Schüler, N.; Fengler, S.; Dittrich, T.; Nikonova, V.; Abou-Ras, D.; Weitz, S.; Dornich, K.: Surface photovoltage spectroscopy for defect investigation of diamond. Diamond and Related Materials 153 (2025), p. 112038/1-8
10.1016/j.diamond.2025.112038
Abstract:
Defect related transition energies and charge transfer along grain boundaries were studied in polycrystalline diamond by using a new type of mirrorless double-prism monochromator based on fused silica and by introducing modulated transient surface photovoltage spectroscopy. Polycrystalline diamond served as a model system containing small crystallites at the seed and large crystallites at the growth sides. Illumination was performed between 0.4 and 7.3 eV for seed and growth side orientations of the sample which allowed for homogeneous excitation of defect related transitions across the sample and for variation of the penetration depth under fundamental absorption in diamond. Photogenerated electrons were separated towards the seed side independently of the defect related transition for excitation below the range of the bandgap of diamond. Under strong absorption, photogenerated electrons were preferentially separated towards the surface. We found that photogenerated electrons are transferred faster than photogenerated holes along grain boundaries and that photogenerated holes are preferentially trapped at defects in crystallites. The enhancement of electron transfer via grain boundaries also explains the observed preferential electron trapping at surface states of diamond.