According to , in HfSiO x films, two types of O vacancies coexist: one is an O vacancy surrounded by Si atoms (Si-related O vacancy), while the other is an O vacancy surrounded by Hf atoms (Hf-related). Since the HfO2 phase is ionic, it is obvious that it forms easier in the HfSiO x film upon annealing, and thus, Hf-related O vacancy formation is most preferable than Si-related O vacancy . Herein, a particular interest is focused on the emissions from the defects: the Pr-doped
film Small molecule library concentration shows a broad band peaked at 420 nm, while the peak positions redshift to about 450 and 490 nm for HfSiO x and HfO2 films, respectively. The 450-nm band can be fitted in energy into four Gaussian bands centered
at 3.1, 2.84, 2.66, and 2.11 eV (table inset of Figure 6). The former two peaks are related to defects of the SiO x phase, for instance, Si-related oxygen deficient centers [13, 28]. The peak at 2.66 eV is ascribed to O vacancies related to the HfO2 phase. The disappearance of the 2.66-eV PL component is accompanied with the appearance of the strong 487-nm emission and series of other Pr3+ transitions in Pr-doped HfSiO x film, which implies the energy transfer from O vacancies to the Pr sites. Figure 6 PL spectra of Pr-doped and undoped HfSiO x and undoped pure HfO 2 films excited at 285 nm. The films were annealed at 1,000°C. Inset TNF-alpha inhibitor table is data of the fitting peaks. As a result, the Si-rich HfO2 host not only serves as a suitable matrix to achieve efficient Pr3+ emission,
but also provides a sufficient amount of O vacancies acting as effective sensitizers of rare-earth ions. Conclusions In summary, we have fabricated the Pr3+-doped hafnium silicate layers by RF magnetron sputtering. The effect of the annealing temperature on the film properties has been investigated by means of Ruboxistaurin clinical trial ellipsometry, XRD, and FTIR spectroscopies. We showed that the highest Pr3+ PL intensity is obtained for 1,000°C annealing. The Silibinin PL and PLE measurements demonstrate that the Pr3+ ions were efficiently excited by oxygen vacancies in the films, and thus, remarkable Pr3+ PL can be obtained by a non-resonant excitation process. The present results show the promising application of Pr-doped films for future optoelectronic devices. Acknowledgments The authors would like to thank Dr. Ian Vickridge from SAFIR, Institut des NanoSciences de Paris for the RBS data as well as Dr. Sophie Boudin from CRISMAT Lab for the measurement of PL and PLE spectra. This work is supported by the CEA/DSM/ENERGY contract (Project HOFELI) and the Chinese Scholarship Council (CSC) program. References 1. Birkhahn R, Garter M, Steckl AJ: Red light emission by photoluminescence and electroluminescence from Pr-doped GaN on Si substrates. Appl Phys Lett 1999, 74:2161.CrossRef 2.