Effect of oxygen ambient on structural, optical and electrical properties of epitaxial Al-doped ZnO thin films on r-plane sapphire by pulsed laser deposition

Manoj Kumar,최세영,R.M. Mehra 한국물리학회 2009 Current Applied Physics Vol.9 No.4

Al-doped ZnO (ZnO:Al) thin films were grown epitaxially on r-plane sapphire substrate by pulsed laser deposition. Substrate temperature of 400 ℃ and pulsed repetition rate of 5 Hz was kept constant during the deposition. The effect of oxygen ambient pressure from 0.1 to 10 mTorr on structural, optical and electrical properties of the ZnO:Al films were investigated. The lowest resistivity was found to be 2.14 × 10-3 Ω-cm with a carrier concentration of 6.89 × 1019 cm-3 for the film deposited in 1 mTorr of oxygen pressure. ZnO:Al film revealed smoother surface obtained at oxygen ambient pressure of 1 mTorr. The epitaxial relationship between ZnO:Al films and r-plane sapphire was found to be (0001)ZnO // (0112)sapp and [1010]ZnO // [0111]sapp. Photoluminescence spectra of the film grown at the oxygen ambient pressure of 1 mTorr exhibited peak at 3.34 eV, without any deep level. Al-doped ZnO (ZnO:Al) thin films were grown epitaxially on r-plane sapphire substrate by pulsed laser deposition. Substrate temperature of 400 ℃ and pulsed repetition rate of 5 Hz was kept constant during the deposition. The effect of oxygen ambient pressure from 0.1 to 10 mTorr on structural, optical and electrical properties of the ZnO:Al films were investigated. The lowest resistivity was found to be 2.14 × 10-3 Ω-cm with a carrier concentration of 6.89 × 1019 cm-3 for the film deposited in 1 mTorr of oxygen pressure. ZnO:Al film revealed smoother surface obtained at oxygen ambient pressure of 1 mTorr. The epitaxial relationship between ZnO:Al films and r-plane sapphire was found to be (0001)ZnO // (0112)sapp and [1010]ZnO // [0111]sapp. Photoluminescence spectra of the film grown at the oxygen ambient pressure of 1 mTorr exhibited peak at 3.34 eV, without any deep level.

Effect of Sources of Supplementary Protein on Intake, Digestion and Efficiency of Energy Utilization in Buffaloes Fed Wheat Straw Based Diets

Mehra, U.R.,Khan, M.Y.,Lal, Murari,Hasan, Q.Z.,Das, Asit,Bhar, R.,Verma, A.K.,Dass, R.S.,Singh, P. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.5

Sixteen adult male buffaloes (average body weight $443{\pm}14kg$) were equally distributed into four groups in an experiment to study the effect of supplementary protein sources on energy utilization efficiency in buffaloes fed a wheat straw-based diet. The animals in the control group were offered a basal diet composed of 700 g deoiled ground nut cake and ad libitum wheat straw. Animals of other groups were offered 1.8 kg of soyabean meal (SBM), linseed meal (LSM) or mustard cake (MC) along with the basal diet. Protein supplementation increased the digestibility of DM (p<0.01), OM (p<0.01) CP (p<0.01) and CF (p<0.05). Maximum CP digestibility was observed on SBM, followed by LSM and MC when compared to the control. Total DMI and DOMI was significantly (p<0.01) higher in protein supplemented groups with no differences between treatment groups. Digestible crude protein (DCP) intake and N balance were significantly (p<0.01) different between the groups; maximum response was obtained with SBM supplementation, followed by LSM and MC. Faecal energy was significantly (p<0.01) lower in SBM and LSM groups in comparison to other groups. Methane production (% DEI) was significantly (p<0.05) lower on the SBM treatment. Metabolizable energy (ME) intake increased significantly due to protein supplementation. Metabolizable energy intake (MEI) of animals in the MC group was less than LSM and SBM. Energy balance was increased significantly (p<0.01) due to protein supplementation and within supplement variation was also significant with maximum balance in SBM followed by LSM and MC groups. Protein supplementation significantly (p<0.05) increased the digestibility and metabolizability of energy from whole ration. Metabolizable energy (ME) content (Mcal/kg DM) of SBM, LSM and MC was 4.49, 3.56 and 2.56, respectively. It was concluded that protein supplementation of wheat straw increased intake, digestibility and metabolizability of energy and maximum response could be obtained when soybean meal was used as a supplement.

