diamond

Section: User Manuals (1)
Updated: Thu Jun 28, 2001

NAME

diamond - simulate single electron transistors

SYNOPSIS

diamond [ action-option ] [ other-options... ]

DESCRIPTION

This program is intended to simulate the I-V curves measured on a single electron transistor in the regime where tunneling takes place through individual electron quantum states. It reads a configuration file containing the description of the device as well as the experimental conditions. The latter can be overriden by command-line options. The I-V curve is output to stdout as numbers in ASCII form.

OPTIONS

Action options

The following mutually exclusive options select what the program will do:

-h: Print a short help message and quit.
-R: Print the current profile of a right Fermi energy sweep. The Fermi energy of the left lead is kept constant and the current is output as a function of the Fermi energy of the right lead.
-L: Print the current profile of a left Fermi energy sweep. The Fermi energy of the right lead is kept constant and the current is output as a function of the Fermi energy of the left lead.
-B: Print current profile of a bias voltage sweep. The gate voltage is kept constant.
-T: Print a current table at 0 K. The left and right Fermi energies take a set of discrete values: one value below the lowest energy level, one value between every pair of consecutive levels and one value above the highest energy level. The currents are displayed in tabular form were the right Fermi energy varies from line to line and the left Fermi energy varies from column to column.
-2: Print current in a 2D (bias, gate) sweep. The currents are displayed in tabular form were the gate voltage varies from line to line and the bias voltage varies from column to column.

Other Options

-c file: Specify the parameter file overriding the default diamond.conf.
-t temperature: Specify the temperature in K.
-o voltage: Specify the other voltage/Fermi energy for a 1D sweep, i.e. the value that is kept constant.
-i voltage: Specify initial voltage/Fermi energy for 1D sweep.
-f voltage: Specify final voltage/Fermi energy for 1D sweep.
-n steps: Specify number of steps in 1D sweep.

CONFIGURATION FILE

The configuration file is used to define a set of parameters that describe the device as well as the experimental conditions. Parameters can be scalars or arrays. Scalar parameters are set by statements of the form

ParameterName = value

while array parameters use the form

ParameterName = value1 value2 value3 ...

Empty lines and lines starting with # are valid comments. The parameters listed below are all scalar unless otherwise stated.

Device description

LevelPos (array): Energy level positions in meV relative to the Fermi energy of the island.
LevelSpacing: Level spacing. Alternative to LevelPos if the levels are equally spaced.
RightGammas and LeftGammas (arrays): Tunneling rates for each level to the right and left lead respectively.
Interactions: If non zero, there will be random interactions between energy levels. The interaction strengths are gaussian distributed around zero. This parameter gives the standard deviation.
RandomSeed: Random seed for the interactions. If left undefined, a pseudo-random initialisation will be done using the current time and the PID of the process.
RightCap, LeftCap and GateCap: Capacitances between the island and the leads. They can be given in any units since only the capacitance ratios are relevant.

Experimental Conditions

Temperature: Sets the temperature. Same as option -t.
ScanType: Single character. Can be b (bias scan, same as option -B), r (right lead Fermi energy scan, same as -R), l (left lead Fermi energy scan, same as -L), t (table of currents as 0 K, same as -T) or 2 (2D sweep, same as -2).
OtherVoltage: Other (constant) voltage/Fermi energy for a 1D sweep. Same as option -o.
InitialVoltage and FinalVoltage: Range in voltage or Fermi energies for a 1D sweep. Same as options -i and -f.
InitialGate and FinalGate: Range in gate voltage for a 2D sweep. There is no option equivalent to this parameter.
XSteps: Number of steps in a 1D sweep. Same as option -n.
GSteps: Number of gate voltage steps in a 2D sweep. There is no option equivalent to this parameter.

FILES

./diamond.conf: Default configuration file

BUGS

Maximum 15 levels, but the program will be unacceptably slow before that limit.

For n levels it will consume at least 2^(n+2) bytes of memory.

AUTHOR

Edgar Bonet <edgar@edgar-bonet.org>