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Adolescents, pregnant women and mothers of children under 2 years of age are in stages of life characterized by higher nutritional demands. The study measured the dietary diversity of 17,680 adolescent girls, pregnant women and mothers of children under age 2 years in the eastern Indian states of Bihar, Chhattisgarh and Odisha using data from the Swabhimaan baseline survey conducted in 2016. The association of women’s mean Dietary Diversity Scores with socioeconomic, health and nutrition service indicators was assessed. The sampled population was socioeconomically more vulnerable than the average Indian population. There was not much variation in the types of foods consumed daily across target groups, with diet being predominantly cereal (98%) and vegetable (83%) based. Nearly 30% of the mothers had low Dietary Diversity Scores, compared with 25% of pregnant women and 24% of adolescent girls. In each target group, more than half of the respondents were unable to meet the Minimum Dietary Diversity score of at least five of ten food groups consumed daily. Irrespective of their background characteristics, mean Dietary Diversity Scores were significantly lower in Bihar than in Chhattisgarh and Odisha for all target groups. Having at least 6 years of education, belonging to a relatively rich household and possessing a ration card predicted mean dietary diversity. Project interventions of participatory women’s group meetings improved mean Dietary Diversity Scores for mothers and adolescent girls. Considering the association between poverty and dietary diversity, the linkage between girls and women and nutrition-focused livelihoods and supplementary nutrition programmes needs to be tested.
Spiking Neural Networks propose to mimic nature’s way of recognizing patterns and making decisions in a fuzzy manner. To develop such networks in hardware, a highly manufacturable technology is required. We have proposed a silicon-based leaky integrate and fire (LIF) neuron, on a sufficiently matured 32 nm CMOS silicon-on-insulator (SOI) technology. The floating body effect of the partially depleted (PD) SOI transistor is used to store “holes” generated by impact ionization in the floating body, which performs the “integrate” function. Recombination or equivalent hole loss mimics the “leak” functions. The “hole” storage reduces the source barrier to increase the transistor current. Upon reaching a threshold current level, an external circuit records a “firing” event and resets the SOI MOSFET by draining all the stored holes. In terms of application, the neuron is able to show classification problems with reasonable accuracy. We looked at the effect of scaling experimentally. Channel length scaling reduces voltage for impact ionization and enables sharper impact ionization producing significant designability of the neuron. A circuit equivalence is also demonstrated to understand the dynamics qualitatively. Three distinct regimes are observed during integration based on different hole leakage mechanism.
Ziziphus mauritiana Lam. is an important fruit crop of the Thar Desert of India. About 330 accessions and cultivars collected from various parts of India are currently being maintained at a farm in the Central Institute for Arid Horticulture. Utilization of such a large collection of germplasm for breeding and crop improvement is difficult. Therefore, in the present study, using a heuristic approach based on phenotypic characters, we identified 52 accessions that represented a core collection, with a coverage of 100% and a coincidence rate of 98.1%. No significant difference was observed with respect to either the Shannon–Weaver or the Nei diversity index for qualitative traits, mean values and ranges for quantitative traits or clustering patterns between the core and whole collections. The core collection represents the entire range of diversity with minimum redundancy and should be useful for the conservation and utilization of Z. mauritiana germplasm.
Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films with different individual layer ZrO2 thicknesses are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process. The current versus voltage (I-V) measurements of the above multilayered thin films in metal-insulator-metal (MIM) device structures are taken in the temperature range of 310 to 410K. The electrical conduction mechanisms contributing to the leakage current at different field regions have been studied in this work. Various models are used to know the different conduction mechanisms responsible for the leakage current in these devices. It is observed that Poole-Frenkel mechanism is the dominant conduction process in the high field region with deep electron trap energy levels (φt) whereas space charge limited current (SCLC) mechanism is contributing to the leakage current in the medium field region with shallow electron trap levels (Et). Also, it is seen that Ohmic conduction process is the dominant mechanism in the low field region having activation energy (Ea) for the electrons. The estimated trap level energy varies from 0.2 to 1.31 eV for deep level traps and from 0.08 to 0.18 eV for shallow level traps whereas the activation energy for electrons in ohmic conduction process varies from 0.05 to 0.17 eV with the increase of ZrO2 sub layer thickness. An energy band diagram is given to explain the dominance of the various leakage mechanisms in different field regions for these heterostructured thin films.
Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process. The current versus voltage (I-V) measurements of metal-insulator-metal (MIM) devices using the above multilayered thin film as the dielectric have been taken in the temperature range of 310 to 410K. The electrical conduction mechanisms contributing to the leakage current at different field regions have been studied in this work. Various models are used to know the different leakage mechanisms contributing to the conduction current in these devices. It is observed that Poole-Frenkel mechanism is the dominant conduction process in the high field region with a deep trap level energy (φt) of 1.31 eV whereas space charge limited current (SCLC) mechanism and Ohmic conduction process are contributing to the leakage current in the medium and low field regions respectively. The estimated shallow trap level (Et) for SCLC mechanism is 0.26 eV whereas the activation energy (Ea) for the electrons in the Ohmic conduction process is about 0.07 eV. An energy band diagram is given to explain the various leakage mechanisms in different field regions for these heterostructured thin films.
Ba0.8Sr0.2TiO3 (BST) thin films and Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films have been successfully fabricated on Pt/Ti/SiO2/Si substrates by a sol-gel process. The dielectric properties of these films were measured as a function of temperature in the frequency range of 1 kHz to 1 MHz. It is clearly observed that the dielectric peaks exist and shift to high temperature with the increase of frequency indicating the presence of relaxor-type behavior in the films. Also it is seen that one dielectric peak is observed in single layer BST thin films whereas two dielectric peaks are observed in BST/ZrO2 heterostructured thin films due to the presence of two dielectric layers having different band gap energies. The variation of peak temperature Tm, corresponding to dielectric loss maximum, with frequency and fitting to Arrhenius law gives activation energy of 1.24 eV which is very close to the activation energy of oxygen vacancies in BaTiO3. Hence, oxygen vacancies are the active defects which are contributing to the relaxation process in these films.
Though organic light emitting diodes are being commercialized in many applications, issues relating to lifetime and degradation remain as fundamental concerns limiting performance. A coherent understanding of degradation mechanisms is yet to emerge. We focus on intrinsic degradation of high quality Alq3 based diodes due to electrical stressing. We monitor progressive luminance degradation and recovery by introducing well defined relaxation time windows in the current stress cycles. The method helps to clearly distinguish between recoverable and permanent degradation systematically. The voltage shift due to degradation and recovery is also monitored as a function of time. Further, we introduce a method of reconstructing the transients of the recoverable part using progressive isolated current pulses as a probe. The recovery of degradation is related to the charging and discharging of the traps in the device and our method provides a technique of measuring significant parameters of trapping through luminance transients. The origin and distinguishing features of the two types of degradation are discussed.
Recently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [BaxSr1-xTiO3, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO2 layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO2/BST multilayer structure is studied. The multilayer Ba0.8Sr0.2TiO3/ZrO2/Ba0.8Sr0.2TiO3 film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO2 layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO2 layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO2 layer thickness.
Raman spectra of a variety of polymorphous (pm-Si:H) and amorphous silicon
(a-Si:H) samples deposited by plasma enhanced chemical vapor deposition
(PECVD) at different pressures were recorded in the range of 150 cm-1 to 750 cm-1 using a 514 nm excitation source. A comparison of Raman
spectra between a-Si:H and pm-Si:H samples reveals significant differences.
