Week+of+Oct+20


 * Monday, Oct 20**

I have been worked with STM which stands for Scanning Tunneling Microscope. I was previously working on SEM which was really nice but it did not quite work. So started working on STM.

STM was quite different from SEM in the way of its composition, but it was similar that we could observe the details of the surface. Different from SEM that we can actually look into their surface closely, we could look at the structure (should I say structure?) of the surface with STM. We could observe the atomic structure of the surface. It shows the surface at atomic level by using a tip which is very tiny.

The procedure would be that we put the sample as close as we can to the tip at first. Then, using the computer software, we control the tip to approach as close as possible to the surface. When a conducting tip is brought very near to a metallic or semiconducting surface, a bias between the two can allow electrons to tunnel through the vacuum between them. (wikipedia). This is the reason why we try to place the tip as close as to the surface. When the tip approached to the surface, then the images start to be scanned to the computer screen. Basically, variations in current as the probe passes over the surface are translated into an image. STM can be a challenging technique, as it requires extremely clean surfaces and sharp tips. (wikipedia)



after we got scanned imgaes, we could play around the images as we want by changing the values. We could observe the images in more details thus we could figure out the distance between the atoms such as carbon bond length as seen below.

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