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The high brightness SFE source combined with the innovative GEMINI® column enables the small sport sizes for ultra high resolution combined with high contrast and high probe currents | | The Schottky field emission (SFE) source used in the GEMINI® column has been developed to overcome the weaknesses of the cold field emission (CFE) source, whilst maintaining its strengths on the form of high beam brightness and low energy spread.
Because of their many advantages, Schottky emitters are used for high precision imaging and measurement. The table below shows the operating parameters and performance of various electron emitter types.
The Schottky emitter combines the high brightness and low energy spread of the cold field emitter with the high stability and low beam noise of the thermal emitters. As the emitting area is approximately 100 times larger than that of the cold field emitter, it has the capability to deliver much higher probe currents required. Moreover, the SFE source achieves a similar energy spread as the CFE source, but at an emission current level more than 50 times higher. The larger size of its virtual source gives the SFE source another advantage: its susceptibility to vibration is much reduced.
Due to the direct link of the SFE gun with the beam booster, the dynamic ratio at the gun level is only about 3:1 and the U0/U1 ratio is always larger than unity. This allows a column beam path without any intermediate cross-over of electrons. The classical designs are therefore prone to electron energy broadening in beam cross-overs and have difficulty operating at the very low beam energies which are now increasingly required for many applications.
The SFE incorporated in the GEMINI® column provides excellent beam brightness, unsurpassed probe current stability and probe current suitable for quantitative analytical applications.
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