We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient postprocessing to produce crystalline silicon thin films.

A growing body of scholarly work indicates that student performance on physics problems stems from many factors, including relevant conceptual understanding. However, in contexts in which significant conceptual difficulties have been documented via research, it can be difficult to pinpoint and isolate such factors because students' written and interview responses rarely reveal the full richness of their conscious and, perhaps more importantly, subconscious reasoning paths. In this investigation, informed by dualprocess theories of reasoning and decision making as well as the theoretical construct of accessibility, we conducted a series of experiments in order to gain greater insight into the factors impacting student performance on the "five-block problem," which has been used in the literature to probe student thinking about buoyancy. In particular, we examined both the impact of problem design (including salient features and cueing) and the impact of targeted instruction focused on density-based arguments for sinking and floating and on neutral buoyancy. The investigation found that instructional modifications designed to remove the strong intuitive appeal of the first-available response led to significantly improved performance, without improving student conceptual understanding of the requisite buoyancy concepts. As such, our findings represent an important first step in identifying systematic strategies for using theories from cognitive science to guide the development and refinement of research-based instructional materials.

After targeted instruction designed to improve student conceptual understanding of physics, a significant fraction of students are not able to answer many questions in a consistent manner. Prior research suggests that even those students who demonstrate that they acquired the relevant knowledge and skills (i.e., possess the requisite "mindware") still tend to rely on their intuitively appealing (and often incorrect) ideas. This study aims to provide insights into cognitive mechanisms that may lead to the identified inconsistencies in student reasoning. We present results of an empirical investigation guided by dual process theories of reasoning and accompanying theoretical constructs of cognitive reflection and mindware. Specifically, we proposed a set of hypotheses to establish a link between student abilities to mediate intuitive responses and performance on physics questions that elicit strong intuitive responses. The cognitive reflection test (CRT), developed by cognitive psychologists, was used to measure students' ability to engage in analytic processing in a more productive manner (i.e., cognitive reflection skills). Additionally, we developed a set of screening-target questions in the context of Newton's third law to assess student reasoning approaches in physics. Results suggest that, in the presence of the necessary mindware, those students who possess a higher level of cognitive reflection skills are more likely to (i) arrive at a correct answer on a question that tends to elicit a strong intuitive, but incorrect response; (ii) recognize the need for justifying their answers, even if a correct answer does not require rejecting an intuitively appealing response; and (iii) engage in consistent reasoning.

We present a detailed study of the laser crystallization of amorphous silicon thin films as a function of laser fluence and film thickness. Silicon films grown through plasma-enhanced chemical vapor deposition were subjected to a Q-switched, diode-pumped solid-state laser operating at 355 nm. The crystallinity, morphology, and optical and electronic properties of the films are characterized through transmission and reflectance spectroscopy, resistivity measurements, Raman spectroscopy, X-ray diffraction, atomic force microscopy, and optical and scanning-electron microscopy. Our results reveal a unique surface morphology that strongly couples to the electronic characteristics of the films, with a minimum laser fluence at which the film properties are optimized. A simple scaling model is used to relate film morphology to conductivity in the laser-processed films.