The Transverse Optical (TO) peak in case of pm-Si:H is asymmetric and
shifted to higher wave numbers. In the literature, discrepancies between
predictions of various quantum confinement models and experimental spectra
have typically been attributed to either strain or negligible fraction of
nanocrystallites. We show that a quantum confinement model along with a
Gaussian size distribution is able to accurately predict particle size of
nanocrystallites embedded in the amorphous matrix. The crystallite size and
size distribution obtained by fitting the TO peak is consistent with
high-resolution transmission electron microscopy observations. In our case
typical mean crystallite size obtained is about 3 nm with FWHM of the
distribution varying in the range 0.2–1 nm. A comparison of ratio of heights
in TA and TO peaks of a-Si:H and pm-Si:H material indicates that pm-Si:H as
a material has higher medium range order (MRO). This ratio has been used to
compare the degree of MRO in pm-Si:H samples prepared under different
conditions. Thus, we demonstrate that Raman Spectroscopy along with our
model can be used to obtain the crystallite size distribution and provide a
measure of degree of medium range order.
This is a copy of the slides presented at the meeting but not formally written up for the volume.
At heterojunctions between different oxide perovskite phases both lattice and electronic structure is modified by the junction. One interesting question that several groups have studied is just how far into the neighboring materials these perturbations extend. We have studied this for insulating phases as well as conducting phases. For insulating phases it appears that the lattice distortions are healed in a layer about one unit cell thick. By stacking different materials each of which is only a single unit cell thick we have obtained materials that exhibit new properties determined by the stacking architecture. For example, superlattices that lack inversion symmetry have a built-in polarization that is controlled by the direction of the strain asymmetry. For conducting phases, the electronic structure also seems to be modified mainly in a layer only a few unit cells thick. We have studied this in superlattices of SrTiO3 and LaMnO3 in which we vary the thickness of the layers. We use optical conductivity to probe the electronic structure in the near infrared to near ultraviolet spectral region. The conductivity is close to the average of the two constituents, but differs in certain spectral regions, especially for the films with the thinnest supercells.This work was supported by the Department of Energy Basic Energy Sciences program at the Fredrick Seitz Materials Research Laboratory at the University of Illinois, Urbana, IL.
The development of rice blast disease in four slow-blasting (SB) genotypes was compared with that in the fast-blasting (FB) genotype Karuna, under natural field epidemics over a period of 3 years at five levels of nitrogen, in order to determine if the application of high doses of nitrogen influenced the expression of disease progress in the SB types. The treatment effects were compared through estimation of nine parameters viz. (i) lesion number (LN); (ii) area under disease progress curve (AUDPC); (iii) relative area under disease progress curve (RAUDPC); (iv) logistic apparent infection rate (r); (v) Gompertz apparent infection rate (k); (vi) logit line intercept (logit-a); (vii) gompit line intercept (gompit-a); (viii) time required for the disease to reach 0·25 severity in logistic (T25r); and (ix) Gompertz (T25k) models. There was a significant increase in LN, AUDPC, RAUDPC, r and k with increased levels of nitrogen application in all genotypes, but the rate of increase in disease severity was much lower in SB genotypes than the FB one and did not lead to breakdown of resistance in the SB genotypes, since severity level was much below the economic injury level. Among the nine derived parameters for evaluation of resistance LN, AUDPC, RAUDPC, r and k were best. The AUDPC and RAUDPC had lower degrees of error variance compared with the other parameters and hence were considered superior measures for characterization of disease progress curves.
Hydrogenated polymorphous silicon (pm-Si:H) has steadily emerged as a potential replacement of hydrogenated amorphous silicon. Possible changes in the density of gap states due to the presence of crystallites is of central importance in understanding steady state and dynamic characteristics of devices using these materials. We have studied a-Si:H and pm-Si:H grown by PECVD at optimized conditions through the measurement of the steady state reverse current and their transients in PIN devices. The transients are analyzed using isothermal spectroscopic techniques such as Time Analyzed Transient Spectroscopy (TATS), and high resolution Laplace DLTS as a function of temperature. In case of a-Si:H, we obtain the expected signature of emission from a broad density of states in the form of stretched exponentials. In contrast the corresponding spectra for pm-Si:H are dominated by nearly exponential fast current decay processes with discrete energies between 0.20 and 0.26 eV. It is shown that the study of the density of states by dynamic methods such as transient techniques reveal features not accessible to steady state measurements.
