The authors present developments in the design of a new type of voltage contrast detector. Voltage contrast measurements are made by recording transit times of secondary electrons as they are emitted from a specimen and collected above the final lens of an SEM. The study shows that such a voltage contrast detector can be designed to combine a high spatial resolution with a large field of view: voltage measurements using sub- mu m probe sizes can be maintained over a 6 mm by 6 mm square region. The detector is also predicted to have data-acquisition times that are at least a factor of 30 times shorter than those of conventional retarding field-type detectors. The detector is expected to sample waveforms in its normal multi-stroboscopic mode of operation at frequencies up to 20 MHz.

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Computer programs have been written which plot high accuracy trajectory paths for electrons through irregular finite-element meshes. The technique used to achieve this revolves around mapping irregular regions onto a normalized plane, where the usual operations of locating the electron’s position and interpolating for field information is greatly simplified. Results show that if a method of bi-cubic Hermite interpolation is used to derive field information in the normalized plane, then the resulting error in an electron’s energy can typically be kept to below 20 mV, per 1 kV change in the electron’s kinetic energy, for electrostatic fields created on numerical meshes containing as few as 20 by 20 mesh lines.

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