Hundred-fold reduction in Iron diffusivity in titanium nitride diffusion barrier on steel by microstructure engineering

Kumar, P and Jithin, MA and Mohan, S and Avasthi, S (2020) Hundred-fold reduction in Iron diffusivity in titanium nitride diffusion barrier on steel by microstructure engineering. In: Thin Solid Films, 716 .

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Abstract

Titanium nitride (TiN) barrier films can enhance the efficiency of thin-film solar cells on steel by preventing Fe contamination in semiconductor layers. This work uses microstructure engineering to obtain low diffusivity of iron in TiN barrier layers. Three different microstructures were analyzed, each obtained by tuning deposition parameters using pulsed direct current sputtering. We show that metal diffusion in TiN proceeds via two mechanisms � bulk and grain-boundary diffusion. The performance of polycrystalline TiN barrier layers is limited by grain-boundary diffusion. By tuning the microstructure, a remarkably low diffusivity was achieved, only 1.5�10�18cm2s�1 at 700°C, a 100-fold improvement over the state-of-the-art. Activation energy suggests that the diffusion in TiN barrier proceeds via N-vacancies, not grain-boundary defects. For application where electrical insulation is also required, the TiN can be combined with insulating SiNx to form a bilayer barrier, without any loss in performance. The optimized TiN barrier can also be used for stainless steel with a Fe diffusivity of just 9�10�18cm2s�1 at 700°C. However, the TiN barrier on stainless steel suffers from very high chromium diffusion, a previously unknown effect. This suggests that counter to accepted wisdom; stainless steel is not always superior to mild-steel for electronic applications. The work provides quantitative data to aid design of diffusion barriers for electronic devices on steel. © 2020

Item Type:	Journal Article
Publication:	Thin Solid Films
Publisher:	Elsevier B.V.
Additional Information:	Copyright to this article belongs to Elsevier B.V.
Keywords:	Activation energy; Diffusion barriers; Grain boundaries; Iron compounds; Microstructure; Stainless steel; Thin film solar cells; Titanium nitride; Tuning, Deposition Parameters; Electronic application; Electronic device; Grain-boundary defects; Grain-boundary diffusion; Microstructure engineering; Pulsed direct current; Semiconductor layers, Titanium alloys
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	06 Jan 2021 10:03
Last Modified:	06 Jan 2021 10:03
URI:	http://eprints.iisc.ac.in/id/eprint/67167

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