Effect Of Substrate Strain Research Articles

Effect of Substrate Strain, Aluminum Thickness and Corona Pretreatment on the Electrical Resistance of Physical Vapor Deposited Aluminum Coatings

Aluminum coatings applied to polymer films by physical vapor deposition should be defect-free for applications such as packaging and electronic devices. However, cracks can appear in the aluminum coating as the polymer film stretches, becoming manifest as an increase in resistance. We evaluated the effect of different aluminum thicknesses (10–85 nm), polymer films (polyethylene terephthalate or polypropylene), and corona doses (0–280 W∙min/m2) on the relative increase in resistance during stretching (strain = 0–100%). We found that the thickness of the aluminum coating was inversely related to the increase in resistance. Corona pretreatment led to an increase in surface energy (≤40 mN/m for polypropylene; ≤50 mN/m for polyethylene terephthalate) although high corona doses resulted in overtreatment, which limited the adhesion of aluminum to the substrate and led to a greater increase in resistance. Varying the coating thickness had a much greater effect than the corona pretreatment, suggesting that thicker aluminum coatings are more effective than corona pretreatment as a strategy to increase coating stability. The effect of aluminum thickness and strain on resistance was described using a fit function containing three fit factors.

Strain Effects on the Growth of La0.7Sr0.3MnO3 (LSMO)-NiO Nanocomposite Thin Films via Substrate Control.

Oxide-oxide-based vertically aligned nanocomposites (VANs) have demonstrated a new material platform for enhanced and/or combined functionalities because of their unique vertical geometry and strain coupling. Various factors contribute to the growth of VANs, including deposition parameters, phase composition, phase ratios, crystallography, etc. In this work, substrate strain effects are explored through growing a two-phase oxide-oxide La0.7Sr0.3MnO3 (LSMO):NiO system, combining antiferromagnetic NiO and ferromagnetic LSMO, on various substrates with different lattice parameters. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetic property measurements all suggest that substrate strain plays a critical role in the epitaxial growth of a VAN structure and their two-phase separation, and thus results in different physical properties. This work sheds light on the fundamental nucleation and growth mechanisms of the two-phase VAN systems and the effects of substrate strain on the overall orientation and growth quality of the VAN films.

Creation and Ordering of Oxygen Vacancies at WO3-δ and Perovskite Interfaces.

Changes in the structure and composition resulting from oxygen deficiency can strongly impact the physical and chemical properties of transition-metal oxides, which may lead to new functionalities for novel electronic devices. Oxygen vacancies (VO) can be readily formed to accommodate the lattice mismatch during epitaxial thin film growth. In this paper, the effects of substrate strain and oxidizing power on the creation and distribution of VO in WO3-δ thin films are investigated in detail. An 18O2 isotope-labeled time-of-flight secondary-ion mass spectrometry study reveals that WO3-δ films grown on SrTiO3 substrates display a significantly larger oxygen vacancy gradient along the growth direction compared to those grown on LaAlO3 substrates. This result is corroborated by scanning transmission electron microscopy imaging, which reveals a large number of defects close to the interface to accommodate interfacial tensile strain, leading to the ordering of VO and the formation of semi-aligned Magnéli phases. The strain is gradually released and a tetragonal phase with much better crystallinity is observed at the film/vacuum interface. The changes in the structure resulting from oxygen defect creation are shown to have a direct impact on the electronic and optical properties of the films.

Effects of substrate strain and electrical stress on lattice dynamics, defects, and traps in strained-Si/Si0.81Ge0.19 n-type metal-oxide-semiconductor field effect transistors

Defects and traps in strained-Si n-type metal-oxide-semiconductor field effect transistors (MOSFETs) are studied in detail. The inelastic electron tunneling spectroscopy (IETS) technique is shown to be capable of probing traps in ultrathin gate dielectrics and obtain the energies and spatial locations of the traps. Detailed analyses of electrical stress-induced build-up of traps and electrically active bonding defects and identification of the trap-features including trap-assisted conduction and charge-trapping have been performed. The location and energies of the traps are estimated from the IETS spectra measured at both bias polarities. Identification of the acoustic and optical phonon modes (inelastic) as well as trap-features (elastic) helps in better understandings of the complex transport-mechanisms in gate dielectrics on strained layers.

