Pt layer

Jakoh P, Schlapka A. 2007. CO adsorption on epitaxially grown Pt layers on Ru(OOOl), Surf Sci 601 3556. 

The emission spectrum of some PT and PBD polymer bilayer devices cannot be explained by a linear combination of emissions of the components. Thus, white emission of the PLEDs ITO/422/PBD/A1 showed Hof 0.3% at 7 V, and consisted of blue (410 nm), green (530 nm), and red-orange (620 nm) bands. Whereas the first and the last EL peaks are due to the EL from the PBD and the PT layers, respectively, the green emission probably originates from a transition between electronic states in the PBD layer and hole states in the polymer... 

A silicon wafer with anisotropically KOH-etched openings was used as shadow mask. The shadow mask is accurately positioned with the help of an optical microscope and fixed using a custom-made wafer holder. A 50-nm-thick TiW-film is deposited by sputtering through the shadow mask. This film serves as adhesion layer and diffusion barrier and covers the rough surface of the CMOS-Al-metallization. A Pt-layer with a thickness of 100 nm was sputtered on top of this TiW-layer. 

Hirano, S., Kim, J., and Srinivasan, S. High-performance proton exchange membrane fuel cells with sputter-deposited Pt layer electrodes. Electrochimica Acta 1997 42 1587-1593. 

Nakshima et al. have fabricated p-n junction devices by employing A1 implantation to yield a p-doped layer in n-type 6H-SiC [66]. A Pt layer on top of the p-type ohmic contact (PtSi) provided both protection and a catalytic metal contact to create a chemical gas sensor device. A response (30 and 60 mV, respectively) was obtained to both 50 ppm and 100 ppm of ammonia in nitrogen at 500°C. 

One problem for the coated system is that the film is peeled off after prolonged irradiation. In order to have a more adhesive film, the surface of n-Si was modified with N-(3-trimethoxysilyIpropyl)pyrrole (22). Pyrrole was then electrodeposited on this modified electrode as shown in Eq. (24) 85). The durability of the coated poly(pyrrole) was improved by such a treatment of n-Si surface. The n-Si electrode coated only with poly(pyrrole) gave a declined photocurrent from 6.5 to 1.8 mA cm-2 in less than 18 h, while the poly(pyrrole) coated n-Si treated at first with 22 as Eq. (24) gave a stable photocurrent of 7.6 mA cm-2 for 25 h. When an n-Si electrode was coated with Pt layer before the deposition of poly(pyrrole), the stability of the semiconductor was improved remarkably (ca. 19 days)85b). A power conversion efficiency of 5.5% was obtained with iodide/iodine redox electrolytes. 

More recently, Stamenkovic et al. [95,107] reported on the formation of Pt skins on Pt alloy electrocatalysts after high-temperature annealing. Pt skins were reported to exhibit strongly enhanced ORR activity. It was argued that the electronic properties of the thin Pt layer on top of the alloy alter its adsorption properties in such a way as to reduce the adsorption of OH from water and therefore to provide more surface sites for the ORR process (see Section 5.2 in Chapter 4 for a detailed discussion of skin catalysts, compare also Section 4.1.5 in the present Chapter). 

The stability of sputtered Pt on TCO substrate which is used as a counterelectrode has also been investigated. It was reported that the electrocatalytically active Pt layer did not seem to be chemically stable in an electrolyte solution of Lil, I2, and methoxypropionitrile [158]. 

Figure 15. Effect of different I-layer and C-layer on the device sensitivity and response time to a) 1000 PPM H2 in air at 150°C. The device is a Pd/Top I-layer (Si02. AI2, O3, Ta2 O3, Si3 N4)/ Si02/p-Si capacitor and the initial ambient is air (after Ref. 16, 1984 IEEE) and b) 7 PPM, 25 PPM, and 70 PPM NH3 in air at 150 C, device used here is an ultra thin Pt-layer/Pd/Si02/p-Si capacitor (after Ref. 9, with permission).

Catalyst Pt/Rh-gauze Pt-layer on tube wall Supported Pt-cat. Fixed bed... 

It is essential that oxygen was contained in subsurface Pt layers, dissolving there with increasing temperature. This oxygen, whose removal is extremely difficult, can affect the constants of surface reactions. For example, the initial sticking coefficient of 02 on the oxidized sample is S02 = 0.05, whereas for the Ir sample that was not exposed to oxygen we have Sq2 - 0.26 [78,106,142]. Since the literature lacks detailed information, our model does not account for this fact. 

The ECL reaction can occur at room temperature in aqueous buffered solutions and in the presence of dissolved 02 or other impurities. To provide the electric field for ECL to occur at the detector region, a pair of connecting floating Pt electrodes (50 pm wide, 50 pm apart, and 100 nm thick) has been used. To improve the adhesion of the Pt layer, a Cr underlayer was used. Unfortunately, Cr was corroded in the presence of CL [725]. 

Fig. 8. Schematic of the procedure used for fabrication of nanoscale molecular-switch devices by imprint lithography [62]. (a) Deposition of a molecular film on Ti/Pt nanowires and their micron-scale connections to contact pads, (b) Blanket evaporation of a 7.5 nm Ti protective layer, (c) Imprinting of 10 nm Pt layers with a mold that was oriented perpendicular to the bottom electrodes and aligned to ensure that the top and bottom nanowires crossed, (d) Reactive ion etching with CF4 and O2 (4 1) to remove the blanket Ti protective layer.

Fig. 15.9. Depth profiles of the Pt Af and 2s photoelectron signal of the electron beam-evaporated Pt layer on Si and the concentration profiles of Pt, Si, O and C. (Reprinted from C. U. Maier, Hydrogen Evolution on Platinum-Coated p-Silicon Photocathodes, Int. J. Hydrogen Energy21 840,1996. Reproduced with permission of the International Association for Hydrogen Energy.)...

Figure 9. Patterns made by IL using Co/Pt multilayers cover with resist top of the Co/Pt layer (a), TEM cross section of the ion etched structure through the Co/Pt in the Si substrate (b).

Figure 14 Spectroelectrochemical cell for in situ multiple internal reflectance mode ATR. The working electrode is a thin Pt layer deposited on the ZnSe paralleloid. The polyethylene body which contains the electrolyte and the other electrodes is pressed against the prism to form good sealing [44]. (Reprinted with copyright from The Electrochemical Society Inc.)...

Figure 3.3.12 The effect of surface lattice strain on adsorbate chemisorption energies. Lattice strain modulates chemisorption and can be used to tune the reactivity of electrocatalysts. Compressed Pt surface layers (right portion) bind adsorbates more weakly stretched Pt layers bind adsorbates more strongly.

From combined theoretical and experimental insights, nanostructured Pt core-shell electrocatalyst architectures have recently emerged as promising, cost-effective cathode fuel cell catalysts. Pt-enriched multilayer surface shells surround Pt-poor cores that modify the reactivity of the surface Pt layer. 

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