Optimisation and fabrication of ultra violet emitting CuC1 thin films by RF sputtering

Wide direct band gap CuCl is a promlslng candidate for the next generation Si based optoelectronics, thanks to its excellent properties such as high excltonic binding energy (190 meV) and a close lattice matching with Si. In this thesis, growth of CuCl using RF magnetron sputtering is investigated in detail. Stoichiometry and microstructure are the two major deciding factors for the UV emission from the film. We have successfully controlled both these properties by varying the sputtering parameters. Chemical stoichiometry was mainly controlled by the spacing between the target and substrate. An optimum spacing of 6 cm was found to yield films with Cu/Cl ratio almost close to stoichiometry (Cu/Cl = 0.94). A more fine control was achieved providing a suitable bias to the substrate and high quality stoichiometric CuCl films were obtained. Microstructural evaluation revealed that the grain interface area of the film increases on increasing the sputtering pressure. UV emission properties were found to be influenced by the existence of meso- and nanostructural interfaces within the thin film. Cathodoluminescence studies showed a strong UV exciton emission and a green emission from deep levels in a non-stoichiometric and lower crystalline quality samples. CuCl films deposited with optimum sputtering parameters showed good optical quality with an intense and sharp UV emission at room temperature without any deep level emission. Excitonic line transitions of sputtered CuCl films were investigated using temperature dependant PL spectroscopy. The thermal activation energy was calculated to be 112 meV. Our results show that the sputtered CuCl films have relative higher optical quality compared to the other UV emitting materials such as epitaxially grown GaN and ZnO, demonstrating the potential for Si based UV photonic devices. Preliminary electrical studies were carried out to identify the conduction mechanism associated with the sputtered CuCl thin films. Field dependant DC conduction studies on CuCl/Si structure indicates that ohmic conduction prevails in the lower field region and an electrode limited Schottky emission process was found to dominate the mechanism of charge carrier transport through these structures at higher fields

Stoichiometry control of sputtered CuCl thin films: Influence on ultraviolet emission properties

We demonstrate that the chemical composition of the sputtered CuCl thin films could be finely controlled by adjusting the bias to the substrate. The films deposited without any intentional bias were Cl rich (CuCl1+x), a bias of −22 V yielded stoichiometric CuCl, and a further increase in the negative bias resulted in Cl deficient films (CuCl1−x). The crystalline and optical properties were found to be associated with the chemical composition. Cl rich films showed a deep level green emission at around 515 nm in addition to ultraviolet (UV) excitonic emission. The stoichiometric films have higher optical quality, exhibiting a sharp UV emission at around 385 nm at room temperature, compared to nonstoichiometric samples. Visible luminescence related to deep level defects was not observed in the stoichiometric films. Changes in energy of the flux from the target and the subsequent ion bombardment on the substrate surface are correlated with the variations in chemical composition and their impact on the film microstructure and UV emission

Calculation and comparison of heat transfer coefficient & heat flux by varying the parameters for SCWR through CFD simulations

In the present study, CFD simulation was conducted for 2•2 rod bare bundle using water at supercritical pressures. Main objective of the simulation was to compare working of different turbulence models. K-epsilon, K-omega and Spalart-Allmaras turbulence models were chosen for our study. K-epsilon and K-omega turbulence models are two equation models and are widely used for industrial research. Whereas Spalart-Allmaras is one equation model which is least computationally expensive of all the models. All three turbulence models come under the Reynolds Average Navier Strokes model (RANS). CFD results were found to be sensitive with the appropriate turbulence model and this variation is documented through various plots

Growth of CuCl thin films by magnetron sputtering for ultraviolet optoelectronic applications

Copper (I) chloride (CuCl) is a potential candidate for ultraviolet (UV) optoelectronics due to its close lattice match with Si (mismatch less than 0.4%) and a high UV excitonic emission at room temperature. CuCl thin films were deposited using radio frequency magnetron sputtering technique. The influence of target to substrate distance (dts) and sputtering pressure on the composition, microstructure, and UV emission properties of the films were analyzed. The films deposited with shorter target to substrate spacing (dts=3 cm) were found to be nonstoichiometric, and the film stoichiometry improves when the substrate is moved away from the target (dts=4.5 and 6 cm). A further increase in the spacing results in poor crystalline quality. The grain interface area increases when the sputtering pressure is increased from 1.1×10–³ to 1×10–² mbar at dts=6 cm. Room temperature cathodoluminescence spectrum shows an intense and sharp UV exciton (Z₃) emission at ~385 nm with a full width at half maximum of 16 nm for the films deposited at the optimum dts of 6 cm and a pressure of 1.1×10–³ mbar. A broad deep level emission in the green region (~515 nm) is also observed. The relative intensity of the UV to green emission peaks decreased when the sputtering pressure was increased, consistent with an increase in grain boundary area. The variation in the stoichiometry and the crystallinity are attributed to the change in the intensity and energy of the flux of materials from the target due to the interaction with the background gas molecules

Effect of dietary supplementation of cinnamon oil and sodium butyrate on carcass characteristics and meat quality of broiler chicken

Aim: An in vivo experiment was conducted to investigate the effect of supplementation of cinnamon oil (CO) and sodium butyrate on carcass characteristics and meat quality of broiler chicken compared with the antibiotic supplementation. Materials and Methods: A biological experiment was carried out with 216-day-old Vencobb-400 broiler chicks randomly distributed to six experimental treatments with six replicates, each replicate containing six chicks with equal numbers of male and female chicks. The experimental diets were prepared with isocaloric and isonitrogenous basis. The experimental groups, namely control (T1), control with antibiotic (T2), control with CO at 250 mg/kg and coated sodium butyrate (CSB) either at 0.09 (T3) or 0.18% (T4), and control with CO at 500 mg/kg and CSB either at 0.09 (T5) or 0.18% (T6). The trial was carried out in deep litter pen for 35 days. The carcass characteristics such as ready to cooked yield, eviscerated weight, heart, liver, gizzard, giblet, and abdominal fat percent in slaughtered birds and meat quality properties such as pH, water-holding capacity (WHC), tyrosine, shear force, cooking loss, thiobarbituric acid, sensory characteristics, and muscle cholesterol in breast muscle samples were evaluated. Results: The carcass characteristics such as ready-to-cook yield, eviscerated weight, and weight of heart, liver, gizzard, giblet, and abdominal fat as a percent of live body weight were not influenced by supplementation of CO and CSB at the levels attempted or by antibiotic supplementation in broilers. The pH, cooking loss, shear force and WHC of meat, appearance, flavor, texture, mouth coating, juiciness and overall acceptability of meat were not influenced by the supplementation of different levels of CO and CSB or by antibiotic supplementation but decreased meat cholesterol level in broilers. Conclusion: The results indicated that the supplementation of CO and CSB in broiler diet did not alter the carcass characteristics and meat quality parameters except meat cholesterol content in broilers