High-quality materials are critical for advances in plasmonics, especially as researchers now investigate quantum effects at the limit of single surface plasmons or exploit ultraviolet- or CMOS-compatible metals such as aluminum or copper. Unfortunately, due to inexperience with deposition methods, many plasmonics researchers deposit metals under the wrong conditions, severely limiting performance unnecessarily. This is then compounded as others follow their published procedures. In this perspective, we describe simple rules collected from the surface-science literature that allow high-quality plasmonic films of aluminum, copper, gold, and silver to be easily deposited with commonly available equipment (a thermal evaporator). Recipes are also provided so that films with optimal optical properties can be routinely obtained.

http://pubs.acs.org/doi/pdf/10.1021/ph5004237

Plasmonic Films Can Easily Be Better: Rules and Recipes

Reactive element-sulfur interaction and oxide scale adherence

A new and a radically different mechanism to account for the beneficial effects that small additions of elements such as yttrium have on the adherence of oxide scales is proposed. It has been long:known and has been reaffirmed here that indigenous impurities such as sulfur, known to be present at tramp levels (<100 ppm) within nickel and nickel-based alloys, can segregate to metal surfaces. However, here it has been disclosed that such sulfur segregation can also markedly affect the adherence of the protective oxide scale. In the absence of elements like yttrium, such segregation effects weaken the bond between the protective scale and the substrate metal. The role of the yttrium is to interact with such indigenous sulfur to form a refractory sulfide. This interaction lessens the amount of sulfur available to segregate to and concentrate at the critical scale-metal interface. Results reported here have focused on sulfur because sulfur has been long known to be a common tramp impurity in nickel and nickel-based alloys. However other elements, e.g., phosphorus, chlorine, etc., could very probably produce similar effects. The results of experiments involving Auger spectroscopy, optical, scanning electron microscopy, scanning electron microprobe, and scanning transmission electron microscopy techniques in conjunction with isothermal and cyclic oxidation testing which have led us to propose this mechanism are presented.

A Relationship between Indigenous Impurity Elements and Protective Oxide Scale Adherence Characteristics

Experiments on commercial and laboratory heats of a 5 pct Ni steel have delineated a wide range of hydrogen-induced cracking behavior. Both precracked and notched specimens were tested in 0.21 MPa H2 gas at room temperature; the microstructure and hardness were held essentially constant. One extreme of behavior was exhibited by specimens with negligible amounts of intergranular weakening due to impurity segregation; here, strain-controlled, plasticity-related cracking occurred along surfaces of maximum shear stress within the prior austenitic grains. As impurity segregation increased (due to 480 °C aging of samples with Mn and Si) increasing amounts of stress-controlled cracking occurred along prior austenite grain boundaries. The latter produced a steady decrease in the stress intensity for crack extension and the local stress for fracture of the notched bars. The mechanisms involved and the practical implications of these phenomena are discussed.

Strain controlled vs stress controlled hydrogen induced fracture in a quenched and tempered steel

The Segregation Behavior of Sulfur, Oxygen and Phosphorus at the (100) Surface of Iron Single Crystal

The Growth Process of Oxide Layers in the Initial Stage of Oxidation of 80Ni–20Cr Alloy

The mechanism by which ODS alloys are provided with excellent oxidation resistance remains still ambiguous. The ambiguity originates from a wide variety of scale features: pores, composition, stress etc. We used Al2O3 coating film prepared under a same condition in order to avoid the ambiguity and in addition to obtain fundamental information for the development of ceramic coating technique. This work was made on the basis of the following five models. I. Dispersed oxide suppresses the spalling of Al2O3 film through trapping a detrimental element S. II. ODS alloys form a diffusion barrier enriched in Y at the Al2O3 film/alloy interface and suppress the penetration of alloying elements into the film. III. The above barrier acts as an adhesive of Al2O3 to the substrate alloy. IV. Incorporation of Y into the Al2O3 film retards the diffusion of alloying elements within the film. V. The above incorporation of Y suppresses the spalling of Al2O3 film by increasing the plasticity of the film. We examined these models directly or by simulation experiment using Y2O3 undercoat as a barrier and an Al2O3 coating film doped with Y2O3. The following conclusions are reached: (1) Model I is the most important for suppressing the spalling of Al2O3 film. (2) Models II and IV have also remarkable importance for diffusion retardation. (3) Models III and V have minor importance.

Kazuyoshi Nii

Papers

The Segregation Behavior of Sulfur, Oxygen and Phosphorus at the (100) Surface of Iron Single Crystal

The Growth Process of Oxide Layers in the Initial Stage of Oxidation of 80Ni–20Cr Alloy

Y2o3 dispersion effect on al2o3 protective coating examined on the basis of five models

Effects of Tensile Stress on High Temperature Oxidation of a Ni–2OCr–4Al Alloy

The Effect of Oxygen Potential on the Surface Self-Diffusion Coefficient of Silver