Examining Impacts of Acidic Bath Temperature on Nano-Synthesized Lead Selenide Thin Films for the Application of Solar Cells

The influence of bath temperature on nano-manufactured PbSe (lead selenide) films was successfully generated by utilizing CBD on the acid solution’s metal surface tool. Pb (NO3)2 was employed as a lead ion source as a precursor, while Na2O4Se was used as a selenide ion source. The XRD characterization revealed that the prepared samples are the property of crystalline structure (111), (101), (100), and (110) Miller indices. The scanning electron microscope indicated that the particles have a rock-like shape. There was a decrement of energy bandgap that is from 2.4 eV to 1.2 eV with increasing temperature 20°C–85°C. Thin films prepared at 85°C revealed the best polycrystal structure as well as homogeneously dispersed on the substrate at superior particle scales. The photoluminescence spectrophotometer witnessed that as the temperature of the solution bath increases from 20°C to 85°C, the average strength of PL emission of the film decreases. The maximum photoluminescence strength predominantly exists at high temperatures because of self-trapped exciton recombination, formed from O2 vacancy and particle size what we call defect centres, for the deposited thin films at 45°C and 85°C. Therefore, the finest solution temperature is 85°C.

Hybrid device of hexagonal boron nitride nanoflakes with defect centres and a nano-fibre Bragg cavity

Solid-state quantum emitters coupled with a single mode fibre are of interest for photonic and quantum applications. In this context, nanofibre Bragg cavities (NFBCs), which are microcavities fabricated in an optical nanofibre, are promising devices because they can efficiently couple photons emitted from the quantum emitters to the single mode fibre. Recently, we have realized a hybrid device of an NFBC and a single colloidal CdSe/ZnS quantum dot. However, colloidal quantum dots exhibit inherent photo-bleaching. Thus, it is desired to couple an NFBC with hexagonal boron nitride (hBN) as stable quantum emitters. In this work, we realize a hybrid system of an NFBC and ensemble defect centres in hBN nanoflakes. In this experiment, we fabricate NFBCs with a quality factor of 807 and a resonant wavelength at around 573 nm, which matches well with the fluorescent wavelength of the hBN, using helium-focused ion beam (FIB) system. We also develop a manipulation system to place hBN nanoflakes on a cavity region of the NFBCs and realize a hybrid device with an NFBC. By exciting the nanoflakes via an objective lens and collecting the fluorescence through the NFBC, we observe a sharp emission peak at the resonant wavelength of the NFBC.

Hybrid Device of Hexagonal Boron Nitride Nanoflakes with Defect Centres and a Nano-Fibre Bragg Cavity

Solid-state quantum emitters coupled with a single mode fibre are of interest for photonic and quantum applications. In this context, nanofibre Bragg cavities (NFBCs), which are microcavities fabricated in an optical nanofibre, are promising devices because they can efficiently couple photons emitted from the quantum emitters to the single mode fibre. Recently, we have realized a hybrid device of an NFBC and a single colloidal CdSe/ZnS quantum dot. However, colloidal quantum dots exhibit inherent photo-bleaching. Thus, it is desired to couple an NFBC with defect centres in hexagonal boron nitride (hBN) as stable quantum emitters. In this work, we realize a hybrid system of an NFBC and defect centres in hBN nanoflakes. In this experiment, we fabricate NFBCs with a quality factor of 807 and a resonant wavelength at around 573 nm, which matches well with the fluorescent wavelength of the defect centres in hBN, using a helium focused ion beam (FIB) system. We also develop a manipulation system to place hBN nanoflakes on a cavity region of the NFBCs and realize a hybrid device with an NFBC. By exciting the nanoflakes via an objective lens and collecting the fluorescence through the NFBC, we observe a sharp emission peak at the resonant wavelength of the NFBC.

Radiation damage effects on the structure and properties of radioactive waste glasses

The performance assessment of glass matrices currently being used in different nuclear energy producing countries to contain and immobilise high-level waste (HLW) waste is crucial for safe and economic disposal. During the first ~500 years of geological disposal fission products will me the main source or radiation and they decay by beta-gamma emission. We studied different borosilicate glasses used in different countries to immobilise HLW, such as Indian glass (NaBaBSi), UK glasses (LiNaBSi), also called MW- Mixture Windscale, UK-CaZn a modified version of MW, French glass (SON68) and a glass proposed by six collaborating nations, called the International Simple Glass (ISG), to see whether / how irradiation defects are dependent on glass composition. Glasses were externally irradiated using a 60Co gamma source to study the effects of beta-gamma radiation (a gamma emitter loses it energy to atomic electrons they then further interact via coulombic interactions); and by He2+ ion implantation to study the effects of alpha particles. A multi-spectroscopic approach was used to characterise glass specimens before and after irradiation. NaBaBSi and LiNaBSi glasses were irradiated using 60Co gamma photons and we found boron-oxygen hole centres (BOHC), electrons trapped at alkali cations or ET centres and peroxy-radicals (PORs) as common defect in these glasses. In addition, E- or polaron centres which may be related to formation of elemental / metallic sodium colloids formed in NaBaBSi glass. Time-dependent thermal annealing of the irradiated glasses revealed that POR’s are the most thermally stable of the defect centres. BOHC and ET centres were common to SON68, ISG and CaZn glasses. In NaBaBSi, LiNaBSi and SON68 glasses loaded with non-active simulated HLW no sharp and intense signals indicative of radiation-induced paramagnetic defect centres was observed. In the study of NaBaBSi and LiNaBSi glasses doped with 0.19. 0.99, and 4.76 mol% Fe2O3 prepared in an oxidising melting environment, electron paramagnetic resonance (EPR) spectroscopy showed that gamma irradiation induced sharp and intense signals exist for only the 0 and 0.19 mol% Fe2O3 doped samples and disappeared for samples containing higher molar concentrations of Fe2O3. It is postulated that, upon gamma irradiation, in LiNaBSi glass Fe2+ is oxidised to Fe3+ by the capture of holes, whereas in NaBaBSi glass Fe3+ is reduced to Fe2+ due to capture of electrons. Further research is needed to understand the reasons behind these different behaviours.