Room-temperature method for minimizing light-induced degradation in crystalline silicon

Although light-induced degradation (LID) in crystalline silicon is attributed to the formation of boron-oxygen recombination centers, copper contamination of silicon has recently been observed to result in similar degradation. As positively charged interstitialcopper stays mobile at room temperature in silicon, we show that the bulk copper concentration can be reduced by depositing a large negative charge onto the wafer surface. Consequently, light-induced degradation is reduced significantly in both low- and high-resistivity boron-doped Czochralski-grown silicon.Peer reviewe

Underperforming Students: Factors and Decision-Making in Occupational Therapy Programs

The purpose of this study was to better understand factors related to occupational therapy (OT) educators’ decisions to fail underperforming students and to clarify why educators sometimes fail to fail or pass students despite sub-standard performance. Assessing student competence is an essential part of ensuring the safety of those receiving occupational therapy services and ensuring the integrity of the OT profession. Educators in academic and fieldwork settings are responsible for confirming that students who graduate from their programs are able to demonstrate skills required for entry into the profession. A total of 323 OT academic and fieldwork educators responded to a researcher developed survey. Results were analyzed using descriptive statistics and linear regressions. 82% of OT academic educators and 34% of OT fieldwork educators reported failing a student at one time and results revealed common reasons for both groups. In addition, 60% of OT academic educators and 26% of OT fieldwork educators thought there had been a time when they should have failed an underperforming student but did not. Common reasons for failure to fail included lack of proof, vague procedures, giving students the benefit of the doubt, and decreased confidence in handling a failing situation. Recommendations to minimize failure to fail are discussed

Reduction of Light-induced Degradation of Boron-doped Solar-grade Czochralski Silicon by Corona Charging

This study aims at the reduction of light-induced degradation of boron-doped solar-grade Czochralski silicon wafers by corona charging. The method consists of deposition of negative charges on both surface sides of wafer and keeping the wafer in dark for 24 hours to allow the diffusion of positively-charged interstitial copper towards the surfaces. This method proves to be useful to reduce or eliminate light-induced degradation caused by copper. The degradation was significantly reduced in both intentionally (copper-contaminated of the negative charge was found to be proportional to the reduction strengthPeer reviewe

Light-induced degradation in copper-contaminated gallium-doped silicon

To date, gallium-doped Czochralski (Cz) silicon has constituted a solar cell bulk material free of light-induced degradation. However, we measure light-induced degradation in gallium-doped Cz silicon in the presence of copper impurities. The measured degradation depends on the copper concentration and the material resistivity. Gallium-doped Cz silicon is found to be less sensitive to copper impurities than borondoped Cz silicon, emphasizing the role of boron in the formation of copper-related light-induced degradation.Peer reviewe

Experimental evidence on removing copper and light-induced degradation from silicon by negative charge

In addition to boron and oxygen, copper is also known to cause light-induced degradation (LID) in silicon. We have demonstrated previously that LID can be prevented by depositing negative corona charge onto the wafer surfaces. Positively charged interstitial copper ions are proposed to diffuse to the negatively charged surface and consequently empty the bulk of copper. In this study, copper out-diffusion was confirmed by chemical analysis of the near surface region of negatively/positively charged silicon wafer. Furthermore, LID was permanently removed by etching the copper-rich surface layer after negative charge deposition. These results demonstrate that (i) copper can be effectively removed from the bulk by negative charge, (ii) under illumination copper forms a recombination active defect in the bulk of the wafer causing severe light induced degradation.Peer reviewe

Valuable occupational therapy fieldwork educator behaviors

Objective: The purpose of this study was to investigate fieldwork educator behaviors that are valuable from the perspective of Level II occupational therapy and occupational therapist assistant students and fieldwork educators. Participants: 85 fieldwork educators and 37 students from Eastern and Western parts of the United States. Methods: The 5 competency categories of the Self Assessment Tool for Fieldwork Educator Competency were used as the basis for developing the survey items and data was analyzed with non-parametric statistics to check for differences among groups of respondents. Results: Students and fieldwork educators generally ranked the value of the behaviors in the survey as the same. There were differences noted between responses of level II students on first, second, and third placements regarding supervision behaviors of fieldwork educators. (Chi square=6.59, p=0.04 and Chi square=7.95, p=0.02). Conclusion: The alignment of opinion of students and fieldwork educators is important in that it reinforces the common goal of academic programs, students, and fieldwork educators. More research needs to be done in order to understand the impact of placement order on the rankings of valued fieldwork educator behaviors