M. Adamik

Fundamental structure forming phenomena of polycrystalline films and the structure zone models

Previous structure zone models used for the interpretation of the experimental results were constructed by compiling the various structures found in thick polycrystalline films deposited at different temperatures and parameters. The present paper shows that while the temperature dependence of surface and bulk diffusion can not adequately describe the evolution mechanisms of various polycrystalline thin film structure, the fundamental structure forming phenomena, including the contribution of impurities introduced by the authors make possible the comprehensive description of the structure forming mechanisms. Real structure zone models including also the related textures, are constructed by considering the concentration of impurities (co-deposited additives) in the vapour beam as a new deposition parameter, and the fundamental structure forming phenomena. These are phenomena composed of atomic processes, and can give account for the global effect of the atomic processes and are directly responsible for the structure evolution. Impurities (additives) can promote or inhibit the operation of the structure forming phenomena (promoter or inhibitor resp.). The new structure zone models can be used to tailor polycrystalline film structures of large variety (from large grained through columnar to the micro- or nanocrystalline structures) and to diagnose technologies.

Formation of polycrystalline and microcrystalline composite thin films by codeposition and surface chemical reaction

The formation mechanisms of nanocrystalline composite structures are discussed, and results on co-deposited material system of C 60 ‐Au, C 60 ‐Cu as well as Al‐SiO x are presented. Three type of structures are distinguished in the composite films, depending on the concentration of the additive. The decisive structure-forming phenomena are the kinetic segregation of the minority species and the chemical reaction of the deposited components.

Columnar structures in polycrystalline thin films developed by competitive growth

Abstract The formation mechanism of columnar structures is analysed by the investigation of texture and morphology of oxygen-contaminated aluminium thin films. The responsible mechanism for the structure evolution is the oxygen-induced competitive growth that results in an inhomogeneous structure of small-grained and V-shaped columnar morphology and in the appearance of 〈311〉 and 〈100〉 texture. The increase in the oxygen incorporation induces competitive growth of initially formed randomly oriented crystals due to the anisotropy of the chemical interaction of oxygen with the different crystallographic faces. At high-oxygen contamination level, the growth morphology of films is changing to a lower zone of the structure zone models.

Correlation between texture and average grain size in polycrystalline Ag thin films

Abstract The texture and average grain size are investigated in series of silver thin films deposited at various substrate temperatures and different vacuum conditions, by introducing the ‘structure curve’, which describes their correlation. Its slope gives information on the relative contribution of normal and abnormal grain growth to the structure evolution. In contaminated films normal grain growth is suppressed. The texture sharpness has a maximum both in clean and contaminated films above 200°C. This maximum corresponds to 1 and 0.5 μm average grain size in clean and contaminated films, respectively.

Epitaxial growth and characterization of Ni films grown on MgO(001) by biased direct‐current sputter deposition

Ni films thinner than 180 nm are deposited on MgO(001) substrates at a temperature Ts of 190 or 280 °C by dc sputtering at 2.5 kV in Ar gas. A dc bias voltage Vs between 0 and ‐140 V is applied to the substrate during the deposition. A study of structural and physical properties of the Ni film is made by the use of reflection high‐energy electron diffraction (RHEED), cross‐sectional transmission electron microscopy (XTEM), x‐ray reflection diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and by measuring (TCR) in the temperature range from 35 to 135 °C. When Ts=190 °C the Ni film retains a polycrystalline structure at any Vs. When Ts=280 °C, as Vs increases from 0 to −140 V the film transforms from the polycrystal to the single crystal with the orientation as Ni(001)∥MgO(001) and Ni〈010〉∥MgO〈010〉, indicating that an optimal value of Vs for the epitaxial growth ranges from −80 to −110 V. Besides, an analysis of RBS spectra in comparison with XTEM images explains that the atomic density of t...

