Scanning tunneling microscopy constant current mode

Fig. 7.2. Scheme of scanning tunneling microscopy in the constant height mode (left) and the constant current mode (right) X, Y and Z designate the respective piezodrives, dashed line indicates tip position... 

Measurements. Absorption spectra measurements on the film and solutions of the metal complexes were measured on a modified Cary 14 spectrometer. Luminescence spectra were recorded with a custom photon counting spectrometer or a PTI (Deer Park Drive, South Brunswick, NJ 08852) luminescence spectrometer system. The FT-IR spectra were recorded with a PE-1600 spectrometer or a Bio-Rad FTS-40 spectrometer (Professor R. Crooks, Chemistry Department, University of New Mexico). RA spectra for LB films were measured on the FTS-40 with a Hanick gra2dng angle attachment and MCT detection system. Typically 256 scans were requir to obtain adequate intensity for the monolayer films. The scanning tunneling microscopy measurements employed a Nanoscope II system (Digital Instruments, Inc.). Etched Pt-Ir tips were used with the standard, 0.6 micron head. The system can be operated in either the constant current or constant height mode but the film contours were similar for either. 

Scanning tunneling microscopy (STM) (characterization) In STM, the electrons that tunnel between a probe tip and a surface are measured. The system is typically operated in a constant current mode and the movement of the tip is determined to about 0.1 A. 

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