Click here for input/output files and main program source code for Example 2
This example illustrates a band bending computation for a GaAs(110) surface with the probe tip located between two linear areas of extrinsic charge density (i.e. surface steps), located between -6 nm < x < -4 nm and 4 nm < x < 6 nm. The spatial extent of the areas are defined in the routine IGETAR, located in the same file as the Mult3.f main program:
INTEGER FUNCTION IGETAR(X,Y)
C
IGETAR=1
IF ((X.GT.-6.AND.X.LT.-4.).OR.(X.GT.4.AND.X.LT.6.)) IGETAR=2
RETURN
END
with the parameters defining the regions given in the FORT.9 input file.
The sample voltage as specified in the FORT.9 input file is 0 V, with a contact potential of 0 eV. This problem has a mirror plane lying along the x-axis, so line 41 in the FORT.9 file is set to 1 thus including that mirror plane in the computation.
Output to FORT.11 and FORT.12 gives the electrostatic potential energy (column 2) vs. the z-distance through the vacuum and semiconductor (column 1, in FORT.11) or the radial distance along the surface (column 1, FORT.12). The latter cut is taken at a user-specified angle of 0 degrees relative to the x-direction, with the cut actually corresponds to the closest available angle to that which is 2.8 degrees relative to the x-direction (as listed near the bottom of the FORT.16 output file). When plotted, these potentials appear as: