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Investigation of phase segregation in sol–gel derived ZnMgO thin films
Singh, Amanpal,Vij, Ankush,Kumar, Dinesh,Khanna, P K,Kumar, Mukesh,Gautam, Sanjeev,Chae, K H Institute of Physics 2013 Semiconductor science and technology Vol.28 No.2
<P>Highly c-axis-oriented Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O multilayered thin films have been deposited on p-type Si substrates with different concentration of Mg (x = 0.00−0.40) using a sol–gel spin-coating technique. The x-ray diffraction (XRD) shows that single-phase wurtzite thin films start showing phase segregation for a Mg content of x = 0.25 for the sol–gel-derived ZnMgO thin films. The element specific near edge x-ray fine structure (NEXAFS) collected at O K-edge also clearly evidence the phase segregation at x = 0.25. These results also show that films are deposited with wurtzite structure as dominant phase even after phase segregation. The NEXAFS spectra collected at Zn L<SUB>3</SUB>-edge rule out the presence of any Zn-related defect due to Mg doping. The atomic force microscopy (AFM) depicts the spherical shape of nanosized grains, and grain size varies slightly with Mg content. The single-phase ZnMgO thin films show a band gap tuning from 3.38 to 3.84 eV, which is also consistent with blue shifting of near-band edge PL emission. The electrical resistivity of thin films increases with Mg content before phase segregation. However, the optical band gap, photoluminescence and electrical resistivity show anomalous behavior at phase segregation limit which has been discussed and correlated with each other.</P>
Effect of Oviductal Cell Co-Culture on Cleavage and Development of Buffalo IVF Embryos
Yadav, P.S.,Khanna, S.,Hooda, O.K.,Sethi, R.K. Asian Australasian Association of Animal Productio 2000 Animal Bioscience Vol.13 No.7
In vitro fertilization can be used for salvaging superior buffalo germplasm which otherwise goes waste after the slaughter of animals. This technology has also increased our basic understanding of growth of germ cells and embryos. The requirement of growing embryos is peculiar and stage specific. In the present study the cleavage and development of buffalo embryos were studied with homologous (buffalo) and heterologous (goat) oviductal cell co-culture systems. The cleavage rate improved significantly (p<0.01) in both homologous and heterologous co-culture as compared to control (55.3, 46.8 and 11.4%). The morula formation using homologous and heterologous oviductal cells also increased significantly as compared to control group (43.6, 21.9 & 1.9%). There was no blastula formation in control group, but addition of oviductal cells either from homologous or heterologous species significantly increased the blastula formation (9.5, 12.5%). The cleavage rate and embryo development was slightly better (non significant) in homologous as compared to heterologous oviductal cell culture. It was concluded that the use of oviductal cell co-culture (homologous and heterologous species) have significantly improved cleavage and development of buffalo embryos in vitro.
Synthesis and band-gap photoluminescence from cadmium phosphide nano-particles
P.K. Khanna,N. Singh,Priyesh More 한국물리학회 2010 Current Applied Physics Vol.10 No.1
Cadmium phosphide (Cd3P2) when synthesized from the direct reaction of cadmium metal salt and trioctylphosphine (TOP) in presence of sodium metal showed band-gap emissions with engineered bandgap energy in between 2.85 and 2.75 eV. Optical studies showed pronounced quantum confinement effect from nano-particles so prepared. X-ray diffraction (XRD) pattern of black powders revealed hexagonal Cd2P3 crystal structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed mixed morphology of fluffy particles likely to be amorphous in nature. Far-infrared (far-IR)spectroscopy revealed peaks associated with (Cd3P2).
Rupinder K. Beri,Priyesh More,B.G. Bharate,P.K. Khanna 한국물리학회 2010 Current Applied Physics Vol.10 No.2
Single-step green synthesis of ZnSe quantum dots (QDs) from 1,2,3-selenadiazole and zinc acetate resulted in formation of high-quality mono-disperse ZnSe with engineered band-gap. The present method is a non-TOP green route where oleic acid is used as a surfactant. The size quantization effect can be monitored by UV–visible spectroscopy which shows in the range 370–387 nm (3.20–3.35 eV), a blue shift of about 70–90 nm with respect bulk ZnSe. Photoluminescence measurement revealed bandgap emission at ~390 nm (3.18 eV, Stokes shift of <10 nm with FWHM <30 nm). Broadened XRD pattern indicated formation of cubic ZnSe and the estimation of particle size from the line broadening at h1 1 1i matched well the TEM analysis.
전기원,Anisha Gokarna,P. K. Khanna,백진욱,석상일 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.11
Formation of octahedral shaped PbSe quantum dots at higher synthesis temperature is being reported in this paper. The synthesis includes the reaction between lead oleate and trioctylphosphine selenide under inert gas conditions to produce PbSe. TEM, SEM, XRD and EDS were used to characterize the samples. The SEM exhibited the formation of spherical shaped nanocrystals at temperature below 140 oC and octahedral shaped nanoparticles at higher temperatures. Moreover, the TEM also showed the well resolved (111) lattice fringes proving that the nanocrystals were crystalline in nature. Synthesis of highly pure PbSe nanocrystals was another interesting aspect of this research.
Arun Barvat,Nisha Prakash,Gaurav Kumar,Dilip K. Singh,Anjana Dogra,Suraj P. Khanna,Prabir Pal 한국물리학회 2018 Current Applied Physics Vol.18 No.2
We report the electronic structure of Molybdenum disulfide (MoS2) ultrathin 2D films grown by pulsed laser deposition (PLD) on top of GaN/c-Al2O3 (0001) substrates annealed up to 550 C in an ultrahigh vacuum. Our X-ray photoemission spectroscopy (XPS) study shows that the grown films are mixed phase character with semiconducting 2H and metallic 1T phases. After ultrahigh vacuum (UHV) annealing, the 1T/2H phase ratio is significantly modified and film-substrate bonding becomes the leading factor influencing variation of mixed phase compositions. The semiconducting phase is partially transformed to metallic phase by thermal annealing; suggesting that the metallic phase observed here may indeed have more stability compared to the semiconducting phase. The notable enhancement of the 1T/2H ratio induces significant changes in Ga 3d core level spectra taken from bare GaN and MoS2/GaN sample. The impact of S and/or Mo atoms on the Ga core level spectra is further pronounced with the thermal annealing of grown films. The analysis shows that an enhancement of 1T metallic phase with thermal annealing in MoS2 layers is manifested by the occurrence of new spectral component in the Ga 3d core level spectra with the formation of Ga-S adlayer interaction through the Ga bonding in defect assisted GaN structure.
Gokarna, Anisha,Jun, Ki-Won,Khanna, P.K.,Baeg, Jin-Ook,Seok, Sang-Il Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.11
Formation of octahedral shaped PbSe quantum dots at higher synthesis temperature is being reported in this paper. The synthesis includes the reaction between lead oleate and trioctylphosphine selenide under inert gas conditions to produce PbSe. TEM, SEM, XRD and EDS were used to characterize the samples. The SEM exhibited the formation of spherical shaped nanocrystals at temperature below 140 ${^{\circ}C}$ and octahedral shaped nanoparticles at higher temperatures. Moreover, the TEM also showed the well resolved (111) lattice fringes proving that the nanocrystals were crystalline in nature. Synthesis of highly pure PbSe nanocrystals was another interesting aspect of this research.