Surface states and photo-induced charge transfer on oxygen-terminated chemical vapor deposition diamond

Abstract

Time-of-Flight (ToF) experiments were carried out to study the electrical transport and charge trapping properties of oxidised freestanding single crystalline (100) CVD diamond crystals. It is shown that the diamond surface and properties of the electrical contacts are of extreme importance, influencing measured charge carrier mobility values. While sputtered Al contacts yield textbook ToF spectra and electron mobilities µe exceeding 1860 cm²/Vs, thermally deposited contacts suffer from enhanced trapping. We propose a model in which the observed polarization effects can be explained by charge transfer to oxygen-related surface states, which interact with surface adsorbates, according to the well-known transfer-doping model.