Subsurface hydrogen bonds at the polar Zn-terminated ZnO(0001) surface

TY - JOUR

T1 - Subsurface hydrogen bonds at the polar Zn-terminated ZnO(0001) surface

AU - Hellström, Matti

AU - Beinik, Igor

AU - Broqvist, Peter

AU - Lauritsen, Jeppe V.

AU - Hermansson, Kersti

PY - 2016/12/27

Y1 - 2016/12/27

N2 - The role of hydrogen and other defects in the stabilization of polar oxide interfaces is a matter of significant fundamental and practical interest. Using experimental (scanning tunneling microscopy, x-ray photoelectron spectroscopy) and theoretical (density functional theory) surface science techniques, we find that the polar Zn-terminated ZnO(0001) surface becomes excessively Zn deficient during high-temperature annealing (780 K) in ultrahigh vacuum (UHV). The Zn vacancies align themselves into rows parallel to the [10-10] direction, and the remaining surface Zn ions alternately occupy wurtzite (hcp) and zinc-blende (fcc) lattice positions, giving a characteristic “striped” c(√12×√12)R30° surface morphology with three types of rows: wurtzite Zn, zinc-blende Zn, and Zn vacancies. Interstitial H plays a central role in such a reconstruction, as it helps to compensate the excessive Zn deficiency. We propose a model in which hydrogen occupies positions in half of the vacancy rows to form hydroxide ions that can participate in hydrogen bonds in the O subsurface layer as a result of the mixed wurtzite/zinc-blende stacking.

AB - The role of hydrogen and other defects in the stabilization of polar oxide interfaces is a matter of significant fundamental and practical interest. Using experimental (scanning tunneling microscopy, x-ray photoelectron spectroscopy) and theoretical (density functional theory) surface science techniques, we find that the polar Zn-terminated ZnO(0001) surface becomes excessively Zn deficient during high-temperature annealing (780 K) in ultrahigh vacuum (UHV). The Zn vacancies align themselves into rows parallel to the [10-10] direction, and the remaining surface Zn ions alternately occupy wurtzite (hcp) and zinc-blende (fcc) lattice positions, giving a characteristic “striped” c(√12×√12)R30° surface morphology with three types of rows: wurtzite Zn, zinc-blende Zn, and Zn vacancies. Interstitial H plays a central role in such a reconstruction, as it helps to compensate the excessive Zn deficiency. We propose a model in which hydrogen occupies positions in half of the vacancy rows to form hydroxide ions that can participate in hydrogen bonds in the O subsurface layer as a result of the mixed wurtzite/zinc-blende stacking.

KW - ZnO

KW - DFT

KW - STM

U2 - 10.1103/PhysRevB.94.245433

DO - 10.1103/PhysRevB.94.245433

M3 - Journal article

SN - 2469-9950

VL - 94

JO - Physical Review B

JF - Physical Review B

IS - 24

M1 - 245433

ER -