Dear Lena and Luis, I'd like to add something about the issue. If I'll wrong about, someone will gently correct me.
1- when you use the 'ISO' button e select a cut-off, Gwyddion automatically filter your data (I think it digitalizes the data, makes a DiscreteFourierTransform and applies a gaussian filter ... or something similar). Larger the cut-off selected more data are filtered. The first two or three cut-off values just correct your data for the main profile shape (plane, circular, etc..). So I don't think you have to do anything before. You can verify it directly, selecting different cut-off values and looking at the 'texture' and 'waviness' profiles, that have been eliminating, and the roughness profile, on which gwyddion compute the roughness parameters. 2- I agree with Luis: it depends on the features size. In order to characterize some surface features you have to be sure to select a scan step suitable to make a good sampling of your object (Nyquist problem). At the same time you have to select a scan area that includes a lot of singular features (that is, it should be 20 or 30 times the linear dimension of the features you are interested to). If your roughness and waviness features have very different sizes, maybe you have to make two different scannings. Those consideration are deeply handled in metrology handbooks. Besides, the size-dependence of your roughness parameters is nearly eliminated through this filtering procedure. I hope to have been helpful, regards Palma. 2012/2/13 luis vazquez <[email protected]>: > Dear Lena, > > I am a Gwyddion and AFM user, I will try to answer as far as I know: > > > > >> >>1. I read: to calculate the rougness and >>waviness data I need to filter the AFM-Data >>first. So my question: In gwyddion when I use >>the roughness parameters application, do I first >>have to filter the data, or does gwyddion filter >>the data automatically in this application? > > I think you should first filter (whatever: plane > fit, flatten, etc) the image and then calculate > the roughness data (for instance if you do not > correct the plane, the image may have very different roughness values) > > > >>2. Does it make sense, to calculate the >>roughness in smaller areas of the sample, and >>the waviness in a greater areas? Because of the >>different structural size which matters. I >>thought about that, because I realized that when >>I change the thickness of the Scan line the >>roughness value drops with expanded lines, the >>waviness as well. So how should I use the >>application of the roughness parameters to describe my topographies best? > > From my point of view, the roughness does depend > on the area sampled compared to the typical > wavelength (or lateral extension) of the surface > features. If you have a characteristic surface > feature with an average size of L, once your > scan size is larger (2 or 3 times, for instance) > than L your roughness should more or less > saturate (there are papers on this issue). > Perhaps the roughness could drop as you see > because your scan size is so large that you do > not have enough resolution to image properly > each characteristic surface feature. Regarding > waviness I do not work with this parameter, so I cannot tell you. > > > > >>3. I have a glass substrate covered. But >>the coating doesn´t cover the glass everywhere. >>Has gwyddion any way to calculate the coverage factor? > > I think Philipp has answered this question already. > > regards, > > Luis > > >> >>Thanks Lena >> >>------------------------------------------------------------------------------ >>Try before you buy = See our experts in action! >>The most comprehensive online learning library for Microsoft developers >>is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, >>Metro Style Apps, more. Free future releases when you subscribe now! >>http://p.sf.net/sfu/learndevnow-dev2 >>_______________________________________________ >>Gwyddion-users mailing list >>[email protected] >>https://lists.sourceforge.net/lists/listinfo/gwyddion-users > > > ------------------------------------------------------------------------------ > Try before you buy = See our experts in action! > The most comprehensive online learning library for Microsoft developers > is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnow-dev2 > _______________________________________________ > Gwyddion-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/gwyddion-users -- Palma D'Antonio Laboratorio di Fisica Applicata Dipartimento di scienze biomediche- Facoltà di Medicina e Chirurgia Università degli studi di Foggia email: [email protected] tel. 0881 732086 ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Gwyddion-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/gwyddion-users
