CONTACT INTERFACES

Th Elastic Properties and Adherence of Thin Flhiis and Cgatlims on Cemmlo Substrates - Debra l, Joslln (Department of Materials Science and Engineering, University of Tennessee-Knoxville, Knoxville, Tennessee 37966-2200) 

The objective of this research Is the examination of the effects of ion bombardment on the structure of thin ceramic films on ceramic substrates. The material combinations will Include oxide films that have (a) no solid solubility, (b) limited solid solubility, and (c) complete solid solubility with the substrate material (also an oxide). Techniques for determination of elastic and plastic properties of thin films or coatings on ceramic substrates and for the determination of the strength of the bond between the film and substrate, which are currently being developed, will be used to determine the hardness, elastic modulus, and adherence of each material combint tion. The main testing techniques will be the ultra-low load micro-indentation tester (Nanaindenter) and thermal cycling tests. 

Implantation and analysis were performed on two specimens during the first part of this report period (1) oxygen implanted into a chromium layer on sapphire, and (2) chromium implanted into a Ti.Oy/AlgOg multilayered structure on silicon. 

For (1), it Is desired that the implanted oxygen come to rest at the Cr/Aip., Interface, so that the possibility of reaction to form Cr O., exists. The chromium layers deposited for system (1) were analyzed before implantation using Rutherford Backscattering Spectroscopy (RBS). From the analysis, It is known that the Cr layer already contains a small amount of oxide which may affect the implantation. After implantation with 80 keV oxygen at a fluonce of 1 x 10 ions/cm RBS analysis showed no mixing effects. The Cr film will now be etched from this sample, and both the implanted and unimplanted areas will be reanalyzed using RBS to determine which area contains more chromium. Transmission Electron Microscopy (TEM) analysis will also be performed. 

For (2), it is desired that the implanted chromium come to rest at a position far beyond the first four layers of the specimen (distance greater than 100 nm). A multilayer sample of crystalline Ti Oy and amorphous Alj,0., on a silicon sulbstrate was obtained for use. in this study. The sample was made up of 38 repetitions of alternating layers of crystalline Ti,Oy and amorphous Al,03. In the implanted area, the thickness of each layer was approximately 190 nm. The sample was implanted with 350 KeV Cr at room temperature, While RBS did not detect the presence of the multilayered structure either before or after implantation, TEM cross-section samples of the as lmp anteci specimen did show that a multilayer was Indeed present. From this sample, some evidence of Implantation damage could be discerned. 

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Fig. 13. Schematic of a microscopic view of contact interface where constriction resistance originates in the constriction of current flow through the touching metallic junctions (a spots) of the mating surfaces. The arrows and lines indicate the flow of current.

Because a length of metal associated with the connector contact is ordinarily in the path between the contact end to which a wire is terminated and the contact interface, its resistance (bulk resistance) must be added to contact resistance when considering the connector as a circuit element. This overall resistance is sometimes erroneously called contact resistance. 

Each subunit contributes a tower helix (residues 262 to 278) to the sub-unit-subunit contact interface in glycogen phosphorylase. In the phosphorylase dimer, the tower helices extend from their respective subunits and pack against each other in an antiparallel manner. 

Grenzenlinie,/. boundary line, grenzenlos, a. unlimited, botmdless, infinite. Grenz-fall, m. limiting case borderline case, -fl che, /, boundary surface, surface of contact, interface. 

The boundary conditions are given by specifying the panicle currents at the boundaries. Holes can be injected into the polymer by thermionic emission and tunneling [32]. Holes in the polymer at the contact interface can also fall bach into the metal, a process usually called interlace recombination. Interface recombination is the time-reversed process of thermionic emission. At thermodynamic equilibrium the rates for these two time-reversed processes are the same by detailed balance. Thus, there are three current components to the hole current at a contact thermionic emission, a backflowing interface recombination current that is the time-reversed process of thermionic emission, and tunneling. Specifically, lake the contact at Jt=0 as the hole injecting contact and consider the hole current density at this contact. 

Since, in both these reactions (i.e. KI or Rbl and Agl), product formation occurs on both sides of the original contact interface, it is believed that there is migration of both alkali metal and silver ions across the barrier layer. Alkali metal movement is identified as rate limiting and the relatively slower reaction of the rubidium salt is ascribed to the larger size and correspondingly slower movement of Rb+. The measured values of E are not those for cation diffusion alone, but include a contribution from... 

ZnCl2, aq denotes an aqueous solution of ZnClj). Vertical lines in the scheme denote the areas of contact (interfaces) between two adjacent conductors. 

The low efficiencies could be due to lack of intimate contact (interface) between the sensitizer (which is hydrophilic) and the spirobifluorene (which is hydrophobic). Moreover, the surface charge also plays a significant role in the regeneration of the dye by the electrolyte.98 In an effort to reduce the charge of the sensitizer and improve the interfacial properties between the surface-bound sensitizer and the spirobifluorene hole-carrier, amphiphilic heteroleptic ruthenium(II) complexes ((48)-(53)) have been used as sensitizers. These complexes show excellent stability and good interfacial properties with hole-transport materials, resulting in improved efficiencies for the solar cells. 

The interface at which the interfacial charge,, is zero is called the interface of zero charge or the zero charge interface. The inner potential difference across the zero charge interface is determined by the interfacial dipole only, thus, it is characteristic of the contacting interface of the two phases as indicated in Eqn. 4-6 ... 

Fig. 6-13. Potential created at a contact interface between metal M and a<)ueoii8 solution S (a) before contact, (b) after contact, (c) charge-induced and dipole-induced potentials X = surface potential at free surfaces gdip = potential due to an interfadal dipole gun = potential due to an interfadal charge = potential across an interfadal compact layer.

Avachat US, Dheere NG (2006) Preparation and characterization of transparent conducting ZnTe Cu back contact interface layer for CdS/CdTe solar cell for photoelectrochemical application. J Vac Sci Technol A 24 1664-1667... 

Figure 1. (a) X-ray crystal structure of horse-heart ferricytochrome c.8 All protein atoms are shown in the C.-P.-K. form, while the heme group is shown in the stick form. All Arg and Lys residues are colored blue, while Glu and Asp are colored in red, to contrast the destribution of the most ionizable side chains, (b) The X-ray crystal structure of horse heart ferricytochrome c in complex with horse cytochrome c peroxidase (cep).9 The peroxidase is shown as a molecular surface model, with blue regions depicting positive and red representing negative electrostatic potential. Note the cluster of negative potential on ccp that surrounds the contact interface. 

For the case in Fig. 2.17, the tangential velocities of the colliding spheres are not equal to each other before the impact, which would most likely lead to a sliding on the contact interface. Consider the simple case of two colliding spheres without relative rotation. To... 

A thin i-ZnO (intrinsic ZnO) layer is often used as a buffer layer in CIS/CIGS solar cells, between the absorber part of the cell and the front TCO. The role of this resistive (buffer) layer is mainly to provoke suitable field-assisted hole collection at the contact interface, reducing, thus, the recombination rate at and near the ZnO/CIS or ZnO/CIGS interface (see also Chap. 9). 

A gross slip condition, where sliding is induced within the whole contact interface after a preliminary partial slip stage. This condition is associated to trapezoidal tangential load/displacement loops. The plateau value of the tangential load provides a measurement of the coefficient of friction, //. = Q /P, where Q and P are the plateau value of the tangential load and the imposed normal load respectively. 

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