Contact Resistance Of Ti Research Articles

Cost-Effective PEM Electrolysis: The Quest to Achieve Superior Efficiencies with Reduced Investment

Hydrogen can directly replace fossil fuels in transport and industry when produced by water electrolysis with renewable energies such as solar or wind. The relevant technologies are either alkaline electrolysis or proton exchange membrane (PEM) water electrolysis. For PEM electrolysis in particular, key components that determine the stack cost are the bipolar plates (BPP), current collectors (CC), and membrane electrode assemblies (MEA). This paper discusses strategies for cost reduction by synthesizing highly active electrocatalysts with the aim of lowering the high Ir loading in the MEA. Additionally, we use vacuum plasma spraying (VPS) to apply either dense Ti coatings for corrosion protection of stainless steel components or build up Ti backing layers with defined porosity as contact elements with the MEA. The contact resistance of Ti can be reduced with the addition of Nb. The VPS coating and production procedure is adaptable to large-scale industrial production.

Improved Thermal Stability and Reduced Contact Resistance of Ohmic Contacts on N-Face n-Type GaN With Laser-Assisted Doping

The authors report reduced contact resistance and improved thermal stability of Ti/Al ohmic contacts to N-face n-GaN via laser-assisted Si doping. The contact resistivity of Ti (30 nm)/Al (200 nm) electrodes was reduced from 7.61 ×10-4 to 8.72 ×10-5 Ω·cm2 by applying laser-assisted Si diffusion to the GaN surface before Ti/Al deposition. Moreover, no degradation in specific contact resistivity was observed for the highly doped samples after annealing at 300 °C. During this process, Si dopant atoms are believed to diffuse into GaN, whereas Ga-N bonds are broken by laser-assisted doping, which eventually increases the number of nitrogen vacancies and generates sites at which Si atoms are substituted for Ga on the GaN surface. This suggestion was verified by secondary ion mass spectrometry and X-ray photoelectron spectroscopy.

Low-Resistance Nonalloyed Ti/Al Ohmic Contacts on N-Face n-Type GaN via an $\hbox{O}_{2}$ Plasma Treatment

The authors report improved electrical properties of nonalloyed Ti/Al ohmic contact to N-face n-type GaN via oxygen (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) plasma treatment. The contact resistivity of Ti (50 nm)/ Al (35 nm) electrodes is reduced significantly from 4.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> Ω · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 2.53 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> Ω · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> by applying O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma to the GaN surface before the Ti/Al deposition. In this process, Ti-N bonds are expected to form, while the Ga-N bonds are broken by the O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma, which eventually increases the nitrogen vacancies as well as the Ti-N phases at the GaN surface. This suggestion has been verified by X-ray photoelectron spectroscopy and transmission electron microscopy analyses.