Electron and hole generation in anthracene under electron bombardment

Abstract

In order to study the effect of trapping and release of carriers in anthracene, short electron pulses of energy up to 50 KeV and dose 2.5×10⁻¹⁴ C per pulse were used to excite the anthracene crystals and the induced charge transferred was measured for a series of increasing bias voltages of either sign at room temperature. It is found that the hole charge collected at transit time is only half of the total hole charge eventually collected which always equalled the electron charge. An interpretation is given in terms of a trap release mechanism. Shallow hole traps with an activation energy of the order of 0.13 eV are estimated in anthracene crystals at room temperature. The electron mobility normal to ‘ab’ crystallographic plane is 0.38±0.02 cm²V⁻¹s⁻¹ and agrees well with other published values.