Design and construction of a scanning tunnelling microscope (STM) and biological applications

Scanning tunneling microscope (STM) is a new generation microscope which can image topography of surface from angstrom (Å) level to micron (?) level. STM could image the biological molecules in their native environment without deform their 3D conformation. This is the main advantage against to other techniques, because of the reason, no high power radiations is used. Another advantage is no complicated sample preparation steps are required.The aim of this thesis is contributing to the investigation of the surface properties of various biological molecules by fabricating a STM. It has four main parts, which are mechanical, electronic, data acquisition and computer software.Scanning process in STM is based on sensing of the tunneling current between a metallic tip and a conducting substrate, which are in very close proximity but not actually in physical contact. For the piezoelectric tube that performs the scanning process, a bipolar power supply and a current/voltage converter are designed, fabricated and both are tested for their electronic performance. A PI control unit is designed and fabricated to accumulate the control of the current, detected by the mechanical unit which operates the scanning process. Detected current data are displayed as an image by computer software. Captured image is compared with the images from other devices those commercially used and perfection of the system is observed.