Abstract
Energy dispersive X-Ray detectors are among the most common tools installed on scanning electron microscopes and, as they are sensitive to light, they can be used to get panchromatic cathodoluminescence information. This article presents practical considerations about the parameters to choose to obtain a good cathodoluminescence signal on a silicon drift detector. Probe current is the most important but other parameters of electron microscope and energy dispersive X-Ray detector are also explored. Filament brightness, if not fixed, influences the number of electrons incident on the sample and modifies cathodoluminescence response. Beam voltage and working distance must be adapted to the sample and to the electron microscope geometry. Acquisition and shaping times are important parameters for spectrum quality: the high sensitivity of silicon drift detector to light allows the use of low acquisition times and high shaping times. As cathodoluminescent materials are mostly high band gap materials, charge effects can influence their response and the size of the acquisition area must be carefully chosen. The influence of all these parameters is studied through two scintillating materials. Some examples of application are described to show the potential of this method. They include localization of luminescent particles, a demonstration of the effect of strong electron beam on a needle of material and the characterization of light emitted by a structural defect in a scintillator material.
Highlights
Energy dispersive X-Ray (EDX) detectors are among the most common tools installed on scanning electron microscopes (SEM)
When facing a new sample, the microscopist must ask itself the following question: which parameters should I choose on my equipment to get the best signal? These parameters can be divided in two sets: parameters linked with the SEM like beam voltage, beam current or working distance, and parameters useful for EDX spectrum acquisition
Working distance and shaping time can be set at the same value for cathodoluminescence and for X-ray studies
Summary
Energy dispersive X-Ray (EDX) detectors are among the most common tools installed on scanning electron microscopes (SEM). EDX detectors are made from silicon, a material in which X-ray photons and visible light can create electron-hole pairs, which are further collected to give the useful signal. F. Smet et al studied the behavior of a Si-Li detector exposed to the light of luminescent BaAl2S4: Eu+ films [11]. Smet et al studied the behavior of a Si-Li detector exposed to the light of luminescent BaAl2S4: Eu+ films [11] They found that the effect of light on the EDX detector is a peak at very low energy. The count rate increases first with the probe current, reaches a maximum and decreases It looks like the electronics are not able anymore to detect the incoming photons when the quantity of emitted light is too high. The working of a SDD is explained and a few useful terms are defined
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