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Temperature and power dependent photoluminescence (PL) measurements were employed in order to study defects in close-space-sublimation grown polycrystalline cadmium telluride layers that had been activated with different chlorine containing compounds. The samples were either measured as-grown or after thermal treatment in an oxygen containing ambient with and without the chlorine containing compounds such as cadmium chloride, hydrochloric acid, and sodium chloride. The as-grown sample is discussed in detail, in order to then demonstrate the changes in the PL spectra induced by the postdeposition treatments. A deep level transition at 1.32 eV was observed in the as-grown sample which can be correlated with cadmium vacancies. Due to postdeposition treatments this deep level transition disappears and a broad band correlated with A-centers arises instead at about 1.43 eV. Another transition band at 1.479 eV in the as-grown sample is not influenced by any postdeposition treatment. Furthermore, by processing solar cells out of the respective samples, the PL results can be related to the solar cell parameters. [ABSTRACT FROM AUTHOR]

An approach to evaluate the microwave-detected photoconductance decay (MWPCD) is developed, which allows to extract the minority carrier lifetime as a function of the excess carrier density from a single MWPCD measurement. The method is shown to be applicable to thin (w≤200 μm) silicon wafers with low minority carrier recombination at the surfaces and bulk lifetimes in the range of about 1–100 μs. Comparison of the MWPCD results with minority carrier lifetime measurements using the quasi-steady-state photoconductance method reveals very good agreement between both types of measurement. Only when the photoconductance exceeds 30% of the dark conductivity, is a deviation observed, because then the MWPCD signal is no longer directly proportional to the excess carrier density. Minority carrier trapping is found to affect the MWPCD signal only in the tail of the measured photoconductance decay. The evaluation method is used to map the interstitial iron content with high spatial resolution, as well as to determine the minority carrier trap density. An excellent agreement between numerical simulation and measured MWPCD signal is found revealing the assumptions made for the evaluation approach to be valid. This evaluation of the MWPCD measurement is well suited to characterize silicon of low purity and low crystalline quality, which is often employed to solar cells with high spatial resolution. [ABSTRACT FROM AUTHOR]

Using molecular beams, polycrystalline CuInS2 (CIS) films were deposited on Mo-covered Si substrates. In order to investigate the influence of growth-induced strain on the optical and structural properties, detailed photoluminescence, photoreflectance and x-ray diffraction (XRD) measurements were performed. The transition energy of the free A-exciton (FXA) transition decreases with (i) decreasing thickness of the CIS layer at a constant thickness of the Mo buffer layer and (ii) increasing thickness of the Mo buffer layer at a constant CIS layer thickness. This appreciable redshift of FXA is accompanied by an increase of the energetic splittings between FXA, FXB, and FXC. When we compare theoretically predicted valence band splittings as a function of the crystal field—obtained from the calculated relative valence band energies—to our experimental values, a completely coherent picture is obtained. We also derived the structure of the conduction band as a function of crystal field, based on the theoretically expected valence band structures combined with the measured transition energies of FXA, FXB, and FXC. The XRD data show the increasing strain to occur with decreasing lattice spacings in growth direction. [ABSTRACT FROM AUTHOR]

Presents a study which investigated copper-indium (Cu-In) thin films used as precursors for the production of solar-cell absorber material via reactive annealing. Application of copper compounds in solar cell production; Bulk phases of Cu-In; Preparation of Cu-In thin films.

Focuses on the application of perturbed angular correlations (PAC) of gamma rays using indium (In) nuclear probes to study the phase formation in thin copper (Cu)-In films. Overview of the phase investigations and improvement of the PAC parameter set; Cu-In precursor characterization; Interpretation of phase formation processes.

We report on Perturbed Angular Correlation measurements in polycrystalline In2S3 samples in the temperature range from 8 K to 1000 K where two different crystallographic phases β and α occur. As probes, implanted 111In nuclei have been used. The three observed EFGs are attributed to probes residing substitutionally in the different sulfur-octahedra and -tetrahedra of β-In2S3. A strong damping between 150 K and 300 K has been attributed to EFG fluctuations following the 111In(EC)111Cd decay. The α-phase (above 680 K) is characterized by a different dynamical damping of the perturbation functions, caused by mobile In atoms. Therefore, the semiconductor In2S3 shows, in two different temperature ranges, dynamical PAC-spectra which correspond to different types of mobile charge carriers. Since 111In is a self atom in In2S3, this compound is an ideal substance to study the charge transport phenomena by the PAC technique. [ABSTRACT FROM AUTHOR]

Using 111In–111Cd perturbed angular correlations, we investigated the behaviour of In in heavily As-doped polycrystalline silicon. The nuclear In tracers were either introduced by means of grain boundary (GB) diffusion or ion implantation. We find, that the in-diffused In tracers exclusively probe GBs which give rise to a broad distribution of static quadrupole frequencies. The implanted tracers exclusively probe Si bulk material, where they encounter As-dopants during thermal annealing and form the well-known In–As complexes #1 and #2, and the previously unknown complex #4 (eQVzz=117 MHz, η=0) which involves three As atoms on nearest neighbor sites with respect to the probe. The implications of the present experiment on acceptor doping and GB probing are discussed. [ABSTRACT FROM AUTHOR]

