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Microstructural properties of thin-film absorber layers play a vital role in developing high-performance solar cells. Scanning probe microscopy is frequently used for measuring spatially inhomogeneous properties of thin-film solar cells. While powerful, the nanoscale probe can be sensitive to the roughness of samples, introducing convoluted signals and unintended artifacts into the measurement. Here, we apply a glancing-angle focused ion beam (FIB) technique to reduce the surface roughness of CdTe while preserving the subsurface optoelectronic properties of the solar cells. We compare the nanoscale optoelectronic properties “before” and “after” the FIB polishing. Simultaneously collected Kelvin-probe force microscopy (KPFM) and atomic force microscopy (AFM) images show that the contact potential difference (CPD) of CdTe pristine (peak-to-valley roughness > 600 nm) follows the topography. In contrast, the CPD map of polished CdTe (< 20 nm) is independent of the surface roughness. We demonstrate the smooth CdTe surface also enables high-resolution photoluminescence (PL) imaging at a resolution much smaller than individual grains (< 1 μm). Our finite-difference time-domain (FDTD) simulations illustrate how the local light excitation interacts with CdTe surfaces. Our work supports low-angle FIB polishing can be beneficial in studying buried sub-microstructural properties of thin-film solar cells with care for possible ion-beam damage near the surface. 

This linguistic anthropological case study examines one episode of play involving refugee-background teenagers participating in an informal STEM learning experience. This empirical case shows how the disciplinary practices of cosmic ray detector building were productively interwoven with spontaneous play directed by participating youth. The analysis reveals the need for a greater focus on play, which designers and researchers may initially dismiss as “off-task,” but may in fact be an important component of disciplinary practice. Furthermore, we call for attention to play as a potentially important feature of designing and researching culturally sustaining pedagogies (CSPs) with and for diverse learners in informal STEM learning contexts. 

Refugee youth resettled in the United States experience two main barriers to long-term participation in STEM fields: (a) access to STEM skills and knowledge which is impacted by relocation and interrupted schooling, and (b) access to crafting positive learner identities in STEM as multi- lingual, multicultural, and multiracial youth. In this paper, we share a model for engaging refugee teens in cosmic ray research through constructing scintillator cosmic ray detectors, creating digital stories about cosmic rays, and hosting family and community science events where students share their learning with their families. This context serves as the site for ongoing ethnography exploring how refugee-background teens construct STEM-related identities and identifying supportive and unsupportive instructional practices. This paper summarizes the key program details and findings to date.