Estimation of Rumen Microbial Protein Supply Using Urinary Purine Derivatives Excretion in Crossbred Calves Fed at Different Levels of Feed Intake

Singh, M.,Sharma, K.,Dutta, N.,Singh, P.,Verma, A.K.,Mehra, U.R. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.10

A study was carried out to study the response of total purine derivatives (PD) excretion in urine to determine microbial N (MN) supply at four fixed levels of feed intake (namely 95, 80, 60 and 40% of voluntary intake). The crossbred (CB) calves were allocated according to a $4{\times}4$ Latin Square Design and fed wheat straw and concentrate (1:1). The rate of PD excretion (mmol/d) as a linear function of feed intake was 15.85/kg DMI and 20.12/kg DOMI. Based on the endogenous and PD excretion rates obtained in this study, a relationship between daily urinary PD excretion (Y, mmol) and daily microbial protein supply (X, mmol) was developed for crossbred calves as Y = 0.83X+0.296 kg $W^{0.75}$. The derived microbial N values using this equation differed (p<0.001) among the 4 groups and was the highest in L-95 followed by L-80, L-60 and L-40. The relationship between urinary nitrogen loss (Y, g/d) and DOMI (X, kg/d) was established as: Y = 6.038X+21.753 ($r^2$ = 0.663, p<0.01). When urinary excretion of PD (Y, mmol/d) was plotted against intake of DM and DOM (X, kg/d), the equations obtained were: Y = 7.1711X+8.674 ($r^2$ = 0.889, p<0.01) and Y = 12.434X+7.683 ($r^2$ = 0.896, p<0.01), respectively. The proportional contribution of allantoin and uric acid to total PD remained stable irrespective of level of feed intake. Similarly, urinary excretion of creatinine did not differ (p>0.05) between animals fed at different levels. The MN supply was the highest to animals at intake levels L-95, and decreased linearly with corresponding decrease in feed intake. However, the MN supply when expressed per kg DOMI remained statistically (p>0.05) similar irrespective of level of intake. The results revealed that the excretion of urinary purine derivatives were positively correlated with the level of feed intake as well as rumen microbial supply and thus it could be a good indicator for measuring the microbial protein supply and nutritional status of animals.

Growth kinetics of ZnO nanocrystallites: Structural, optical and photoluminescence properties tuned by thermal annealing

R.G. Singh,Fouran Singh,Vinod Kumar,R.M. Mehra 한국물리학회 2011 Current Applied Physics Vol.11 No.3

In this paper, we report temperature dependent studies of ZnO nanocrystallites deposited by the sol-gel spin coating process. The films are annealed at different temperature from 500 to 900 ℃ to grow the size of crystallites in controlled environment. The crystallite size, lattice parameters, and strain in the nanocrystallites are calculated. A coarsening kinetics is understood by Lifshitz, Slyozov and Wagner (LSW) theory and the activation energy of the coarsening process is estimated. Optical absorption and Photoluminescence (PL) measurements were carried out to investigate the effect of coarsening on optical properties of the ZnO thin films. The origin of PL spectra is explained in terms of the stabilization of structural defects and size of the crystallites.

