Optical anisotropy of tilted columns thin films of chromium deposited at oblique incidence
Introduction
Shadowing effects during growth of thin films at oblique angles together with limited adatoms diffusion induce the formation of well spaced columns with nanometric diameter [1], [2], [3]. This deposition technique, referred to as Glancing Angle Deposition (GLAD), allows design of a wide range of structures when the deposition angles or azimuth are varied during growth [4]. The nanosculptured thin films obtained may find applications in optics thanks to the optical anisotropy engineering allowed by GLAD [5], [6], [7]. The optical properties of nanosculptured thin films of various materials have been extensively studied because of their possible use in angle and polarization selective filters. For Cr GLAD thin films, the structural, mechanical and electrical properties of nanosculptured thin films have been reported [1], [8], [9]. Chromium structures with lateral periodicity have also been obtained by nucleating the structures on a template substrate [10]. Transmission measurements of polarized light have been performed on 54 nm thick Cr films obtained by GLAD and containing column at 45° from the normal to the surface [11], [12]. Very recently, the effective optical properties of one 160 nm thick sample containing Cr columns tilted by 45° with respect to the normal of the substrate have been interpreted using a monoclinic model [13]. However, the optical properties of thick Cr nanosculptured thin films and their evolution with deposition angle are still not well understood. In this work we use generalized spectroscopic ellipsometry to show the influence of columnar growth on the optical properties of nanosculptured Cr thin films. We will pay a particular attention to the off-diagonal elements of the Jones matrix.
Section snippets
Experiments
Chromium thin films with columnar microstructures were sputter deposited from a chromium target (50 mm diameter and purity 99.6%) with an argon pressure PAr = 0.53 Pa in a chamber with a base pressure lower than 10−6 Pa. The Si(1 0 0) substrates were ultrasonically cleaned in acetone and alcohol before introducing them into the reactor. The target was dc powered with a constant current density J = 66 A m−2. The target-to-substrate holder distance was fixed at about 10 cm, and the growth was carried out at
Results and discussion
Before measuring the optical properties of the films, the chemical and structural properties of the films were determined using complementary methods.
The surface compositions of the films were determined from X-ray Photoelectron Spectroscopy (XPS) measurements (not shown here). Two different contributions for the Cr2p core level were observed. Their relative positions and splitting corresponded to the emissions of Cr2p in metal and in oxide. The O1s-Cr2p3/2 oxide distance was found equal to
Conclusions
Thin films of chromium have been deposited using GLAD, resulting in columnar growth with column angles comprised between 0° and 25° with respect to the normal to the surface. The structural properties of the films have been determined using X-ray diffraction and reflectivity, XPS and AFM. The optical properties of the films have been investigated using generalized ellipsometric measurements. A simple multilayer model using effective medium approximation allowed extracting physical values of the
References (26)
- et al.
Appl. Surf. Sci.
(2007) - et al.
Thin Solid Films
(2006) - et al.
Appl. Phys. Lett.
(1989) - et al.
J. Phys. D: Appl. Phys.
(1997) - et al.
J. Opt. Soc. Am. A
(1991) - et al.
Thin Solid Films
(2008) - et al.
J. Vac. Sci. Technol. A
(2000)et al.J. Appl. Phys.
(1993) - et al.
J. Appl. Phys.
(1960) J. Vac. Sci. Technol.
(1974)- et al.
J. Opt. Soc. Am. A
(1985)
J. Vac. Sci. Technol. B
Rev. Sci. Instrum.
Appl. Opt.
Appl. Phys. Lett.
J. Appl. Phys.
Cited by (23)
Optical, structural and electrical properties of sputtered ultrathin chromium films
2021, Optical MaterialsResistivity anisotropy of tilted columnar W and W–Cu thin films
2021, Surface and Coatings TechnologyCitation Excerpt :Since properties of thin films are directly related to their structure, strategies to modify their structure at the micro- and nano-scale have always been a major topic. Nanofabrication techniques attempt to control thermal [1], mechanical [2], electrical [3–5], acoustic [6–8], optical [9] and magnetic [10] properties, and can create new effects. Among these nanofabrication techniques, an original approach has been developed since the end of the 90s, called GLAD (GLancing Angle Deposition) [11].
Anisotropic conductivity enhancement in inclined W-Cu columnar films
2018, Materials LettersEllipsometric characterization and optical anisotropy of nanostructured CuIn<inf>3</inf>S<inf>5</inf> and CuIn<inf>5</inf>S<inf>8</inf> thin films
2017, Materials Science in Semiconductor ProcessingCitation Excerpt :Nanostructured films fabricated by GLAD find application as antireflection coating [12], photovoltaic solar cells [13], sensors [14], photonic band-gap crystals [15], etc. Many materials have been deposited by GLAD such as, WO3 [16] for NO2 sensing [17], platinum coated polystyrene spheres [18], molybdenum nanorods [19], sculptured porous titania films as photoanode in solar cell [20], titanium [21], silver [1], structured thin films [2], indium [3], cadmium telluride [4], chromium [22], ZnO [23], CuInS2, CuIn3S5, CuIn5S8 [10,24]. The Cu-In-S (CIS) materials are well studied as nanostructures for solar cell applications [25–27].
Influence of the sputtering pressure on the morphological features and electrical resistivity anisotropy of nanostructured titanium films
2017, Applied Surface ScienceCitation Excerpt :The elaboration of these novel thin film architectures mainly depend on the materials used in the deposition process, the particle incident angle and the substrate rotation. However, few studies report on the relation between the sputtering pressure conditions used during the GLAD process and the obtained morphologies [7,17,18] as well as on the anisotropic behaviour of the resulting properties [19–21], namely the electrical resistance [22]. The understanding of these anisotropic electrical properties is in turn critical for the functional use of these materials in pressure and temperature sensors based on thin films [4,5].