Nanoindentation study on the phase transformation of single crystal silicon of different crystallographic orientations using a spherical indenter probe

The effect of the crystallographic orientation on the primary and secondary phase transformations of single-crystal silicon (Si) during indentation was investigated in a statistical instrumented-indentation study using a spherical diamond probe with a nominal tip radius of 5 µm. The primary phase transformation from the Si-I to Si-II phase were initiated above a threshold pressure during loading and assumed to be reflected as change in slope or a plateau-like discontinuity in the loading curve (pop-in event). Secondary transformations to polycrystalline high-pressure phases (Si-XII and Si-III) and/or amorphous Si (a-Si) occurred during unloading. It is believed that elbow events correspond to the presence of a-Si; pop-out and kink pop-out events were associated with Si-XII and Si-III phases. The presence of and the pressure at which phase-transformation events occurred during indentation were analyzed and compared for three crystallographic orientations: Si(001), Si(110), and Si(111).In load sequence indentations, the applied maximum force was varied from (20, 25, 30, 45, 60, 80, 100, 150 to 200) mN to study its effect on the phase transformation for the three orientations. In these tests, the force was increased and decreased at fixed (un)loading rates of 5 mN/s. For the majority of the tests, the maximum force was held constant for 5 s before unloading. In selected tests, the force was immediately decreased after reaching its maximum value. For each maximum force, 50 indentation tests were performed.In the partial-unload series, indentations were carried out in the multiple partial unloading technique to study the onset of the primary phase transformation during loading. In this technique, the force was stepwise increased, but before continuing to the next, greater, force value, the force was partially released. The resulting force-displacement curve had two branches corresponding to the fully loaded and partially unloaded state. For elastic deformation, the two branches coincided, but they diverged on plastic deformation, which was associated with the start of the primary phase transformation for Si. The maximum indentation forces applied was 50 mN or 100 mN (in a few selected tests on Si(001)). For each orientation, 50 indentation tests were performed.The indentation moduli of the three Si orientations were determined at maximum indentation loads guaranteeing a purely elastic response of the materials: 20 mN for Si(001) respective 15 mN for Si(110) and Si(111). In each test, the indentation force was linearly increased to the maximum value, then held constant for 5 s and afterwards linearly decreased. The (un)loading rates were fixed at 5 mN/s. For each orientation, 25 indentation tests were performed.The raw experimental indentation data collected in this study are compiled in datasets A through E of this data publication. In this context, raw indentation data are defined as being direct from the instrument corrected for machine compliance and thermal drift. Note: Outliers in indentation curves were not included in the data sets.The aforementioned indentation datasets built the foundation of and serve as companion to the paper: Y.B Gerbig, S.J. Stranick, D.J. Morris, M.D. Vaudin, R.F. Cook, J. Mater. Res. 24/3, 1172 - 1183 (2009) https://doi.org/10.1557/jmr.2009.0122.More details about data collection and processing than already described in this summary can be found in the paper. Data directly underlying figures 1, 2, 3, 5, and 6 of the companion paper are compiled in datasets F through J of this data publication. The accompanying Readme document contains details about organization, content and format of the individual data sets.

Tags: crystallographic-orientation, nanoindentation, phase-transformation, silicon
Organization: National Institute of Standards and Technology