Bi Lines Research Articles

Diallel analysis of common bean (Phaseolus vulgaris L.) genotypes for seed dietary fibre, carbohydrate, calcium and phosphorus contents

Genetic information of bean seed traits can be an immense help to the breeder in selection of suitable genotypes and the appropriate breeding strategies. Therefore, the investigation aims to assess the genetic variability and to elucidate the genetic analysis of seed dietary fibre, carbohydrate, seed calcium and phosphorus contents of Phaseolus vulgaris in the high Guinean Savannah zone conditions. 5 × 5 half-diallel crosses of these traits were conducted in randomized complete block design with three replications. Results revealed high differences between five lines beans (p < 0.05), suggesting the sufficient genetic diversity for these traits. High broad sense heritability values were recorded for seed dietary fibre, carbohydrate and seed calcium content, attesting a strong implication of the genetic factors in the control of these traits; thereby, these traits can be improved through regular selection. The ratio GCA/SCA was greater than unity only for seed phosphorus content. It indicates the prevalence of additive gene effect in the involvement of the genetic control for this trait. The combining ability analysis revealed highly significant differences between parental GCA effects and F1 cross SCA effects. The PB, BI, CT and PR lines beans will prove useful in common bean breeding programmes as donor genotypes, in the development of bean genetic resources for betterment improvement of nutritional traits.

Spectroscopic and analytical characteristics of an inductively coupled argon plasma combined with hydride generation with or without simultaneous introduction of the sample aerosol for optical emission spectrometry

A radially viewed inductively coupled argon plasma was used for optical emission spectrometry of volatile species formed by reaction with NaBH(4) (hydride generation). The volatile hydrides were either introduced into the plasma alone or at the same time as a sample aerosol generated by pneumatic nebulization with a commercially available Concomitant Metals Analyzer. The effects of the forward power, the presence of pre-reducing agents [(NH(2))(2)SC, KI, KBr and hot HCl], the occurrence of easily ionized elements (Ca, K, Mg and Na) in the analyte solutions on the excitation temperature (as measured via Ar atomic lines) and the electron number density were investigated for both of the sample introduction modes applied. The detection limits and the signal-to-background intensity ratios for As, Bi, Sb, Se and Sn lines were also evaluated and were observed to deteriorate with increasing power. When simultaneous hydride generation and pneumatic nebulization was employed under optimized experimental conditions, detection limits of 3.5, 2.9, 4.3, 1.5 and 2.1 microg L(-1) for As, Bi, Sb, Se and Sn, respectively, were obtained, and the intensities of the analytical lines for elements that do not form volatile hydrides were found to be 40% (Cd), 30% (Ni), 20% (Co, Cr, Fe, Mn and Zn) and 10% (Cu, Mg, V) greater than those obtained when only pneumatic nebulization was used.

Electronic structure of Bi lines on clean and H-passivated Si(100)

By means of scanning tunnelling microscopy and spectroscopy, we have investigated theelectronic structure of Bi nanolines on clean and H-passivated Si(100) surfaces. Maps of thelocal density of states (LDOS) images of the Bi nanolines are presented for the first time.The spectra obtained for nanolines on a clean Si surface and the LDOS imagesagree with ab initio predicted spectra for the Haiku structure. For nanolines ona H-passivated surface, the spectra obtained suggest that the Bi nanoline maylocally pin the surface Fermi level, and the LDOS images taken at low bias show adistribution of states different to what was expected at the Bi nanolines. The results arediscussed with respect to use of the nanolines as atomic wire interconnections.

Theoretical investigation of Mn adsorbates aside self-organised Bi nanolines on hydrogenated Si(0 0 1) surface

We have theoretically investigated the atomic structure, magnetic behaviour, and electronic properties of Mn adsorbates on hydrogen passivated self-organised Bi nanolines on the Si(0 0 1)surface. It is found that the most stable geometry for 1 6 monolayer (ML) coverage of Mn is just underneath the first Si(0 0 1) surface layer. The Mn atoms in the optimised configuration are seven-fold coordinated with their neighbouring Si atoms. Total energy calculations suggest that the Mn adsorbates form a degenerate state of ferromagnetic and anti-ferromagnetic lines parallel and adjacent to the self-assembled Bi lines. The density functional band structure calculation within the local-spin density approximation shows that the ferromagnetic system behaves like a metal in both spin channels. On the other side, the anti-ferromagnetic phase exhibits a half-metallic phenomenon with semiconducting character for the majority spin channel and semi-metallic character for the minority spin channel.