Measurement of Microbial Protein Supply in Murrah Buffaloes (Bubalus bubalis) Using Urinary Purine Derivatives Excretion and PDC Index

Dipu, M.T.,George, S.K.,Singh, P.,Verma, A.K.,Mehra, U.R. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.3

A study was conducted to predict the rumen microbial protein production based on urinary excretion of purine derivatives in buffaloes fed a diet of wheat straw and concentrate (40:60) at four fixed levels of feed intake. (95, 80, 60 and 40% of preliminary voluntary feed intake) following experimental protocol of IAEA (Phase I). The buffaloes were allocated according to a $4{\times}4$ latin square design. The urinary allantoin, uric acid, total PD excretion (mmol/d) in treatments L-95, L-80, L-60 and L-40 was 20.13, 16.00, 12.96 and 9.17; 1.88, 2.12, 2.11 and 2.15; 22.01, 18.12, 15.07 and 11.32, respectively and were significantly (p<0.05) different among treatments except for uric acid. The rate of PD excretion (mmol/d) was positively correlated with the digestible organic matter intake. Variations were observed in PD and creatinine concentration in spot samples collected at 6-hour interval. However, daily PD:Creatinine ratio (PDC index) appears to be a reasonably good predictor of microbial-N supply. The contribution of basal purine excretion to total excretion of purine derivatives (PD) was determined in pre-fasting period followed by a fasting period of 6 d (Phase II). Daily PD and creatinine excretion (mmol/kg $W^{0.75}$) during fasting averaged 0.117 and 0.456 respectively for buffaloes. The excretion rates of PD decreased significantly (p<0.01) during fasting compare to pre-fasting period, the urinary creatinine excretion remained almost similar. Except for creatinine, plasma concentration of target parameters significantly (p<0.01) declined during fasting. Likewise, glomerular filtration rate (GFR) and renal clearance of allantoin and uric acid also decreased. Based on the PD excretion rates during fasting and at different levels of feed intake obtained in this study, a relationship between daily urinary PD excretion (Y-mmol) and microbial purine absorption (X-mmol) was developed for buffaloes as Y = 0.74X+0.117 kg $W^{0.75}$. The microbial N supply (g/kg DOMI) remained statistically similar irrespective of dietary treatment. The results showed that excretion of urinary purine derivatives is positively correlated with the levels of feed intake in Murrah buffaloes and thus, estimation of urinary purine derivatives and PDC index could be used to determine microbial nitrogen supply when there is large variation in level of feed intake.

A comprehensive study of chalcogenide quantum dot sensitized solar cells with a new solar cell exceeding 1V output

Surana, Karan,Mehra, R.M.,Bhattacharya, B.,Rhee, Hee-Woo,Polu, Anji Reddy,Singh, Pramod K. Elsevier 2015 RENEWABLE & SUSTAINABLE ENERGY REVIEWS Vol.52 No.-

<P><B>Abstract</B></P> <P>In the last two decades quantum dots (QDs) have attracted research interest all across the globe owing to their unique size-dependent optical and electronic properties. Generally, smaller the size of the crystal, the larger is the energy gap and greater is the difference in energy between the highest valence band and the lowest conduction band. Therefore more energy is needed to excite the dot, and concurrently more energy is released when the crystal returns to its resting state. Chalcogenide QDs have gained worldwide acceptance for their application in quantum dot sensitized solar cells (QDSSC). This review article focuses chiefly on the progress made in chalcogenide QD based solar cells (SC) over the years along with a new type of QDSSC giving an output voltage of over 1V.</P>

Improvement in the Electrical Properties of Se- and S-doped Hydrogenated Amorphous Silicon Thin Films by Annealing

샤르마,김득영,R.M. Mehra 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.9

We studied the effect of annealing on the dark and photo conductivity of Se- and S-doped hydrogenated amorphous silicon (a-Si:H) thin films. The films were prepared on corning glass by using conventional plasma-enhanced chemical vapor deposition (PE-CVD). The samples were subsequently annealed in a vacuum (1 × 10−6Torr) at an annealing temperature of 300 ◦C for an hour. The conductivity was measured in the temperature range of 300 - 470 K, which exhibited two different transport mechanisms. In the high-temperature range (370 - 470 K), the conduction was found to be an activated type while in the low-temperature range (less than 370 K), it was observed to follow variable range hopping. Arrhenius plots of the conductivities for S- and Se-doped a-Si:H films revealed that the activation energy was lower after annealing, owing to the removal of the surface defects created during deposition. The characteristic energy, EMN, was lower in the annealed films for both types of dopant concentrations, which suggests a reduction in the number of traps. The photoconductivity was increased by vacuum annealing at 300 ◦C by a factor of more than 10.

