SPMwikiLattice correction by gwyddion 2018-04-18
The measured lattice constant by high resolution STM images is relied on the piezo parameters you set into the operating software.However, the piezo parameters are varying at different tips and temperature. Gwyddion, a free SPM data analysis software offers the affine function which could help you to correct the distorted lattice when you are sufferring from the image processing task.
The following image shows the atomic resolution of ZnO single crystal surface (10-10). Obviously, the rectangular unit cell was distorted and the angle between a and c is large than 90°. This distortion was caused by the replacement of a new tip which is not fit with the saved piezo parameters.
For correcting this distortion, please go to “Data Process — Distortion — Affine” in the menu of gwyddion software, then the following window would appera. The left image will present you the real-time processing data if you chose the “Corrected data” in the preview options. The lattice vectors give out a mesh which is fitted to the distorted lattice. These parameters is estimated by the computer at the begining, and the accuracy is highly depended on the reolution of original data. You can modify these parameters by yourselves to improve the matching. After you have finished matching, put the ideal lattice constants into correct lattice. Then, just click ok.
The corrected image is presented on a new window as the following picture. It shows an ideal rectangular unit cell which marked by the white lines.
Actually, the distortion menu in gwyddion contains several other funtions for correcting the distortion. You can find all the manual in the official document.
Gwyddion homepage:http://gwyddion.net
Gwyddion developement is supported by Department of Nanometrology, Czech Metrology Institute.