Stability of SiN<Subscript>X</Subscript>/SiN<Subscript>X</Subscript> double stack antireflection coating for single crystalline silicon solar cells

Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiN_X:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiN_X:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiN_X:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiN_X:H films to external stresses has never been studied. In this paper, the stability of SiN_X:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress.     

Hydrogen uptake of reduced graphene oxide and graphene sheets decorated with Fe nanoclusters

Graphene oxide (GO) has been prepared by employing modified Staudenmaier's method through thermal exfoliation of graphite oxide. High pressure hydrogen sorption isotherms up to 50 bar of GO, reduced by thermal reduction (TR-GO), chemical reduction (CR-GO) and graphene sheets decorated with Fe nanoclusters (Fe-GS) have been investigated. Thermal reduction of GO at 623 K under high vacuum yields TR-GO. Chemical reduction of GO using hydrazine forms CR-GO. Fe-GS was synthesized through arc-discharge between the ends of two graphite rods with one rod carrying Fe nanoparticles. The surface areas of these graphene samples were determined from the nitrogen adsorption isotherm employing Brunauer, Emmett and Teller (BET) method. Kelvin's equation was used to determine the pore size distribution of all graphene based samples. Hydrogen pressure-composition isotherms (PCI) were determined at 300 K and at 77 K, between 0.1 and 50 bar. Further, in this paper, we present a comparative adsorption isotherm analysis of hydrogen and helium on TR-GO. This reveals that the volume of hydrogen and helium adsorbed by TR-GO is nearly equal. The similar uptake volume determined for both hydrogen and helium indicates the possibility of monolayer adsorption of hydrogen and also nearly similar binding energy between TR-GO and H₂/He.     

Investigating the role of key ingredients on cathodic delamination resistance of high-build pigmented epoxy coatings

Organic coatings applied on cathodically protected metallic structures must have good resistance to cathodic delamination or disbonding (CD). Both environmental conditions and coating composition influence the CD resistance. In the present study, the effect of types of epoxy resin, curing agents and their mixing ratio on cathodic delamination rate was studied in a high-build pigmented coating. Furthermore, the influence of platey fillers on CD resistance was also studied. In order to bring out correlations, if any, between adhesion and CD resistance, pull-off adhesion strengths (both dry and wet) of these coatings were also measured. Fairly good correlation was found between residual (wet) pull-off adhesion strength and CD resistance. When tested at 60 and 90°C, all the coatings under investigation showed chalking. Among the coatings under investigation, the one based on Bisphenol F epoxy and modified cycloaliphatic amine adduct exhibited excellent CD resistance.     

Fish science research in China: How does it compare with fish research in India?

Fish and aquaculture research in the People's Republic of China over the six years 1994-1999 has been mapped using data from six databases– three abstracting services and three citation indexes. The results are compared with fish science research in India. During the six years China has published 2035 papers (roughly 4.5 –5% of the world output) and India 2454. More than 95% of China's papers are journal articles, compared to 82.8% of Indian papers. About 78% of China's journal paper output has appeared in 143 domestic journals compared to 70% from India in 113 Indian journals. Less than one-eighth of the journal articles published by Chinese researchers are published in journals indexed in SCI, compared to 30% of journal articles by Indian researchers. Less than a dozen papers from each of these countries have appeared in journals of impact factor greater than 3.0. Fish research institutes and fishery colleges are the major contributors of the Chinese research output in this area. In India academic institutions are the leading contributors (61%), followed by central government institutions (>25%). Qingdao, Wuhan, Beijing and Shanghai are the cities and Shandong, Hubei and Fujian are the provinces contributing a large number of papers. As we do not have addresses of all authors in most of the papers, we are unable to estimate the extent of international collaboration. Although China's research output and its citation impact are less than those of India, China's fish production and export earnings are far higher than those of India. Probably China is better at bridging the gap between knowhow (research) and do-how (technology and creation of employment and wealth). China is pretty strong in extension. This revised version was published online in June 2006 with corrections to the Cover Date.     

