Mole fraction (x) of an alloy is a geometry-dependent property and can be set in two ways. One is through the user interface and the other is through the "set" script command. This page will describe both methods.

## Setting the alloy mole fraction through user interface

The alloy mole fraction (x) can be adjusted through the Material tab in the property editor window of any geometric structure object as shown in the screen shot below. The feature is only available when a material of type alloy is selected for the object.

There are a variety of functions available for the x value which include:

- FIXED: This means that fraction x will be a constant value between 0 and 1.
- LINEAR X/Y/Z: This means that the mole fraction x will vary as a function x or y or z. In this case, user can specify the min and max fraction values for the min and max spatial points and the fraction will be interpolated linearly in between. x,y,z here are those of the unrotated object. x,y,z are local to the object.
- EQUATION: The user can enter an equation for the fraction that varies with u,v and w. u is (x-x0), v is (y-y0) and w is (z-z0), all in the unit of microns (um), where x0, y0 and z0 are the center coordinates of the object. This means that u,v and w are local to the object.

## Setting the alloy mole fraction through script commands

The following commands will add a new material to the objects tree, name it, and assign the properties of the SiGe alloy to it using a material model in the Electrical/Thermal material database. Then the "setnamed" command is used to set the mole fraction to a linear x model with min and max values of 0.3 and 0.6, respectively. The same can be accomplished using the "set" command however the use of "select" command is needed to select the rectangle object before adjusting the mole fraction.

addmodelmaterial;

set("name","Alloy Material");

addmaterialproperties("CT","SiGe (Silicon Germanium)");

addrect;

set("name","rect");

set("material","Alloy Material");

setnamed("::model::geometry::rect","mole fraction.active model","linear x");

setnamed("::model::geometry::rect","mole fraction.linear x.min",0.3);

setnamed("::model::geometry::rect","mole fraction.linear x.max",0.6);

Note: Mole fraction properties only affect the simulation if the associated material is an alloy. Setting mole fraction in script while associated material is undefined, or not an alloy, will not affect the simulation and the user will not receive a warning. |