| Summary: | The deformation behaviors and fracture features of GaP(100) single-crystal are investigated by using nano- and micro-scale indentation techniques. The hardness and Young’s modulus were measured by nanoindentation using a Berkovich diamond indenter with continuous contact stiffness measurements (CSM) mode and the values obtained were 12.5 ± 1.2 GPa and 152.6 ± 12.8 GPa, respectively. In addition, the characteristic “pop-in” was observed in the loading portion of load-displacement curve, which was caused by the nucleation and/or propagation of dislocations. An energetic estimation methodology on the associated nanoindentation-induced dislocation numbers resulting from the pop-in events was discussed. Furthermore, the Vickers indentation induced fracture patterns of GaP(100) single-crystal were observed and analyzed using optical microscopy. The obtained fracture toughness <i>K<sub>C</sub></i> of GaP(100) single-crystal was ~1.7 ± 0.1 MPa·m<sup>1/2</sup>, which is substantially higher than the <i>K</i><sub>IC</sub> values of 0.8 MPa·m<sup>1/2</sup> and 1.0 MPa·m<sup>1/2</sup> previously reported for of single-crystal and polycrystalline GaP, respectively.
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