Unprecedented Thermal Stability of Plasmonic Titanium Nitride Films up to 1400 °C. Issue 16 (29th May 2021)

• Record Type: Journal Article
• Authors: Krekeler, Tobias; Rout, Surya S.; Krishnamurthy, Gnanavel V.; Störmer, Michael; Arya, Mahima; Ganguly, Ankita; Sutherland, Duncan S.; Bozhevolnyi, Sergey I.; Ritter, Martin; Pedersen, Kjeld; Petrov, Alexander Yu; Eich, Manfred; Chirumamilla, Manohar
• Is Part Of: Advanced optical materials. Volume 9:Issue 16(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-29
• Subjects: high‐temperature stability -- photonics -- plasmonics -- thin films -- titanium nitride; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202100323
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: Titanium nitride (TiN) has emerged as one of the most promising refractory materials for plasmonic and photonic applications at high temperatures due to its prominent optical properties along with mechanical and thermal stability. From a high temperature standpoint, TiN is a substitution for Au and Ag in the visible to near‐infrared wavelength range, with potential applications including thermophotovoltaics, thermoplasmonics, hot‐electron and high temperature reflective coatings. However, the optical properties and thermal stability of TiN films strongly depend on the growth conditions, such as temperature, partial pressure of the reactive ion gas, ion energy, and substrate orientation. In this work, epitaxial TiN films are grown at 835 °C on an Al2 O3 substrate using a radio frequency sputtering method. The oxidization behavior of TiN is investigated at 1000 °C under a medium vacuum condition of 2 × 10 –3 mbar, which is relevant for practical technical applications, and the thermal stability at 1400 °C under a high vacuum condition of 2 × 10 –6 mbar. The TiN film structure shows an unprecedented structural stability at 1000 °C for a minimum duration of 2 h under a medium vacuum condition, and an exceptional thermal stability at 1400 °C, for 8 h under a high vacuum condition, without any protective coating layer. The work reveals, for the first time to the authors' knowledge, that the TiN film structure with columnar grains exhibits remarkable thermal stability at 1400 °C due to low‐index interfaces and twin boundaries. These findings unlock the fundamental understanding of the TiN material at extreme temperatures and demonstrate a key step towards fabricating thermally stable photonic/plasmonic devices for harsh environments. Abstract : Thermal stability of plasmonic titanium nitride structure is investigated at high temperatures, up to 1400 °C. The formation of columnar grains with low‐index surfaces and twin boundaries enhances the thermal stability of the titanium nitride. Titanium nitride shows unprecedented structural stability at high temperatures when there is no protective coating layer. These results represent a significant step toward high temperature plasmonic and photonic applications.