Recombination activity of iron-gallium and iron-indium pairs in silicon

The recombination activity of iron-gallium (FeGa) and iron-indium (FeIn) pairs in crystalline silicon is studied by means of injection-dependent carrier lifetime measurements on Fe-implanted, Ga- and In-doped p-type silicon wafers of different resistivities (0.3–15Ωcm). Compared to FeB pairs, FeGa and FeIn pairs are found to be much more effective recombination centers in p-type silicon. Using Shockley–Read–Hall statistics we determine the energy level Et of the FeGa-related center to be 0.20eV above the valence-band edge Eν. The strong recombination activity of FeGa is assigned to its large electron-capture cross section σn of 4×10⁻¹⁴cm². The hole-capture cross section σp is 2×10⁻¹⁴cm². For the FeIn-related recombination center, our measurements show that Et=Eν+0.15eV, σn=3.5×10⁻¹³cm², and σp=1.5×10⁻¹⁴cm². Strong illumination with white light is found to dissociate both types of pairs. Storage of the samples in the dark leads to a full repairing of FeGa and FeIn pairs. Lifetime changes measured before and after illumination can be used to determine the interstitialiron concentration in Ga- and In-doped silicon using calibration factors determined from the measured defect parameters.J.S. thanks A. Cuevas and A. Blakers for their hospitality during his research stay at ANU and acknowledges the financial support of the Alexander von Humboldt Foundation. D.M. acknowledges the financial support of the Australian Research Council

Security pattern evaluation

Current Security Pattern evaluation techniques are demonstrated to be incomplete with respect to quantitative measurement and comparison. A proposal for a dynamic testbed system is presented as a potential mechanism for evaluating patterns within a constrained environment.Postprin

What's the PREMES behind your pattern?

Design patterns are supposed to be the well documented, tried and tested solutions to recurrent problems. Current evaluation techniques do not provide a demonstrable and holistic means to evaluate pattern quality. This paper introduces Pattern Report Cards an evaluation process for software design patterns that is demonstrable, measurable, and reproducible. A set of quality indicators for determining pattern quality has been identified, and a set of qualitative and quantitative evaluation techniques assembled to determine the quality of adherence to these indicators. Further, management and execution of the evaluation process is controlled by the PREMES framework. This framework describes a management cycle that facilitates the construction of bespoke evaluation systems for design patterns. Process tailoring is achieved by providing guidance over the selection and construction of the techniques used to assess pattern quality. Use of these techniques will help bolster existing evaluation processes, and lead to the improvement of design pattern evaluation techniques.Postprin

Providing additional information about the benefits of statins in a leaflet for patients with coronary heart disease : a qualitative study of the impact on attitudes and beliefs

OBJECTIVE: To explore the impact of providing additional information about the potential benefits of simvastatin in a patient leaflet on attitudes and beliefs. DESIGN: Interview-based study using a generic qualitative approach and framework analysis. PARTICIPANTS: 21 participants receiving a prescription for simvastatin were recruited from a general practitioner practice (from a total of 120). 8 participants were women; the age range was 55-92. INTERVENTION: Participants were provided with leaflets showing one of 3 types of additional benefit information: (1) textual statement, (2) number needed to treat (NNT) or (3) natural frequency. Semistructured interviews explored patient's attitudes and beliefs. RESULTS: A descriptive narrative of preferences for format suggested patients prefer textual as opposed to numerical benefit information. Significant barriers to the acceptance of numerical benefit information included difficulty in understanding the numbers. Patients overestimated the benefits of statins and expressed surprise at the numerical information. CONCLUSIONS: Textual information was preferred but numerical information, in particular in the form of a natural frequency, may help patients make judgements about their medicines. NNTs were found to be very difficult to understand. This raises the prospect that some patients might reject medicines because of disappointment with the perceived low benefits of their medicines. The self-reported impact on behaviour appeared minimal with reports of intentions to 'do what the doctor tells me'. Further research is needed to explore the impact of such statements on people who are yet to be prescribed a statin

Impact of dopant compensation on the deactivation of boron-oxygen recombination centers in crystalline silicon

The boron-oxygen recombination center responsible for the light-induced degradation of Czochralski silicon solar cells can be permanently deactivated by illumination at elevated temperature. In this study, we examine the impact of dopant compensation on the deactivation process. The experimental results show that the deactivation rate depends inversely on the total boron concentration instead of the net doping concentration, suggesting that boron is directly involved in the deactivation process. A linear dependence of the activation energy on the total boron concentration further supports this conclusion.Funding was provided by the State of Lower Saxony and the DAAD/Go8 Australia Germany Joint Research Cooperation Scheme

Issues affecting Security Design Pattern engineering

Security Design Patterns present the tried and tested design decisions made by security engineers within a well documented format. Patterns allow for complex security concepts, and mechanisms, to be expressed such that non domain experts can make use of them. Our research is concerned with the development of pattern languages for advanced crypto-systems. From our experience developing pattern languages we have encountered several recurring issues within security design pattern engineering. These issues, if not addressed, will affect the adoption of security design patterns. This paper describes these issues and discusses how they could be addressed.Publisher PD

Electronic properties of iron-boron pairs in crystalline silicon by temperature- and injection-level-dependent lifetime measurements

Iron-boron pairs in crystalline silicon are studied by measuring the recombination lifetime as a function of injection density, doping concentration, and temperature. The characteristic crossover point of the injection-level-dependent carrier lifetime curves measured before and after optical dissociation of the iron-boron pairs is analyzed to determine the energy level as well as the electron- and hole-capture cross sections of the acceptor level of iron-boron pairs, assuming known recombination parameters for interstitialiron. The doping concentration dependence of the crossover point gives an electron-capture cross section of (1.4±0.2)×10¯¹⁴cm², while the temperature dependence results in a hole-capture cross section in the range from 0.5×10¯¹⁵to2.5×10¯¹⁵cm² and an energy level of (0.26±0.02)eV below the conduction-band edge