Electron diffraction based analysis of phase fractions and texture in nanocrystalline thin films, part III: Application examples

In this series of articles, a method is presented that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions and degree of fiber texture are determined for the nanocrystalline components. The effect of the amorphous component is minimized by empirical background interpolation. First, the two-dimensional SAED pattern is converted into a one-dimensional distribution similar to X-ray diffraction. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. These Markers are calculated not only for kinematic conditions, but the Blackwell correction is also applied to take into account dynamic effects for medium thicknesses. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX. The method is implemented in a computer program that runs under the Windows operating system. Part I presented the principles, while part II elaborated current implementation. The present part III demonstrates the usage and efficiency of the computer program by numerous examples. The suggested experimental protocol should be of benefit in experiments aimed at phase analysis using electron diffraction methods.

Growth structure investigation of MgF2 and NdF3 films grown by molecular beam deposition on CaF2 (111) substrates

Abstract The growth structure of MgF 2 and NdF 3 films grown on polished CaF 2 (111) substrates deposited by molecular beam deposition has been investigated using transmission electron microscopy (TEM) of microfractographical and surface replications as well as cross-sectional TEM, atomic force microscopy, packing density, and absorption measurements. It has been shown that by taking advantage of ultrahigh vacuum environments and a special stratification property of MgF 2 and NdF 3 films, the preparation of nanocrystalline films of high packing density and low optical absorption is possible at a substrate temperature of 425 K.

RBS and XHRTEM characterization of epitaxial Ni films prepared by biased d.c. sputter deposition on MgO(001)

Abstract Rutherford backscattering spectrometry (RBS) channelling and cross-sectional high-resolution transmission electron microscopy (XHRTEM) have been applied to characterize the structure of Ni films grown epitaxially on MgO(001) by biased d.c. sputter deposition. The RBS spectra indicate that the Ni films have a high density of lattice imperfections near to the MgO surface. The XHRTEM investigations revealed a lattice expansion in the [010]direction confirming the existence of the slightly distorted cubic lattice of Ni in the vicinity of the substrate surface which was detected by RBS channelling measurements. Regularly distributed edge dislocations due to the mismatch of Ni and MgO lattices have been clearly demonstrated by XHRTEM.

Epitaxial growth, structure and properties of Ni films grown on MgO(100) by d.c. bias sputter deposition

Abstract Ni films of 70–240 nm thickness were deposited on an MgO(100) substrate at temperatures T s ⩾190°C by d.c. sputtering at 2.5 kV in pure Ar gas. A negative bias voltage V s between zero and −110 V was applied to the substrate during the deposition. Reflection high energy electron diffraction, X-ray diffraction, cross-sectional transmission electron microscopy. Auger electron spectroscopy, ferromagnetic resonance and the measurement of the temperature coefficient of resistance were used to determine the structure and properties of the films. The degree of epitaxy of Ni increases with increasing T s as well as increasing V s . The optimum conditions for epitaxial growth of Ni are T s ⩾280°C and V s ⩾80 V. In this range epitaxial films with Ni(100) ∥ MgO(100) and Ni〈100〉 ∥ MgO〈100〉 can be prepared. A magnetic anisotropy is induced in the film plane. This anisotropy may be a result of superposition of a magnetocrystalline anisotropy originating from the epitaxial Ni film and of a uniaxial magnetic anisotropy induced during the film formation. In conclusion, as V s ranges −80 to −110 V the bombarding effect of both energetic ions and fast neutrals of Ar will rule the epitaxial growth of the Ni film by increasing the mobility of Ni adatoms and by resputtering the impurities. This effect is pronounced at T s ⩾280°C.

Texture, twinning and secondary extinction of vacuum deposited silver thin films

Abstract In the present work the texture, secondary extinction and twinning of vacuum evaporated Ag films have been studied using standard X-ray diffractometer and texture diffractometer techniques. The films exhibit a sharp multicomponent texture: a main 〈111〉 component accompanied with a twin-related 〈511〉 component and a weak 〈100〉 component. It is shown that the correct evaluation and interpretation of the structural properties requires secondary extinction to be taken into account. The effect of secondary extinction on volume fraction measurements of texture components is evaluated on {111} pole figures. The systematic error due to extinction could be considerably decreased when the {200} pole figures were used for the calculation of volume fractions, where the extinction effect is much smaller compared to that of the former one. The correct evaluation of pole-density values in low-index crystal directions was performed allowing for secondary extinction.