Effect of surface defects by RF oxygen plasma on the electrical properties of thin boron-doped diamond layers in electrolyte

The effect of surface defects induced by RF oxygen plasma treatment on the electrical properties of thin boron-doped epitaxial diamond layers was investigated by electrochemical analysis in the modes of electrochemical electrode and ion sensitive field-effect transistor (ISFET). The doping profile employed allowed almost full depletion in the electrolyte used within the potential window of water electrolysis. The high near surface defect density leads to an extremely high free carrier sheet charge density (approximately 3 × 1014 cm−2) concentrated within the first nm below the surface accompanied by a high channel sheet resistance in the 10 MΩ range. The analysis, also taking into account earlier measurements, points thus towards a channel carrier mobility of 10−3 cm2/Vs, comparable to what is seen in highly disordered thin film transistors.

► Thin boron doped diamond layers are exposed to RF oxygen plasma.
► ISFET and electrode structures are analysed after plasma exposure.
► High surfacial disorder is induced, affecting the electronic characteristics.
► Transport properties in boron doped layer dominated by extremely low carrier mobility.