A Study of the Surface Texture of Polycrystalline Phosphor Films Using Atomic Force Microscopy

Abstract

Stimulable phosphor thin films are being investigated for use as optical data storage media. We have successfully applied atomic force microscopy (AFM) to the measurement of the surface texture of these films. Determination of the surface texture of the films is important for evaluating the effect of surface quality on optical scatter. In other thin film material systems it has been found that the surface “bumps” revealed by AFM correspond to grains in the film. This is not the case for the stimulable phosphor films used in our study. We have determined the grain size of our phosphor films by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The grain size from TEM and XRD does not correlate with the size of the AFM surface “bumps.” For example, in two of the five films studied, the XRD derived grain size varies by a factor of two but the size of the surface “bumps” remains the same. We conclude that the texture of the film surface is not directly determined by the grain size of the phosphor material.

Algorithms for scanned probe microscope image simulation, surface reconstruction, and tip estimation

“…(Dimensions in nanometers are supplied in the figure for greater concreteness. The scale is set by the actual granular surface [ 29 ] upon which the simulation was based.) The fidelity of the result is typical of cases in which the specimen contains features somewhat sharper than the tip.…”

“… Illustration of results of blind tip reconstruction. A 2 µm × 2 µm simulated surface (a 1 µm × 1 µm piece of which is shown at top), similar to an experimentally observed granular surface [ 29 ], was constructed with minimum feature radius 25 nm. An image was computed by dilation with the actual tip (shown), constructed with 40 nm radius at the apex.…”

A study of X-ray reflectivity data analysis methods for thin film thickness determination

“…5 " 7 Stimulable photoluminescent thin films are being investigated for use as erasable information storage media. 8 ' 9 Materials of interest include SrS and BaF 2 . Determination of thickness is important for thin film process development.…”