurement of low concentrations of elements segregated to or near grain boundaries with a spatial resolution of ca . 1 nm has recently become possible with the introduction of the imaging atom probe (i.a.p.). This development of the original atom probe field ion microscope uses a time-gated image intensifier as the detector of a time-of-flight mass spectrometer and displays an elemental map of ions desorbed from the surface of a field-ion specimen. The sensitivity of the analysis is uniform for both light (e.g. B, C, O) and heavy (e.g. Sn) elements, and concentrations down to 100 pg/g can be detected; accurate quantitative analyses are obtained by using the more conventional type of atom probe.


1987 ◽  
Vol 48 (C6) ◽  
pp. C6-305-C6-310
Author(s):  
H. B. Elswijk ◽  
P. M. Bronsveld ◽  
J. Th. M. De Hosson

Author(s):  
J. J. Hren ◽  
S. D. Walck

The field ion microscope (FIM) has had the ability to routinely image the surface atoms of metals since Mueller perfected it in 1956. Since 1967, the TOF Atom Probe has had single atom sensitivity in conjunction with the FIM. “Why then hasn't the FIM enjoyed the success of the electron microscope?” The answer is closely related to the evolution of FIM/Atom Probe techniques and the available technology. This paper will review this evolution from Mueller's early discoveries, to the development of a viable commercial instrument. It will touch upon some important contributions of individuals and groups, but will not attempt to be all inclusive. Variations in instrumentation that define the class of problems for which the FIM/AP is uniquely suited and those for which it is not will be described. The influence of high electric fields inherent to the technique on the specimens studied will also be discussed. The specimen geometry as it relates to preparation, statistical sampling and compatibility with the TEM will be examined.


Author(s):  
G. L. Kellogg ◽  
P. R. Schwoebel

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.


Author(s):  
Amanda K. Petford-Long ◽  
A. Cerezo ◽  
M.G. Hetherington

The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP) microanalysis without exposure to atmosphere) and onto the flat (001) surface of oxidised silicon wafers (for subsequent study in cross-section using high-resolution electron microscopy (HREM) in a JEOL 4000EX. Deposi-tion was from W filaments loaded with material in the form of wire (Co, Fe, Ni, Pt and Au) or flakes (Cr). The base pressure in the chamber was around 8×10−8 torr during deposition with a typical deposition rate of 0.05 - 0.2nm/s.


1988 ◽  
Vol 49 (C6) ◽  
pp. C6-55-C6-59 ◽  
Author(s):  
O. NISHIKAWA ◽  
K. HATTORI ◽  
F. KATSUKI ◽  
M. TOMITORI

1984 ◽  
Vol 41 ◽  
Author(s):  
S. D. Walck ◽  
J. J. Hren

AbstractAccurate depth profiling of implanted hydrogen and its isotopes in metals is extremely important. Field ion microscopy and atom-probe techniques provide the most accurate depth profiling analytical method of any available. In addition, they are extremely sensitive to hydrogen. This paper reports our early work on hydrogen trapping at defects in metals using the Field Ion Microscope/Imaging Atom Probe (FIM/IAP). Our results deal primarily with the control experiments required to overcome instrumental difficulties associated with in situ implantation and the influence of a high electric field. Transmission Electron Microscopy (TEM) has been used extensively to independently examine the influence of high electric fields on emitters.


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