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Metal Penetration (metal + penetration)

Distribution by Scientific Domains
Polymers and Materials Science80%

Selected Abstracts

Electronic Contact Deposition onto Organic Molecular Monolayers: Can We Detect Metal Penetration?

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Hagay Shpaisman
Abstract Using a semiconductor as the substrate to a molecular organic layer, penetration of metal contacts can be clearly identified by the study of electronic charge transport through the layer. A series of monolayers of saturated hydrocarbon molecules with varying lengths is assembled on Si or GaAs and the junctions resulting after further electronic contact is made by liquid Hg, indirect metal evaporation, and a "ready-made" metal pad are measured. In contrast to tunneling characteristics, which are ambiguous regarding contact penetration, the semiconductor surface barrier is very sensitive to any direct contact with a metal. With the organic monolayer intact, a metal,insulator,semiconductor (MIS) structure results. If metal penetrated the monolayer, the junction behaves as a metal,semiconductor (MS) structure. By comparing a molecule-free interface (MS junction) with a molecularly modified one (presumably MIS), possible metal penetration is identified. The major indicators are the semiconductor electronic transport barrier height, extracted from the junction transport characteristics, and the photovoltage. The approach does not require a series of different monolayers and data analysis is quite straightforward, helping to identify non-invasive ways to make electronic contact to soft matter. [source]

Forming Al2O3,Al Composites with Controlled Compositions by Reactive Metal Penetration of Dense Aluminosilicate Preforms

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000
William G. Fahrenholtz
Alumina,Al composites with controlled compositions containing 17 to 31 vol% Al were formed by reactive metal penetration (RMP) of molten Al into dense aluminosilicate preforms. A reaction model has been developed to accurately predict composite Al content from the SiO2:Al2O3 ratio of the preform. The model was tested and validated by comparing predicted composite compositions to those measured for RMP composites made from preforms of known compositions. Aluminosilicate preforms containing 28.1, 39.0, and 54.1 wt% SiO2 were reacted with Al to produce composites with 17, 25, and 31 vol% Al, respectively. These values compare favorably to Al contents of 17.7, 22.7, and 28.6 vol% Al predicted using the reaction model. The differences between predicted and measured values are attributed to the presence of porosity and Si in the composites, as well as impurities in the SiO2 glass phase and porosity in the preforms, none of which is specifically accounted for in the reaction model. [source]

Electronic Contact Deposition onto Organic Molecular Monolayers: Can We Detect Metal Penetration?

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Hagay Shpaisman
Abstract Using a semiconductor as the substrate to a molecular organic layer, penetration of metal contacts can be clearly identified by the study of electronic charge transport through the layer. A series of monolayers of saturated hydrocarbon molecules with varying lengths is assembled on Si or GaAs and the junctions resulting after further electronic contact is made by liquid Hg, indirect metal evaporation, and a "ready-made" metal pad are measured. In contrast to tunneling characteristics, which are ambiguous regarding contact penetration, the semiconductor surface barrier is very sensitive to any direct contact with a metal. With the organic monolayer intact, a metal,insulator,semiconductor (MIS) structure results. If metal penetrated the monolayer, the junction behaves as a metal,semiconductor (MS) structure. By comparing a molecule-free interface (MS junction) with a molecularly modified one (presumably MIS), possible metal penetration is identified. The major indicators are the semiconductor electronic transport barrier height, extracted from the junction transport characteristics, and the photovoltage. The approach does not require a series of different monolayers and data analysis is quite straightforward, helping to identify non-invasive ways to make electronic contact to soft matter. [source]

Forming Al2O3,Al Composites with Controlled Compositions by Reactive Metal Penetration of Dense Aluminosilicate Preforms

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000
William G. Fahrenholtz
Alumina,Al composites with controlled compositions containing 17 to 31 vol% Al were formed by reactive metal penetration (RMP) of molten Al into dense aluminosilicate preforms. A reaction model has been developed to accurately predict composite Al content from the SiO2:Al2O3 ratio of the preform. The model was tested and validated by comparing predicted composite compositions to those measured for RMP composites made from preforms of known compositions. Aluminosilicate preforms containing 28.1, 39.0, and 54.1 wt% SiO2 were reacted with Al to produce composites with 17, 25, and 31 vol% Al, respectively. These values compare favorably to Al contents of 17.7, 22.7, and 28.6 vol% Al predicted using the reaction model. The differences between predicted and measured values are attributed to the presence of porosity and Si in the composites, as well as impurities in the SiO2 glass phase and porosity in the preforms, none of which is specifically accounted for in the reaction model. [source]

Influence of top layer geometries on the electronic properties of pentacene and diindenoperylene thin films

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008
M. Scharnberg
Abstract Top layers have a pronounced influence on the electronic properties of molecular organic thin films. Here, we report about the changes induced by metallic and polymeric top layers and contacts. As test structures, model systems of diindenoperylene and pentacene crystalline molecular organic thin films are used. A very sensitive radiotracer technique is introduced to study the details of metal penetration during top contact formation. The influence of temperature, evaporation time, adhesion promoter and grain size of the organic film were examined. The electric currents passing through metal top contacts were found to vary by more than a factor of three, depending on the preparation conditions of the metal contact. Furthermore, the series resistance of chemically identical contacts that only differed in the morphology of the interface were found to show pronounced asymmetric conductivity behaviour. We also show that with the help of electret top layers, based on the Teflon-AF fluropolymer, the threshold voltage of an organic field effect transistor can be tuned by several volts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]