Epitaxial growth of highly transparent and conducting Sc-doped ZnO films on c-plane sapphire by sol.gel process without buffer

Ruchika Sharma,Kiran Sehrawat,R.M. Mehra 한국물리학회 2010 Current Applied Physics Vol.10 No.1

Highly transparent and conductive scandium doped zinc oxide (ZnO:Sc) films were deposited on c-plane sapphire substrates by sol.gel technique using zinc acetate dihydrate [Zn(CH3COO)2·2H2O] as precursor,2-methoxyethanol as solvent and monoethanolamine as a stabilizer. The doping with scandium is achieved by adding 0.5 wt% of scandium nitrate hexahydrate [(ScNO3·6H2O)] in the solution. The influence of annealing temperature (300-550 ℃) on the structural, optical and electrical properties was investigated. X-ray Diffraction study revealed that highly c-axis oriented films with full-width half maximum of 0.16˚ are obtained at an annealing temperature of 400 ℃. The surface morphology of the films was judged by SEM and AFM images which indicated formation of grains. The average transmittance was found to be above 92% in the visible region. ZnO:Sc film, annealed at 400 ℃ exhibited minimum resistivity of 1.91 × 10-4 Ω cm. Room-temperature photoluminescence measurements of the ZnO:Sc films annealed at 400 ℃ showed ultraviolet peak at ~3.31eV with a FWHM of 11.2 meV, which are comparable to those found in high-quality ZnO films. Reflection high-energy electron diffraction pattern confirmed the epitaxial nature of the films even without introducing any buffer layer.

Influence of Level of Feed Intake on Concentration of Purine Derivatives in Urinary Spot Samples and Microbial Nitrogen Supply in Crossbred Bulls

George, S.K.,Dipu, M.T.,Mehra, U.R.,Verma, A.K.,Singh, P. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.9

The potential of the spot urine sampling technique as an alternative to performing a total urine collection to predict the microbial nitrogen supply was evaluated in crossbred bulls. In a completely randomized design, 20 growing crossbred bulls were assigned four levels of feed intake (120, 100, 80 and 60% of voluntary dry matter intake) on diets comprised of wheat straw and concentrate mixture (50:50). After three months of experimental feeding, a metabolism trial was conducted for ten days, during which spot urine collections were performed every 6 h post feeding on days 9 and 10. The daily urinary excretion of allantoin (A) and purine derivatives (PD) decreased with the reduction in feed intake while creatinine (C) excretion remained similar in animals fed at different levels. The microbial nitrogen (MN) supply calculated from the PD excreted in total urine (35.08 to 72.08 g/d) was higher at increased levels of feed intake. PD concentration in spot urine samples had poor correlation with feed intake except at 12 h post feeding. A/C ratio and PD/C ratio in spot urine samples remained similar irrespective of sampling time and significantly (p<0.01) correlated with daily urinary PD excretion, digestible organic matter intake and dry matter (DM) intake. However, no significant differences were evident in these ratios among animals fed at levels 120, 100 and 80% of voluntary dry matter intake (VDMI) at different times post feeding. These results suggests that the spot urine sampling technique to predict the microbial protein supply is not suitable for detecting small differences in MN supply and hence, estimation of PD excreted in total urine (mmol/d) is necessary to assess precisely the MN supply in crossbred bulls.

Plasticizer doped ionic liquid incorporated solid polymer electrolytes for photovoltaic application

Pramod K. Singh,B. Bhattacharya,R.M. Mehra,이희우 한국물리학회 2011 Current Applied Physics Vol.11 No.3

Polyethylene oxide base polymer electrolyte has been modified by doping of EMImDCN and PEG as plasticizers. Doping by IL resulted to enhanced conductivity and improved DSSC response. The DSSC using the modified electrolyte showed 3.02% efficiency at 1 sun condition.