Steady State, Modulated and Transient Surface Photovoltage Spectroscopy of Diamond

Diamond is a promising material for applications in fields of electronics, optoelectronics, spintronics, energy conversion etc. For further development and deeper understanding, there is a need for highly sensitive and contactless characterization of electronic transitions and transport phenomena in single crystal and nanocrystalline diamond and at diamond interfaces. Light induced charge separation in space causes a surface photovoltage (SPV) on photoactive materials which can be studied with highly sensitive techniques such as steady state, modulated and transient SPV spectroscopy [1]. Recently, we developed a charge amplifier in combination with a perforated electrode that allows for complex SPV spectroscopy measurements on ultrawide bandgap semiconductors in dc (Kelvin probe), ac (modulated and transient) regimes at photon energies from near infrared to deep ultraviolet [2] [3] [4]. In this work, measurement principles of steady state, modulated and transient SPV spectroscopy will be explained, highlighting the high sensitivities of these techniques. Examples will be demonstrated for numerous transitions around and below the band gap of diamond which have been distinguished for differently terminated single crystal, polycrystalline and nanocrystalline diamond samples.<br/><br/>Acknowledgement: S. F. and I. L. are grateful to the BMWi (ZIM-KK-5085302DF0 and ZIM-KK-5123601DF0, respectively).<br/><br/>[1] Th. Dittrich, S. Fengler, Surface photovoltage analysis of photoactive materials, World Scientific, 2020.<br/>[2] Th. Dittrich, S. Fengler, N. Nickel, Surface photovoltage spectroscopy over wide time domains for semiconductors with ultrawide bandgap: example of gallium oxide, Phys. Stat. Sol. A 11 (2021) 2100176.<br/>[3] Th. Dittrich, Transient surface photovoltage spectroscopy of diamond, AIP Advances 12 (2022) 065206.<br/>[4] Th. Dittrich, S. Fengler, Transitions in polycrystalline diamond probed by steady state, modulated and transient surface photovoltage spectroscopy, 2022 (submitted).