A "region" is a compact region in 2D-space occupied by a homogeneous material. From this definition it follows that a region cannot have voids and that a region cannot contain more than one type of material. The boundary of a region cannot be self-intersecting.
2. Material:
A material denotes a structureless substance with definable properties, which generally occupies a region(s). The term structureless here may be confusing. It is only used to explicitly state that the structure and other properties of the material are immaterial as far as the surface evolution model is concerned and all its properties are translated into the model through the user-defined angular dependence of the erosion/growth rate. In this context, a "material region" is equivalent to a mathematically compact set of points which constitutes a 2D-region.
3. Structure:
A structure is a compact entity of regions. There are no voids between the individual regions. The structure has three flat boundaries: bottom, right and left respectively. This means that the regions should be defined in such a way as to satisfy this condition.
In simple terms, a structure is the physical structure, the evolution of which is simulated. What you see in a Process Window is the whole structure.
Internally, however, the structure is considered infinite in the lateral directions.
N.B.
a) The condition that the structure is laterally infinite is very important and is used implicitly in the simulations as follows. Mathematically speaking, in order to simulate the evolution of a particular structure, 2Dinese has to solve a specific first order nonlinear partial differential equation. For unique solutions, however, one needs to specify the so-called boundary conditions. To relieve the user from this duty, 2Dinese assumes that all regions which have common boundary with the leftmost and rightmost boundaries of the structure (as defined by the user) extend to infinity and that the surface at the two boundaries remains always "sufficiently" flat. The last condition means that the slopes at both ends should remain unchanged throughout a simulation. To fulfill this condition the user is advised to define a large (wide) enough structure so that the surface at both ends remains flat during the whole duration of a simulation. In any case 2Dinese will make every effort to determine the boundary conditions assuming that the surface at the ends is flat. Avoid very steep slopes at the ends!
Note: Flat does not necessarily mean horizontal.
b) The condition that a structure cannot contain void regions means that this version of 2Dinese does not handle deposition situations where voids are formed, although it does alert the user when this happens.
4. Vacuum:
The Boolean negation of a structure. It can be a reactive medium (gas, liquid), vacuum, etc. The interface between the Vacuum and the structure is the surface (topography).
5. It is important to keep in mind that all regions are referenced by the name of their respective materials. This means that if two or more different regions have the same name then changing whatever properties (see the "Material’s Data" command in the Edit menu) of any of them will result in the same changes to all equivalent by name regions. The only exception to this rule is the default name "none".
N.B. Materials' names are case sensitive and all characters (upto 256) are significant!
6. Process Window:
A Macintosh window which displays a given structure. The major portion of the window constitutes a pane in which the structure is actually drawn. This pane is sometimes called a graphic. The top portion of the window is divided into two narrow parallel stripes: the Control bar and the Message line respectively.
The Control bar displays the "Start" and "Pause" controls, as well as the "Process" and "Status" controls. The latter two are redundant and are used for status display only.
The Message line displays various text information at various stages of execution.
7. Spatial and Temporal units.
These can be specified in the preferences dialog box (See "Preferences" in the Edit menu). Since the model used treats the material regions as mathematical ones the user may end up with regions or parts of regions which are a fraction of an Angstrom thick and still be considered as compact material regions, that is, they could still be barriers (masks) for etching, etc. For this purpose the program makes an internal check at the end of each process and eliminates these parts of a region which are thinner than 2 spatial units.
8. Physical space and graphical space.
2Dinese uses a 2D Cartesian coordinate system (physical space). The y-axis coincides with the vertical direction on the screen (positive is "Up"), while the x-axis coincides with the horizontal direction (positive is "Right"). The origin is defined implicitly by the user through the structure definition.
A direction in space is defined with respect to the positive y-axis. Clockwise rotation defines a positive angle.
The graphical space is the image displayed in a window. It is used for visualisation purposes, as well as for interaction with the user - single or double clicks over a specific region, etc. The graphical space is easily manipulated (magnified, translated, etc) without any effects on the physical space.
Clicking the mouse over the graphic always defines the coordinates of the click point in the physical space of the structure which are then used according to the specific situation. These coordinates are normally displayed in the Message line above the graphic (usually in MouseDown position).
9. Graphics manipulation is achieved via all possible combinations of the following commands: Key(s) pressed: "Shift", "Control" and "Option" combined with a Mouse click and drag (see the "Shrink", "Blow up", "Restore" and "Fit to window" commands in the Simulation Menu).
Copyright 1996 I.V.Katardjiev. All rights reserved.
