THE DEPENDENCE OF THE INVERSION LAYER THICKNESS ON THE FILM THICKNESS IN THIN-FILM SOI STRUCTURES

The dependence of the inversion-layer thickness on the film thickness in thin-film SOI structure is analyzed theoretically by using computer simulation. A new concept and parameter, the critical thickness of thin film all-bulk inversion, is introduced for the design of thin-film MOS/SOI devices. It is necessary to select the film thickness T(s1) close to the all-bulk strong inversion critical thickness in order to get high-speed and high-power operation of ultra-thin film MOS/SOI devices.

Field emission mechanism from a single-layer ultra-thin semiconductor film cathode

Field emission (FE) from a single-layer ultra-thin semiconductor film cathode (SUSC) on a metal substrate has been investigated theoretically. The self-consistent quantum FE model is developed by synthetically considering the energy band bending and electron scattering. As a typical example, we calculate the FE properties of ultra-thin A1N film with an adjustable film thickness from 1 to 10 nm. The calculated results show that the FE characteristic is evidently modulated by varying the film thickness, and there is an optimum thickness of about 3 nm. Furthermore, a four-step FE mechanism is suggested such that the distinct FE current of a SUSC is rooted in the thickness sensitivity of its quantum structure, and the optimum FE properties of the SUSC should be attributed to the change in the effective potential combined with the attenuation of electron scattering.

Epitaxial SiC grown on silicon-on-insulator substrate with ultra-thin silicon-over-layer

We report on the comparative studies of epitaxial SiC films grown on silicon-on-insulator (SOI) and Si bulk substrates. The silicon-over-layer (SOL) on the SOI has been thinned down to different thicknesses, with the thinnest about 10 nm. It has been found that the full-width-at-half-maxim in the X-ray diffraction spectrum from the SiC films decreases as the SOL thickness decreases, indicating improved quality of the SiC film. A similar trend has also been found in the Raman spectrum. One of the potential explanations for the observation is strain accommodation by the ultra-thin SOI substrate. (c) 2005 Elsevier B.V. All rights reserved.

Size Effect and Geometrical Effect of Polycrystals and Thin Film/Substrate System in Micro-indentation Test

Micro-indentation test at scales on the order of sub-micron has shown that the measured hardness increases strongly with decreasing indent depth or indent size, which is frequently referred to as the size effect. Simultaneously, at micron or sub-micron scale, the material microstructure size also has an important influence on the measured hardness. This kind of effect, such as the crystal grain size effect, thin film thickness effect, etc., is called the geometrical effect by here. In the present research, in order to investigate the size effect and the geometrical effect, the micro-indentation experiments are carried out respectively for single crystal copper and aluminum, for polycrystal aluminum, as well as for a thin film/substrate system, Ti/Si3N4. The size effect and geometrical effect are displayed experimentally. Moreover, using strain gradient plasticity theory, the size effect and the geometrical effect are simulated. Through comparing experimental results with simulation results, length-scale parameter appearing in the strain gradient theory for different cases is predicted. Furthermore, the size effect and the geometrical effect are interpreted using the geometrically necessary dislocation concept and the discrete dislocation theory. Member Price: $0; Non-Member Price: $25.00

Microscale mechanics for metal thin film delamination along ceramic substrates

The metal thin film delamination along metal/ceramic interface in the case of large scale yielding is studied by employing the strain gradient plasticity theory and the material microscale effects are considered. Two different fracture process models are used in this study to describe the nonlinear delamination phenomena for metal thin films. A set of experiments have been done on the mechanism of copper films delaminating from silica substrates, based on which the peak interface separation stress and the micro-length scale of material, as well as the dislocation-free zone size are predicted.

Assessment of Microscale Test Methods of Peeling and Splitting along Surface of Thin-Film/Substrates

Peel test methods are assessed through being applied to a peeling analysis of the ductile film/ceramic substrate system. Through computing the fracture work of the system using the either beam bend model (BB model) or the general plane analysis model (GPA model), surprisingly, a big difference between both model results is found. Although the BB model can capture the plastic dissipation phenomenon for the ductile film case as the GPA model can, it is much sensitive to the choice of the peeling criterion parameters, and it overestimates the plastic bending effect unable to capture crack tip constraint plasticity. In view of the difficulty of measuring interfacial toughness using peel test method when film is the ductile material, a new test method, split test, is recommended and analyzed using the GPA model. The prediction is applied to a wedge-loaded experiment for Al-alloy double-cantilever beam in literature.

Multiscale Treatment of Thin-Film Lubrication

A multiscale technique that combines an atomistic description of the interfacial (near) region with a coarse-grained (continuum) description of the far regions of the solid substrates is proposed. The new hybrid technique, which represents an advance over a previously proposed dynamically-constrained hybrid atomistic-coarse-grained treatment (Wu et al.J. Chem. Phys., 120, 6744, 2004), is applied to a two-dimensional model tribological system comprising planar substrates sandwiching a monolayer film. Shear–stress profiles (shear stress versus strain) computed by the new hybrid technique are in excellent agreement with “exact” profiles (i.e. those computed treating the whole system at the atomic scale).

