Reduced optical losses in refractory plasmonic titanium nitride thin films deposited with molecular beam epitaxy

Abstract

Refractory plasmonic materials that have optical properties close to those of noble-metals and at the same time are environmentally friendly, commercially viable and CMOS-compatible could lead to novel devices for many thermo-photonic applications. Recently developed TiN thin films overcome some of the limitations of noble-metals, as their optical loss is larger than noble metals and conventional methods to deposit TiN films are not compatible for its integration with other semiconductors. In this work, high-quality epitaxial single-crystalline TiN thin films are deposited with plasma-assisted molecular beam epitaxy (MBE) that exhibit optical losses that are less than that of Au in most part of the visible (300 nm – 580 nm) and near-IR spectral ranges (1000 nm - 2500 nm). In addition, a large figure-of-merit for surface plasmon polariton (SPP) propagation length compared to the previously reported TiN films is achieved with the MBE-deposited films.

A Platform for Complementary Metal‐Oxide‐Semiconductor Compatible Plasmonics: High Plasmonic Quality Titanium Nitride Thin Films on Si (001) with a MgO Interlayer

“…b) Comparison of FOMs obtained in this work with TiN films grown on sapphire, Si, and MgO substrates under deposition temperatures ranging from room temperature to 1000 °C, reported in previous studies. [ 23,24,28,30,34,42,44,62–64 ]…”

“…Figure 4. a) FOM ¼ Àε 0 /ε 00 TiN thin films grown on Si (001), Si (001)/MgO, and bulk MgO (001) substrates as a function of wavelength. b) Comparisonof FOMs obtained in this work with TiN films grown on sapphire, Si, and MgO substrates under deposition temperatures ranging from room temperature to 1000 C, reported in previous studies [23,24,28,30,34,42,44,[62][63][64]. …”

High‐Quality Plasmonic Materials TiN and ZnO:Al by Atomic Layer Deposition

“…[ 37 ] The MBE method allows for substantial improvement of material quality that results in low optical loss. The ε ″ value as low as 10 was obtained by Maurya et al [ 56 ] for TiN films grown on sapphire by plasma‐assisted MBE at 600 °C. Using very high substrate temperature of 1000 °C during MBE growth allowed Guo et al [ 38 ] to achieve single‐crystalline, stoichiometric, highly metallic TiN films with an electron concentration of 9.2 × 10 22 cm −3 and low optical loss ( ε ″ = 18) due to improved structural quality that resulted in a peak plasmonic FoM as high as ≈5.8 (see Table 1).…”

Etchless Fabrication of High‐Quality Refractory Titanium Nitride Nanostructures

“…TiN is usually grown in industrial scale by reactive MS, [ 11,45,47–51 ] while alternative techniques include pulsed laser deposition (PLD) from a TiN target, [ 52–54 ] reactive PLD from a Ti target in N 2 ambient, [ 55 ] dual ion beam sputtering (DIBS), [ 56 ] ion beam‐assisted evaporation (IBAE), [ 57,58 ] plasma‐assisted molecular beam epitaxy (MBE) [ 59–62 ] (note that IBAE and MBE are similar equipment‐wise and pressure‐wise), and atomic layer deposition (ALD). [ 63–66 ]…”

“…With the major exception of PLD from a TiN target, the combination of all the other aforementioned techniques with NSL for the formation of well‐defined islands is a challenge due to the inherent limitations regarding the shadow effects through the nanosphere mask. DIBS, IBAE, and MBE have usually working pressure of the order of 10 −4 mbar, set by the operation of the N 2 plasma sources, [ 56–62 ] but the main obstacle for their implementation in combination with NSL is the different angle of incidence of the Ti and N + species that originate from different sources. ALD by its own conception is designed to achieve conformal growth and to eliminate any shadow effects, making it inherently incompatible with NSL.…”