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

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. [Display omitted] • A new approach is used to reveal the distribution of impurity atoms in diamond films. • Porous silicon oxides are formed when grain boundaries are oxidized in Si doped diamond films. • It is confirmed that Si atoms segregate along grain boundaries in diamond films. • The in-situ formed oxide film act as an anti-reflection film to enhance the optical collection efficiency of SiV centers. [ABSTRACT FROM AUTHOR]