/**
* Find the distance to the conduction band in Cm when the energy is set to the
* provided level.
*
* @param energy - energy level used to evaluate the structure.
*
* @return thickness - distance to conduction band in Cm.
*/
public Length DistanceToConductionBand(Energy energy)
{
// find between which points the energy of interest lies
// if energy is above all the points return 0 distance
if (EvalPoints.All(p => ConductionBandEnergy(p) <= energy))
{
return(Length.Zero);
}
EvalPoint abovePoint = null;
EvalPoint belowPoint = null;
var aboveEnergy = Energy.FromElectronVolts(1E10);
var belowEnergy = Energy.FromElectronVolts(-1E10);
// a ridiculus start energy if we
// find a point above the energy it will definately be lower than this value.
foreach (var p in EvalPoints)
{
var cbEnergy = ConductionBandEnergy(p);
if (cbEnergy > energy && cbEnergy < aboveEnergy)
{
aboveEnergy = cbEnergy;
abovePoint = p;
}
if (cbEnergy < energy && cbEnergy > belowEnergy)
{
belowEnergy = cbEnergy;
belowPoint = p;
}
}
// if we didn't find a point in energy below the input energy then tunnel through whole dielectric
if (belowPoint == null)
{
return(Thickness);
}
// make sure that we have above and below points
if (belowPoint == null || abovePoint == null)
{
// we did something wrong
return(null); // negative thickness so we know something is wrong
}
// interpolate cross points
var slope = (aboveEnergy - belowEnergy).ToPotential()
/ (abovePoint.Location - belowPoint.Location);
var intercept = aboveEnergy.ToPotential() - slope * abovePoint.Location;
var distance = (energy.ToPotential() - intercept) / slope;
return(distance);
}
public void Evaluate()
{
var phiS = SurfacePotential;
var storePotential = EvalPoints[0].Potential;
// First remove all the points
EvalPoints.Clear();
// Find the thickness through integration
// Integrate from 0 to the surface potential
// Integrate 2000 times so change stepSize depending on the surface potential
var stepSize = phiS / 20;
stepSize = phiS > ElectricPotential.Zero ?
ElectricPotential.Abs(stepSize) : -ElectricPotential.Abs(stepSize);
var previousValue = 1 / GetElectricField(phiS).VoltsPerMeter;
var runningThickness = Length.Zero;
var previousThickness = Length.Zero;
var point = new EvalPoint
{
Location = runningThickness,
ChargeDensity = GetChargeY(phiS),
ElectricField = new ElectricField(1 / previousValue),
Potential = phiS
};
EvalPoints.Add(point);
for (var i = 1; ElectricPotential.Abs(phiS - stepSize * i)
> ElectricPotential.FromMillivolts(1) && i < 10000; i++)
{
var potentialValue = phiS - stepSize * i;
var value = 1 / GetElectricField(potentialValue).VoltsPerMeter;
previousThickness = runningThickness;
runningThickness += new Length(((previousValue + value) / 2) * stepSize.Volts);
if (double.IsNaN(runningThickness.Meters))
{
Debug.WriteLine("Por que Nan??");
}
point = new EvalPoint
{
Location = runningThickness,
ChargeDensity = GetChargeY(potentialValue) * 1E-8,
ElectricField = new ElectricField(1 / value),
Potential = potentialValue
};
EvalPoints.Add(point);
previousValue = value;
}
// Now add the offset in potential
var checkCharge = ChargeDensity.Zero; // check and see if the charges add up
foreach (var checkPoint in EvalPoints)
{
checkPoint.Potential = checkPoint.Potential + storePotential;
checkPoint.Potential = checkPoint.Potential - phiS;
checkCharge += checkPoint.ChargeDensity;
}
}
/**
* The energy value for the valance band at the given point's location.
*
* @param index - index value for the point to evaluate.
*
* @return energy - energy value at the specified point.
*/
public Energy ValenceBandEnergy(EvalPoint p)
{
return(-p.Potential - ElectronAffinity - BandGap);
}
/**
* The energy value for the conduction band at the given point's location.
*
* @param index - index value for the point to evaluate.
*
* @return energy - energy value at the specified point.
*/
public Energy ConductionBandEnergy(EvalPoint p)
{
return(-p.Potential - ElectronAffinity);
}
