Effects of temperature on strain engineering and transition-metal adatom magnetization in phosphorene: Ab initio molecular dynamics studies

Using first-principles and ab initio molecular dynamics calculations, effects of temperatures on ferroelastic transition, band gap engineering, anisotropic carrier effective masses, and stability of transition metal adatom magnetization in phosphorene under tensile strains are investigated, which determine mainly its unique properties for designing novel low-dimensional electronic and spintronic devices. We find that (i) the ferroelastic transition of phosphorene under tensile strains predicted at 0 K is replaced by developments of a series of twinning structures above the room temperature (300 K), which will modify predictions on the band structure, carrier mobility, and thermal conductivity of phosphorene in strain engineering processes; (ii) the emerging twinning structure brings about strong ductility in phosphorene, which can sustain stretching up to a tensile strain of 73% at 300 K before the structural breakdown; (iii) the stable sites for the adsorbed TM atoms (V, Cr, and Mn) on phosphorene are higher in energy compared to those of the (interstitially) doped TM atoms in phosphorene. However, the potential barriers between the adsorbed and doped states are high enough to stabilize the adsorbed TM atoms on phosphorene even at high temperatures (450 K); (iv) under moderate tensile strains ($\ensuremath{\sim}10%$) at room temperature, the adsorbed TM atoms start to move into phosphorene as interstitial dopants. Such room or high temperature stretching may provide a possible way to prepare dilute magnetic semiconducting phosphorene using adsorbed TM atoms from simple chemical vapor depositions; (v) for some TM atoms (V, Cr), whose magnetic moments come from the $3d$ electron states near the Fermi level, their magnetic moments decrease substantially as they move into phosphorene, while for other TM atoms (Mn), whose magnetic moments come from the $3d$ electron states deep below the Fermi level, their magnetic moments are stable as their positions change. These results will deepen our understandings of phosphorene and broaden its technological applications as a versatile two-dimensional material.