Arkadeep Kumar

The chemo-mechanical effect of cutting fluid on material removal in diamond scribing of silicon

The mechanical integrity of silicon wafers cut by diamond wire sawing depends on the damage (e.g., micro-cracks) caused by the cutting process. The damage type and extent depends on the material removal mode, i.e., ductile or brittle. This paper investigates the effect of cutting fluid on the mode of material removal in diamond scribing of single crystal silicon, which simulates the material removal process in diamond wire sawing of silicon wafers. We conducted scribing experiments with a diamond tipped indenter in the absence (dry) and in the presence of a water-based cutting fluid. We found that the cutting mode is more ductile when scribing in the presence of cutting fluid compared to dry scribing. We explain the experimental observations by the chemo-mechanical effect of the cutting fluid on silicon, which lowers its hardness and promotes ductile mode material removal.

Care as a Resource in Underserved Learning Environments

We present results from an ethnographic inquiry of technology-based learning at an after-school learning center in Mumbai (India) that caters to students from neighboring slum communities.We conducted participant observation for 120 hours and 58 semi-structured interviews with different stakeholders (including teachers, staff, parents, and students) at the center over nine weeks from December 2015 to July 2016. Taking an assets-based approach in an underserved context, we uncover the role of care as a resource and present the rich and varied caring behaviors enacted in this sociotechnical system.We then discuss how care effects a greater sense of ownership, interdependency, and community. Examining the role of aligning values in motivating caring behavior, we conclude with recommendations for supporting, leveraging, and extending care via technology design in an underserved, technology-enhanced learning environment.

Crystallographic Orientation Identification in Multicrystalline Silicon Wafers Using NIR Transmission Intensity

Near-infrared (NIR) polariscopy is a technique used for the non-destructive evaluation of the in-plane stresses in photovoltaic silicon wafers. Accurate evaluation of these stresses requires correct identification of the stress-optic coefficient, a material property which relates photoelastic parameters to physical stresses. The material stress-optic coefficient of silicon varies with crystallographic orientation. This variation poses a unique problem when measuring stresses in multicrystalline silicon (mc-Si) wafers. This paper concludes that the crystallographic orientation of silicon can be estimated by measuring the transmission of NIR light through the material. The transmission of NIR light through monocrystalline wafers of known orientation were compared with the transmission of NIR light through various grains in mc-Si wafers. X-ray diffraction was then used to verify the relationship by obtaining the crystallographic orientations of these assorted mc-Si grains. Variation of transmission intensity for different crystallographic orientations is further explained by using planar atomic density. The relationship between transmission intensity and planar atomic density appears to be linear.

Designing for Intersections

In response to the recent call for a more intersectionally-aware field of human-computer interaction (HCI), we aim to operationalize intersectionality for technology design in HCI. We develop our lens of intersectionality by drawing on the work of Rita Kaur Dhamoon, and use it to analyze data collected from a multi-sited ethnographic study of seven low-resource learning environments in the Indian states of Maharashtra, Tamil Nadu, and West Bengal. Our research contributions are threefold. First, we extend conversations in Intersectional HCI by expanding its scope from understanding users to recognizing social processes. Second, we emphasize the importance of factoring in both penalties and privileges when conducting research in underserved contexts. Finally, we engage situated comparisons as a methodology to identify pathways for designing interactive systems across intersectionally diverse environments.

Wear of diamond in scribing of multi-crystalline silicon

A practical challenge in slicing of low-cost multi-crystalline silicon (mc-Si) wafers by the fixed abrasive diamond wire sawing process is increased wire consumption due to greater wear of the diamond compared to slicing of the more expensive mono-crystalline silicon (mono-Si) wafers. In this paper, we present the results of scribing of mc-Si and mono-Si materials with two conical tip diamond indenters of the same geometry to understand the possible reasons for increased diamond wear in cutting of multi-crystalline silicon. Specifically, the scribing forces and the diamond indenter wear produced in scribing of the two silicon materials are analyzed. The results show that the forces generated in scribing of mc-Si are higher than in scribing of mono-Si. The higher forces in scribing of mc-Si are consistent with the corresponding higher tip radius of curvature (due to wear) of the diamond indenter compared to the tip radius produced in scribing of mono-Si. Scanning electron microscopy and confocal microscopy of the diamond indenters show that wear is primarily due to physical micro-fracture and blunting of the diamond. Raman spectroscopy shows evidence of stress-induced phase transformation of the diamond and the formation of compressive residual stress in the diamond. Plausible physical reasons, including the role of material inhomogeneity in mc-Si, for the wear of diamond during scribing are given.A practical challenge in slicing of low-cost multi-crystalline silicon (mc-Si) wafers by the fixed abrasive diamond wire sawing process is increased wire consumption due to greater wear of the diamond compared to slicing of the more expensive mono-crystalline silicon (mono-Si) wafers. In this paper, we present the results of scribing of mc-Si and mono-Si materials with two conical tip diamond indenters of the same geometry to understand the possible reasons for increased diamond wear in cutting of multi-crystalline silicon. Specifically, the scribing forces and the diamond indenter wear produced in scribing of the two silicon materials are analyzed. The results show that the forces generated in scribing of mc-Si are higher than in scribing of mono-Si. The higher forces in scribing of mc-Si are consistent with the corresponding higher tip radius of curvature (due to wear) of the diamond indenter compared to the tip radius produced in scribing of mono-Si. Scanning electron microscopy and confocal microscopy...

Learning about Teaching in Low-Resource Indian Contexts

Online learning environments are being deployed globally to offer learning opportunities to diverse student communities. We propose the deployment of such an environment in low-resource after-school settings across India. We draw on preliminary research conducted in summer 2015 that leveraged existing ties with an NGO working across 35 after-school classrooms. Our larger goal is to (1) support tutors in curating and distributing learning content to students, (2) engage students in a mobile, networked learning environment where they can share and collaborate, and (3) evaluate the feasibility of online learning environments for low-resource contexts. In this submission, our focus is on the first component.