Fig. 3: Anisotropic electric properties of 4HPA single crystals.

a schematic diagram of α-TOF method for measuring electron-only transient pulse, b architectures of sandwich and coplanar devices for measuring electric properties along a and c axes, respectively, c energy deposition of 5.49 MeV α particles in 4HPA detectors changes with detector thickness, energy distribution spectra of electrons ionized by 5.49 MeV α particles of d first ionization and e multiple ionization, f (from down to up) time-resolved average electron-only drift pulses from α-TOF method measurement along a axis of 4HPA with bias voltages from 800 V cm⁻¹ to 4000 V cm⁻¹, g average electron-only drift time along a and c axes under the bias of 2800 V cm⁻¹, h average hole-only drift time along a and c axes under the bias of 2800 V cm⁻¹, i anisotropic electron drift velocity changes with electric fields along a and c axes, j single electron-only pulse with a rising time of 0.52 μs with a bias voltage of 2800 V cm⁻¹ along a axis.