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The Ge1-yCy semiconductor alloy system offers promise as a material for use in heterostructure devices based on Si as well as other materials. We have grown Ge1-y Cy alloys by solid source molecular beam epitaxy on Si substrates. Layer thicknesses ranged from 0.01 to 3 µm, and Auger electron spectroscopy and secondary ion mass spectrometry indicated C fractions up to 3 at. %. Optical absorption in the near-infrared region indicated a shift in the energy bandgap from that of Ge which was attributed to the effects of alloying. The dependence of the bandgap on composition was consistent with linear interpolations of the Ge and C conduction band minimums. We observed a fundamental absorption edge characteristic of an indirect bandgap material. Photoluminescence spectra at 11K of thick, relaxed layers indicated single broad peaks near the expected bandgap energy.

La reduction electrochimique des trois sulfures (S 6 , S 7 et S 8 )sur une electrode d'or ou de graphite est dans l'acetonitrile et le methanol est examinee en les separant par chromatographie HPLC et en utilisant une cellule a flux

The advancement rate of mono‐ and polyatomic growth steps was measured on perfect, screw dislocation‐free cubic faces of silver single crystals during electrocrystallization of silver. For low overvoltages, a linear dependence of the rate on overvoltage was found. It was established that the advancement rate of the steps depends on the surface conditions of the crystal face and is about two times larger on a "fresh" surface than on an "aged" one. It was also found that mono‐ and polyatomic steps advance with the same rate on a fresh surface. A polyatomic step is considered as a ledge composed of monoatomic steps. The ledge spacing of this composite step was estimated. On the basis of these experimental results as well as on the experimentally determined value of the exchange current of adatoms with metal ions of the electrolyte, it is concluded that the electrolytic deposition of silver in 6M solution of silver nitrate is carried out according to the direct transfer mechanism. The value of the exchange current of the edge atoms at the steps with ions of the electrolyte was determined to be for an aged surface and for a fresh surface.

Semiconducting films of CdS are produced by the cathodic deposition of Cd on inert electrodes in the presence of dissolved S8 in dimethylsulfoxide solution. Linear potential scans and potential pulse measurements show that the first layers are formed by underpotential deposits of Cd reacting with S8 from the solution. With increasing coverage of the surface the mechanism changes to a mixed reduction of Cd and a reduction of S8 to sulfide, which forms the deposit with Cd2+ from the solution. Photoeffects are observed with deposits greater than three or four equivalent monolayers of CdS, demonstrating the n-type character of the deposits. The photocurrent spectrum of films in the micrometer range differs considerably from that of single-crystal CdS. Films produced in this way need further treatment before they could be useful as low-cost electrodes for solar cells.

Performance characteristics of electrochemical detectors for high performance liquid chromatooraphy are difficult to predict from presently avaliable information relating response to design parameters. A fiqure of merit is proposed which allows an operational comparison to be made, based upon specific response, noise and band spread. On this basis, it is shown that a meaningful comparison of an amperometric design with a coulometric design can be obtained and that, contrary to previous predictions, this coulometric type is generally superior.

Barium is determined in aqueous solution by direct injection graphite furnace atomic absorption spectrometry. NH/sub 4/NO/sub 3/ modifier eliminates seawater NaCl in a slow 1400 /sup 0/C char step. Atomization is at 2700 /sup 0/C. Detection is at 553.6 nm, and calibration is by peak area. Sensitivity is 0.2 abs s/ng (abs = absorbance unit) and is independent of matrix salinity. Detection limits are 30 pg of Ba (600 ng L/sup -1/) for 50-..mu..L sample injections of seawater and 10 pg of Ba (200 ng L/sup -1/) for freshwaters. Precision is about +/-13%. There are no spectral interferences due to calcium or Ba halides. Results of the analyses of seawater agree well with values determined by isotope dilution.

The advancement rate of mono‐ and polyatomic growth steps was measured on perfect, screw dislocation‐free cubic faces of silver single crystals during electrocrystallization of silver. For low overvoltages, a linear dependence of the rate on overvoltage was found. It was established that the advancement rate of the steps depends on the surface conditions of the crystal face and is about two times larger on a "fresh" surface than on an "aged" one. It was also found that mono‐ and polyatomic steps advance with the same rate on a fresh surface. A polyatomic step is considered as a ledge composed of monoatomic steps. The ledge spacing of this composite step was estimated. On the basis of these experimental results as well as on the experimentally determined value of the exchange current of adatoms with metal ions of the electrolyte, it is concluded that the electrolytic deposition of silver in 6M solution of silver nitrate is carried out according to the direct transfer mechanism. The value of the exchange current of the edge atoms at the steps with ions of the electrolyte was determined to be for an aged surface and for a fresh surface.