Formation of an ordered pattern of Bi nanolines on InAs(100) by self-assembly

Self-assembly of uniform patterns of nanolines over large surface areas has been proven to be difficult. The authors report that bismuth (Bi) adsorbate self-assembles into an ordered pattern of Bi nanolines separated by 4.3nm on the Bi-stabilized InAs(100)(2×1). The resulted nanoline surface is studied by scanning tunneling microscopy (STM) and low-energy electron diffraction. The plausible atomic models for the Bi nanolines are proposed on the basis of the STM results. The Bi lines are suggested to consist of two chains of adjacent Bi dimers positioned parallel to the chain and parallel to the Bi dimers of the (2×1) substrate.

A theoretical study of Fe adsorption along Bi-nanolines on the H/Si(0 0 1) surface

We have investigated the energetic stability and equilibrium geometry of the adsorption of transition metal Fe atoms near the self-organized Bi lines on hydrogen passivated Si(0 0 1) surface. Our total energy results show that there is an attractive interaction between Fe adatoms along the Bi-nanolines. For the energetically most stable configuration, the Fe adatoms are seven-fold coordinated, occupying the subsurface interstitial sites aside the Bi-nanolines. With increased coverage, Fe atoms are predicted to form two parallel lines, symmetrically on both sides of the Bi line. Within our local spin-density functional calculations, we find that for the most stable geometries the Fe adatoms exhibit an antiferromagnetic coupling.

Surface bismuth removal after Bi nanoline encapsulation in silicon

Recently, several kinds of atomic-scale wires have been reported for nano-scale device and interconnect applications. The Bi nanoline is one of the most promising candidates because of its structural perfection and the capability to be buried in an epitaxial Si layer. A surfactant layer of Bi is necessary for the encapsulation process, and this remains on the sample surface after the burial, but it needs to be removed so that the buried Bi line may be properly characterized by I– V measurements, X-ray diffraction, etc. without perturbations from the surface layer. It is shown by RHEED observation that the thermal desorption is not suitable for this purpose, because the one-dimensional structure of the buried Bi line is disrupted over the same time scale as for removal of the surfactant Bi. Chemical wet etching of the surface layer was found to be a better solution to the removal of the surfactant Bi atoms without destroying the buried Bi lines.

The equilibrium geometry and electronic structure of Bi nanolines on clean andhydrogenated Si(001) surfaces

The equilibrium geometry, electronic structure and energetic stability of Bi nanolines onclean and hydrogenated Si(001) surfaces have been examined by means of ab initio totalenergy calculations and scanning tunnelling microscopy. For the Bi nanolines on a clean Sisurface the two most plausible structural models, the Miki or M model (Miki et al 1999Phys. Rev. B 59 14868) and the Haiku or H model (Owen et al 2002 Phys. Rev. Lett. 88226104), have been examined in detail. The results of the total energy calculations supportthe stability of the H model over the M model, in agreement with previous theoreticalresults. For Bi nanolines on the hydrogenated Si(001) surface, we find that an atomicconfiguration derived from the H model is also more stable than an atomic configurationderived from the M model. However, the energetically less stable (M) model exhibitsbetter agreement with experimental measurements for equilibrium geometry. Theelectronic structures of the H and M models are very similar. Both models exhibit asemiconducting character, with the highest occupied Bi-derived bands lying at∼0.5 eV below the valence band maximum. Simulated and experimental STM images confirm thatat a low negative bias the Bi lines exhibit an ‘antiwire’ property for both structural models.

The electronic origin of contrast reversal in bias-dependent STM images of nanolines

Self-organized Bi lines that are only 1.5 nm wide can be grown without kinks or breaks on Si(0 0 1) surfaces to lengths of up to 500 nm. Constant-current topographical images of the lines, obtained with the scanning tunneling microscope, have a striking bias dependence. Although the lines appear darker than the Si terraces at biases below ≈∣1.2∣ V, the contrast reverses at biases above ≈∣1.5∣ V. Between these two ranges the lines and terraces are of comparable brightness. It has been suggested that this bias dependence may be due to the presence of a semiconductor-like energy gap within the line. Using ab initio calculations it is demonstrated that the energy gap is too small to explain the experimentally observed bias dependence. Consequently, at this time, there is no compelling explanation for this phenomenon. An alternative explanation is proposed that arises naturally from calculations of the tunneling current, using the Tersoff–Hamann approximation, and an examination of the electronic structure of the line.

