Donald E. Mencer

Electroless deposition of amorphous Ni–Re–P alloys from acidic hypophosphite solutions

Abstract Amorphous Ni–Re–P alloys of varying composition (at.% rhenium 0.0–3.5%) were prepared using electroless deposition from acidic solutions of Ni 2+ , perrhenate, hypophosphite and succinic acid/succinate. A pH of 4.5 produced deposits more readily than other pH values. All of the alloys prepared in this study were amorphous and the crystallization temperatures of the alloys increased with increasing rhenium (decreasing phosphorus) composition. The composition of each alloy was determined using microprobe analysis and varies as a function of solution composition. The mole ratio of rhenium to nickel in the alloys is approximately one half the value for that ratio in the solution from which it is deposited.

Surface Analysis by SNMS: Femtosecond Laser Postionization of Sputtered and Laser Desorbed Atoms

This paper examines the photoionization efficiency of a femtosecond laser ionization source on several atomic species. Use of femtosecond laser ionization pulses to photoionize the desorbing flux from a sample surface is examined. Example of mass spectra produced is given using 248 nm pulse on sputtered Au. Al and Mo have widely different ionization potentials and show that 248 nm pulses are more efficient at photoionization than longer wavelengths; this is enhanced for Mo with high ionization potential. It is concluded that efficient photoionization occurs for atoms with ionization potentials low enough for two-photon ionization to occur.

Surface Mass Spectrometry of Biotinylated Self-Assembled Monolayers

Biotin and biotinylated self-assembled monolayers (SAMs) on gold have been investigated using time-of-flight secondary ion mass spectrometry, direct laser desorption, laser desorption with 193 nm photoionization of ion- and laser-desorbed species, and laser desorption with vacuum ultraviolet (VUV, 118 nm) photoionization. Our results indicate that direct laser desorption and laser desorption combined with 193 nm multiphoton ionization can detect a chromophoric molecule like biotin that is covalently bound to a SAM. However, secondary ion mass spectra were dominated by fragmentation, and ion desorption/193 nm photoionization detected no species related to biotin. The dominant features of the laser desorption/VUV mass spectra were neat and Au-complexed dimers of intact and fragmented biotinylated SAM molecules. Multiphoton and single-photon ionization of laser-desorbed neutrals from biotinylated SAMs both led to the production of ions useful for chemical analysis of the monolayer. Multiphoton ionization with ultraviolet radiation was experimentally less challenging but required a chromophore for ionization and resulted in significant fragmentation of the adsorbate. Single-photon ionization with VUV radiation was experimentally more challenging but did not require a chromophore and led to less fragmentation. X-ray photoelectron spectra indicated that the biotinylated SAM formed a disordered, 40-60 Å thick monolayer on Au. Additionally, projection photolithography with a Schwarzschild microscope was used to pattern the biotinylated SAM surface and laser desorption/photoionization was used to detect biotinylated adsorbates from the ∼10 μm sized pattern.

Prediction of alloy component oxidation order from a kinetic model using free energies of oxide formation

Described is a method based on the modified Cabrera–Mott model to predict the order of oxidation of alloy components under conditions of varying temperature and oxygen pressure.

Example of Sacrificial Unit Using Two Different Click Reactions in Coupling and Decoupling (CAD) Chemistry

An example of a specific coupling and decoupling (CAD) chemistry is described. It takes advantage of propargyl acrylate as a sacrificial unit (SU). The addition of a selected compound representing a molecular unit equipped with an azide functionality to the terminal triple bond of the SU and another compound acting as a molecular unit equipped with a thiol functionality to the conjugated double bond of the SU proceeded at very good yields. The construct containing two molecular units can be decoupled using a few different reactions and the decoupling can take place at two positions.

Electrochemical Properties Of Copper Oxide Surfaces, Buried Interfaces, And Subsurface Zones And Their Use To Characterize These Entities

Electrochemistry of oxides is an expanding area of oxide characterization. Although, interfacial characterization techniques including surface science methods have contributes substantially to our current understanding of the processes involved in the oxidation of metals and alloys. The characterization of subsurface zones and buried interfaces still remain a major challenge. Copper reactions with oxygen have been studied by high vacuum based techniques of AES, ELS, ISS, XPS. SIMS, LEED. STM, SEXAFS, HEIS and PFDMS and with optical methods, like UV-Vis-NIR, diffuse reflectance spectroscopy, FTIR and photoluminescence spectroscopes. However it has become evident that the processes that produce thermally and plasma grown oxide films on metals and alloys are electrochemical in nature and can be modeled by electrochemical concepts. Therefore, it is important that the oxide over layers, thin films and thick films be characterized by electrochemical means -with electrochemical methods, such as linear potential sweep voltammetry, cyclis voltammetry, galvanostatic reduction and coulometry which allow the identification of copper (I), copper (II) and copper (III) oxides. Interest in copper as a technologically important material needs to be met with greater understanding of the fundamental nature of copper oxide structures. In this study, the authors demonstrate the use of Linear Sweep Voltammetry (LSV) to study buried structures in the thermally grown oxide layers on copper. In particular, LSV can be used to detact reactions at buried interfaces. It also recognizes Cu 3 O 2 and the decomposition of copper oxides at the metal-oxide layers on copper. In particular, LSV can be used to detect reactions at buried interface. The two key parameters that drive oxide growth and decomposition are demonstrated to be oxygen activity and the free energies of formation of the oxides. The complex nature of the oxidation of copper, as well as other metals and alloys, will be described qualitatively using the Modified Cabrera-Mott (C-M) Model. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as electrochemical methods.

A novel use for gold diffusion barriers in studies of oxygen absorption in titanium films

The use of an intervening gold layer between a copper substrate and a titanium film is shown to be a novel method to determine the effect of oxygen absorption on the surface oxidation of titanium.