@article{oai:repo.qst.go.jp:00080305,
 author = {Narahara, Takuma and Sato, Shinichiro and Kojima, Kazutoshi and Yamazaki, Yuichi and Hijikata, Yasuto and Ohshima, Takeshi and Takuma, Narahara and Shinichiro, Sato and Yuichi, Yamazaki and Takeshi, Ohshima},
 journal = {Materials Science Forum},
 month = {Aug},
 note = {Spin defects of which states can be manipulated in Silicon Carbide (SiC) have drawn considerable attention because of their applications to quantum technologies. The single negatively-charged pairs of VSi and nitrogen atom (N) on an adjacent C site (NcVsi- center) in SiC is suitable for them. This paper reports the formation of NcVsi- centers on 4H-SiC epilayers with different nitrogen concentrations using light/heavy ion irradiation and subsequent thermal annealing. The formation of NcVsi- centers is characterized by the near infrared photoluminescence (PL) spectroscopy. It is shown that the PL intensity from NcVsi- centers depends on the N concentration and the ion irradiation conditions. The PL intensity increases monotonically with increasing the N
concentration when the N concentration is above 2.6×10^16 cm^-3 , whereas no linear correlation between them does not appear below that N concentration. Although the PL intensity increases with increasing defects induced by ion irradiation, the PL quenching due to neighboring residual defects appear at above the areal vacancy concentration of 10^17 vac/cm^2 and the broad Raman scattering spectra originated from vibration modes of amorphized regions hinder the PL from NcVsi- centers at above 10^18 vac/cm^2. The formation mechanism and the charge state stability of NcVsi- centers are discussed based on the obtained results.},
 pages = {349--354},
 title = {Effects of Nitrogen Impurity Concentration on Nitrogen-Vacancy Center Formation in 4H-SiC},
 volume = {1004},
 year = {2020}
}