The EIGER detector for low-energy electron microscopy and photoemission electron microscopy

Abstract

EIGER is a single-photon-counting hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland. It is designed for applications at synchrotron light sources with photon energies above 5 keV. Features of EIGER include a small pixel size (75 µm × 75 µm), a high frame rate (up to 23 kHz), a small dead-time between frames (down to 3 µs) and a dynamic range up to 32-bit. In this article, the use of EIGER as a detector for electrons in low-energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) is reported. It is demonstrated that, with only a minimal modification to the sensitive part of the detector, EIGER is able to detect electrons emitted or reflected by the sample and accelerated to 8-20 keV. The imaging capabilities are shown to be superior to the standard microchannel plate detector for these types of applications. This is due to the much higher signal-to-noise ratio, better homogeneity and improved dynamic range. In addition, the operation of the EIGER detector is not affected by radiation damage from electrons in the present energy range and guarantees more stable performance over time. To benchmark the detector capabilities, LEEM experiments are performed on selected surfaces and the magnetic and electronic properties of individual iron nanoparticles with sizes ranging from 8 to 22 nm are detected using the PEEM endstation at the Surface/Interface Microscopy (SIM) beamline of the Swiss Light Source.

Characterization of a hybrid pixel counting detector using a silicon sensor and the IBEX readout ASIC for electron detection

“…The tail to lower energies originates from events with partial energy loss due to charge sharing. At the electron energy of 20 keV the peak is shifted to lower energies by roughly 6 keV, in agreement with previous measurements [8]. This is due to the low penetration depth of electrons -1-5 μm for Al and Si -in the energy range of 10-20 keV [8].…”

“…At the electron energy of 20 keV the peak is shifted to lower energies by roughly 6 keV, in agreement with previous measurements [8]. This is due to the low penetration depth of electrons -1-5 μm for Al and Si -in the energy range of 10-20 keV [8]. Thus, electrons entering the sensor by the Al layer and Si backplane loose their energy and are scattered.…”

“…many existing HPD like EIGER [8], MEDIPIX [9] or TIMEPIX [10] have been used for electron detection. Counting HPD have a very high dynamic range, can operate at frame rates of several thousand images per second, exhibit no noise associated to the readout operation nor to the sensor's dark current, and are radiation hard [4].…”

MAXPEEM: a spectromicroscopy beamline at MAX IV laboratory

“…With the new generation of AC-SPELEEM microscopes, the old MCP-CCD detector will limit the overall system performance. To overcome this problem, several types of solid-state detectors that convert the electron events directly into electronic signal were once tested in PEEM/LEEM systems after many years of application in X-ray diffractometers and transmission electron microscopes (Tinti et al, 2017;Tromp, 2015;van Gastel et al, 2009). Recently, a more economic camera system that combines the traditional scintillator and the latest CMOS chip was adopted by several LEEM/PEEM systems (Janoschka et al, 2021; see also https://www.bnl.gov/cfn/facilities/probes.php).…”

Enhanced DQE and sub-pixel resolution by single-event processing in counting hybrid pixel electron detectors: A simulation study

“…Doseindependent DQE is also a noteworthy property [9]. For these reasons, these technologies have started being introduced to the field of electron microscopy, and many existing counting HPD like MEDIPIX2 [10], MEDIPIX3 [11], EIGER [12], EIGER2 [13], and IBEX [14] were investigated. For all electron detectors in general, and for dose-sensitive applications such as cryoEM [15] in particular, the quest for an optimization of the DQE performance is one of the driving forces of all the design phases, from the hardware to the image processing methods.…”