In the view of developing high performance metal-oxide-diamond field effect transistor (diamond MOSFET), recent reports presents different approach in the choice of the gate material and, in particular, on the dielectric layer [1-2]. However, a nanometric analysis of the band levels is necessary to understand the electron dynamic across the MOS stack. Recently, STEM-EELS have been revealed as reliable technique to estimate the bandgap of SiO2 dielectric materials. Nevertheless, its applicability has been limited to SiNx materials.
To evaluate electron transitions near the bandgap energy in the EELS spectra, researchers have to overcome several experimental difficulties. Here, we evaluate the effect of Čerenkov radiation and volume plasmon-related peaks in low-loss range of EELS spectra. In this study, STEM-EELS techniques are used to analyse the O-terminated diamond/Al2O3 interface (similarly to previous studies presented in SiO2 by other authors ). Indeed, volume plasmons (VP) and Čerenkov (Ch) radiation contribution are evidenced in Fig.1, which also shows diamond-related D1-2 peaks and Al2O3-related peak A1 however, in the Al layer, only plasmon-related peaks are revealed. Probe position of the previously presented EELS spectra are shown in Fig.2, as numbered dots. Figure 2 shows 001-BF TEM micrography of the diamond/Al2O3/Al layers. Inset of Fig.2 shows HREM micrography of the diamond/Al2O3 interface, revealing variations in the crystalline quality of the low temperature (100ºC) ALD-deposited Al2O3 layer.
In this work, we present a methodology to evaluate the influence of the Čerenkov losses and plasmon-related peaks in the low-loss EELS spectra. In some cases, such peaks are shown to mask the interband-related transition. Indeed, in such cases, Čerenkov-related and plasmon-related peaks have to be deconvoluted and removed, in order to accurately apply the linear-fit method , which allows calculating the diamond/oxide bandgaps.
The previously described methodology allows determining the bandgap variations in the oxygen-terminated diamond/oxide interfaces.
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To cite this abstract:José Piñero, Daniel Araújo, Pilar Villar, Julien Pernot; Diamond-based MOSFETs: Bandgap interface profiling by STEM-EELS. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/diamond-based-mosfets-bandgap-interface-profiling-by-stem-eels/. Accessed: July 13, 2020
EMC Abstracts - https://emc-proceedings.com/abstract/diamond-based-mosfets-bandgap-interface-profiling-by-stem-eels/