An atom-probe field-ion microscope for the study of the interaction of impurity atoms or alloying elements with defects

Abstract

A time-of-flight (TOF) atom-probe field-ion microscope (FIM) designed for the study of defects is described. This atom probe features: (l) a variable magnification internal-image-intensification system; (2) a liquid-helium goniometer stage; (3) a lowenergy (£3 keV) gas-ion gun for in-situ irradiations; (h) an ultra-high vacuum (~3-10 torr) chamber; (5) a high vacuum (-10 torr) specimen-exchange device; (6) a Chevron ion detector; and (7) an eight-channel digital timer with a ±10 nsec resolution for measuring the TOFs. The entire process of applying the evaporation pulse to the specimen, measuring the voltages, and analyzing the TOF data is controlled by a computer. With this system we can record and analyze 600 TOF/min. Results on unirradiated specimens of molybdenum, tungsten, W/25 &t% Re, Mo/l.O &t% Ti, Mo/l.O at% Ti/0.08 &t% Zr and a special low swelling stainless steel alloy (LS1A) demonstrate the instrument's ability to quantitatively determine concentrations at the 5*10 at fr level and to determine their spatial distribution with a resolution of a few angstroms.

Diffusivity of 3He atoms in perfect tungsten crystals

“…However, the quantitative experimental picture concerning the diffusive behavior of helim atoms-in the absence of radiation damage-is much poorer. 18 From a combination of isothermal annealing experiments at several implantation temperatures, in conjunction with a suitable diffusion model, we have determined-for the first time-the ditfusivity [D'He (T)] and the enthalpy change of migration of 3He atoms (. At Cornell we have established that for 300and 475-eV 4He+ implantations in tungsten the 4He atoms are located in the interstices of the lattice and are immobile at 60, 61, 80, and 90 K-while they are highly mobile at 110 K. 15 Employing a first-order diffusion model a value of the enthalpy change of migration of 4 He (.…”

Direct observation of solute segregation to voids in a fast-neutron irradiated (Mo/1. 0 at. % Ti alloy

“…The alloy specimen was examined in our atom-probe FIM; this instrument has been described in some detail in earlier publications [20][21][22][23][24] and hence we only discuss a few important aspects of it in this paper. The atom-probe Table 1) the Ti concentration is 0.37 ± 0.06 at%.…”

“…The FIM image is observed with the aid of an internal image-intensification system which contains a 3 mm diameter probe hole at its center; seeFig. 1in Ref [23]…”

Perspective: From field-ion microscopy of single atoms to atom-probe tomography: A journey: “Atom-probe tomography” [Rev. Sci. Instrum. 78, 031101 (2007)]

“…This situation changed radically and permanently with the interfacing of an APFIM at Cornell University to a Data General Nova computer with 8 K of discrete memory in 1975. [41][42][43] The APFIM is a revolutionary instrument because it combines atomicresolution FIM images with TOF mass spectrometry. It has been applied to a wide range of problems in materials science and engineering that cannot be studied by any other technique.…”