The structural, electrical and optical properties of RF sputtered In2O3 : Sn (ITO) thin films and the effect of post-deposition annealing have been studied. The thickness ranges from 225 to 862 nm. X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM) experiments were performed to study the structure and the surface morphology of these samples. We found that thinner films have a ⟨100⟩ texture and as the film grows the preferred orientation changes from ⟨100⟩ to ⟨111⟩. The lattice parameters are found to be larger than the bulk value, indicating that the samples are under a tensile stress. The grain size increases with increasing thickness. SEM images show a dense granular structure with grains having different shapes and sizes. From AFM images, the average surface roughness (rms) was estimated to be 3.89 nm. The energy gap was found to decrease from 3.65 to 3.50 eV as t increases from 225 to 866 nm. Annealing experiments were done, in the air, at temperature T in the 100–500 °C range. We found that the ⟨111⟩ texture becomes stronger after the annealing treatment. A large increase of the grain size with increasing T is observed. The lattice constant decreases with T to become closer to the bulk value, i.e. annealing seems to relieve the stress present in the as-deposited films; T = 400 °C seems to be the best temperature to obtain practically a stress free sample. We observe a large decrease in the electrical resistivity ρ after annealing. The lowest ρ value (16 × 10−4 Ω cm) was noted in the 699 nm thick sample annealed at 500 °C. The decrease of ρ seems to be the consequence of a larger grain size and a stronger ⟨111⟩ texture.

Articles you may be interested inBandgap renormalization in titania modified nanostructured tungsten oxide thin films prepared by pulsed laser deposition technique for solar cell applications J. Appl. Phys.Experimental and theoretical study of bulk light scattering in Ca F 2 monocrystals J. Appl. Phys. 98, 053501 (2005); 10.1063/1.2034085Electron field emission properties of gamma irradiated microcrystalline diamond and nanocrystalline carbon thin films Ex situ spectroscopic ellipsometry investigation of the layered structure of polycrystalline diamond thin films grown by electron cyclotron resonance-assisted chemical vapor deposition Effect of nitrogen addition on the microstructure and mechanical properties of diamond films grown using highmethane concentrations Brillouin light scattering, Raman light scattering and x-ray diffraction were used to investigate the elastic and microstructural properties of polycrystalline and smooth fine-grained diamond films of varying diamond quality. They were deposited on a titanium alloy by a two-step microwave plasma-assisted chemical vapor deposition process at 600°C. Their morphology and roughness were studied by scanning electron microscopy and atomic force microscopy. Their refractive indices were determined by the M-line spectroscopy technique. The diamond purity of all these coatings in terms of the sp 3 bonding fraction was deduced from visible and UV Raman spectroscopy as a function of the deposition conditions. All the samples were found to be textured with a ͗011͘ crystallographic direction normal to the film plane, leading to essentially hexagonal symmetry of the elastic tensor. By taking advantage of the detection of a number of different acoustic modes, complete elastic characterization of the films was achieved. The elastic constants C 11 and C 66 , respectively, were selectively determined from the frequency of the longitudinal and shear horizontal bulk modes traveling parallel to the film surface. The three remaining elastic constants, namely, C 44 , C 33 and C 13 , were obtained from detection of the Rayleigh surface wave a bulk shear wave and the bulk longitudinal wave propagating at different angles from the normal to the surface. The values of the elastic constants depend on the deposition conditions and on the microstructural properties of the films, especially the diamond quality and the polycrystalline or smooth fine-grained nature of the diamond. For the polycrystalline diamond film with the best quality, the elastic constants are rather close to the Voigt or Reuss average estimate values using known bulk elastic constants of diamond, whereas those of the smooth fine-grained diamond films are reduced because of the poorer diamond quality leading to lower residual stress in the films.

Articles you may be interested inEpitaxial Sr 1.8 Ca 0.2 NaNb 5 O 15 thin film waveguides grown by pulsed laser deposition: Optical properties and microstructure

Thick films of lithium niobate (LiNbO3) have been epitaxially grown on sapphire substrates by multistep radio-frequency magnetron sputtering. We have investigated the optical properties of the deposited layers by the m-line spectroscopy technique. The relationship between the film-substrate interface, the surface morphology of the LiNbO3 layer, and the optical measurements has been carefully established. Since this optical technique is sensitive to material defects, a detectable degradation of the optical data is observed when the microstructure of the LiNbO3 film changes. In particular, the angular width of the excited optical guided modes (Δθ) varies with the film thickness. This agrees perfectly with the evolution of the surface roughness as a function of the film thickness. We report a surface roughness rms of 2 nm corresponding to an angular width Δθ of 0.1° for the TE0 mode. The accuracy and the sensitivity of this technique can be advantageously compared to the classical tool of atomic force microscopy.

Highly textured hexagonal aluminum nitride (AlN) thin films were deposited on silicon substrates by radio-frequency magnetron sputtering at a substrate temperature below 400 °C and annealed in the temperature range of 400–450 °C by rapid thermal annealing. The optical and the electro-optical properties have been investigated using the prism-coupling technique. Both ordinary and extraordinary refractive indices (n0=2.0058 and ne=2.0374 at 632.8 nm) were respectively determined from the transverse electric and the transverse magnetic mode excitations. Furthermore, refractive index profiles analysis by using an improved inverse Wentzel–Kramer–Brillouin method reveals a step-like behavior of AlN thin films. The optical losses have been evaluated to be around 7 dB cm−1. The electro-optic coefficient r13 of 0.98 pm/V has been measured from the variation of the shift of guided-modes spectrum as a function of the applied electric field in the experiment.

We report on the influence of the structural properties on the refractive index of AlN films grown on Si(111) substrates by molecular-beam epitaxy using ammonia. The structural properties are assessed by reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and x-ray diffraction. Refractive index values are deduced from room-temperature spectroscopic ellipsometry. Optical data analysis is performed using the Kramers-Krönig relation in the transparent spectral region, from 1.6 to 3.2 eV. Evidence is presented showing the influence of strain and dislocation density on the AlN layer refractive index.

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