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How to Use KikuchiLines X |
KikuchiLines X is a simple program to simulate Kikuchi lines and RHEED (reflection high-energy electron diffraction) patterns. It is very simple so that it can not calculate line and spot intensities but only their positions.
When you launch the application, the following window will appear.
To edit calculation conditions, press a lower right button .
Then the following setting sheet will appear.
Details of the calculation parameters are shown in the "Details of Setting Parameters". After setting desired parameters, close the settings sheet and press Calculate button. After the calculation, the window will look like below.
By default, blue lines are excess (bright in a real pattern) Kikuchi lines and yellow ones are defect (dark in a real pattern) lines. If you click on a line or a spot, it is highlighted by red color and its index will be shown in the index field.
In addition, you can overlay an experimentally obtained RHEED pattern. To add a RHEED pattern, click Choose Pattern button and select an image file. Most of the image formats such as TIFF/JPEG/GIF/PICT/PDF etc. (all of them can be treated by Preview application) are supported. This software does not have image processing functions, so that it is better to modify the pattern before using it. It is also recommended to set the image resolution to 72 dpi. If it has higher resolution, it will be degraded.
When you choose a RHEED pattern, it looks like this.
Initially, RHEED pattern and calculated lines/spots does not fit. To move the pattern, drag it with option key. To change a size of the pattern, move the scale slider or enter a magnification number in the text field just right the scale slider. To change a rotation angle of the pattern, move angle slider or enter an angle (in degree) in the corresponding text field. After these adjustment, it should be like the following. Here, if the image resolution is 72 dpi and the camera length is set correctly, image size exactly matches the calculated one with magnification number of 1.
You can show/hide Kikuchi lines/RHEED spots/RHEED pattern by checking/unchecking corresponding check boxes below.
You can also save calculated lines/spots and RHEED pattern with calculation conditions. The RHEED pattern is included in the saved file (.kklx), thus you do not need to keep the original pattern.
Click on button opens a subwindow, in which calculation parameters are shown (Figure below).
This text can not edit or save, however, you can select it and copy to anywhere else you want.
Before explaining setting parameters, you should know the following definitions. Axes are defined as the below figure. As shown in the figure, z axis is a surface normal direction, y axis is parallel to the surface and azimuthal index, x = y × z. The incident electron vector k0 comes from an azimuth direction which is rotated by φ (azimuthal rotation) and a glancing angle of θ.
The screen is placed at the opposite side of the incident electron beam as shown below. A camera length and a screen tilt angle are defined as shown in the figure.
The following figure shows a top view of the surface. A screen azimuthal angle ρ is defined as shown in the figure. Here, surface 2D structural unit vectors (a1 and b1) are also shown. For 1×1 unit, both a1 and b1 vectors are defined by corresponding x and y components in a0 unit, which is a lattice constant. For example, Si(111) case (a0 = 5.43Å), the surface unit is a diamond as shown in the figure and both of the unit vectors have length of a0/√2. In this case, a1 = (-1/2√2, √3/2√2) and b1 = (-1/2√2, -√3/2√2). For super structures such as 7×7, unit vectors are defined using a1 and b1. Therefore unit vectors for 7×7 are a2 = (7, 0) and b2 = (0, 7), those for √3×√3 are a2 = (1, -1) and b2 = (2, 1).