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We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO 2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation. [ABSTRACT FROM AUTHOR]

Optical constants and micro-structure characteristics of SiO 2 films deposited by ion beam sputtering were studied. The samples were prepared on substrates of silicon and silica with different oxygen flow rates ranged from 0 sccm to 40 sccm with a step of 10 sccm. Refractive index of the samples were obtained by spectra inversion technique. It's suggested that the value of refractive index presents first decrease and then increase as the oxygen flow rate larger, and the turning point is about 30 sccm both at 0.633 μm and 10.6 μm. And the SiO 2 thin films were confirmed all amorphous structure by the XRD measurement. The proportion of hydroxyl in SiO 2 thin film were determined by XPS, which is beneficial to analyze the film defects. Also the Si-O-Si angle and vibration frequency in TO mode and LO mode were researched by FTIR spectra. [ABSTRACT FROM AUTHOR]

In this work, undoped CdSiO 3 samples with different luminescence spectra and light persistence were obtained by controlling the parameters of sol–gel synthesis. The process of monoclinic phase formation was monitored through XRD and TG-DTA measurements, combined to microstructural characterization using FTIR and SEM. The optical energy bandgap (E g ) of CdSiO 3 was estimated from Tauc equation and indicates the dependency of bandgap energy on the starting pH used for synthesis. Three main peaks could be identified from PL and XEOL spectra, at 590 nm, 490 nm and 406 nm. Their relative intensities yielded overall distinct luminescence colours, such as indigo or red. The luminescent mechanisms of CdSiO 3 related to an intrinsic defect (V Cd ) were further investigated to show its key role in the charge trapping that causes long lasting luminescence. [ABSTRACT FROM AUTHOR]

We propose and demonstrate the principle of a sub-diffraction-limited optical imaging technique for rare-earth ion crystals that preserves the ions’ homogeneous line width. Our method uses a combination of applied electric field gradients and optical pumping to create a resonant nanoscopic volume within an otherwise non-resonant macroscopic crystal. We present the concept of the Stark activation technique and perform a demonstration in Pr 3 + : Y 2 SiO 5 in which we create a 10 μm-thick absorption feature in a 1 mm thick crystal. By modeling the system we show that it is possible to increase the resolution of the technique to the 5 nm range for single Pr 3 + ions. We also discuss the physical properties that will fundamentally limit the resolution of Stark activation. Because the proposed technique simultaneously achieves high spatial and high spectral resolution it is an enabling protocol to realize technology based on single rare-earth ions and harness short-range interactions in ensembles. [ABSTRACT FROM AUTHOR]

This work presents the charge transport and electroluminescent properties of silicon rich oxide (SRO) films with ~41 at% silicon content and different thicknesses (t SRO =24, 53 and 80 nm), as dielectric layer in metal-oxide-semiconductor (MOS) capacitive structures. SRO films were thermally annealed at high temperature to induce the silicon nanoparticles (Si-nps) formation. Light emitting capacitors (LECs) with SRO thickness about 80 nm behave like a normal MOS structure with a current level at about 10 −10 to 10 –12 A (equipment sensitivity) at low electric fields. However, a high conduction state (HCS) and then a resistance switching (RS) behavior to a low conduction state is observed when the thickness of the SRO film reduces to (and below) 53 nm. When the SRO thickness reduces to 24 nm, the electric field required to obtain RS behavior increases. The presence of the HCS and RS is related with silicon diffusion from the polysilicon film, used as gate electrode, towards the SRO bulk. The silicon content within the SRO film increases by the Si diffusion as the thickness reduces allowing the formation of preferential conductive paths. Once RS is obtained, LECs emit a broad visible and near infrared (IR) electroluminescence (EL) spectra with several maximum peaks at ~455, 490, 540, 650 and 800 nm. For SRO thickness ≥ 53 nm, the most intense EL peak is the placed at 650 nm. It becomes narrower and stronger when the thickness increases to 80 nm as compared to the other ones making a uniform red EL. Nevertheless, when the SRO thickness decreases to 24 nm, an additional IR EL peak above 1000 nm is observed. This IR band is slightly stronger than that observed at 650 nm and results from the silicon substrate emission enhanced by the high current flow through thin SRO films. By other hand, two narrow spectral lines of low intensity in the deep ultraviolet region (253 and 288 nm) are observed when the thickness is above 53 nm, which are related to the resonant coherent fluorescence effect. The electrical behavior and optical power emission and its relation with the electroluminescent behavior of LECs are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the phase evolution, microstructure changes, and element diffusion for the formation of BaSnO 3 from BaCO 3 and SnO 2 were extensively investigated. It was found that BaCO 3 rapidly diffused on surface of SnO 2 at the initial stage of the reaction (approximately 700 °C), forming a uniform BaSnO 3 shell. Subsequently, BaSnO 3 grew via two different routes depending on the calcination temperature. When the reaction was carried out below 820 °C, BaSnO 3 phase further grew by diffusion of barium ions across BaSnO 3 layer to SnO 2 phase, since the BaSnO 3 interlayer prevented the direct reaction between surface BaCO 3 and SnO 2 core. Once a higher temperature above 820 °C was provided, Ba 2 SnO 4 were generated by reaction between BaCO 3 and BaSnO 3 shell. Under such circumstances, pure BaSnO 3 was obtained by diffusion of barium ions from Ba 2 SnO 4 across BaSnO 3 to SnO 2 . The rate-determining step in both cases was assigned to the diffusion of barium ions. [ABSTRACT FROM AUTHOR]