Tecnai on-line help manual -- Alignments - UT Southwestern

<strong>Tecnai</strong> on-line help Alignments 65<strong>Tecnai</strong> 12 Software version 213 LM-STEM procedure13.1 LM-STEM PreparationPurpose: Set up microscope for aligning the column in LM-STEM.Importance: CONVENIENCE as a reminder to set up the proper conditions before starting the actualalignment.For STEM alignment a number of pre-conditions must be met, otherwise no proper alignment can bedone:• First of all, LM-STEM relies on a proper setting of several optical parameters for which the Gun, LMBeam and LM Image as well as HM-TEM Image alignment must have been done.• Second, Tem Imaging & Analysis (TIA) must be running when for STEM alignment.• Third, the settings for the Preview view mode must be set so as to give an image size of 512x512pixels and a frame time of approximately 6 seconds and the Search view mode to an image size of256x256 and a frame time of approximately 3 seconds.• Finally, the Bright-Field (BF) detector must be selected (and all other detectors deselected) in theSTEM Detector Control Panel.Note: The diffraction focus (LAD) is LM-STEM is kept as set in LAD (proceed to LM, then todiffraction). In most cases this should be kept at the default setting. Unless there is a reason todeviate from this, it is important to make sure the setting is properly done. Go to LM, then LADand press the Eucentric focus button to reset the LAD focus to the default value.13.2 LM-STEM Intensity presetPurpose: Set up Intensity setting for focused beam in LM-STEM.Importance: ESSENTIAL for proper setting for LM-STEM (Intensity settings).Method: First focus the image, then focus the beam.Important : During STEM alignment TIA (Tem Imaging & Analysis) must be running.ProcedureThe alignment procedure consists of three steps :• A first step in which the image is focused and the beam is centered.• A second step in which the beam is focused accurately (sets the Intensity setting).• A third step in which the focusing of the beam is repeated for all spots (except 3 which has alreadybeen done in the previous step).13.3 LM-STEM Beam-shift pivot pointsPurpose: Align beam shift pivot point = make sure that the beam does not tilt when it is shifted in LM-STEM.Importance: ESSENTIAL for for keeping the beam parallel to the optical axis when shifting so that :• The STEM magnification calibration remains accurate.• The STEM image is not distorted.• The diffraction pattern does not move off the detector during scanning.• The image is in focus from one edge to the other.