Organic thin-film transistors (OTFTs) appear to have become strong contenders to silicon based MOSFET devices whenever low-cost and relatively low performance circuits are required in applications such as radio frequency identification (RFID) for large volume supply chains. In order to develop circuits based on OTFTs, circuit designers require circuit models that predict the operation of OTFT with a reasonable accuracy. Although, generally, OTFT operation is similar to ordinary silicon MOSFET devices, there are several characteristics that clearly differentiate them. One important difference between the operation of the OTFT and the silicon MOSFET (that is a direct consequence of the physical implementation of OTFT) is that the organic transistor is normally operated in the accumulation mode, while the silicon transistor regularly operates in the inversion mode. Due to the molecular nature of the semiconductor, the carrier mobility is orders of magnitude lower than for the silicon MOSFET. Variable carrier mobility law, low on/off ratio, and the Schottky barrier at the interface between the source/drain metal contact and the organic semiconductor are among other important effects that had to be considered for developing of an accurate circuit model of the organic transistor. The developed model has been used to simulate DC characteristics and also simple circuits such as logic gates, ring oscillators, rectifiers, etc.
This paper presents the developed model as well as a comparison between the simulated data and the experimental data. The experimental circuits were fabricated on flexible plastic substrates and employed a solution-cast dielectric. Pentacene was the semiconductor of choice with carrier mobility in the range of 0.1 – 1.5 cm2/V.s.
One of the potential application areas for organic and polymers transistors is in radiofrequency identification (RFID) tags. One of the key components of an RFID tag is the front-end rectifier that must rectify a 13.56 MHz AC signal received from a resonant tuned antenna. The rectifier supplies operating power to the tag. Organic transistor circuits have hitherto not operated at this high frequency. We show that by operating pentacene transistors in the non-quasi-static (NQS) regime such operating speeds can be achieved in rectifier circuits. The circuits were fabricated on flexible plastic substrates and employed a solution-cast dielectric. The pentacene mobilities are in the range 0.1-1.5 cm2/V-s. The channel lengths of the transistors are in the range 2-4 μm. Full-wave NQS mode rectifiers were measured to have voltage rectification efficiency in excess of 28% at 14 MHz, demonstrating that such circuits can be used in RFID tags. These circuits operated successfully at speeds up to 20 MHz.
We have studied photovoltage spectra of PPV thin films using both conventional single layer LED structure (ITO/PPV/Al), and capacitive structure consisting of ITO/Mica/PPV/ITO films. The photovoltage spectra for both types of devices have sharp features and are identical indicating that the features observed are primarily due to PPV material itself. We observed two sharp peaks in the energy range of 2.5 -2.7 eV (i.e. above HOMO-LUMO gap) in photovoltage spectrum. The lineshape of the peaks strongly suggests that the peaks are most probably associated with photoionization of excitons. Temperature dependence of spectral lineshape of photocurrent peaks has been studied in the range of 80K-300K. The magnitudes of photocurrent peaks are weakly dependent on temperature, while other spectral features such as peak position and peak width are nearly independent of temperature. On the basis of absorbance, photovoltage and PL spectra, we conclude that both polarons and photoionization of excitons contribute to steady state photovoltage spectra.
Thin films of Ba1-x SrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and low fatigue. Several approaches have been used to improve the properties of thin films such as doping with aliovalent dopants, graded compositions, and layered structures. We have found that interposing layers of an electronic insulator such as ZrO2 in between BST layers results in a significant reduction in the leakage current. In this paper the low temperature electrical properties of these multilayer structures are reported. The structures consist of alternate layers of Ba0.8Sr0.2TiO3 and ZrO2 deposited by a sol-gel process on platinized Si substrates. The thickness and the number of layers are varied while keeping the total thickness of the film constant. Multiple peaks in the dielectric constant vs temperature plots at all frequencies are observed in the multilayered films. The properties of the multilayer films are a complex function of the number of layers and their thicknesses. A structure with several thin layers of ZrO2 interposed between the BST layers produces smoother plots than a single layer of ZrO2 of same total thickness. This is attributed to more uniform distribution, as determined by XPS, of ZrO2 in the multilayer structure due to smaller diffusion distances.
