Another Sample to Use

A project log for The PVC Scanning Tunneling Microscope

An easy-to-build scanning tunneling microscope.

tom-ekkensTom Ekkens 02/04/2018 at 21:270 Comments

Aluminum Foil - Shiny side.

The previous sample - a piece of DVD - is easy to image but only has good repeated features at the 740 nm level.  Another sample is needed for additional size scales. 

Preparation:  A cheap option for the second sample is a piece of aluminum foil.  It is mounted to a washer so that the magnet in the stage will hold it down.  In the picture, I have made two additional electrical connections using silver paint but this really wasn't necessary.  I have mounted it so the shiny side is up.

Imaging:  Two images of the aluminum foil are shown below.  On the top is the foil as it appears when imaged using a light microscope.  This microscope has a magnification of 800 times so the field of view (top to bottom) is about 230 μm.  Ridges from the manufacturing process are all in the same direction, but the ridge separation is not consistent.  Some of the ridges are vary wide but some smaller ones are in the range of 10 to 30 μm.  On the bottom is an image taken by a scanning electron micrscope with a field of view (top to bottom of about 3600 nm.  This scan size matches the largest field of view that the STM has so the picture should be similar.  At this magnification, there are smaller lines and bumps in the range of 100 to 300 nm.

Two pictures taken from the STM are shown below.  Both pictures are taken at approximately the same location with the same field of view (2500 nm) and the same scan speed (400 mS per line).  The image on the right was taken with a bias of 600 mV and is completely worthless.  The image on the left was taken with a bias of 3000 mV and has excellent detail.  A major ridge can been seen with additional small ridges and bumps in the range of 100 to 300 nm.  Other bias settings of -600 mV and 2000 mV were tried but were not as good as the 3000 mV image.