QR code–based ECG signal encryption/decryption algorithm

The paper presents a novel and enhanced bio-signal (ECG) cryptographic technique in which a QR code has been successfully utilized as a data container. The bio-signal encryption process considers ECG samples in the form of integers in order to create corresponding binary pair sequences that are converted as equivalent ciphertext information. Subsequently, the generated ciphertexts are transformed into QR code by using a QR code generator/reader in order to ensure further security. The encryption process generates a binary key for each binary pair that will be used during signal decryption. The imperceptibility of a reconstructed ECG signal is evaluated by analyzing performance metrics in terms of PSNR and PRD values. The average PSNR values are found to be above 42?dB, whereas PRD values observed were less than 3.43 percent. It is further proved that the proposed technique can encrypt a maximum of 226?kb of diagnose data by using merely seven QR codes.     

A Qualitative Review on Tunnel Field Effect Transistor- Operation,Advances, and Applications

Silicon - Tunnel Field Effect Transistor (TFET) has become one of the promising devices to be part of Integrated circuits as the technology advances to the nanoscale. A TFET has many advantages...     

Synthesis of highly pure and dense 0.9(KNbO3)-0.1(BaNi1/2Nb1/2O3-δ) ceramic with superior magnetic properties

Residual NiO phase is generally detected in 0.9(KNbO₃)–0.1(BaNi_1/2Nb_1/2O_3-δ) (KBNNO) synthesized using NiO as a nickel precursor by solid-state reaction. In this work, NiO phase is found to exist in the form of the residual NiO particles with a size of 100-200 nm using energy dispersive X-ray elemental mapping. These NiO residual particles are eliminated by using nickel acetate as a nickel precursor and a 100% perovskite phase KBNNO is successfully synthesized at as low as 600°C temperature. Furthermore, using the two-step sintering technique, 100% relative density is achieved in this material. The nickel acetate–based KBNNO shows a robust ferromagnetism with the saturation magnetization of 11.42 memu/g and the remanent magnetization of 3.89 memu/g which is 38 times higher than that of previously reported value in NiO-based KBNNO. Thus, a highly pure and fully dense KBNNO ceramic with superior magnetic properties is obtained using nickel acetate and by the two-step sintering method. This is a key step forward in the processing of KBNNO and is likely to have a significant impact on other physical properties of this newly invented and promising photovoltaic perovskite material.     

Mn4+-activated KLaMgWO6: A new high-efficiency far-red phosphor for indoor plant growth LEDs

Novel Mn⁴⁺-activated KLaMgWO₆ red phosphors with different Mn⁴⁺ concentrations were successfully synthesized via a high-temperature solid-state reaction method. The phase formation, microstructure, photoluminescence properties, decay lifetimes and internal quantum efficiency were discussed to analyze the properties of the as-prepared phosphors. The samples belonged to monoclinic crystal system with enough WO₆ octahedrons that provided suitable sites for Mn⁴⁺ ions. Upon the excitation of 348?nm, KLaMgWO₆:Mn⁴⁺ phosphors gave bright far-red emission around 696?nm due to the ²E_g→⁴A_2g transition of Mn⁴⁺ ions. The critical concentration of Mn⁴⁺ was 0.6?mol% and the concentration quenching mechanism belonged to electric multipolar interaction. Besides, the CIE chromaticity coordinates of the KLaMgWO₆:0.6%Mn⁴⁺ phosphor were (0.7205, 0.2794) which located in deep red range, and its color purity reached up to 96.6%. The KLaMgWO₆:0.6%Mn⁴⁺ sample also exhibited high internal quantum efficiency of 43%. All of the admirable optical properties indicate that the KLaMgWO₆:Mn⁴⁺ phosphors can be applied to indoor plant growth illumination.