Theoretical analysis of the crystal structure, band-gap energy, polarization, and piezoelectric properties of ZnO-BeO solid solutions

Abstract

The electrical properties, the spontaneous polarization, and the piezoelectric response of ZnO can be tailored by alloying ZnO with BeO for applications such as electrodes in flat panel displays and solar cells, blue and ultra-violet (UV) light emitting devices, and highly sensitive UV detectors. We present here the results of a study that employs density functional theory to analyze the crystal structure, the band structure, spontaneous polarization, and piezoelectric properties of

Understanding the origin of phase segregation of nano-crystalline in a BexZn1−xO random alloy: a novel phase of Be1/3Zn2/3O

“…5 More recently, recognizing the wurtzite hexagonal structure of BeO that has a wide bandgap (10.8 eV), Be x Zn 1−x O was proposed by Ryu et al as a candidate for the solar-blind devices. 27 In the previous studies, however, sizes of supercells were quite small such that the x values are limited to the multiples of 1/16 and 1/8, respectively. This is probably due to the phase separation and compositional fluctuation of Be in the Be x Zn 1-x O alloy.…”

“…36. [25][26][27] Based on a search for the atomistic configurations with a supercell containing 32 atoms, Fan et al found that the Be x Zn 1−x O alloy favoured local phase segregation, where three kinds of crystallites with Be concentration values of x = 1/4, 1/2 and 3/4 arise. 5 More recently, recognizing the wurtzite hexagonal structure of BeO that has a wide bandgap (10.8 eV), Be x Zn 1−x O was proposed by Ryu et al as a candidate for the solar-blind devices.…”

Magnetic properties of ZnO nanowires with Li dopants and Zn vacancies

“…The two Li Zn sites for each configuration are chosen among all the possible substitutional sites to ensure that the two V Zn have the lowest formation energy. We also find that the Li dopants and V Zn tend to stay close to each other, therefore the most stable sites of Li dopants for each configurations are as follows: (10,8), (3,7), (4,9), and (4,5). In order to find out the magnetic properties of V ZnZnO NW with Li-dopant, all models are fully relaxed, and these optimized Li-doped ZnO NWs with V Zn are subject to calculate magnetic properties of system.…”

“…[1]. As one of the II-VI low-dimensional nanomaterials, ZnO NW has been applied to photovoltaics, gas sensors, and field-effect transistors [2][3][4]. ZnO NW also possesses a large magnetic coercive force and high blocking temperature, which would be useful for fabricating nano-magnetic devices well [5].…”

Optimal growth and thermal stability of crystalline Be0.25Zn0.75O alloy films on Al2O3(0001)

“…This is unlike Mg x Zn 1Àx O alloys which are limited by a Mg mole fraction of x ¼ 0.38. 3,8 However, in principle, the phase instability of Be x Zn 1Àx O alloys could occur due to: (i) internal strain effect from different bond lengths between Zn-O (aand c-axis bond lengths: 1.97 Å and 1.99 Å ) and Be-O (a-and c-axis bond lengths: 1.65 Å and 1.66 Å ) and the subsequent lattice deformation of wurtzite structure; 9 (ii) a large difference in thermal expansion coefficients [2.49 and 3.98 Â 10 À6 K À1 (5.35 and 7.18 Â 10 À6 K À1 ) at 300 K and 700 K for c-axis ZnO (c-axis BeO), respectively]; 10 and (iii) substantial strain from the lattice mismatch between the alloy film and the underlying substrate, e.g., Al 2 O 3 (%18%) and Si (111) (%15%). 11 These can readily induce phase separation and compositional splitting in the ternary alloy system.…”