Electron Correlation Microscopy: A New Technique for Studying Local Atom Dynamics Applied to a Supercooled Liquid

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electron Microscopy

Background:

• Electron correlation microscopy (ECM) is an emerging technique for studying dynamic atomic processes.
• It offers nanometer-scale spatial resolution, analogous to photon correlation spectroscopy but using electron scattering.
• Understanding atomic dynamics is crucial for material properties.

Purpose of the Study:

• To apply ECM to a Pd40Ni40P20 metallic glass.
• To measure the structural relaxation time (τ) in the supercooled liquid state.
• To investigate the temperature dependence of τ between the glass transition temperature (Tg) and crystallization temperature (Tx).

Main Methods:

• Utilized time-resolved coherent electron nanodiffraction within a scanning transmission electron microscope.
• Applied ECM to a Pd40Ni40P20 metallic glass heated into its supercooled liquid phase.
• Analyzed the mean diffraction intensity autocorrelation function g2(t) to determine τ.

Main Results:

• Structural relaxation time (τ) exhibited an Arrhenius-like decrease with temperature from Tg to Tg + 25 K.
• Beyond Tg + 25 K, τ increased as the temperature approached Tx.
• The distribution of τ, derived from single speckle analysis, was broad and varied significantly with temperature.

Conclusions:

• ECM successfully measured temperature-dependent structural relaxation in a metallic glass.
• The observed behavior of τ suggests complex dynamics in the supercooled liquid state.
• The broad distribution of τ indicates heterogeneity in atomic rearrangements.