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The first systematic study for the first phase to form during cobalt germanidation was conducted. Hexagonal β-Co5Ge3 was the first phase to form in case of cobalt germanidation on (100) Ge. This phase formed at a temperature as low as 227 °C. Monoclinic CoGe was experimentally shown to be the second phase to form at the same temperature. Our results are contrary to the previous reports suggesting monoclinic CoGe to be the first phase to form. This is mainly due to the experimental setup that was designed to detect all forming phases: in-situ XRD monitoring at constant low temperature long time anneals of 24-48 h. We also report for the first time that both β-Co5Ge3 and monoclinic CoGe phases that formed during cobalt germanidation were highly ordered partial epitaxial crystal orientations. [ABSTRACT FROM AUTHOR]

A model for the oxidation of SiGe that takes into account the participation of both the Si and the Ge in the oxidation reaction as well as the replacement of Ge in mixed oxide by Si is demonstrated. An effective diffusivity approximation to the Si-Ge interdiffusion on the underlying layer, together with approximate boundary conditions, give reasonable agreement with published results on the formation of a Ge-rich layer.

Electrical characteristics of two polymer thin-film transistors (TFTs) fabricated by spin-coating of P3HDT and P3HT are investigated. Higher field-effect mobility, a lower off current, a lower inverse subthreshold slope and a larger on current ratio is demonstrated by experimental results from the TFTs based on P3HDT.

We propose a physically based model that describes the diameter and the density of voids in silicon introduced via high dose helium ion implantation and subsequent annealing. The model takes into account interactions between vacancies, interstitials, small vacancy clusters, and voids. Void evolution in silicon occurs mainly by a migration and coalescence process. Various factors such as implantation energy and dose, anneal temperature, atmospheric pressure, and impurity level in silicon can influence the migration and coalescence mechanism and thus play a role in the void evolution process. Values for model parameters are consistent with known values for point defect parameters and assumed diffusion limited reaction rates. A single 'fitting parameter' represents the rate of cavity migration and coalescence and is, therefore, related to surface diffusion of adatoms. Results obtained from simulations based upon the model were compared to our experimental results and to previously reported experimental results obtained over a wide range of conditions. Data from the literature included experiments with helium ion implantation energies in the range 30-300 keV, doses of 1 × 1016-1 × 1017 cm-2, subsequent annealing temperatures in the range 700-1200 °C, and annealing duration in the range 15 min-2 h. Excellent agreement is found between the simulated results and those from reported experiments. The extracted migration and coalescence rate parameter show an activation energy consistent with surface diffusivity of silicon. It shows a linear dependence on helium dose, and increases with decreased implantation energy, decreased ambient pressure, decreased substrate impurities, increased temperature ramp rate, or increased Ge fraction in cavity layer, all consistent with the proposed physical mechanism. [ABSTRACT FROM AUTHOR]

Voids were formed in silicon (Si) and silicon germanium/silicon (Si1-xGex/Si) samples containing 5% or 9% Ge (at. %) by 30 keV, 5 × 1016 cm-2 helium (He+) implantation followed by annealing in nitrogen (N2) or dry oxygen (O2) atmospheres in the temperature range 960-1110 °C. Si1-xGex thicknesses were 60 nm and 20 nm for 5% and 9% Ge, respectively. He+ implantation energy was set such that in Si1-xGex/Si samples voids were formed inside the Si substrate. An increase in annealing temperature resulted in an increase in the average void diameter and decrease in the average void density. Due to the presence of implantation damage and the relatively high temperature anneals, Ge diffusion occurs, which results in a stress gradient in the sample that interacts with the void layer. The presence of Ge also results in weaker Si-Ge bonds (compared to Si-Si bonds). This leads to an increase in the rate of cavity migration providing a likely explanation for the increase in the average void diameter and decrease in the average void density in Si1-xGex/Si samples when compared to the similarly prepared Si samples. No impact on the void evolution process was observed as a result of changing the anneal atmosphere from N2 to dry O2. [ABSTRACT FROM AUTHOR]

We present a model for the interdiffusion of silicon (Si) and germanium (Ge) in silicon germanium/silicon (Si1-xGex/Si) superlattice (SL) structures. Both a vacancy exchange mechanism and an interstitial diffusion mechanism are considered in the proposed model. The effects of Ge on the diffusion properties of the SL are also considered and the conservation of lattice site constraints is accounted for. Output from the model is compared to experimental Ge interdiffusion profiles for samples annealed in the temperature range 770–1125 °C in inert ambient and in some cases in oxidizing ambient, where the experimental samples contained Ge fractions up to 30%. For anneal temperatures up to 1075 °C a vacancy exchange mechanism is sufficient to describe the interdiffusion mechanism in Si1-xGex/Si SL structures. For higher anneal temperatures interstitial diffusion mechanism dominates the interdiffusion process. [ABSTRACT FROM AUTHOR]

A model is used for the interdiffusion of silicon (Si) and germanium (Ge) in silicon germanium/silicon ([Si.sub.1-x][Ge.sub.x]/Si) superlattice (SL) structures. A vacancy exchange mechanism and an interstitial diffusion mechanism are considered and the effects of Ge on the diffusion properties of the SL are considered.

Wearable sensors are of interest for several application areas, most importantly for their potential to allow for the design of personal continuous health monitoring systems. For wearable sensors, flexibility is required and imperceptibility is desired. Wearable sensors must be robust to strain, motion, and environmental exposure. A number of different strategies have been utilized to achieve flexibility, imperceptibility, and robustness. All of these approaches require the integration of materials having a range of chemical, mechanical, and thermal properties. We have given a concise review of the range of materials that must be incorporated in wearable sensors regardless of the strategies adopted to achieve wearability. We first describe recent advances in the range of wearable sensing materials and their processing requirements and then discuss the potential routes to the integration of these heterogeneous materials. [ABSTRACT FROM AUTHOR]

Inexpensive, easy-to-process, light-weight polymer-based materials that are biocompatible, mechanically flexible, and optically transparent have emerged as alternatives to metals and ceramics in the packaging of implantable sensors. These materials have been used to package components such as microelectrode arrays, telemetric coils and structural membranes. Polymers are also being used for the encapsulations and coatings of the implants. The devices and packages require fine-pitch, low-loss, and highly-conductive paths on mechanically and chemically reliable polymer films. In this review, several polymers used for implantation and related integration technologies are identified. We give an overview of novel applications of polymers in implantable sensor packages, and identify future directions for their application. Polymers exhibit high moisture absorption rate, high-frequency electrical loss, and low mechanical stability. These properties are aggravated when polymers are used for in vivo applications. Also, the integration of polymers with polymers/metals at high bonding temperatures and pressures may degrade their properties and interfaces. Furthermore, adhesive bonding and physical/chemical deposition methods for the integration may introduce non-hermetic, permeable, optically opaque, and poorly conductive interfaces. Thus, creating polymer-based high-density and small-dimension structures are critical for packaging. To address these issues, polymers with improved characteristics as well as integration techniques using low bonding temperature and pressure are indispensable. Liquid crystal polymer (LCP) and surface activated bonding (SAB) technologies meet these requirements. SAB technologies enable nanoscaled polymer-polymer/metal bonding to realize reliable, miniaturized, and high-performance packages for implantable sensors. This article is meant to serve as a reference for future research in the emerging field of implantable sensors by critically assessing the specific merits and drawbacks of several material-process combinations. [ABSTRACT FROM AUTHOR]