Search

We have investigated the structure of disordered gold-polymer thin films using small angle x-ray scattering and compared the results with the predictions of a theoretical model based on two approaches-a structure form factor approach and the generalized Porod law. The films are formed of polymer-embedded gold nanoclusters and were fabricated by very low energy gold ion implantation into polymethylmethacrylate (PMMA). The composite films span (with dose variation) the transition from electrically insulating to electrically conducting regimes, a range of interest fundamentally and technologically. We find excellent agreement with theory and show that the PMMA-Au films have monodispersive or polydispersive characteristics depending on the implanted ion dose. [ABSTRACT FROM AUTHOR]

The thermoelectric power SF of thin film thermocouples is related to the bulk thermopower Sbulk by ΔSF(t)=Sbulk-SF as a linear function of 1/t when t>ℓ, where ℓ is the electron mean free path and t the film thickness. For these conditions quantum size effects (QSEs) are negligible. However, when t<ℓ QSEs become relevant. In recent work we have shown that for Pt/Au thermocouples with film thickness t<ℓPt≈10 nm, ΔSF(t)=0.194+26.7(1/t)-93.6(1/t)2+112.0(1/t)3. Here we show that this nonlinear 1/t behavior is due to QSE. [ABSTRACT FROM AUTHOR]

The authors present here a summary of their investigations of ultrathin films formed by gold nanoclusters embedded in polymethylmethacrylate polymer. The clusters are formed from the self-organization of subplantated gold ions in the polymer. The source of the low energy ion stream used for the subplantation is a unidirectionally drifting gold plasma created by a magnetically filtered vacuum arc plasma gun. The material properties change according to subplantation dose, including nanocluster sizes and agglomeration state and, consequently also the material electrical behavior and optical activity. They have investigated the composite experimentally and by computer simulation in order to better understand the self-organization and the properties of the material. They present here the results of conductivity measurements and percolation behavior, dynamic TRIM simulations, surface plasmon resonance activity, transmission electron microscopy, small angle x-ray scattering, atomic force microscopy, and scanning tunneling microscopy. [ABSTRACT FROM AUTHOR]

A quantum mechanical approach is developed to calculate the surface-induced electrical conductivities of very thin metallic films with isotropic and anisotropic surfaces. Two particular cases are analyzed with this formalism: (1) films with isotropic surfaces and (2) films with anisotropic surfaces which have different morphological properties along two orthogonal directions. It is shown that, depending on the differences between these morphological properties, the surface-induced resistivities can be different along these directions. In order to investigate the validity of these predictions we have fabricated Pt films, with thickness in the 0.90 ≤ d ≤ 11.10 nm range, with very different morphological properties along two orthogonal directions. Measuring the electrical resistivities of these films, we have found different resistivities along these directions. We show that this anisotropic resistivity can be well explained by our theoretical approach. [ABSTRACT FROM AUTHOR]

Platinum thin films with thickness in the range of 0.4–12 nm were formed by filtered vacuum arc plasma deposition on a substrate with anisotropic roughness. The electrical resistivity was measured in directions parallel and perpendicular to the surface modulation as a function of film thickness, and the resistivity was found to be anisotropic with the degree of anisotropy increasing with decreasing film thickness. The very small thickness of the films calls for a quantum model for film resistivity, and it is shown that the measured resistivity can be interpreted as due to quantum electron scattering by the thin film anisotropic surface roughness. [ABSTRACT FROM AUTHOR]

We report electrical resistivity measurements of platinum and gold thin films over a range of film thickness d(1.3 ≤ d ≤ 11.7nm), together with associated measurements of the film morphological and crystallographic grain size. The resistivity results are compared to predictions of the Fuchs–Sondheimer and the Mayadas–Shatzkes models, based on the electron mean free path and crystallographic grain size, and the agreement is not satisfactory. We describe an alternative model based on elastic electron scattering with morphological granularity (grain structure as measured on the film surface) and film surface roughness, and good agreement is obtained with the experimental results. This suggests that electron scattering by morphological granularity and surface roughness plays an important role in determining the electrical resistivity of thin metal films. [ABSTRACT FROM AUTHOR]

