Search

Thin-film sensors based on evaporated layers of pure and doped chalcogenide glasses with thickness in the nanometer range have been developed. The layers have been investigated by means of scanning electron microscopy and AES spectroscopy. Electrochemical characterization has been performed by potentiometric measurements. The heavy-metal sensors showed high sensitivity towards Ag+ and Cu2+ ions, down to the concentration range of 10−6 mol/l, short response time and good selectivity to interfering ions. The electrochemical performance of sensors for Pb2+ ions, however, is not at the same level. The reasons for this difference have been established.

The ion-induced structural changes in evaporated layers of a-As 2 S 3 under the action of Ga + ions with energy 19 keV and doses between 10 12 and 10 15 ions cm −2 are studied. It is shown that the solubility of the evaporated layers of As 2 S 3 increases under Ga + ion irradiation at a dose up to 10 14 ions/cm 2 and decreases at a dose of more than 10 14 ions/cm 2 . It is found that the ion-induced changes in the solubility of the layers occur at a depth greater than the penetration range calculated by the TRIM code of the Ga + ions. It is found that the effect of Ga + ions irradiation on As 2 S 3 layers is similar to that observed with Au + ions. The ion-induced changes in the solubility of As 2 S 3 layers irradiated with Au + , Ga + (19 keV) and Au + , Pd + (500 keV) are followed. It is established that the mass and the energy of the ions are a predominant factor for ion-induced phenomena. The results obtained provide the data for understanding ion-induced phenomena in evaporated layers of chalcogenide glasses. The results are promising for nanotechnologies, nonconventional optics, etc.

The possibilities of using photodoped chalcogenide layers evaporated on standard Si/SiO 2 /Si 3 N 4 substrates as Cu ion sensitive membranes for ion selective field-effect transistors (ISFETs) are investigated. The optimal concentrations of the doped metals (Cu, Ag) are determined providing linearity of some properties at concentrations 10 −1 –10 −6 M. The membrane samples show a selectivity in the presence of Na, less in the presence of Fe, Zn, Pb, Cr and lack of selectivity to Ag. The depth distribution of Cu and Ag in chalcogenide layer is measured by atomic electron spectroscopy. The effect of the depth profiles of the dopants on the electrochemical properties of the Si/SiO 2 /Si 3 N 4 /Cr/Cu x Ag y (As 2 S 3 ) 100−( x + y ) membranes are measured. The results obtained indicate that ISFETs are possible.

The possibilities of using thin layers of As 2 S 3 and AgI as ion sensitive membranes for ion selective field-effect transistors (ISFETs) are investigated. The thin films have been prepared by vacuum deposition on static and rotating substrates. The As 2 S 3 layers were additionally doped with silver. The influence of the type of substrates and preparation conditions on electrochemical properties of the layers was studied. Electrochemical measurements revealed a reasonable sensitivity of chalcogenide and halide layers to silver and iodide ions, respectively. The near Nernstian behavior of sensitivity of As 2 S 3 layers to Ag + ions and of AgI layers to I − ions is observed. The results obtained are promising for the development of ISFETs.

Thin-film sensors based upon evaporated layers of chalcogenide glasses and sensitive to silver, copper, and lead ions have been developed. The optimal contents of the membranes were established and the electrochemical characteristics were investigated. It was shown that the sensitivity, detection limit, response time, reproducibility, and selectivity to interfering ions are in good agreement with those for traditional bulk ion-selective electrodes.

The photo- and thermally induced changes in the dissolution rate of a-As x S 1−x and Ag/As x S 1−x evaporated layers are followed at different temperatures and As contents (x). The activation energy for thermoinduced changes as dependent on x coincides with that of the kinematic viscosity suggesting a similar mechanism. The activation energies for photostimulated changes coincide with the activation energies of changes in the intensity of Raman spectra of AsS 3 and S 2 AsAsS 2 . Comparison of the activation energies for photoinduced relaxation with the dissolution rate and the sensitivity as dependent on x shows that AsS 3 structures are responsible for the photostructural changes. The photostructural changes in As x S 1−x are the rate determining factor during the photodoping with Ag.

The ion induced structural changes in evaporated layers of a-As 2 S 3 under the action of Au + ions with energies in the range of 6–19 keV and beam fluxes between 10 12 to 10 15 ions\cm 2 are studied. It is shown that the solubility of the evaporated layers of As 2 S 3 increases under Au + ions irradiation at a fluence up to 10 14 ions\cm 2 and decreases at a fluence of more than 10 14 ions\cm 2 . Thus, a positive or a negative ion resists with high resolution can be developed depending on the irradiation dose. Ion-induced changes in the solubility of the layers occur at a depth greater than the penetration range calculated by the TRIM code of the Au + ions. XPS study supports the TRIM results and provides the data for understanding this phenomenon.

