First-Principles Study on Physical Properties of a Single ZnO Monolayer with Graphene-Like Structure

By Z. C. Tu. 2009

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The elastic, piezoelectric, electronic, and optical properties of a single ZnO monolayer (SZOML) with graphene-like structure are investigated from the first-principles calculations. The phonon dispersion curves contain three acoustic and three optical branches. Atpoint, the out-of-plane acoustic mode has an asymptotic behavior ��q� = Bq 2 with B = 1� 385 × 10 −7 m 2 /s, while two in-plane acoustic modes have sound velocities 2.801 km/s and 8� 095 km/s; the other three optical modes have fre- quencies 250 cm −1 , 566 cm −1 , and 631 cm −1 . The elastic and piezoelectric constants are obtained from the relaxed ion model. It is found that the SZOML is much softer than graphene, while it is a piezoelectric material. The electronic band gap is 3.576 eV, which implies that the SZOML is a wide band gap semiconductor. Many peaks exist in the linear optical spectra, where the first peak at 3.58 eV corresponds to the band gap of SZOML.

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