RESUMEN
An apparatus is developed for transmission electron microscopy (TEM) to acquire image and spectral data, such as TEM images, electron holograms, and electron energy loss spectra, synchronized with the measurement of the dynamic response of a specimen under an applied alternating current (AC) electric potential (voltage, denoted VAC). From a VAC of frequency f, a shutter pulse signal is generated to open and close a pre-specimen shutter in a base TEM apparatus. A pulse is generated per VAC cycle from the targeted phase Φ to Φ +∆Φ with phase width ∆Φ (∆Φ <2π). ∆Φ corresponds to the temporal pulse width τ (τ < 1/f) of an electron beam; i.e., ∆Φ =2πfτ. Because of the high sensitivity of the TEM camera used in this study, the images and spectra that are acquired at the same target phase are integrated by means of stroboscopic illumination to obtain the final phase-locked images and spectra with sufficiently small S/N ratio. Phase-locked (strobe) images and/or spectra are obtained for model specimens of polycrystalline aluminum and an all-solid-state lithium ion battery (LIB). In the phase-locked TEM conditions, f ranges from 1Hz to about 40kHz and ∆Φ from 2π/80 to π. VAC ranges from 2mV to 1V depending on observation conditions. The quality of phase-locked strobe images can be improved markedly using a phase-locked strobe electron beam. Under specific conditions, the spatial resolution in images is better than 0.12nm, even though the spatial resolution generally depends on VAC, f, the base TEM, and the conductivity of the specimen. For the model specimens, it is shown that electrochemical impedance spectroscopy and cyclic voltammetry can be performed in a TEM apparatus, and could potentially be synchronized with phase-locked (strobe) imaging and spectroscopy. Severe electron irradiation damage is detected during phase-locked (strobe) electron holography of the model LIB.
RESUMEN
The introduction of scanning/transmission electron microscopes (S/TEM) with sub-Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in-situ at the atomic scale. Thereby, in-situ specimen holders play a crucial role: accurate control of the applied in-situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in-situ S/TEM experiment. For those reasons, MEMS-based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in-situ parameter for more reproducible data. A newly developed MEMS-based microheater is presented in combination with the new NanoEx™-i/v TEM sample holder. The concept is built on a four-point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (<4%) and uniform temperature distribution over the heated specimen area (<1%), enabling not only in-situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy-dispersive X-ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments.
RESUMEN
A sample chamber has been constructed for studying the growth of thin films by pulsed laser deposition in situ with surface X-ray diffraction. The achievable temperature ranges from room temperature to 1073 K in a controlled oxygen environment. The partial pressure of the oxygen background gas covers the range from 0.1 to 10(5) Pa. The first results, showing intensity oscillations in the diffracted signal during homoepitaxial deposition of SrTiO(3), are presented.
