Low-Voltage Electron Microscopy (LVEM): Part I — Benchtop and Compact TEMs with Heightened Contrast for Soft Materials

Transmission electron microscopy (TEM) is a critical tool for nanoscale imaging and can provide resolution as low as 0.1nm. However, high-voltage TEMs (HV-TEMs) operated at energies over 100kV can only provide sufficient contrast for lower atomic number samples when the sample is stained with heavy metals, and, in some cases, samples risk being damaged by the beam. In addition, HV-TEMs are typically large, expensive, and complex devices. Low-voltage electron microscopy (LVEM), operating in transmission mode between 5–25kV, offers higher image contrast for organic samples and lower knock-on damage for electrically conductive samples. LVEM systems are smaller, less expensive, and simpler when compared to HV-TEM systems. These advantages make LVEM ideal for increasing the greater accessibility of electron microscopy. This work discusses the physical principles behind improved image contrast and the simplification and miniaturization enabled by lower voltages. This present paper is the first part of a series about LVEM. Current applications of LVEM and how it is improving and making electron microscopy education accessible will be presented in parts II and III.