Three-Dimensional Chemical Characterization of Complex Silver Halide Microcrystals by Scanning Ion Microprobe Mass Analysis

Abstract

A new procedure based on scanning ion microprobe mass analysis (SIMS) is developed to characterize populations of silver halide microcrystals present in a photographic emulsion with emphasis on the thickness distribution of the surface layers usually found on these microcrystals in the 5−30 nm range. Using a Cameca IMS-4f instrument one is able to image the lateral and in-depth distributions of the halides in individual microcrystals. A digital image processing system interfaced with the SIMS instrument permits the acquisition of spatially resolved mass-selected data (ion images) for a number of single microcrystals. Small regions (∼300 nm in diameter) within each crystal are selected a posteriori for local area “retro” depth profiling by computer reconstruction. By averaging the gray values measured in suitable parts of the crystal, the thickness of the surface layers can be determined, allowing one to make a three-dimensional reconstruction of the chemical composition of the microcrystals. Using this methodology, the characteristics (thickness and chemical composition) of surface and subsurface layers of different samples can be compared and subclasses in one population can be detected. With the aid of home-developed hardware and software, the image acquisition procedure was automated, making it possible to automatically measure a sufficiently large number of microcrystals. In this way the analysis time was decreased and the statistical relevance of the data improved. Two examples are given which illustrate the power and practical use of the developed methodology.

Imaging with Mass Spectrometry

“…There are many silver halide crystal formations, the composition and distribution of which affect the film quality. Levi-Setti and co-workers have used SIMS to characterize the location of the halide content of these microcrystals and ion etching to reveal the interior structures. , Similar work has been reported by Verlinden et al Holographic interference fringes were imaged with very high spatial resolution in an emulsion using SIMS . The coincident distribution of Ag and Br in the holographic fringes is shown in Figure .…”

Chemical Microcharacterization of Ultrathin Iodide Conversion Layers and Adsorbed Thiocyanate Surface Layers on Silver Halide Microcrystals with Time-of-Flight SIMS

“…and by the group of Gijbels et al 1987!. Further experiments were performed by Wu~1992!. An analytical method to visualize halide distributions in the surface and subsurface layers of individual crystals based on scanning imaging ion microprobe mass analysis using a primary Cs ϩ beam was then developed~Geuens et al., 1992a, 1994Geuens, 1993!, andin a later stage further optimized andquantified~Janssens, 1995;Verlinden et al, 1997, 1999b!. More recently~Verlinden et al, 1998, 1999a we have also presented a method based on imaging TOF-SIMS and local image depth profiling for the analysis of silver halide microcrystals with subpercent global iodide concentrations confined in surface layers with a thickness well below 5 nm.…”

Combined characterization of composite tabular silver halide microcrystals by cryo-EFTEM/EELS and cryo-STEM/EDX techniques

“…The quality/speed ratio of the former is higher at medium and high densities. During the last decade an increased interest has been demonstrated to the structural and analytical characterization of individual microcrystals and their compositional arrangement by various instrumental methods, i.e., conventional transmission electron microscopy (CTEM, Goessens et al, 1991Goessens et al, , 1994Goessens et al, , 1995; high-resolution electron microscopy (Shiozawa et al, 1987); scanning electron microscopy (SEM) and lowtemperature luminescence microscopy (Maskasky, 1987a,b); scanning transmission electron microscopy (STEM) and analytical electron microscopy (AEM) techniques (Gao et al, 1989;Gregory et al, 1997;King et al, 1987;Lavergne et al, 1994a,b;Oleshko et al, 1995aOleshko et al, ,b, 1996Wu et al, 1992Wu et al, , 1993; secondary ion mass spectrometry (Maternaghan et al, 1990;Verlinden et al, 1997) and scanning probe microscopies (Keyes et al, 1992;Rogers et al, 1995;Schwarz et al, 1992). This activity was stimulated by the introduction of novel types of silver halide systems with improved photographic functions such as efficiency of light quanta detection, photohole trapping, and storage of the latent image, etc.…”