We study the hardness and Young’s modulus of CdSiP2 (CSP) and ZnGeP2 (ZGP), two widely used chalcopyrites for mid-IR nonlinear frequency conversion. Nanoindentation with a Berkovich tip is applied for precise load control. Microhardness values from the literature are scattered but still indicate higher hardness for the compound with wider bandgap and higher melting point, i.e. CSP. Our measurements with optically polished single-crystal samples of random orientation give nanohardness of 9.9 and 11.5 GPa, and Young’s modulus of 136 and 150 GPa, for CSP and ZGP, respectively. We compare the obtained results with GaP, the binary isoelectronic analog of ZGP.
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