Eunjeong Choi

Surface and interface states of Bi2Se3 thin films investigated by optical second-harmonic generation and terahertz emission

We investigate the surface and interface states of Bi2Se3 thin films by using the second-harmonic generation technique. Distinct from the surface of bulk crystals, the film surface and interface show the isotropic azimuth dependence of second-harmonic intensity, which is attributed to the formation of randomly oriented domains on the in-plane. Based on the nonlinear susceptibility deduced from the model fitting, we determine that the surface band bending induced in a space charge region occurs more strongly at the film interface facing the Al2O3 substrate or capping layer compared with the interface facing the air. We demonstrate that distinct behavior of the terahertz electric field emitted from the samples can provide further information about the surface electronic state of Bi2Se3.

Exploring Possible Selves through Sharing Stories Online: Case Studies of Preservice Teachers in Bilingual Classrooms.

We examined how narrative was used in online classroom discussion as preservice bilingual teachers experimented with possible future selves. Considering associations between narrative and identity construction, we explored the complementary roles of stories from personal past experiences and backgrounds, experience as teacher interns, and imagined experiences of possible future selves as four preservice teachers endeavored to understand what it means to be a teacher of bilingual children. Data came from transcripts of nine computer-mediated discussions (CMDs) incorporated as a classroom activity in a theory-into-practice teacher preparation course. Findings suggest that preservice teachers’ diverse trajectories to becoming bilingual and their motivations for becoming teachers as expressed in narratives during CMD have the potential to increase the specificity and diversity of possible selves for all discussion participants. Narratives shared in discussion allow all preservice teachers to borrow from a library of lived experiences to inform their imagined future teaching selves.

“I wonder if …” The Process of Inquiry in Support of Students’ Co-Learning From Online Discussion

Current views of literacy have expanded to encompass how individuals in sociocultural systems make meaning as they “read” and “write” their world. From this view, the work of students involved in pursuing deeper understandings as they discuss course concepts is a literacy act. This study focused on the inquiry and questioning moves of graduate students as they participated in nine online classroom discussions about course concepts. A coding scheme adapted from several researchers interested in inquiry and knowledge co-construction was applied to the students’ comments posted in synchronous online discussion. Findings indicated that students used various inquiry moves to engage actively with course ideas, with some moves more popular than others, and with some students using a wider variety of moves than others. Although the most common moves were of those reacting to others’ comments with an interpretation, supporting evidence, or more thoroughly explaining a previously shared idea, threads often developed into more sophisticated inquiry exchanges through “inferences” and “critical evaluations.” Implications are offered for the use of an inquiry lens on the contributions of students involved in online classroom discussion as a way to highlight students’ active, meaningful knowledge construction.

Common language assessment for English learners

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