Layer-by-layer growth of TiN by pulsed laser deposition onin-situannealed (100) MgO substrates

Abstract

We have grown atomically smooth heteroepitaxial TiN thin films on (100) MgO single crystals by pulsed laser deposition (PLD). To generate optimal conditions for two-dimensional growth of TiN on MgO, the substrates were annealed in-situ using a CO2 laser heater. The MgO surface is smooth and uniformly stepped with a terrace height of half a unit cell; a value of 0.21 nm was measured by atomic force microscopy (AFM). In-situ RHEED oscillations during deposition of TiN indicate two-dimensional growth mode up to a film thickness of about 43 nm. This is confirmed by AFM. The TiN films show smooth, stepped surfaces with a uniform terrace height of 0.211 nm. X-ray diffraction measurements indicate a high film quality, as well. High resolution scans feature intensity fringes around the (200) TiN peak, indicating an abrupt interface between MgO and TiN. On asymmetric reciprocal space maps the peak broadening only in due to finite film thickness proves a high crystalline quality. Maximum electrical conductivity of the films is 2 × 106 S/m at 300 K. AFM topography images (5 × 5 μm2) of the surface of a (100) MgO substrate with a miscut angle of γ = 0.10°, annealed at 950 °C (height scale is 0 to 3.2 nm, left) and a 43 nm thick TiN/MgO thin film grown by PLD (height scale is 0 to 2.4 nm, right). Step height is half a unit cell in both cases.