Boron In Samples Research Articles

Solution growth and properties of octadecyl hydrogen succinate crystals for ultrasoft X-ray spectroscopy

Single crystals of octadecyl hydrogen succinate (OHS, 2d = 90.94 AA) up to 70 * 30 * 1.0 mm3 in size have been grown by the solution cooling method. The crystal data and X-ray-diffraction characteristic parameters of OHS were determined. The results of measuring normal samples of carbon and boron using OHS in an electron probe spectrometer are reported and compared with those obtained using the soap film 'pseudo-crystal' of lead stearate (STE).

Spectroscopic investigation of lattice vacancies in hexaborides

AbstractRaman microprobe and diffuse‐reflectance Fourier transform IR spectra of a series of seven metal hexaborides show that the basic cubic symmetry of these systems is lowered owing to lattice vacancies. The resulting wave vector is oriented along the C4 axis of the first Brillouin zone. Studies of enriched boron samples indicate that the vacancies in the B6 structure are located at boron sites.

Phosphorus diffusion in isoconcentration backgrounds under inert conditions in silicon

The diffusivity of phosphorus in isoconcentration backgrounds under inert conditions in silicon is investigated. Phosphorus is implanted at low dose into silicon wafers that are constantly doped with arsenic and boron. These samples are annealed to remove any damage. Secondary ion mass spectroscopy (SIMS) measurements are taken of these as-implanted samples. The wafers are then diffused at both 900 and 1100 °C for 60 and 30 min, respectively. The wafer profiles are then measured using SIMS. The diffusivity of phosphorus is measured for five different dopant concentrations. The results show that a double-negative interstitial component of phosphorus is needed to adequately model the data. Also, the heavily doped boron sample shows a significantly retarded diffusivity at 1100 °C which suggests phosphorus-boron pairing or significant strain effects on diffusion.

Comparison of Boron Profiles by the Spreading Resistance Profile and the Secondary Ion Mass Spectrometry Techniques

This paper compares boron profiles measured by spreading resistance and SIMS techniques. The boron samples were prepared under conditions similar to an implanted‐diffused base of an n‐p‐n transistor. Good agreements between the two methods were obtained. Effects of sample preparation on spreading resistance measurements are discussed also.

Preferential sputtering of B studied by low-energy ion scattering using the dual-isotope surface composition (DISC) method

Low-Energy Ion Scattering (LEIS) is a well known technique for obtaining information about the outermost layer of a surface. The Dual-Isotope Surface Composition (DISC) method for quantification of atomic compositions, which does not require the use of calibration samples, is presented in this article. This method is used to study the preferential sputtering of a natural boron sample (20% 10 B and 80% 11 B). Using 3.5 keV 4 He + ions the surface concentration of 10 B is found to be (16 ± 2)%.

Absolute neutron counting based on B-10 alpha-gamma coincidence methods

A new absolute counter for thermal and cold neutron beams has been built, based on the counting of prompt gamma rays from a boron target that totally absorbs the impinging neutrons. The system can be calibrated by two independent methods without reference to either the boron sample mass or the 10B reaction cross section. Both calibration methods are potentially capable of approaching the accuracy level of ±0.1% (1 σ). In the calibration experiments, the totally absorbing boron target is replaced by a thin 10B target, and either (1) alpha-gamma coincidence counting or (2) calibration by standard alpha sources is used to derive the efficiency of the gamma counter per neutron impinging on the totally absorbing target. Systematic corrections and estimated residual uncertainties are discussed.

Formula omitted] Structure of boron enriched Si(111) surfaces investigated by Auger, LEED and scanning tunneling microscopy

Boron enrichment of the Si(111) surface was realized by long time annealing at 900 ° C of highly boron doped Si samples ( p≈10 19cm −3). Boron Auger peak (179 eV) and LEED patterns of boron induced 3 × 3 R30° reconstructions could be detected after such a treatment. Preparation and characterization of the samples by averaging surface sensitive techniques have been performed in an UHV chamber equipped with a STM unit. High resolution STM images of the 3 structure have been obtained. Simultaneous imaging in both polarities, thus probing filled or empty surface states, allowed us to observe spectroscopic effects which are discussed in this paper. On the basis of our data, a modification of the T 4 adatom model of the 3 structure is proposed.

