Atomistic Insights into Aluminum Doping Effect on Surface Roughness of Deposited Ultra-Thin Silver Films (original) (raw)
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Applied Surface Science, 2016
We used atomic force microscopy (AFM) to study surface morphology and kinetic roughening of Ag films. X-ray diffraction (XRD) technique is used to verify the films crystalline structure. The influence of film thickness on the kinetic roughening was investigated using AFM data and roughness calculation. It is revealed that the surface roughness increases with increasing the film thickness. The data also consist with a complex behavior which is called as anomalous scaling. Scaling laws analysis for Ag films presents two distinct dynamics including large local and scale roughness and indicates a power law dependency on the thickness of film. AFM images have been characterized by the multifractal analysis. This analysis shows that the selfsimilar and multifractal characteristics as well as anomalous scaling exist in the Ag film morphologies. Description of the quantitative growth and surface morphology was done by the multifractal spectra, f (˛) − ˛. It is found that the multifractal spectrum shape is left hook-like (that is difference of height interval of the multifractal spectrum, f = f (˛m in) −f (˛m ax) > 0). The results indicate that the surfaces having greater roughness give rise the wider multifractal spectrum width(˛) and the greater f, thus, the nonuniformity of the height probabilities becomes larger. It indicates that the multifractality of the films becomes more pronounced at the higher thickness.
Influence of thickness on micro-structural characterizationof Silver films
Materials Today: Proceedings, 2019
Thin silver(Ag) films have found many applications in different optical devices such as solar cells, light emitting diodes, to improve the properties of organic semiconductors and to launch new materials. The primary objective of this paper is to explore the micro-structural characterization of thin silver films, that is, their responses to film thicknesses. We here start with the phenomenon of electrical conduction in bulk silver metal by estimating the conduction electron mean free path in order to select the thickness range of the films to be grown. Hence, we have selected the range of thickness 10-90 nm as the conduction electron mean free path in bulk silver is 57 nm. Scanning Electron Microscopy (SEM) techniques have been employed to reveal the physical processes of nucleation and growth. Vacuum deposited are usually polycrystalline islands, during the initial stages of growth are single crystals.
Mendeleev Communications, 1993
A silver (l 1 l ) single crystal electrode was roughened in perchlorate solution by a non-conventional oxidation-reduction cycle. The topography of the roughened electrode surface, as determined by in situSTM, was correlated with two optical properties, namely, local photoemission and Raman scattering continuum. An enhancement of these optical properties due to atomic-scale surface features was found and the relationship between this enhancement and the photoexcitation of electron-hole pairs on the electrode surface is discussed.
Metamaterials IX, 2014
We report on measurements of optical, morphological and electrical properties of silver nanolayers. The Ag films of thickness from 10 to 500 nm are deposited in e-beam evaporator. Fused silica and sapphire substrates are used with nominal root-mean-square (RMS) roughness equal 0.3 and 0.2 nm, respectively. Silver is deposited either directly on substrates or on Ge, Ni, or Ti wetting interlayer. The refractive index n and the extinction coefficient of Ag films are derived from spectroscopic ellipsometry and reflectance measurements carried in air in the spectral range from 0.6 to 6.5 eV (2200 -193 nm) using a rotating analyzer ellipsometer (V-VASE, J.A. Woollam Co.). Surface roughness is measured using AFM (Ntegra NT-MDT) under tapping mode in air with sharp etalon probes and 5:1 aspect ratio. Ag layers of 10 and 30 nm thickness have nearly the same RMS roughness when deposited at temperatures from 180 to 350 K. The lowest RMS=0.2 nm is achieved for 10 nm film Ag/Ge evaporated at 295 K. The sheet resistance of the Ag films is measured using two methods: the van der Pauw method with the electrical contacts located on perimeters of the samples and four probes contacting the samples at points lying in a straight line. Specific resistivity of Ag films on fused silica change from >10 9 to 1.80 [μΩ•cm] when thickness increases from 10 to 500 nm. Specific resistivity of 10, 30 and 50 nm thick Ag films on 1 nm Ge wetting layer are equal 14. 01, 7.89, and 5.58 [μΩ•cm], respectively, and are about twice higher than those of Ag films on Ti or Ni interlayers.
