High quality superconducting titanium nitride thin film growth using infrared pulsed laser deposition

Abstract

Superconducting titanium nitride (TiN) thin films were deposited on magnesium oxide, sapphire and silicon nitride substrates at 700 • C, using a pulsed laser deposition (PLD) technique, where infrared (1064 nm) pulses from a solid-state laser were used for the ablation from titanium target in a nitrogen atmosphere. Structural studies performed with X-ray diffraction showed the best epitaxial crystallinity for films deposited on MgO. In the best films, superconducting transition temperatures, T C , as high as 4.8 K were observed, higher than in most previous superconducting TiN thin films deposited with reactive sputtering. A room temperature resistivity down to ∼ 17µΩcm and residual resistivity ratio (RRR) up to 3 were observed in the best films, approaching reported single crystal film values, demonstrating that PLD is a good alternative to reactive sputtering for superconducting TiN film deposition. For less than ideal samples, the suppression of the film properties were correlated mostly with the unintended incorporation of oxygen (5-10 at. %) in the film, and for high oxygen content films, vacuum annealing was also shown to increase the T C. On the other hand, superconducting properties were surprisingly insensitive to the nitrogen content, with high quality films achieved even in the highly nitrogen-rich, Ti:N = 40/60 limit. Measures to limit oxygen exposure during deposition must be taken to guarantee the best superconducting film properties, a fact that needs to be taken into account with other deposition methods, as well.

Superconductivity Behavior in Epitaxial TiN Films Points to Surface Magnetic Disorder

“…The residual resistance ratio, listed in Table I, reaches RRR = 7 emphasizing the high quality of films. The room-T resistivity ρ 300K ≡ R 300K s d attains the values as low as ρ 300K ∼ 20 µΩ·cm for d ≥ 100 nm, which is similar to the best reported results in thin films [14,38] as well as in a thick single crystal [37]. This similarity is not surprising given the fact that ρ 300K is determined by the phonon scattering, rather than disorder, once again emphasizing the quality of the material and its conceptual difference from the disordered TiN films investigated in most previous works [25,30,39].…”

Titanium Nitride as a New Prospective Material for NanoSQUIDs and Superconducting Nanobridge Electronics

“…This behavior may result from the minimal diffusion of oxygen from the substrate into the TiN film for a pure Si substrate. The unintended incorporation of oxygen in a TiN film is the strongest factor in suppressing superconducting properties in TiN films [ 16 ]. The use of a sufficiently low base pressure of <10 −7 mbar in the deposition chamber and outgassing of the chamber at the deposition temperatures helps to reduce deleterious oxygen outgassing during film deposition.…”

Optical, electrical and mechanical properties of TiN thin film obtained from a TiO2 sol-gel coating and rapid thermal nitridation

“…Indeed, TiN has intrinsic physico-chemical and optical properties making it first-choice material: low resistivity, high reflectance in the infrared spectral range, good corrosion resistance, good chemical inertness, good thermal stability, and high hardness [4][5][6]. Generally, TiN thin layer is obtained using a wide range of deposition processes requiring vacuum technology, such as reactive magneton sputtering [1,[7][8][9][10], molecular-beam epitaxy [11,12], chemical vapor deposition (CVD) [13][14][15], atomic layer deposition (ALD) [16][17][18][19] or pulsed laser deposition (PLD) [20][21][22], under a nitrogen or ammonia atmosphere. Unfortunately, due to its good hardness and chemical resistance, TiN is not adapted for being micro or nanostructured using standard etching process (Reactive Ion Etching for example).…”