Abstract
In situ transmission electron microscope (TEM) characterization techniques provide valuable information on structure-property correlations to understand the behavior of materials at the nanoscale. However, understanding nanoscale structures and their interaction with the electron beam is pivotal for the reliable interpretation of in situ/ex situ TEM studies. Here, we report that oxides commonly used in nanoelectronic applications, such as transistor gate oxides or memristive devices, are prone to electron beam induced damage that causes small structural changes even under very low dose conditions, eventually changing their electrical properties as examined via in situ measurements. In this work, silicon, titanium, and niobium oxide thin films are used for in situ TEM electrical characterization studies. The electron beam induced reduction of the oxides turns these insulators into conductors. The conductivity change is reversible by exposure to air, supporting the idea of electron beam reduction of oxides as primary damage mechanism. Through these measurements we propose a limit for the critical dose to be considered for in situ scanning electron microscopy and TEM characterization studies.
Highlights
Disordered dielectric metal and semiconductor oxide thin films are of great technological importance for a wide range of electronic applications, especially in the semiconductor industry (Kingon et al, 2000; Fortunato et al, 2012; Edwards et al, 2015; Yu et al, 2016), as gate oxides in transistors (Robertson, 2006) or tunnel barriers in non-volatile memories (Garcia Ruiz et al, 2009)
At 300 kV and a dose of up to 1.9 × 106 e/nm2 with a dose rate of ∼1.76 × 104 e/nm2 s no silicon nanoparticles are visible in the Energy filtered TEM (EFTEM) images of the film, only a slight cloudy appearance can be noticed
We show that even small amounts of structural damage caused by electron beam induced reduction at low dose can significantly alter the properties of amorphous oxide materials
Summary
Disordered dielectric metal and semiconductor oxide thin films are of great technological importance for a wide range of electronic applications, especially in the semiconductor industry (Kingon et al, 2000; Fortunato et al, 2012; Edwards et al, 2015; Yu et al, 2016), as gate oxides in transistors (Robertson, 2006) or tunnel barriers in non-volatile memories (Garcia Ruiz et al, 2009). A broad understanding and careful characterization of these devices at the nanoscale is of particular importance for further technological advances (Fortunato et al, 2012). Egerton et al, 2004) during TEM characterization, leading, for example, to the generation of oxygen deficient structures (Egerton et al, 2010). While these effects are often quite well understood for ex situ analysis, in situ studies are more sensitive as the effects of these artifacts on the processes and physical properties are typically not well established. Depending on the properties of interest, small structural changes induced by the electron beam can potentially alter reaction pathways or properties of the materials/devices
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