Bismuth nanolines on Si(001) and their influence on mesoscopic surface structure

Experimental studies of Bi heteroepitaxy on Si(001) have recently uncovered a self-organised nanoline motif which has no detectable width dispersion. The Bi lines can be grown with an aspect ratio that is greater than 350 : 1. This paper describes a study of the nanoline geometry and electronic structure using a combination of scanning tunneling microscopy (STM) and ab initio theoretical methods. In particular, the effect that the lines have on Si(001) surface structure at large length scales, l > 100 nm, is studied. It has been found that Bi line growth on surfaces that have regularly spaced single height steps results in a 'preferred' domain orientation.

Single2×1domain orientation on Si(001) surfaces using aperiodic Bi line arrays

Studies of Bi heteroepitaxy on Si(001) have shown that lines grow to lengths of up to $500\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ if the substrate is heated to above the Bi desorption temperature $(500\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ during or after Bi deposition. Unlike many other nanoline systems, the lines formed by this nonequilibrium growth process have no detectable width dispersion. Although much attention has been given to the atomic geometery of the line, in this paper, we focus on how the lines can be used to create a majority $2\ifmmode\times\else\texttimes\fi{}1$ domain orientation. It is demonstrated that the Bi lines can be used to produce a single-domain orientation on Si(001) if the lines are grown on Si(001) surfaces with a regular distribution of single height steps. This is a compelling example of how a nanoscale motif can be used to modify mesoscopic surface structure on Si(001).

Self-organized Bi lines on the Si(001) surface: A theoretical study

We have performed an ab initio theoretical study of the stability, atomic geometry, and electronic structure of the self-organized Bi lines on the Si(001) surface. We have examined the two currently proposed models and two new hybrid models for the structure of Bi lines. Our results confirm the model proposed by Miki et al., in which the Bi lines are formed by Bi dimers parallel to the surrounding Si dimers, with a missing dimer row between the Bi dimers. However, in contrast to the proposal of symmetrically disposed surface Si dimers (i.e., with no buckling) by Miki et al., our total-energy calculations indicate that the buckling of the Si dimers is an exothermic process, reducing the surface total energy by 0.11 eV/dimer. Our theoretically simulated scanning tunneling microscopy results suggest a low density of states close to the valence-band maximum, localized on the Bi lines, supporting the recently proposed model of quantum antiwire systems for Bi lines on the Si(001) surface.

Large magnetoresistance and finite-size effect in electrodeposited bismuth lines

Finite-size effects in Bi lines of cross section 3 μm×w, where w=8–120 μm, have been studied. The lines were made by optical lithography followed by electrodeposition. At T=5 K, the magnetoresistance (MR) decreases monotonically with decreasing line width of the Bi films, from 44 000% at w=120 μm to 4000% at w=8 μm in a field of 50 kOe. The decrease of the MR with decreasing linewidth is due to a decrease of the size-limited effective-mean-free path. At low temperatures, both the resistivity and the magnetoresistivity show a strong dependence on w, whereas at room temperature, they are independent of w. The MR at room temperature remains at about 230% for linewidths w=8–120 μm at 50 kOe. This demonstrates that microstructured Bi lines can be made for field-sensing applications without compromising their MR characteristics.

The growth modes of vapor-deposited Bi on Cu(2 1 0)

This work presents growth modes of vapor-deposited Bi on clean and C contaminated Cu(2 1 0) surfaces, characterized with low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and work-function shifts ( Δeφ). Up to θ Bi=0.5 ML (monolayer, ML) fractional Bi coverage (equivalent to 0.686×10 15 at. cm −2) a p(1×1) structure is observed, associated with a gradual LEED pattern symmetry change from one mirror plane for clean Cu(2 1 0) to two, for θ Bi=0.5 ML. The higher symmetry phase is stable up to 723 K, and no appreciable binding-energy shifts are detected by XPS in the Bi (4f 7/2) and Cu (2p 3/2) core lines. Additional Bi results in Stranski–Krastanov growth of a compact Cu(2 1 0)–(6×1)-Bi structure with eight Bi atoms per unit cell, stable up to 628 K. Impurity levels of both either pre or coadsorbed C lower the stability temperature of the (6×1)-Bi phase. However, C does not have any appreciable influence on the p(1×1)-Bi phase. The presence of as little as θ C=0.1 ML of preadsorbed C produces Frank–Van der Merwe (layer by layer) growth of the p(1×1) c2mm structure, up till completion of the third layer, and as much as 30% variation in Δeφ values with respect to C-free samples. Carbon appears to have no effect on the growth, at 723 K, of Cu(2 1 0)–p(1×1)-Bi facets from the Cu(1 0 0)-c(2×2)–Bi phase when sufficient defects (vacancies) are present in the selvedge.