Analysis of lithium and boron by inductively coupled plasma mass spectrometry

Lithium and boron are two elements for which comprehensive trace element analysis is required. The dissolution methods for these materials are suspected of causing losses of certain elements, either by the formation of volatiles or by precipitation. The purpose of this paper is to demonstrate that acceptable accuracy and precision can be obtained for the determination of trace elements in lithium nitrate and boric acid solutions, using inductively coupled plasma mass spectrometry (ICP-MS) in order to assess trace element losses from the dissolution of matrix materials at some later date. Accuracy and precision have been determined from recoveries of the elements from a spiked lithium nitrate sample and by the analysis of a well characterised boron sample. Three dissolution techniques were assessed for the analysis of boron by comparison with the direct analysis of the solid sample. An assessment of the matrix effects from both of the materials is presented. Some discussion on the analytical methodology, including the use of indium as internal standard is included.

The crystal structure and density of β-rhombohedral boron

The crystal structure of three different samples of melt-grown β-rhombohedral boron has been reinvestigated. There are 20 different symmetry-equivalent atomic positions in the unit cell, four of which have not been previously reported. Six of the 20 are partially occupied. The hexagonal unit cell contains a total of 320.1 boron atoms as determined from the electron density. This gives an X-ray-predicted crystal density of 2.333(5) g/cm 3 compared to a pycnometric value of 2.333(2) g/cm 3. There are local density variations with the large unit cell associated with the partially occupied sites.

Prompt gamma as a fluence rate monitor in neutron beam experiments

An accurate measurement of the neutron lifetime requires a determination of neutron fluence rate to an accuracy of a few tenths of a percent. The10B(n,α)7 Li reaction offers the possibility of achieving this uncertainty. The thermal cross section is large and its departure from 1/v behavior is about 3 parts in 10000. The principal alpha branch is to the first excited state of7Li which then decays by emission of a 478 keV gamma ray. The measurement of the gamma branch can be made with boron samples that totally absorb thermal neutrons, allowing greater sensitivity and eliminating the uncertainty of target thickness. The absolute efficiency of the gamma detector can be determined by an alpha-gamma coincidence technique. Preliminary investigations of this method are presented with a discussion of the problems that must be overcome to achieve the desired uncertainty.

Determination of oxygen in the production of nitrides by means of neutron activation

A procedure is described for the determination of oxygen impurities in ultradisperse and dense samples of titanium, aluminium, niobium, boron and silicon nitrides using the nuclear reaction 16O(n, p) 16N. The samples are placed in a sealed titanium dish and irradiated with 14 MeV neutrons produced in a neutron generator. The activity of the 16N produced is measured by 4–8 MeV γ emission in a scintillation γ spectrometer. The oxygen content to be determined was from n × 10 −1 mass % to n × 10 mass % with a relative standard deviation of 10% and 2% respectively. The results of the nitride analysis are presented.

Determination of Trace Elements in Boron by Instrumental Photon Activation Analysis

An instrumental photon activation analysis has been developed for the determination of trace elements in boron samples. A simultaneous irradiation of the sample and multielement standards with 30MeV bremsstrahlung produced by a linear electron accelerator for 2-3 hours was applied to measure levels for up to 28 elements nondestructively with practical limits of detection ranging from 0.02 to 10μg. Degrees of inter-element interferences were evaluated. Analytical results for boron samples are presented.

Megavolt Bioron and Arsenic Implantation into Silicon

ABSTRACTFormation of buried p-type and n-type layers in (100) silicon has been accomplished by implanting with 4 MeV boron and 11 MeV arsenic ions respectively. The projected range (Rp) of 4 MeV boron is 5.2 microns with a straggle (ΔRp) of .2 microns. The 11 MeV arsenic implant has a Rp of 4.37 microns with a ΔRp of .37 microns. The 4 MeV boron implant was carried out to a dose of l×1015/ cm2 while the 11 MeV arsenic implant dose was 1.9×1015/ cm2. For both dopants the target holder could be cooled with either liquid nitrogen (LN) or flowing room temperature water (RT). Buried amorphous regions are seen by cross sectional transmission electron microscopy (XTEM) for both boron and arsenic when LN cooling is used. Arsenic shows a buried amorphous region for the RT case as well. The extent of the buried amorphous regions are compared with the energy deposited into nuclear stopping as determined by computer simulation. Threshold levels are determined for the creation of these buried amorphous regions. The boron samples were annealed for 30 minutes at 900°C in a nitrogen ambient, and XTEM shows no residual damage for both cooling conditions. The arsenic samples underwent a two step annealing procedure; 545°C for 16 hours followed by a 945°C step for 15 minutes. Regions containing dislocation networks are observed by XTEM for both cooling conditions.The 4 MeV implanted boron buried layer was applied to an NMOS process. Transistors fabricated above the p-type buried layer show channel mobility, threshold voltage, and sub-threshold leakage which are indistinguishable from transistors fabricated without the buried layer. Vertical npn bipolar transistors have been fabricated using the 11 MeV arsenic buried layer to form the collector. Electrical characteristics from both these devices indicate that megavolt ion implantation can be applied to silicon for active device geometries.

