Transmission Electron Microscopy - Crystal Structure

In summary, the conversation discusses a tutorial problem involving determining material properties of a layered semiconductor structure using either scanning or transmission electron microscopy. The structure consists of several monolayers of AlGaAs and a thicker layer of GaAs. The problem requires confirming crystallographic orientation, thickness, and the absence of secondary phases between the layers. It is mentioned that TEM is necessary, but the sample may be too thick for this method. The conversation also mentions the use of tandem samples and the need for transparent samples for TEM. There is also a question about cross-section sample preparation techniques for TEM.
  • #1
happycamper
5
0
Hi

I have a tutorial problem involving determining the ideal methods for identifying material properties of a layered semiconductor structure. The problem states to use either scanning or transmission electron microscopy. THe structure consists of several monolayers (around 5nm) of AlGaAs grown epitaxially on a GaAs substrate. After that, a thicker layer (around 5um) of GaAs is grown on top of the AlGaAs.

I need to a) confirm the materials have identical crystallographic orientation, b) ensure the device has the correct thickness, and c) confirm there is no presence of secondary phases between the layers.

It seems obvious that the TEM has to be used, but from what i have found, the samples need to be no more than about 100nm thick (this sample would be over 5000nm thick). Any help or pushes-in-the-right-direction would be appreciated.

Thanks
 
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  • #2
Hi,
your sample is called as tandem sample (useful for solar cells i guess!).
yes for TEM samples transparent to electron beam.
Do you know the cross-section sample preparation technique for TEM ?
 

What is Transmission Electron Microscopy (TEM)?

Transmission Electron Microscopy is a powerful imaging technique that uses electrons to visualize the internal structure of materials and biological specimens. It provides high-resolution images and detailed information about the crystal structure of a material at the nanoscale level.

How does TEM work?

In TEM, a beam of electrons is transmitted through a thin sample, and the resulting image is formed by the interaction of electrons with the sample. The electrons pass through the sample and are focused by magnetic lenses onto a fluorescent screen or a digital camera. The resulting image is magnified and can be observed in real-time.

What is the difference between TEM and SEM?

TEM and SEM (Scanning Electron Microscopy) both use electrons to create images, but they work in different ways. SEM scans the surface of a sample with a focused beam of electrons, while TEM transmits the electrons through a thin sample to create an image of its internal structure.

How does TEM help in determining the crystal structure of a material?

TEM is capable of producing high-resolution images of the crystal structure of a material, allowing scientists to study the arrangement of atoms and their defects. Electron diffraction patterns produced by TEM can also provide information about the crystal structure, including the lattice parameters, orientation, and symmetry of a material.

What are the limitations of TEM?

One of the main limitations of TEM is the requirement of a thin sample, usually less than 100nm thick. This makes it challenging to study thicker samples or materials with a complex structure. Additionally, the electron beam can damage the sample, and the technique is sensitive to vibrations and electromagnetic interference, which can affect the quality of the images.

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