Systematically prepared ultrathin chromium films were analyzed for their structural, optical, and electrical properties. The films with thickness from 2.5 nm up to 57 nm were deposited by magnetron sputtering, and the deposition process was optimized to obtain compact yet low-stress films. The films were studied by non-destructive techniques like the variable angle spectroscopic ellipsometry (VASE), the spectrophotometry in a wide spectral range, the X-ray diffraction (XRD), the X-ray reflectometry (XRR) and the contactless microwave resistance measurement. Nanoscale thickness measured by XRR was confirmed then by ellipsometry. The films with thickness higher than 5 nm exhibits only metallic chromium phase (c-Cr) with 110 preferred orientation. The obtained optical constants of ultrathin chromium films are significantly higher compared to the traditionally referenced values, particularly in the infrared range. We analyse reliability of the obtained data and, for the thickest of our films, the optical constants are in good agreement with the recently published values obtained for polycrystalline bulky chromium studied by the reflection electron energy loss spectroscopy (REELS). The thickness-dependent resistivity of the films follows the Mayadas and Shatzk's distribution with a modification necessary for the films thinner than the value of the mean free path of electrons in the ideal chromium crystal. For such thin films the resistivity is a function of film thickness value, while the resistivity of the thicker films is governed by the mean size of the film crystallites.
Optical, structural and electrical properties of sputtered ultrathin chromium films
Sytchkova A.;
2021-01-01
Abstract
Systematically prepared ultrathin chromium films were analyzed for their structural, optical, and electrical properties. The films with thickness from 2.5 nm up to 57 nm were deposited by magnetron sputtering, and the deposition process was optimized to obtain compact yet low-stress films. The films were studied by non-destructive techniques like the variable angle spectroscopic ellipsometry (VASE), the spectrophotometry in a wide spectral range, the X-ray diffraction (XRD), the X-ray reflectometry (XRR) and the contactless microwave resistance measurement. Nanoscale thickness measured by XRR was confirmed then by ellipsometry. The films with thickness higher than 5 nm exhibits only metallic chromium phase (c-Cr) with 110 preferred orientation. The obtained optical constants of ultrathin chromium films are significantly higher compared to the traditionally referenced values, particularly in the infrared range. We analyse reliability of the obtained data and, for the thickest of our films, the optical constants are in good agreement with the recently published values obtained for polycrystalline bulky chromium studied by the reflection electron energy loss spectroscopy (REELS). The thickness-dependent resistivity of the films follows the Mayadas and Shatzk's distribution with a modification necessary for the films thinner than the value of the mean free path of electrons in the ideal chromium crystal. For such thin films the resistivity is a function of film thickness value, while the resistivity of the thicker films is governed by the mean size of the film crystallites.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
