Probing electron beam effects with chemoresistive nanosensors during in situ environmental transmission electron microscopy

Abstract

We report in situ and ex situ fabrication approaches to construct p-type (CuO) and n-type (SnO2) metal oxide nanowire devices for operation inside an environmental transmission electron microscope (TEM). By taking advantage of their chemoresistive properties, the nanowire devices were employed as sensitive probes for detecting reactive species induced by the interactions of high-energy electrons with surrounding gas molecules, in particular, for the case of O2 gas pressures up to 20 mbar. In order to rationalize our experimental findings, a computational model based on the particle-in-cell method was implemented to calculate the spatial distributions of scattered electrons and ionized oxygen species in the environmental TEM. Our approach enables the a priori identification and qualitative measurement of undesirable beam effects, paving the way for future developments related to their mitigation.

Thermal Oxidation of Size-Selected Pd Nanoparticles Supported on CuO Nanowires: The Role of the CuO–Pd Interface

“…Experiments were performed using an FEI Titan Environmental TEM instrument (operation voltage of 300 kV) equipped with a spherical aberration image corrector and a postcolumn energy filter for electron energy loss spectroscopy (EELS). A thermal oxidation method was used for in situ CuO nanowire growth in the environmental TEM instrument, 28 relying on the Protochips Aduro 500 TEM holder platform and membrane-based heating chips with closed loop temperature control. Cu microstructures were fabricated on these membranes using electron beam evaporation of a Cu thin film (thickness of ∼650 nm) combined with a photolithographic lift-off process.…”

“…Next, the samples were transferred back to the environmental TEM instrument for in situ thermal oxidation experiments. To avoid any beam effects related to chemically active species resulting from electron-induced ionization of oxygen gas molecules, 28 TEM imaging was performed at room temperature under vacuum after the samples had been heated at 20 mbar O 2 pressure. Furthermore, the electron beam was blanked during the in situ thermal oxidation treatments.…”

Methods for Calibration of Specimen Temperature During In Situ Transmission Electron Microscopy Experiments

“…Recently, micro-electromechanical system (MEMS) devices have been implemented in TEM/STEM heating holders (Allard et al, 2009; Fei et al, 2016; Burke et al, 2017; Chang et al, 2017; Chen et al, 2017; Steinhauer et al, 2017; Zhang et al, 2017 a , 2017 b ). Figures 1b and 1c show examples of MEMS chip designs for TEM/STEM heating holders.…”

In-situ transmission electron microscopy for probing the dynamic processes in materials

“…Figures 12(a)-(c) shows in-situ cyclic voltammetry curve and resistance measurement of SnO 2 nanowire [115]. The formation of contact can be observed from in-situ TEM images and a distinct current step from the electrical measurements as well [115]. Measurement of the input/output electrical signal provides quantitative idea on the dynamic responses of the materials.…”