GaN Holographic focal series ============================ This is a off-axis electron hologram series obtained with a transmission electron microscope of a GaN-crystal in <11-20> zoneaxis at atomic resolution. This directory contains two holographic focal series obtained under equal conditions (no strong changes in illumination or microscope setup) a few minutes apart. The first series (a1) is a focal series of object holograms, where the GaN-crystal was located in one of the partial waves. The second series (empty) is taken with object removed from the field of view. The holograms are double biprisms holograms, the biprism filaments were oriented along the 8 to 2 o'clock direction. The object partial wave passed the filament on the top site, the reference partial wave passed it on the bottom site. The holograms were obtained using the "FEI 80-300 TITAN Berlin Holography Special" operated at 300kV, with all lens aberrations corrected as good as possible. The double biprism setup used is discussed in detail in Genz et al., Ultramicroscopy 147 (2014) 33-43. The focal series was obtained with nominal step sizes of -2.0 nm around the Gaussian focus. The defocus goes into underfocus direction with increasing image index. Please note, that the holograms present in the DM3 files are NOT correctly calibrated. Recalibrating using the +/-(0004) GaN reflections of the centralband gives a sampling rate of 0.00519824 nm/px The MTF of the camera (Gatan US1000) was measured by the edge method. The MTF for binning 1 (as used in the present data) can be approximated by mtf(q) = sin(pi * q) / (pi * q) * [1.02543658e-05 / (1.07409336e-02**2 + q**2) + 2.49224357e-02 / (2.31357313e-01**2 + q**2) + 4.60461599e-01 * exp(-(q / 4.78451068e-02)**2) - 2.25536738e-02], where q is 0.5 at the Nyquist frequency of the camera. The data present in this directory were used to obtain the results shown in the following paper. If you use the data for your own scientific purposes, please cite this paper: T. Niermann and M. Lehmann Averaging scheme for atomic resolution off-axis electron holograms Micron 63 (2014) 28–34 http://dx.doi.org/10.1016/j.micron.2014.01.008 The data itself is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0). For other inquiries regarding the data please contact tore.niermann@tu-berlin.de