The changes in the solubility of a-As2S3 evaporated layers under Au+ ion irradiation occur in a greater depth than the ion penetration range calculated by the TRIM program. An XPS analysis was made to elucidate the phenomenon. Surface and depth distributions of implanted ions, as well of As and S were examined and it was established that under implantation the binding energy (BE) for the Au 4f7\2 peak shifts by 0.65 eV when compared to the sputtered Au standard (83.9 eV). Increase in the concentration of implanted Au+ ions led to the appearance of peaks at both 84.55 and 85.35 eV. It was found out that the shift of BE of S 2p depended on the concentration of implanted Au+ ions, while the BE of As 3d was nearly the same. On the basis of these results the effects of Au irradiation are discussed.

In designing the versioning facility in Ode, a few but semantically sound and powerful concepts are introduced that allow implementation of a wide variety of paradigms. Some of the salient features of these versioning facilities are the following: (1) object versioning is orthogonal to type; (2) reference to an object can be bound statically to a specific version of the object or dynamically to whatever is its latest version; and (3) both temporal as well as derived-from relationships between versions of an object are maintained automatically. These facilities have been incorporated seamlessly into Ode's database programming language, O++. The new language constructs are powerful enough to make O++ a suitable platform for implementing a variety of versioning paradigms and application-specific systems. >

This article gives a critical review of published results mainly on systems of the type (metal/chalcogenide glass), correlating these with phenomena occurring in (metal/photosensitive substance) systems. It is argued that the striking differences in the reaction curves of different pairs of (metal/photosensitive substance) are due only to the inherently different properties of the products of the ‘tarnishing’ reaction that occurs in each case. It is emphasized that the driving force of all the phenomena observed is actually this tarnishing reaction which occurs on illumination.

Most amorphous substances change their physical and chemical properties on illumination. The photosensitive solubility permits the use of amorphous arsenic sulphide as evaporated photoresist. An appropriate solvent was found which fully dissolves the exposed areas without affecting the unexposed ones. Thus extremely thin layers of evaporated amorphous arsenic sulphide can be used as sensitive photoresist with high resolution for the production of chromium masks and sensitized offset printing plates.

The evolution of diffracted power is followed in real time during the recording of simple holographic gratings in Ag-As2S3 sandwich structures by means of a He-Ne laser. Measurements are made of the kinetics in several diffraction orders in which the holographic exposure is combined with uniform pre- or post-illumination of the sample. The results obtained suggest the presence of two recording mechanisms: one, predominantly phase, due to photodiffusion of silver into the sulphide layer and another, mainly amplitude, due to the bleaching of the silver deposit.

This paper describes the problems posed by running the UNIX™ operating system on multiprocessors, as well as some solutions. The resulting systems function like their single-processor counterparts but yield 70 percent better throughput for two-processor configurations. Closely coupled multiprocessor UNIX systems currently run on IBM and AT&T Technologies hardware, but the implementation described in this paper ports to other architectures as well, and the design is not limited to two-processor configurations.

Carefully controlled conditions of evaporation allow the preparation of epitaxial layers of pure AgBr. The temperature dependence of the conductivity of layers with varying thickness is measured. This in principle makes possible the splitting of the conductance into surface and bulk components. The bulk conductivity of the layers is found to be practically identical with that of pure large single crystals of AgBr, which until now has not been observed. For the first time considerable surface conductance is directly observed not only for {111} but for {200} layers too. All parameters characterizing the Frenkel disorder in the subsurface region are evaluated from 150 °C down to room temperature. Dunne Epitaxieschichten aus reinem Silberbromid werden unter sorgfaltig kontrollierten Bedingungen hergestellt. Die Temperaturabhangigkeit der Leitfahigkeit wird fur verschiedene Schichtdicken gemessen. Dies erlaubt im Prinzip, die Leitfahigkeit in eine Oberflachen- und eine Volumenkomponente zu trennen. Es wird gefunden, das die Volumenleitfahigkeit der Schichten mit der von grosen, reinen Silberbromideinkristallen identisch ist, was bis jetzt noch nicht beobachtet wurde. Zum ersten Mal wird eine betrachtliche Oberflachenleitfahigkeit nicht nur fur die {111}-sondern auch fur die {200}-Schichten direkt festgestellt. Alle Parameter, die die Frenkel-Fehlordnung in den oberflachennahen Gebieten charakterisieren, werden in einem Temperaturintervall von 150 °C bis Zimmertemperatur ausgewertet.

Typical ensitization procedures have been applied to change ub tantially the photographic respon e of thin evaporated layers of pure silver bromide, which if untreated build up no surface image at all, but on ensitization yield normal characteri tic curves. The vacuum deposition of invisible but developable silver speck on the surface of untre:lled samples creates direct positive imaging due to bleaching by photoexcited holes. The dark conductance of layers with varied thickness subjected to different sensitization procedures has been followed. The data obtained allows an e timation of the urface potential which for pure ilver bromide, in accordance with earlier observations, is found to repel electrons from the surface. It has been now shown that the sign of the surface potential relative to the bulk is not changed by the ensitization proce s, remaining always negative independently whether the layer builds up on exposure negative, positive or no urface image at all. The variations in the value o...