What's New in Version 4.0

IMD Version 4.0 includes several major new features:

Computations are performed using either a dynamical Born approximation vector theory [4], or the so-called 'Distorted-Wave Born Approximation' formalism [5-8], a scalar theory which is nonetheless valid below the critical angle of total external reflection in the X-ray region.

Two power-spectral-density (PSD) function models are available: a PSD function based on the stochastic model of film growth and erosion developed by D. Stearns (see below), and a more conventional PSD function parameterized by roughness, correlation length, and jaggedness parameters.

The model can be used to account for the evolution of  interfacial roughness through the film stack [9], and can be applied to both specular and non-specular optical function calculations.

A choice of depth-grading profiles is available to model aperiodic multilayer films. When using the conventional PSD function (see above,) depth graded roughness and correlation length parameters can be defined as well.

An unlimited number of structure parameters (optical constants, compositions, densities, layer thicknesses, PSD parameters, etc.,) can be coupled to one another. Thus, a single independent variable or fit parameter can be used to adjust multiple parameters simultaneously.

Atomic scattering factors and optical constants now extend to 100 keV.

Ellipsometric psi and delta functions, and user-defined specular optical functions (for example, R_s/R_p, T³/R, or whatever) can be computed.

Several new features have been added to the IMDXPLOT visualization tool:

• There are now four ways to display 2D optical functions: surface plots, contour plots, filled color contour plots, and superimposed contour/color image plots.
• Interactive zoom and window resizing is now available.
• A new IMDXPLOT Tools menu allows for (a) live cross-hair display on 1D and 2D contour plots (with live 1D-slices), and (b) region-of-interest analysis: periodicities, min and max, average, integral, full-width-half-max, and full-width-half-min.

What's New in Version 4.1

In addition to the Marquardt (CURVEFIT) algorithm, IMD now includes C. W. Markwardt's implementation of the (more robust) Levenburg-Marquardt (MINPACK-1) fitting algorithm.

Fit parameter values - as well as a'live' plot - are now displayed during curve-fitting, showing the progress of the fit with each iteration.

Offsets and/or Scale Factors can be added to your measured data. In addition, Offsets and/or Scale Factors can be designated as fit parameters.

In addition to these changes, uses may wish to consult the RELEASE_NOTES.