Effect of substrate strain on calculated magnetic properties and magnetic anisotropy energy of CoO

Effect of substrate strain on calculated magnetic properties and magnetic anisotropy energy of CoO

Effects of Substrate Strain on Epitaxial Growth by Kinetic Monte Carlo Method

Effects of substrate strain on epitaxial growth are studied, using the kinetic Monte Carlo (kMC) method. The strain dependences of the activation energy barrier and the attempt frequency are considered. The homo-epitaxial growth on Ag (111) surface with uniform tensile strain is simulated, and influences of substrate strain on the nucleation of island and the morphology are investigated. On the tensile-strained surface, the island density increases due to the suppression of the adatom diffusion on terrace. The averaged coordination number of atom constituting of islands decreases and the shape of island is less compact. The growth behavior on the strained substrate is same as at lower temperature.

Effect of substrate strain on lattice structure, electrical resistivity, and optical conductivity of [formula omitted] thin films grown on [formula omitted

In this study, we investigated the lattice structure, electrical resistivity, and optical conductivity of Nd 0.5Sr 0.5MnO 3 thin films grown on SrTiO 3 (001) and SrTiO 3 (011) substrates. The thin film on SrTiO 3 (001) experiences isotropic tensile strain and shows characteristics of the semiconducting ground state. On the other hand, the thin film on SrTiO 3 (011) experiences anisotropic tensile strain, which means that one of the two in-plane lattice axes is fixed by the substrate lattice and the other axis is relaxed. The thin film shows the insulator–metal phase transition at 220 K and characteristics of the charge-ordered insulating ground state below 150 K. By comparing the single crystal data of the lattice along with the resistivity and optical conductivity, we suggest that the substrate strain affects the electronic structure as well as the carrier dynamics of the Nd 0.5Sr 0.5MnO 3 thin films. We propose the possible ground states formed in the thin films.

Possible origin of electronic phase separation in La0.7Ca0.3MnO3

The effect of substrate strain on the electronic valence band structure of La0.7Ca0.3MnO3 thin films has been investigated. For this purpose La0.7Ca0.3MnO3 thin films have been simultaneously grown on SrTiO3 and LaAlO3 substrates using pulsed laser deposition technique. The chemical characterization of these samples is carried out by core level x-ray photoelectron spectroscopy and the structural characterization by x-ray diffraction. Our experiments confirm that all these samples have the same chemical composition but different strain configuration. The electronic structure of these samples is probed through valence band spectroscopy measurements on Indus-1 synchrotron x-ray source. We observe that strain has a large effect on the valence band of La0.7Ca0.3MnO3. The results are explained on the basis of change in the crystal field splitting due to Mn–O bond length.

Strain effects in thin film/Si substrates revealed by X-ray microdiffraction

The local variation in strain and rotation of the Si substrate due to overlying Ni thin film features has been observed using X-ray microdiffraction. Residual tensile stress in 1 μm thick, 190 μm diameter Ni dots of 990 MPa imparted an average compressive stress in the underlying Si substrate. Ni Kα fluorescence scans, acquired simultaneously with Si (333) diffraction data, allow for a precise determination of the Ni feature edge location relative to the observed shift in Si (333) peak position. Rocking curve mesh scans, in which the sample was translated perpendicular and parallel to the diffraction plane, were used to deconvolute the effects of substrate strain due to d-spacing shifts and rotation of the local Si surface. In addition, shear strains at the dot edge imparted a significant shift in the Si (333) diffraction peak, producing a secondary diffraction peak in modified reciprocal space scans.

Effect of substrate strain on adsorption

Direct evidence for the effect of local strain at a surface on the bonding strength for adsorbates is presented. Scanning tunneling microscopy revealed that adsorbed oxygen atoms on Ru(0001) surfaces are located preferentially on top of nanometer-size protrusions above subsurface argon bubbles, where tensile strain prevails, and are depleted around their rim in regions of compression, relative to the flat surface. Such effects can be considered as the reverse of adsorbate-induced strain, and their direct local demonstration can be used to test theoretical predictions.

Substrate-Strain Effects on the Frenkel-Kontorova System

Substrate-strain effects on the Frenkel-Kontorova system are investigated under the continuum approximation. Long-wavelength component of the strain field is shown to give rise to an extra biharmonic potential, modifying the basic equation from the sine-Gordon to the double sine-Gordon equation. A kink propagates accompanied by a localized strain field, thus behaving like a kind of polaron. Implication on the commensurate-incommensurate transition studied by Frank and van der Merwe and others is also given.