Research proposal 1: Semiconductor Devices
Introduction
Scanning electron microscope (SEM) is a kind of electron microscope that produces images by scanning it with the focused electron beam. Transmission electron microscopy (TEM) is a type of microscopy that a beam of electrons can transmit through an very-thin specimen, interacting with the sample when it passes through. Both instruments’ images have the high resolution than the optical images. However, the focus of analysis is different. Only surface region of specimen can be viewed in SEM. On the other hand, TEM seeks to see the structure of the specimen and arrangement of crystals.
Choice of instrument
In this case, we aim to confirm the crystallographic orientation and the thickness of semiconductor devices which is focus on the sample’s structure. Nevertheless, SEM just focuses on the sample’s surface. Therefore, TEM is the suitable instrument.
Choice of techniques & reasoning and justification
The technique of phase contrast ,which is formed with at least two diffracted electron beams through their interference could be used in this experiment due to it is able to deal with the interfacial structure, crystal growth and others.
Firstly, assumed the sample (semiconductor devices) is uniform. As the specimen is too thick (AlGaAs is around 5nm, the thicker layer of GaAs is roughly 5µm) to deal with the technique of phase contrast, it need to be cut to a much thinner thickness which is approximately less than 20nm by the process of ion-thinning or other techniques. Different arrangement, angle, or distribution of the Phase contrast can be seen to confirm that whether both materials have identical crystallographic orientation or not.
Secondly, the cross-section samples (