Structural defects created on natural graphite surface by slight treatment of oxygen plasma: – STM observations

The creation of structural defects on natural graphite surfaces by slight treatment of oxygen plasma was studied by scanning tunneling microscopy (STM) at nanoscopic scale. Most of the defects were vacancies with the depth of one or two layers, while the mean number of defects per μm2 of graphite surface and the mean area of defects increased with the increase in input power, time and temperature of the irradiation. After very slight treatment at room temperature, single carbon atom vacancies were obtained on graphite surfaces with a percentage more than 50%, though some large vacancies were formed. After slight irradiation at a high temperature (400°C), an agglomeration of defects occurred (the mean area increases whereas the defect density decreases), while the defects once formed were difficult to be annealed by heating at high temperatures up to 400°C in vacuum. The present work showed the possibility to control the modification of natural graphite surfaces for further applications by changing the condition of oxygen plasma treatment.