Platinum and gold thin films have been fabricated by filtered vacuum arc deposition perpendicularly on rough silicon and glass substrates. Four sets of samples have been prepared with different thickness (d). Two sets were very thin films of Pt (1.31 ≤ d ≤ 11.66 nm) and Au (1.77 ≤ d ≤ 10.46 nm) and two sets were thicker films also of Pt (7 ≤ d ≤ 80 nm) and Au (34 ≤ d ≤ 200 nm). The roughness mean-square ω of the films have been measured, as a function of the film thickness d, by scanning tunneling microscopy (STM). We verified that the dynamical scaling relation ω(t) ~ tβ, where β is the growth exponent, is obeyed for the thicker films but it is not obeyed for the very thin films. These cases are analyzed taking into account the films growth theory. [ABSTRACT FROM AUTHOR]

A quantum approach is proposed to calculate the surface-induced electrical resistivity of metallic and semiconducting thin films when several subbands of Fermi participate of the electronic transport. The application of this approach to explain the experimental resistivity data of Pt and Au thin films is briefly reported. The surface-induced resistivity is calculated in detail for the particular case of semiconducting films with only one subband. [ABSTRACT FROM AUTHOR]

We have measured the morphological grain sizes of nanostructured platinum and gold thin films. In previous works their electrical resistivities have been measured and a theoretical approach was proposed to explain the resistivity experimental data. It will be shown that within the framework of our theoretical approach, the morphological grain sizes play an essential role in the electrical resistivity of these metallic thin films. [ABSTRACT FROM AUTHOR]

In a recent work we have proposed a quantum-mechanical approach to explaining our resistivity experimental results for platinum and gold thin films. Good agreement was found between theory and experiment. In that work only the main features of our calculations were pointed out. In the present work the quantum approach calculations are shown in detail and the predictions are compared with our experimental data. [ABSTRACT FROM AUTHOR]

We have measured, at room temperature, the resistivity, the surface roughness and the lateral surface correlation lengths of nanostructured platinum and gold thin films. The films' thickness d, deposited by vacuum arc plasma, is in the range 1.31≤d≤11.66 nm for platinum and 1.77≤d≤10.46 nm for gold. A theoretical estimate of our experimental data has been made. [ABSTRACT FROM AUTHOR]

We have fabricated gold thin films by metal plasma ion deposition on silicon substrates. The roughness of these nanostructured films has been measured by scanning tunneling microscopy (STM) and we have determined the growth dynamics critical exponents. We have also measured the grain sizes as a function of the film thickness. [ABSTRACT FROM AUTHOR]

We have uniformly coated the cantilever of an atomic force microscope (AFM) with gold thin films. These films are nanostructured with thickness going from 19 to 62 nm. The resonance frequencies of this cantilever have been measured, before and after the Au coatings. Taking into account these frequencies and the vibrating beam theory, we determined the Young modulus of the Au films, obtaining E[sub 2] = 69.1 ± 2.6 GPa, i.e. about 12% lower than the respective bulk elastic modulus. [ABSTRACT FROM AUTHOR]

The thickness dependence of the thermoelectric power of Pt films of variable thicknesses on a reference Au film has been determined for the case when the Pt film thickness, t, is not large compared to the charge-carrier mean free path. Pt film thicknesses down to 2.2 nm were investigated. We find that ΔSF=SB-SF (where SB and SF are the thermopowers of the Pt bulk and film, respectively) does not vary linearly as 1/t is the case for thin film thermocouples when the film thickness is large compared to the charge-carrier mean free path. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the evolution of surfaces roughness of DLC-coated substrates as a function of film thickness. This is important for DLC applications having to do with friction and wear. We used substrates with three different roughnesses between several nanometers and hundreds of nanometers. The substrates were cut into a number pieces and each piece coated with a different DLC thickness. The coated samples were characterized by atomic force microscopy. The results show that the surface roughness changes with DLC coating thickness. For substrates with original roughness 393 and 278 nm, the coating roughness increased with DLC thickness up to a maximum and then decreased. For the substrate with original roughness around 4 nm, the coating roughness showed no systematic tendency to decrease or increase. These results are interpreted using our previous results and taking into account the thin film growth dynamics. [Copyright &y& Elsevier]