Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers.

D S Badali,R J D Miller,R Y N Gengler

doi:10.1063/1.4949538

Abstract

A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented here. The sensitivity to thin samples is achieved by extending the established technique of ultrafast electron diffraction to the “medium” energy regime (1–10 kV). An extremely compact design, in combination with low bunch charges, allows for high quality diffraction in a lensless geometry. The measured and simulated characteristics of the experimental system reveal sub-picosecond temporal resolution, while demonstrating the ability to produce high quality diffraction patterns from atomically thin samples.

Highlights

Ultrafast structural dynamics is a new and rapidly growing research field, driven by both the desire to witness atomic motions in real-time and the emergence of technology with this capability
A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented
30 keV electron bunches produced in a “compact” electron gun assembly

Summary

INTRODUCTION

Ultrafast structural dynamics is a new and rapidly growing research field, driven by both the desire to witness atomic motions in real-time and the emergence of technology with this capability. Low-dimensionality properties is perpetually growing, the development of techniques used to investigate the structure of these materials is fairly stagnant; the standard techniques have hardly changed in the last couple of decades, with the latest advancement being the development of scanning probe microscopies such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM) in the 1980s With this in mind, we advocate that the field of thin films would certainly be enriched by the availability of an ultrafast structural probe. Several setups have pushed into the true low-energy regime (

DESIGN PRINCIPLES

SIMULATED AND EXPERIMENTAL PERFORMANCE

CONCLUSIONS AND OUTLOOK