IMD

#

# What's New in Version 4.0

IMD Version 4.0 includes several major new features:

- Non-specular reflected intensity calculations

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.

- A stochastic model of thin film growth and erosion

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.

- Depth-graded multilayers

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.

- Coupled parameters

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.

- High-energy optical constants and atomic scattering factors

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

- New specular optical functions

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

- Enhanced graphics

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

- Parameter Estimation

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.

Back | Contents | Next