Microfabricated Nanofluidic cells for in situ liquid TEM

Over the last decade, transmission electron microscopy (TEM) has been revolutionized not only by the introduction of new and very sophisticated hardware for improved resolution, such as aberration correctors and monochromators, but also by the improvement of new methods that have provided more than structural information of materials.

In this regard, in situ liquid cell electron microscopy (EM) is one of the new emerging methods that gained a lot of attention by making possible to observe processes and samples in liquid environments within the chamber of an electron microscope. The main focus of this PhD project is to improve the technologies behind liquid cell TEM by developing a novel and robust liquid cell device able to increase the control over the liquid layer thickness, essential for good imaging conditions.

A new type of nanofluidic cell has been created with an architecture based on wafer bonding of Atomic layer deposited (ALD) Al2O3 on Si3N4 membranes. With the improved liquid layer thickness control, we use the devices to measure the electron mean free path in water which is a fundamental aspect of TEM studies, and present the high-resolution TEM capabilities of the nanofluidic cell.

Furthermore, the first findings on nanoparticle (NP) growth in this particular nanochannel system are presented that also opens up for new types of liquid cell studies with laminar flow. These results demonstrate the capability of the novel nanofluidic cell to provide ultra-thin liquid layers, allowing quantitative and high-precision acquisition of liquid thickness maps, high resolution observations and meaningful information about synthesis of NPs from metal precursor solutions in confined space.

Finally, a new concept device based on a Si3N4 membrane for plunge freezing fixation, which enables ultra-fast cooling rates, is presented.