Formation Of Dendritic Nanostructures In Pyrex Glass Anodically Bonded To Silicon Coated With An Aluminum Thin Film

Anodic bonding with thin films of metal or alloy as an intermediate layer, finds increasing applications in micro/nanoelectromechanical systems. At the bonding temperature of 350 degrees C, voltage of 400 V, and 30 min duration, the anodic bonding is completed between Pyrex glass and crystalline silicon coated with an aluminum thin film with a thickness comprised between 50 and 230 nm. Sodium-depleted layers and dendritic nanostructures were observed in Pyrex 7740 glass adjacent to the bonding interface. The sodium depletion width does not increase remarkably with the thickness of aluminum film. The dendritic nanostructures result from aluminum diffusion into the Pyrex glass. This experimental research is expected to enhance the understanding of how the depletion layer and dendritic nanostructures affect the quality of anodic bonding. (C) 2007 Elsevier B.V. All rights reserved.

Tensile Tests Of Micro Anchors Anodically Bonded Between Pyrex Glass And Aluminum Thin Film Coated On Silicon Wafer

Micro anchor is a kind of typical structures in micro/nano electromechanical systems (MEMS/NEMS), and it can be made by anodic bonding process, with thin films of metal or alloy as an intermediate layer. At the relative low temperature and voltage, specimens with actually sized micro anchor structures were anodically bonded using Pyrex 7740 glass and patterned crystalline silicon chips coated with aluminum thin film with a thickness comprised between 50 nm and 230 nm. To evaluate the bonding quality, tensile pulling tests have been finished with newly designed flexible fixtures for these specimens. The experimental results exhibit that the bonding tensile strength increases with the bonding temperature and voltage, but it decreases with the increase of the thickness of Al intermediate layer. This kind of thickness effect of the intermediate layer was not mentioned in the literature on anodic bonding. (C) 2008 Elsevier Ltd. All rights reserved.

Nanoindentation of thin-film-substrate system: Determination of film hardness and Young's modulus

In the present paper, the hardness and Young's modulus of film-substrate systems are determined by means of nanoindentation experiments and modified models. Aluminum film and two kinds of substrates; i.e. glass and silicon, are studied. Nanoindentation XP II and continuous stiffness mode are used during the experiments. In order to avoid the influence of the Oliver and Pharr method used in the experiments, the experiment data are analyzed with the constant Young's modulus assumption and the equal hardness assumption. The volume fraction model (CZ model) proposed by Fabes et al. (1992) is used and modified to analyze the measured hardness. The method proposed by Doerner and Nix (DN formula) (1986) is modified to analyze the measured Young's modulus. Two kinds of modified empirical formula are used to predict the present experiment results and those in the literature, which include the results of two kinds of systems, i.e., a soft film on a hard substrate and a hard film on a soft substrate. In the modified CZ model, the indentation influence angle, phi, is considered as a relevant physical parameter, which embodies the effects of the indenter tip radius, pile-up or sink-in phenomena and deformation of film and substrate.

Statistical Simulation of Thin-Film Bearings

The information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method are used to simulate the gas flows between the write/read head and the platter of the disk drive (the slider bearing problem). The results of both methods are in good agreement with numerical solution of the Reynolds equation in the cases studied. However, the DSMC method owing to the problem of large sample size demand and the difficulty in regulating boundary conditions at the inlet and outlet was able to simulate only short bearings, while IP simulates the bearing of authentic length ~1000 m ? and can provide more detailed flow information.

Formation of dendritic nanostructures in Pyrex glass anodically bonded to silicon coated with an aluminum thin film

Anodic bonding with thin films of metal or alloy as an intermediate layer, finds increasing applications in micro/nanoelectromechanical systems. At the bonding temperature of 350 degrees C, voltage of 400 V, and 30 min duration, the anodic bonding is completed between Pyrex glass and crystalline silicon coated with an aluminum thin film with a thickness comprised between 50 and 230 nm. Sodium-depleted layers and dendritic nanostructures were observed in Pyrex 7740 glass adjacent to the bonding interface. The sodium depletion width does not increase remarkably with the thickness of aluminum film. The dendritic nanostructures result from aluminum diffusion into the Pyrex glass. This experimental research is expected to enhance the understanding of how the depletion layer and dendritic nanostructures affect the quality of anodic bonding. (C) 2007 Elsevier B.V. All rights reserved.

Linear chirp control of infrared signal in a biased semiconductor thin film

Ultrashort light-matter interactions between a linear chirped pulse and a biased semiconductor thin film GaAs are investigated. Using different chirped pulses, the dependence of infrared spectra on chirp rate is demonstrated for a 5 fs pulse. It is found that the infrared spectra can be controlled by the linear chirp of the pulse. Furthermore, the infrared spectral intensity could be enhanced by two orders of magnitude via appropriately choosing values of the linear chirp rates. Our results suggest a possible scheme to control the infrared signal.

Acceleration of ultra-thin electron layer.Analytical treatment compared with 1D-PIC simulation

In this paper, we apply an analytical model [V.V. Kulagin et al., Phys. Plasmas 14, 113101 (2007)] to describe the acceleration of an ultra-thin electron layer by a schematic single-cycle laser pulse and compare with one-dimensional particle-in-cell (1D-PIC) simulations. This is in the context of creating a relativistic mirror for coherent backscattering and supplements two related papers in this EPJD volume. The model is shown to reproduce the 1D-PIC results almost quantitatively for the short time of a few laser periods sufficient for the backscattering of ultra-short probe pulses.