SEMITIP, VERSION 3, Electrostatic Computations for a Probe Tip near a Semiconductor

R. M. Feenstra
Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213

This program computes the electrostatic potential resulting from a metallic probe tip near a semiconductor. This program is an updated version of the prior VERSION 2, described here, and VERSION 1, described here. Basic usage is described below, and additional details are available in the SEMITIP V3 Technical Information describing changes relative to VERSION 2. A preprint of a paper describing the modifications made to the theory for VERSION 3 is available here, and this paper appeared in J. Appl. Phys. 103, 073704 (2008). The major change in VERSION 3 relative to VERSION 2 is the use of a modified coordinate system in the vacuum, which improves convergence for certain types of problems.

Some background information on the methods used in the program is contained in:

A compiled version of the code, which should run on any Windows PC, is available in the file semitip_v3.exe. Input for the executable code comes from the file FORT.9. Download these two files, into filenames "semitip_v3.exe" and "fort.9". Then, run the code just by double clicking on it. Using a text editor, the input parameters in FORT.9 can be changed to whatever values are desired. In addition to the parameter values, this file also contains comments as to the meaning of each parameter.

Output from the program is contained in the following files (output depends on the value of the output parameter IWRIT as specified in the input file FORT.9):

All of the parameters in the program can be varied using the input file FORT.9, with the exception of the array sizes (NRDIM, NVDIM, NSDIM, and NE), the specification of an auxiliary function other than a hemisphere which defines a protrusion on the end of the probe tip, and the specification of a surface state density other than a uniform one. Modification of those parameters can be accomplished by changing the source code of the program. The source code is also available, in the files:

All routines are written in Fortran. The source code can be downloaded directly from the above locations, and it can be compiled and linked on any platform. Sample output from the above routines is shown in FORT.16.