<title>Pulsed laser deposition of thin refractory metal nitride films</title>

We report on the deposition of thin transition metal nitride (TMN) films by ablating Mo, Ta, V and W targets in low-pressure (1, 10 and 100 Pa) nitrogen atmosphere by KrF excimer laser pulses, and on their characterization. The targets were foils of high purity (99.8%). 3" Si(111) wafers wre used as substrates. Film characteristics (composition, crystalline structure, hardness) were studied as a function of N₂ pressure, KrF laser fluence (4.5-19 J/cm²), substrate temperature (20-750°C) and target to substrate distance (30-70 mm). Rutherford backscattering spectrometery (RBS) was used to calculate thickness of the films and identification of the composition. TMN films ar formed already at low N₂ ambient pressures (1 Pa) and laser fluences (6 J/cm²) on substrates at room temperature. XRD investigations show that films deposited at elevated temperatures are mostly polycrystalline. While Mo, W and Ta nitrides show respectively a γ-Mo2N, β-W2N and δ-TaN phase in almost any deposition condition, vanadium nitride shows a prevalent phase of δ-VN at N₂ pressures of 1-10 Pa, while at higher pressures (100 Pa) and at relatively high laser fluences (16-19 J/cm²) the dominant phase is β-V2N. Generally the crystallinity of the films improves by increasing the substrate temperature. Well-crystallinzed films are obtained on substrates heated at 500°C. Surface morphology, microhardness and electrical resistivity of the films are discussed as a function of both the nitrogen pressure and substrate temperature.