Ferromagnetism in (In,Mn)As Diluted Magnetic Semiconductor Thin Films Grown by Metalorganic Vapor Phase Epitaxy

In1-xMnxAs diluted magnetic semiconductor (DMS) thin films have been grown using metalorganic vapor phase epitaxy (MOVPE). Tricarbonyl(methylcyclopentadienyl)manganese was used as the Mn source. Nominally single-phase, epitaxial films were achieved with Mn content as high as x=0.14 using growth temperatures Tg>475 C. For lower growth temperatures and higher Mn concentrations, nanometer scale MnAs precipitates were detected within the In1-xMnxAs matrix. Magnetic properties of the films were investigated using a superconducting quantum interference device (SQUID) magnetometer. Room-temperature ferromagnetic order was observed in a sample with x=0.1. Magnetization measurements indicated a Curie temperature of 333 K and a room-temperature saturation magnetization of 49 emu/cm^3. The remnant magnetization and the coercive field were small, with values of 10 emu/cm^3 and 400 Oe, respectively. A mechanism for this high-temperature ferromagnetism is discussed in light of the recent theory based on the formation of small clusters of a few magnetic atoms.Comment: 5 pages, 5 figures, accepted for publication in JVST

Antimony doping of Si layers grown by solid-phase epitaxy

We report here that layers of Si formed by solid-phase epitaxial growth (SPEG) can be doped intentionally. The sample consists initially of an upper layer of amorphous Si (~1 µm thick), a very thin intermediate layer of Sb (nominally 5 Å), and a thin lower layer of Pd (~500 Å), all electron-gun deposited on top of a single-crystal substrate (1–10 Ω cm, p type, orientation). After a heating cycle which induces epitaxial growth, electrically active Sb atoms are incorporated into the SPEG layer, as shown by the following facts: (a) the SPEG layer forms a p-n junction against the p-type substrate, (b) the Hall effect indicates strong n-type conduction of the layer, and (c) Auger electron spectra reveal the presence of Sb in the layer

Interaction of Al layers with polycrystalline Si

Auger electron spectroscopy, MeV 4He + backscattering spectrometry and scanning electron microscopy have been used to investigate interactions between Al films and polycrystalline layers of CVD Si deposited on SiO2. Depth profiling techniques showed that intermixing of the Al and Si occurred in the 400–560 °C temperature range (i.e., below the eutectic). Dissolution of the poly Si into the Al film occurs followed by nucleation and growth of Si crystallites in the Al film. The morphology of the final structure depends on the relative thicknesses of the as-deposited Al and Si layers. In the case of the original Al thickness being greater than that of the Si, the Si forms large precipitates in the Al matrix. For Al layers thinner than those of the Si, a nearly continuous Si film is formed on the outer surface. The thickness of this final Si film is approximately that of the original Al layer. The remaining Si and the Al form a two-phase layer between the outer Si film and the SiO2 substrate

A toolkit of mechanism and context independent widgets

Most human-computer interfaces are designed to run on a static platform (e.g. a workstation with a monitor) in a static environment (e.g. an office). However, with mobile devices becoming ubiquitous and capable of running applications similar to those found on static devices, it is no longer valid to design static interfaces. This paper describes a user-interface architecture which allows interactors to be flexible about the way they are presented. This flexibility is defined by the different input and output mechanisms used. An interactor may use different mechanisms depending upon their suitability in the current context, user preference and the resources available for presentation using that mechanism

Understanding concurrent earcons: applying auditory scene analysis principles to concurrent earcon recognition

Two investigations into the identification of concurrently presented, structured sounds, called earcons were carried out. One of the experiments investigated how varying the number of concurrently presented earcons affected their identification. It was found that varying the number had a significant effect on the proportion of earcons identified. Reducing the number of concurrently presented earcons lead to a general increase in the proportion of presented earcons successfully identified. The second experiment investigated how modifying the earcons and their presentation, using techniques influenced by auditory scene analysis, affected earcon identification. It was found that both modifying the earcons such that each was presented with a unique timbre, and altering their presentation such that there was a 300 ms onset-to-onset time delay between each earcon were found to significantly increase identification. Guidelines were drawn from this work to assist future interface designers when incorporating concurrently presented earcons

Painting the ideal home: using art to express visions of technologically supported independent living for older people in North East England

This paper describes the investigation of the development of future technological products to support older people in everyday living through the agency of a community art group. Recent research has identified a number of challenges facing designers seeking to use traditional participatory design approaches to gather technology requirements data from older people. Here, a project is described that sought to get a group of older people to think creatively about their needs and desires for technological support through the medium of paint. The artistic expression technique described in this article allowed the identification of issues that had also been found by previous research that used a range of different techniques. This indicates that the approach shows promise, as it allows information to be gathered in an environment that is comfortable and familiar using methods already known by the participants and which they find enjoyable. It provides a complement (or possible alternative) to standard protocols and has the potential benefit of extracting even richer information as the primary task for participants is enjoyable in its own right and is not associated with an interrogative process. Furthermore, it is argued that some of the key risks of traditional approaches are lessened or removed by the naturalistic setting of this approach