Optimization of the nucleation-site density for the electrodeposition of cadmium sulfide on indium-tin-oxide

Cadmium sulfide (CdS) is a preferred heterojunction partner for a number of chalcogenide-based solar cells. In view of this, interest has grown in the use of solution-based deposition techniques as an alternative route for the preparation of uniform ultrathin films of CdS. However, the quality of the electrodeposited CdS films on indium-tin oxide (ITO) remains far from optimal. This is because the ITO surface is electrochemically heterogeneous due to the presence of indium oxide; nucleation and further electrodeposition of CdS does not transpire on the oxided sites. Hence, only coarse-grained coatings, instead of homogeneous ultrathin films, are generated at un-pretreated ITO surfaces. In the present study, a mitigation of the amount of interfacial In oxide was attempted in order to increase the nucleation-site (indium-metal site) density. The procedure consisted of two steps: (i) Mild electrochemical reduction of the ITO to convert surface In(III) to In(0), followed by (ii) surface-limited redox replacement (SLRR) of In(0) by Cu via an aqueous solution of Cu^(2+). This procedure resulted in the formation of a high density of oxide-free Cu on which CdS nuclei would form; the thickness was such that optical transparency was largely undiminished. A ten-fold increase in CdS site density was observed, and that permitted the epitaxial growth of a second semiconductor, CdTe, atop the CdS film. The influences of applied potential and deposition time on nucleation-site sizes and densities were also studied

Education and National Development

The New England Regional Meeting of the Comparative and International Education Society was held on the campus of Springfield College on April 29, 1977. The Conference was co-sponsored by the Division of Community Education, Springfield College, and the Center for International Education, University of Massachusetts. The theme of the conference was Education and National Development. The papers delivered ranged in topics from a global perspective to the use of ethnic and multicultural education to assist in national development. Case studies of specific cultural areas highlight the conference. The papers provided a format for discussing and recording the experiences and research endeavors of the participants. A total of fourteen papers were delivered. This publication contains the papers delivered at the Conference

Development of a Certificate in Healthcare Improvement for Inter-Professional Teams

Introduction To address gaps in care team improvement-science education and connect geographically dispersed learners, we created a healthcare improvement certificate program, now completing the third program year, for inter-professional (IP) healthcare teams, including third year medical students. Methods This hybrid learning program consists of five modules: Learning Healthcare Systems, Improvement Science, Patient Safety and Diagnostic Error, Population Health and Health Equity and Leading Change. The curricular materials are comprised of focused readings, concise videos, faculty-moderated discussion boards, weekly synchronous calls of participants with faculty, and a longitudinal improvement project. The faculty are content experts, and worked with a curricular designer to define learning objectives and develop content. Results We have completed three years of this six-month program, training 61 participants (17 of whom were medical students) at 14 sites. In the third year, several medical students participated without an IP team. Development of the materials has been iterative, with feedback from learners and faculty used to shape the materials. Discussion We demonstrate the development and rollout of a hybrid-learning program for diverse and geographically dispersed IP teams, including medical students. Time restrictions limited the depth of topics, and scheduling overlap caused some participants to miss the interactive calls. We plan to evaluate the utility of the program for participants over time, using qualitative methods. Conclusion This educational model is feasible for IP teams studying improvement science and implementing change projects, and can be adopted to dispersed geographic settings

Competitive Interactions between Invasive Nile Tilapia and Native Fish: The Potential for Altered Trophic Exchange and Modification of Food Webs

Recent studies have highlighted both the positive and negative impacts of species invasions. Most of these studies have been conducted on either immobile invasive plants or sessile fauna found at the base of food webs. Fewer studies have examined the impacts of vagile invasive consumers on native competitors. This is an issue of some importance given the controlling influence that consumers have on lower order plants and animals. Here, we present results of laboratory experiments designed to assess the impacts of unintended aquaculture releases of the Nile tilapia (Oreochromis niloticus), in estuaries of the Gulf of Mexico, on the functionally similar redspotted sunfish (Lepomis miniatus). Laboratory choice tests showed that tilapia prefer the same structured habitat that native sunfish prefer. In subsequent interspecific competition experiments, agonistic tilapia displaced sunfish from their preferred structured habitats. When a piscivore (largemouth bass) was present in the tank with both species, the survival of sunfish decreased. Based on these findings, if left unchecked, we predict that the proliferation of tilapia (and perhaps other aggressive aquaculture fishes) will have important detrimental effects on the structure of native food webs in shallow, structured coastal habitats. While it is likely that the impacts of higher trophic level invasive competitors will vary among species, these results show that consequences of unintended releases of invasive higher order consumers can be important

Electrochemical Atomic Layer Deposition (ALD)

John Stickney, Professor of Chemistry and Department Head of Chemistry at the University of Georgia, presented a lecture at the Nano@Tech Meeting on February 24, 2009 at 12 noon in room 102 of the Microelectronics Research Center.Runtime: 73:20 minutesRecent results in studies of the formation of compound and metal nanofilms by electrochemical atomic layer deposition (ALD) will be discussed. ALD is the deposition of materials an atomic layer at a time using surface limited reactions. Electrochemical surface limited reactions are generally referred to as underpotential deposition or UPD. By combining UPD and ALD, electrochemical ALD is created. Historically most electrochemical ALD has been performed in the creation of compound semiconductor thin films. More recently a number of elemental deposits have been formed by electrochemical ALD, and a surface limited reaction referred to here as a surface limited redox replacement or SLRR. Recent work on the formation of compound for photovoltaics, thermoelectrics, and for phase change memory may be discussed. In addition, recent work on the growth of Pt and Ru nanofilms for fuel cell electrodes may be described. Deposit characterization involves electron beam microprobe analysis (EPMA) for deposit stoichiometry. Glancing angle X-ray diffraction for structural characterization, while scanning tunneling microscopy (STM) was used to characterize the surface morphology. Optical characterization involves reflection absorption studies as well as photoelectrochemical studies. Optimization studies involve systematic investigation of the conditions which result in the formation of one compound or elemental monolayer with each deposition cycle. In general, deposits formed at a rate of one monolayer per cycle or less show the best structure, stoichiometry and morphology. Nano templates can be used to form nanoclusters, rods or wires, depending on the number of cycles performed. Superlattices can be formed by alternating some finite number of cycles for the growth of one compound with a similar number of cycles of another. X-ray diffraction can then be used to characterize the period of the superlattice