Polymorphous Silicon (pm-Si:H) deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) has emerged as an alternative material to amorphous silicon (a-Si:H). Deposition parameters of pm-Si:H are such that small crystallites get embedded in a relaxed amorphous silicon matrix, thus improving the optical and electrical properties. We study the size of crystallites and degree of order in pm-Si:H using Raman and photoluminescence (PL) spectra of pm-Si:H and a-Si:H. Raman Spectra of a variety of hydrogenated nanostructured silicon (pmSi:H) and amorphous Silicon (a-Si:H) samples grown at different pressures were analyzed. Deconvolution of observed multiple peaks in photoluminescence spectra and fitting to Gaussian size distribution also yields particle size to be in the range of 2.3 to 3.5nm in agreement with Transmission Electron Microscopy and Raman results.
Hydrogenated polymorphous silicon (Pm-Si:H) being an admixture of amorphous and ordered phase silicon shows improved optical and electrical properties due to the presence of nanocrystallites. In order to compare the dynamic and steady state electrical properties in a-Si:H and pm-Si:H, bottom gate Thin Film Transistors (TFT) of these materials were fabricated with SiO2 as the insulating layer. The active materials were deposited using plasma-enhanced chemical vapor deposition (PECVD) by varying pressure, temperature and hydrogen dilution. Transfer characteristics of TFTs made using pm-Si:H show lower leakage current, higher on-current and sharper volt per decade change as compared to similar TFTs made from a-Si:H. Density of states in pm-Si:H as calculated from field effect conductance using incremental method is observed to be an order of magnitude lower than in a-Si:H based devices. To compare dynamic characteristics, we studied the switch-on transient characteristics of polymorphous and amorphous silicon TFTs by pulsing the gate to different voltages in the temperature range of 150-300K. The switch-on transients are trap limited with overall better switching characteristics for pm-Si:H samples. An initial rising transient in case of pm-Si:H is activated with an effective energy of 0.3 eV. The origins of transients are interpreted in terms of trap limited carrier dynamics and charge redistribution within the distribution of localized states.
We study electrical signature of defect clusters in KeV Ar ion-implanted n-silicon using Deep Level Transient Spectroscopy (DLTS) and isothermal capacitance spectroscopies such as time analyzed transient spectroscopy (TATS) and high resolution Laplace-DLTS. The samples are annealed at relatively low temperatures of 350 °C - 600 °C at which defect clusters are known to form and evolve. Contrary to the view that few dominant point-defect like traps are associated with defect clusters, our results show that the band gap may be replete with bands of multiple trap states; however their occupation and hence observation depends on experimental conditions dictated by dynamics of carrier capture and emission at these traps. Charge redistribution among multiple states and deepening of effective emission energy with capture are shown to be commonly occurring at these defects. Isothermal transient spectroscopy is shown to be appropriate tool for recognition of some of these features.
The kinetics of multiple DX related emission centers are studied using the isothermal Time Analyzed Transient Spectroscopy (TATS) of constant capacitance voltage transients. Four distinct emitting centers have been obtained using higher order TATS in the same silicon doped Al0.33As0.67As sample without use of hydrostatic pressure. Accurate identification of the multiple DX states has allowed a better understanding of the charge redistribution process during capture. Improved resolution due to increase in order of spectroscopy has enabled quantitative fitting of spectral lineshape and thus accounting for degree of nonexponentiality associated with each of the four discrete centers. The capture kinetics of these centers are studied over six orders in magnitude of filling time. The resulting quality of kinetic data makes possible detailed quantitative comparison with kinetics predicted by positive U and negative U models of DX centers. We show that our data is in agreement with positive U model of DX center.