Revealing impurity evolution in silicon-doped diamond film via thermal oxidation

Abstract

The incorporation of impurity atoms into diamonds has been an important issue for the application in the area of electronics, opto-electrics, and quantum optics with color centers. To date, it remains a challenge to explore the impurity distribution in diamond films owing to the low incorporation efficiency. In this work, Si-doped diamond films were deposited in microwave CVD system. Thermal oxidation was employed to selectively etch the non-diamond phase to study the impurity distribution and evolution. For micro-/nano-sized diamond films, the micro-sized grains remain intact, while the diamond nanocrystals are oxidized into porous oxides. The diamond needles exhibit strong silicon-vacancy center optical emission at 738 nm, implying that the Si atoms are incorporated into the lattice. Detailed microstructure characterizations reveal that the porous oxides are crystallized in amorphous state, consisting of silicon, oxygen, and carbon elements. Such abundance of Si in the amorphous porous oxides suggests that the Si atoms segregate at the grain boundaries. Therefore, this work provides a new path to reveal the impurity distribution along diamond crystalline defects. Moreover, the in-situ formed silicon oxide can act as an anti-reflection coating to enhance the optical emission of color centers, which is important for their optical applications.