Using Mössbauer spectroscopy with 57Fe probes and perturbed angular correlations with ion implanted 111In–111Cd nuclear tracers, we have investigated decomposition and crystallization in the bulk amorphous alloys and Zr41.2Ti13.8Cu12.5Ni8.5(57Fe)1.5Be22.5 and Zr41.2Ti13.8Cu12.5Ni10Be22.5, respectively. Mössbauer and angular correlation spectra measured during the course of isothermal annealings at typical decomposition temperatures reveal distributions of quadrupole splittings as expected for an amorphous state, but no clear signs of crystallinity. A comparison of both experiments including the measured hyperfine parameters suggests that the Fe and Cd nuclei probe subsets of local environments which are clearly distinct from each other. We conclude that the 57Fe probe has a clear sensitivity to decomposition processes whereas the 111In tracers are insensitive to these phenomena in the studied case. [ABSTRACT FROM AUTHOR]

The perturbed angular correlation of the 173 keV-247 keV γ-γ-cascade inCd was measured for proton-irradiated and quenched cadmium as a function of the annealing temperature. Three distinct defect configurations were identified by the quadrupole interaction frequencies: D with $$\left| {v_Q } \right| = \left| {\frac{{eQV_{zz} }}{h}} \right| = 103\left( 3 \right)$$ MHz visible for annealing temperatures T between 110 K and 130 K, D with | v| between 4 and 22 MHz observed for 110 K ≦ T≦150 K, and D with no electric field gradient. The fraction D is seen from 77 K to room temperature. The defect configurations D and D are of vacancy type. It is argued that D originates from simple defect structures (probably mono- or divacancies) while D is attributed to small vacancy agglomerates. Because of its larger stability, D is ascribed to defect loops. The experiment shows clearly that a vacancy-like defect is mobile in recovery stage III in Cd. [ABSTRACT FROM AUTHOR]

Shippers and carriers are constantly in need of substantial amounts of transportation cost information: shippers are looking for the most economical means of moving freight; carriers need information to determine rates that attract or retain business. The model presented in this paper calculates the costs associated with shipping by barge via the Inland Waterways System. It does so with great improvements in time, money and accuracy over a previously used manual method. [ABSTRACT FROM AUTHOR]

A new apparatus is described which permits pure cultivation of 110 l amounts of phototrophic organisms. Some data are given to prove its utility for mass production (kilogram amounts) of algae and photosynthetic bacteria. [ABSTRACT FROM AUTHOR]

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A correction to the article "Detailed Analysis of the Microwave-Detected Photoconductance Decay in Crystalline Silicon," by K. Lauer and colleagues, published in the 2008 issue, is presented.

We demonstrate the direct heteroepitaxial growth of the quaternary semiconductor CuIn[sub (1-x)]Ga[sub x]S[sub 2] on Si(111) substrates by means of molecular-beam epitaxy. Using Rutherford backscattering, x-ray diffraction, transmission electron microscopy, and photoreflectance, samples of various Ga contents, x, were characterized in detail. Epitaxial growth was achieved in the whole compositional range and perfect lattice match between the epitaxial layer and substrate was obtained for x≈0.5. The epitaxial layers show the coexistence of bulk chalcopyrite and metastable CuAu-type cation ordering. Photoreflectance data reveal a linear increase of the fundamental band gap with increasing Ga content. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate the direct heteroepitaxial growth of the ternary semiconductor CuGaS[sub 2] on Si(111) substrates by means of molecular beam epitaxy. X-ray diffraction data prove the epitaxial growth of the CuGaS[sub 2] films in the highly ordered chalcopyrite structure. Using photoluminescence, we are able to detect strong excitonic emissions up to room temperature, while photocurrent spectra reveal the A, B, and C valence-to-conduction-band transitions as they are typical for the tetragonal chalcopyrite structure. [ABSTRACT FROM AUTHOR]

We demonstrate the direct heteroepitaxial growth of the chalcopyrite semiconductor CuInS2 on silicon (111) substrates by means of three-source molecular beam epitaxy. The pretreatment of the silicon wafers includes sulphur termination which leads to a new surface structure defining the starting condition for successful epitaxy. All stages of the growth process were controlled in situ using Auger electron spectroscopy and low energy electron diffraction. Furthermore, the epitaxial layers were characterized by means of x-ray diffraction methods and by Rutherford backscattering spectrometry including channeling. X-ray rocking curves showed a typical width of 0.2° while the minimum yield due to the channeling effect was found to be 56%. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A method for the simultaneous automatic preparation of 6 paper chromatograms is described. The simple apparatus facilitates the handling, especially of temperature sensitive and radioactive solutions. [ABSTRACT FROM AUTHOR]

Using three-source molecular beam epitaxy, we demonstrate the direct heteroepitaxial growth of the direct semiconductor CuInS[sub 2] on silicon (001) substrates. The pretreatment of the silicon wafers includes a high-temperature exposure to the sulphur beam which leads to an ideal (1×1) sulphur-terminated surface defining the starting condition for successful epitaxy. All stages of the growth process were controlled in situ using Auger electron spectroscopy and low energy electron diffraction. Furthermore, the epitaxial layers were characterized by means of x-ray diffraction methods and by transmission electron microscopy. It is shown that the CuInS[sub 2] epilayers grow with a tetragonal structure which is clearly distinct from chalcopyrite. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]