Boron isotopic composition of fumarolic condensates from some volcanoes in Japanese island arcs

Boron samples from 40 fumarolic condensates from volcanoes in the Ryukyu arc (Satsuma Iwo-jima and Shiratori Iwo-yama) and the North-east Japan arc (Usu-shinzan, Showa-shinzan, Esan and Issaikyo-yama) all have 11B 10B ratios close to 4.07. Higher values, from 4.09 to 4.13, were only observed in condensates from volcanoes in the southernmost end of the North-east Japan arc (Nasu-dake), the northern part of the Izu-Bonin arc (Hakone), and the North Mariana arc (Ogasawara Iwo-jima). These higher values suggest geological interaction of the magmas with sea-water enriched in 11B.

Excited states of sputtered molecules

We present some observations of the N 2 and O 2 molecular spectra induced by ion impact on solids. The N 2 spectra are due to bombardment of a nitrogen implanted silicon sample. The O 2 spectrum is from Ar + bombardment of a boron sample with adsorbed oxygen. The nitrogen spectrum shows rotational but not vibrational excitation. A model for its formation is proposed based on surface recombination followed by vibrational deactivation and ejection. The oxygen spectrum appears to contain fragments of the c 1 Σ u −→X 3 Σ g − Herzberg II band system and exhibits high vibrational but no rotational excitation.

Preparation and study of the electrical properties of n-type boron and SiB alloys with a high boron concentration

We obtained n-type samples of boron and BSi alloys with a high boron concentration by chemical vapour deposition. The experimental growth conditions are described. The temperature dependences of the electrical conductivity and of the thermoelectric power of these samples are given. The results show that the n-type character of the samples disappears in the high temperature range. To explain this anomaly, we propose a sketch for the density of states in the band gap.

The effect of impurities on the mechanical properties of zone-melted boron

The effect of the impurities hydrogen, oxygen and nitrogen on the mechanical properties of crystals of β rhombohedral boron obtained by zone melting pressed powder samples with a binder content (boric acid) ranging from 0 to 18 wt.% was studied using a technique in which a continuous-loading indenter records the load on the pyramidal indenter versus the depth of indentation. An increase in the hydrogen content and decreases in the amounts of oxygen and nitrogen in the solidified boron samples cause a decrease in the tendency to twin, an increase in the microhardness of 6% and an increase in the energy of deformation of 12% when the load on the indenter is 2 N. The approximate size of the twins is 0.5 μm. The values of Young's modulus and the effective surface energy of β rhombohedral boron were estimated.

Determination of homogeneity of standard materials by ion microscopy

Secondary-ion microanalysis is used to investigate the homogeneity (at the microlevel) of a number of standard reference materials. High mass-resolution measurements are accomplished with a CAMECA IMS-300 ion microscope/ion microprobe equipped with an electrostatic analyser. By use of a 5.5-keV16O2 + primary ion beam with approximately 1μA intensity the following materials were investigated: NBS-SRM copper-base alloys, low-alloy steels and zinc-base alloys, and Aluminium Pechiney Al-Si-Cu, Al-Cu and Al-Mn alloys. The sampling-constant concept was applied in order to evaluate the applicability of the reference materials for micro-probe analysis, and other microanalytical techniques. The degree of heterogeneity was estimated and the number of replicate analyses required for achieving 5 and 10% precision were calculated. The results show that care must be taken when using these standards for calibration work in SIMS and other microsampling techniques, since heterogeneity on the microscale is proven for a number of elements. The technique was also applied to the determination of the homogeneity of standard samples of boron in zirconium metal from the Bureau of Reference Materials of the EEC.

Higher borides of cobalt, manganese and tungsten

Because of their thermophysical and elastic properties, transition metal bondes can be used as abrasives and are suitable materials for semiconductor electronics. Thus it is of interest to study the effect of doping elements on the structure formation of boron and on its physical and mechanical properties. Boron samples with high tungsten and cobalt contents prepared by melting in crucibles were studied. Data from X-ray, phase, metallographic and chemical analyses are given. New tungsten and cobalt borides were obtained and were identified as WB 12 and CoB n≈12. The values of the microhardness, the electrical resistance, the thermoelectric coefficient and the specific heat of these borides were determined. The temperature dependence of the magnetic susceptibility of CoB n≈12 was studied in the temperature range between room temperature and 400 °C.

An investigation of the boron electron structure by positron annihilation

The peculiarities of the electron momentum distribution were investigated by determining the angular correlation function of the 7 quanta emitted on positron annihilation in various samples of boron (polycrystals; boron films on silicon substrates) and the threshold energies of these electrons were determined.