  The Planar Model of the Electrode-Vacuum-Electrode configuration for STM in
which electrode surfaces are assumed to be infinite parallel planes, with
atomic size separation and vacuum between them, is used to calculate tunneling
current densities for both low and high bias voltages. Non WKB, Airy function
solutions for the Schr\"odinger Equation for the trapezoidal barrier in the
tunneling region are used to calculate the tunneling probability. Temperature
dependent Fermi Factors for each electrode are introduced and the calculation
involves integration over the electron energies. In order to convert the
current densities obtained in the planar model to tunneling currents the tip
and sample surfaces are modelled as confocal hyperboloids, and the tip sample
distance is replaced by the length of the line of force (field line). The
current is found by integrating the current density over a finite area of the
tip. The calculated tunnel currents for a few electrode pairs at room
temperature are plotted for several values of bias voltage, tip sample
distances, and tip radii of curvature. Pauli Effects are studied as a function
of bias voltage and tip-sample distance. Some estimate of lateral resolution
and its dependence on bias voltage and tip radius is also presented.