On the transport of some metals into inductively coupled plasma during hydride generation process

Transport process of Ca, Cd, Co, Cr, Cu, Fe, Mn, Mg, Ni, Zn and Ti during continuous flow hydride generation in the system with phase separation was investigated using inductively coupled plasma atomic emission spectrometry. The effect of HCl and HNO 3 (for concentrations from 0.01 to 5.0 mol l −1) and arsenic on transport efficiency of the metals into plasma was examined. It was observed that not only Cd but also Cu transport in a form of volatile species was significant. The present study also indicated the formation of Co, Cr, Fe and Ni volatile species during hydride generation reaction. Possibility of spectral interferences between Cd, Cu and Fe lines on the one side and As and Bi lines on the other side was analysed and discussed.

Bismuth-induced structures on Si(001) surfaces

We have examined Bi-induced surface structures of Si(001), formed in the vicinity of its desorption temperature, by means of scanning tunnelling microscopy and reflection high-energy electron diffraction. Below the desorption temperature, adsorption of bismuth results in a (2× n) Bi–Si(001) reconstruction with second-layer Bi dimers either parallel or perpendicular to the underlying dimers. Even after the desorption of the bismuth epitaxial layer, some bismuth remains on the surface with characteristic structures which depend upon the formation pathway. Perfectly straight Bi lines 1 nm wide and hundreds of nanometres long can be formed either by annealing of the saturated Bi epitaxial layer, or by exposure to a large flux of bismuth around the desorption temperature. Exposure to a smaller flux of Bi at the desorption temperature generates a c(4×4) reconstruction. The stability of the c(4×4) reconstruction is thought to be due to a strain effect resulting from incorporated Bi. Both the Bi line and the c(4×4) structures disappear after further annealing and the remaining Bi concentration was below the detection limit of secondary ion mass spectroscopy.

The Lack of a Relationship between Bitterness and Resistance of Cucurbits to Red Pumpkin Beetle (Aulacophora foveicollis)

AbstractPurified cucurbitacin B and E act as feeding stimulants for the red pumpkin beetle, but on testing three pairs of isogenic bitter (Bi) and non‐bitter (bi) lines of cucumber, no relationship was found to exist between the bitter gene and the degree of damage caused by this beetle. In summer squash, both resistant and susceptible lines contain cucurbitacin at the susceptible plant growth stage (cotyledon) but there was no correlation between the quantity of total phenols, free amino acids or reducing sugars in this material and resistance. Bitter gourd, which has cucurbitacin in the cotyledons, was not preferred by the beetle.

Measured stark widths of BI, BII, BIII and Nal spectral lines

Stark widths of six spectral lines from neutral and multiple ionized boron and three spectral lines from neutral sodium spectra have been measured in a pulsed linear arc plasma. All the measurements have been done in the electron density range of 1.66 × 1023–2.55 × 2023m-3 and in the electron temperature range of 40 000-50 000 K. Some of these experimental values are compared with existing theoretical data.

Observations of bismuth and lead ionic emission lines excited from Grimm-type glow discharge plasmas with pure neon and neon-argon mixtures

Some of the ionic emission lines for Bi and Pb were investigated with pure Ne and with Ne-Ar glow discharge plasmas. These lines cannot be observed with pure Ar plasmas. However, only small variations in the emission intensities are observed on addition of Ar to a Ne plasma, whereas the emission intensities of the atomic lines for Bi and Pb are enhanced in the presence of Ar. The excitation of these Bi or Pb ionic lines may be attributed to the collisional charge-transfer reactions between Ne ions and Bi or Pb atoms.

Influence of the isoelectronic dopants and of the excitation rate on the photoluminescence of GaP:(N, Bi)

An analysis of the influence of the Bi dopant concentration on the luminescence associated to N, NN i bound excitons and also the effect of N dopant on the luminescence due to Bi bound excitons makes it possible to propose a model related to the energy transfer of excitons from the N, NN i ( i ⩾ 3) centers to the Bi centers in GaP:(N, Bi). The excitation rate dependence of the luminescence intensities of the A N , NN i , A Bi lines, and the Bi band and investigations on the time-resolved luminescence of the A Bi, A Bi-LOC lines for the GaP(N, Bi), GaP:(Bi) samples support the proposed model.