A systematic study of the negative thermal expansion in zinc-blende and diamond-like semiconductors

Abstract

Upon heating, almost all zinc-blende (ZB) and diamond-like semiconductors undergo volume contraction at low temperature, i.e. negative thermal expansion (NTE), instead of commonly expected expansion. Specifically, CuCl has the largest NTE among these semiconductors with a coefficient comparable with the record value of ZrW 2 O 8 . So far, underlying physical mechanism remains ambiguous. Here, we present a systematic and quantitative study of the NTE in ZB and diamond-like semiconductors using first-principles calculations. We clarified that the material ionicity, which renders the softening of the bond-angle-bending and thus, the enhancement of excitation of the transverse acoustic (TA) phonon, is responsible for the NTE of ZB and diamond-like semiconductors. With the increase in the ionicity from the groups IV, III-V, IIB-VI to IB-VII ZB semiconductors, the coefficient of the maximum NTE increases due to the weakness in bond-rotation effect, which makes the relative motion between cation and anion transverse to the direction of the bond more feasible and the mode Grüneisen parameters of the TA modes more negative. Since CuCl has the highest ionicity among all ZB and diamond-like semiconductors, it is expected to have the largest NTE, in good agreement with the experimental observation. This understanding would be beneficial for tetrahedral materials with specific applications.

s-d coupling enhanced phonon anharmonicity in copper-based compounds

“…As displayed in Fig. 4a, we find that the lattice vibrational potential energy of CuCl increases as U rises, due to the reduced s-d coupling strength resulting from the lowering of Cu 3d energy level and accompanied wave func-tion localization [45][46][47] (Fig. S7).…”

“…In copper-based semiconductors such as copper halides, the copper's 3d orbital dominates the valence band maximum (VBM) state and is below the s-like conduction band minimum (CBM) by a band gap (about 3-4 eV) (Fig. S3) [45][46][47] . The small energy difference between copper's 3d and 4s states enhances their coupling which lowers the lattice vibrational potential energy.…”

Pressure and temperature stability boundaries of cubic SiC polymorphs: a first-principles investigation

“…These calculated negative mode Grüneisen parameters in the B3 phase for the TA modes at X and L special points could be interpreted as a signal for a potential dynamical instability but our phonon calculations at high pressures discussed above do not confirm this hypothesis. In this respect, it is interesting to note that the presence of negative mode Grüneisen parameters in other zinc blende (B3) and diamond-like semiconductors is considered as a necessary condition for the presence of the negative thermal expansion at low temperatures 54 although a study of this phenomenon in SiC is out of the scope of the present work.…”

Reviewing and understanding the stability mechanism of halide perovskite solar cells

“…Emerging halide perovskite is likely the most potential candidate for next-generation solar cell materials, as it is found that the PCE of halide perovskites has increased from 3.8% to 25.2% over the past decade. 9,12 Although the record module efficiency of halide perovskite is 16.1%, lower than that of polysilicon solar cell, 10 it can be fabricated by simple and low-cost ink-jet printing [13][14][15][16] and blade coating [17][18][19][20] techniques. However, for commercialization one must solve the issue of halide perovskite stabilities.…”