Thickness and microstructure effects in the optical and electrical properties of silver thin films
AIP Advances, 2015
The optical and electrical response of metal thin films approaching thicknesses in the range of the electron mean free path is highly affected by electronic scattering with the interfaces and defects. Here, we present a theoretical and experimental study on how thickness and microstructure affect the properties of Ag thin films. We are able to successfully model the electrical resistivity and IR optical response using a thickness dependent electronic scattering time. Remarkably, the product of electronic scattering time and resistivity remains constant regardless of the thickness (τxρ=C), with a value of 59±2 µΩ cm•fs for Ag films in the investigated range from 3 to 74 nm. Our findings enable us to develop a theoretically framework that allows calculating the optical response of metal thin films in the IR by using their measured thickness and resistivity. An excellent agreement is found between experimental measurements and predicted values. This study also shows the theoretical lower limit for emissivity in Ag thin films according to their microstructure and thickness. Application of the model presented here will allow rapid characterization of the IR optical response of metal thin films, with important application in a broad spectrum of fundamental and industrial applications, including optical coatings, low-emissivity windows and semiconductor industry.
Roughening of Ag surfaces by Ag deposits studied by differential reflectivity
Physical Review B, 1984
Differential reflectivity b,R/R measurements between a smooth Ag surface and the same surface covered by silver deposits of various thicknesses were performed in ultrahigh vacuum over the (1.5-5)-eV spectral range for different Ag substrate temperatures. One silver monolayer on silver substrate at 125 K gives rise to relatively large changes in ref1ectivity (-10). For thicker deposits (four monolayers or more) a well-defined absorption at 3.5 eV due to surface-plasmon excitation is found. The experimental results are compared to computed values of hR/R. AR/R variations during sample annealing to room temperature are also investigated and compared to the reported dc resistance and surface-enhanced Raman scattering measurements. Roughness was also investigated by electron microscopy by "pinning" the surface at T=140 K with a superficial oxide. An addi-0 tional absorption found for thick (-10 A) quenched silver films is attributed to a surface effect.
Optimum deposition conditions of ultrasmooth silver nanolayers
Nanoscale Research Letters, 2014
Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10-and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2).
Ab initio simulations of silver film adhesion on α-Al2O3 (0 0 0 1) and MgO (1 0 0) surfaces
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998
The atomic and electronic structure of the Ag/MgO (1 0 0) and Ag/a-A1 2 O 3 (0 0 0 1) interfaces are calculated by means of the ab initio Hartree±Fock approach combined with a supercell model. The electronic density distribution and the interface binding energy/equilibrium distance for both interfaces are analyzed. For a complete (1:1) surface coverage of the MgO surface the energetically most favorable adsorption position for the Ag atom is above the O atom. For the Ag/a-Al 2 O 3 interface the preferable adsorption positions for the Ag atom are over centers of either large equilateral oxygen triangles (in Al-substituted sites of Al-terminated corundum surface) or isosceles oxygen triangles (over O atoms of a ®rst internal oxygen layer) in O-terminated corundum. This interface is less stable than Ag/MgO (1 0 0), due to a large mismatch between lattice constants of Ag (1 1 1) and a-Al 2 O 3 (0 0 0 1) surfaces as well as the instability of Ag atoms on the A1-terminated corundum surface. Ó
Ab initio simulations of silver film adhesion on alpha-Al2O3 (0001) and MgO (100) surfaces
Nucl Instrum Meth Phys Res B, 1998
The atomic and electronic structure of the Ag/MgO (1 0 0) and Ag/a-A1 2 O 3 (0 0 0 1) interfaces are calculated by means of the ab initio Hartree±Fock approach combined with a supercell model. The electronic density distribution and the interface binding energy/equilibrium distance for both interfaces are analyzed. For a complete (1:1) surface coverage of the MgO surface the energetically most favorable adsorption position for the Ag atom is above the O atom. For the Ag/a-Al 2 O 3 interface the preferable adsorption positions for the Ag atom are over centers of either large equilateral oxygen triangles (in Al-substituted sites of Al-terminated corundum surface) or isosceles oxygen triangles (over O atoms of a ®rst internal oxygen layer) in O-terminated corundum. This interface is less stable than Ag/MgO (1 0 0), due to a large mismatch between lattice constants of Ag (1 1 1) and a-Al 2 O 3 (0 0 0 1) surfaces as well as the instability of Ag atoms on the A1-terminated corundum surface.
Structural and morphological characterization of chemically deposited silver films
2006
Silver thin films were deposited on glass slide substrates at room temperature by the chemical bath deposition (CBD) technique, using silver nitrate (AgNO 3) as Ag C1 source and triethanolamine [(N(CH 2 CH 2 OH) 3)] as the complex reductor agent. We determined the conditions of the CBD process to obtain homogeneous, opaque silver films with good adhesion to the substrate and white coloration. The silver films were studied by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The results show that the films are composed of several layers with different morphology depending on the deposition time. In all the cases, the crystalline structure of the films was the face cubic centered phase with a moderate [111] texture. Strains and stresses were calculated by the Vook-Witt grain interaction model.