Plane tab

On this tab user can set scan parameters corresponding to surface scanning Z(X,Y). Scanning can be perfomed in several different modes. Scanning mode can be set using falling list that is in upper part of the tab window. Depending on the mode selected one or several second-level tabs will appear. The first of this tabs contain general surface scanning parameters, the rest - parameters that are specific for chosen scanning mode.

On a Common second-level tab following values can be set:

• Xo, Yo, Size X, Size Y - coordinates of left bottom corner of a scan window and its size in X and Y directions (see pic. 2.7). All these values are sent to the server only in the beginning of scanning process and does not change during scanning. To enter new values user should stop current scan, enter new values then start scanning again. Scan window dimensions has a higher priority than left bottom corner coordinates and if the scan window dimensions become rather large left bottom corner coordinates decreases automatically.

  ''FemtoScan`` program doesn't allow scan window to leave a piezomanipulator dynamic range. Point with (0,0) coordinates is a center of a scan window of maximum size. If user chooses maximum size for the scan window Xo and Yo take maximum values automatically.

• Steps/lines -- number of points in a scan line and number of lines in surface image. This field is inaccessible for direct editing. User can use Samples N field on Common tab to change number of points in a scan line. Number of lines in the scan is calculated from Size X è Size Y parameters ratio.

  Figure 2.7: Scan window dimensions.

  

• Lock button makes the Steps/Lines ratio constant, in other words it constrain scan window proportions. If this button is drawn Size X and Size Y parameters will change simultaneously.
• Scan X-Y -- scanning direction. It is possible to form image scan in two perpendicular directions - along X-axis of piezomanipulator or along Y-axis of piezomanipulator. This item allow to choose this direction.

• Disable vertical sweep -- this item disabling vertical sweep - in this case the probe doesn't move along slow, vertical axis. It moves at the same line on and on, though in scanning window this line will be moving. And all the images will be drawn in the same direction of slow vertical sweep.
• N scans -- State how many times the surface should be scanned. If the word "continuous" written in this field then scanning process will last until user stops it.

In the two frames -- 1st image and 2nd image -- parameters for the 1st and the 2-nd image that concerned to the same surface scan are grouped. Inside the both frames just the same parameters are available.

• Drop list, consisted from Height, Deflection, Friction and other data types (in the 2-nd image frame there is None in addition) sets what data be sorted in this image. If Height item is chosen then surface profile data will be represented in the image. In case Deflection item is chosen it will show the signal of deflection from bearing value (error signal). Friction shows horizontal deflection of cantilever (AFM and RAFM modes). Intensity -- total signal that came from photodiode (AFM, RAFM). Phase -- signal from phase detector (RAFM). Channel 4,5,6,7 -- additional data channels. None -- will show nothing. If this item is chosen program wouldn't show corresponding window.

  If data obtaining from auxiliary device, connected to a COM-port is enabled on the server than Auxiliary data tape will appear in the list.

• Retrace -- Image will contain data that are obtained during backward movement of a probe.

Besides these parameters Common tab can contain some additional parameters (depending on scanning mode). In this version of the software following scanning modes where realized:

• Topography - usual mode of surface scanning.
• Dualtrace - scanning mode when every line is scanned twice. Feedback parameters for this mode can be configured on the tab Dualtrace. If this option is chosen two additional check boxes appear in Common tab - "2nd trace" that allow to show the result of the line's second scan.
• Interleave - scanning mode when every line is scanned twice, and the second scan is preformed by repeating a profile that was obtained during first scan of this line with addition of some displacement on Z-axis. This mode allow a tip to "fly" over the sample at the specified height. This height (or displacement on Z-axis) can be specified on a Interleave tab. Negative displacement corresponds to increase in distance between tip and a sample. On the Common tab two additional check boxes appear - "Interleave" - that allow to show the result of interleave scanning.
• Lift - mode in which whole scan window is rescanned for the second time by lifting tip over the surface. This operation goes in two stages. At the first stage selected region is scanned with the surface height registration during both the forward and backward movement of a probe (Height/Trace and Height/Retrace). On the second stage the probe moves with some constant vertical displacement along the plane that is corresponds to average surface slope, that was calculated by least-square analysis method using the data obtained during the first stage. The vertical displacement (offset) can be set using Lift tab. Negative displacement value corresponds to to increase in distance between tip and a sample.
• Lithography - lithography mode. Lithography can be performed in two modes - lithography by a probe (Z), and litography by a voltage (Ut). On the Litography tab user can choose Mask image, litography mode and parameters for probe-sample interaction during lithography process. By pressing Select button user can call a window that allow to choose mask image (pic. 2.8).If mask dimensions (in points) doesn't coincide with dimensions of scanning region then there are 3 possibilities - 1) Mask resolution will be changed; 2) centers of the mask and the region will be superposed; 3) Dimensions of scanning region will be changed to dimensions of the mask. In the Z mode scanning goes in two stages. On the first stage surface profile in forward (trace) and backward (retrace) direction is acquired. On the second stage average slope plane is calculated and a scaled from 0 to Z image mask scale with Z offset, is added to this plane. And a probe during scanning traces the surface obtained at the second stage.

  In the Ut mode a line profile from the mask image transferred to the Ut DAC. The mask is scaled by Z-axis to make all mask's values fit the region from 0 to Ut . Then mask values shift to Ut offset.

Figure 2.8: Selecting a mask image for lithography.