Heteroepitaxial diamond detectors for heavy ion beam tracking

Abstract

Heteroepitaxy has been shown to produce uniform crystals of single crystal diamond. An advantage of heteroepitaxy is its potential for creating materials suitable for energetic particle detectors that require large-area plates. At this point, there is little information on the electronic properties of heteroepitaxial material and its suitability for detector use is an open question. To address this issue, a heteroepitaxially grown single crystal was used for high-temperature DC transport measurements and for evaluation as a heavy ion particle detector. Using a transverse geometry with an as-grown Ir film as one electrode and a diffused Ti–Au top electrode, the sample showed no detectable current leakage at room temperature up to 100 V bias. At temperatures between 250 and 600 °C, the DC electrical conductivity exhibited thermally activated behavior with an activation energy of 1.4 eV. A 76Ge beam with an energy of 100 MeV/u produced at the Coupled Cyclotron Facility at Michigan State University was used to test detector performance. At typical beam fluences, single events were recorded with instrumentally limited rise times of 0.5 ns and pulse width 1 ns. Single pulses corresponded to an energy loss Δ E = 46 MeV. A pulse-height resolution of the energy loss signal of Δ E / E = 18% was measured. Of particular importance is the fast performance at high beam intensities. No degradation of timing properties and energy resolution could be observed with count rates up to 10 6 particles/s. These measurements reflect the properties of the as-grown heteroepitaxial diamond crystal to which no subsequent processing was applied. It is anticipated that by using thicker crystals that allow the defective initial growth region to be removed mechanically, greatly improved energy resolution can be observed.