The wurtzite crystal structure, named after the mineral wurtzite, is a crystal structure for various binary compounds. Xray diffraction study show that all the films prepared in this work have hexagonal wurtzite structure, with lattice constants a b 3. The transmission electron microscopy measurements show that the obtained zno nanorods have wellproportioned distribution with diameters about 30 nm, and the maximal lengths up to more than 2. Raman, resonant raman and photoluminescence pl properties of zno nanorods that produced by simple solution chemical process are reported in this paper. Surface xray diffraction and ab initio calculations. Compound semiconductors with zincblende or wurtzitetype structureswhere each atom of one element is in 4fold and tetrahedral coordination to atoms of the other element. Thus, hcp clusters can attain their preference with respect to mtps comprising fcc fragments and optimized fcc clusters only for very large sizes. The energy of the valenceband maximum vbm was set to zero. Boronnitride structure to the wurtzite wz structure is observed. Ke1,2,a 1school of physics and nuclear energy engineering, beihang university, beijing 100191, peoples republic of china 2lnm, institute of mechanics, chinese academy of sciences, beijing 100190, peoples republic of china. Wurtzitetotetragonal structure phase transformation and size effect in zno nanorods j. The lattice constants of zno solid structure, its ratio ca 1. Zno nanoparticles were synthesized by microemulsion route in ws ratio of 5 at room temperature.
Thermal conductivity of wurtzite zincoxide from first. Draw wurtzite crystal structure with vesta zno example easyedu. Wang a, a department of materials, school of materials science and engineering, georgia institute of technology, 771 ferst dr, atlanta, ga 303320245, usa b ii. Polar optical phonons in wurtzite spheroidal quantum dots. Band gap and electronic properties of wurtzitestructure zno co. Each zinc atom is surrounded by four oxygen atoms, which are located. Zns can have a zinc blende structure which is a diamondtype network and at a different temperature, zns can become the wurtzite structure type which has a hexagonal type symmetry. Zno zinc blende unit cell the hexagonal structure of zinc oxide zno has a point group 6 mm in hermannmauguin notation or c6vin reported space group is generally p63mc or c6v4. A wedge structure calculation with a new bottom surface passivation scheme of group i and group vii elements was also proposed and performed to show converged absolute surface energy of wurtzite zno polar surfaces, and. Properties of zno piezoelectric zno nanostructure for. C3 coupling and wurtzite structure inversion asymmetry is much larger than that. Ke1,2,a 1school of physics and nuclear energy engineering, beihang university, beijing 100191, peoples.
The nanocrystals of zno with hexagonal wurtzite structure were characterized by xray powder diffraction xrd, transmission electron microscopy tem. Structurewise, the zinc blende structure is more thermodynamically favored, however, because of the wurtzite structures slow construction, both forms of zns can be found. Since the volume per atom is the same, a given volume of reciprocal space for wurtzite contains approximately twice as many reciprocal lattice points. It has a hexagonal close packed array of s and the znii sit in tetrahedral 12 occupied sites in the lattice, giving a unit cell with 8 zn and 16 ss. It is well known that zno has three stable structures. Background wurtzite zno has lattice constants of a 3.
For wurtzite, there are four atoms per unit cell in contrast to two for zincblende. The developed theory is applied to freestanding spheroidal zno quantum dots and to spheroidal zno quantum dots embeddedinto a mgznocrystal. Wurtzite zinc oxide zno is a remarkable multifunctional material with a distinctive property set and a huge range of existing and emerging applications look 2006. Wurtzite zno has polar surfaces, such as 0001 and 0001, and nonpolar surfaces such as 0110 and 2110. Multiple datasets can be downloaded as individual files inside a zip archive by selecting the datasets and then clicking. At different growth stages, the axial growth at polar surfaces is found to have a different relative growth rate to the lateral growth at nonpolar surfaces. In particular, it is a direct wide bandgap semiconductor e g. Cadmoselite cdse, greenockite cds, matraite zns and rambergite mns, in addition to wurtzite. This structure is a member of the hexagonal crystal system and consists of tetrahedrally coordinated zinc and sulfur atoms that are. There are 4 atoms in the hexagonal unit cell leading to 12 phonon branches, 9 optical and 3 acoustic. However what makes them different minerals is that they have different structures. The experimentally observed ca ratios are smallerthanideal, asinthecaseofgan, whereithasbeenpostulatedthatnotbeing so would lead to zinc blende phase 1.
Firstprinciples investigation of the structure and. The wurtzite structure of zno crystal has c6v symmetry. Ab initio calculations on structural, electronic and. Apr 09, 2018 draw wurtzite crystal structure with vesta zno example easyedu. Zinc oxide crystallizes in two main forms, hexagonal wurtzite and cubic zincblende. The wurtzite structure is most stable at ambient conditions and thus most common. The electronic structure and optical properties of zno wurtzite quantum wires with radius r.
The crystal orientation and phase composition of sintered z n, z ng, z a, and z ag samples were analyzed using xrd figure 3. First principles calculations are carried to study the structural stability of sic, gan, inn, zno, and cdse which are found to transform from a fourfold coordinated wurtzite wz structure under ambient conditions to two different crystalline structures under loading of different triaxialities. Its formation is related to oxygen impurities in fe110 hollow sites inducing an anisotropic charge redistribution within the. Hexagonal wurtzite structure of zno is the most stable structure under ambient conditions, which belongs to the space group p6 3mc. Znotemplated synthesis of wurtzitetype zns and znse. All evident peaks could be indexed as the zno wurtzite structure jcpds data card no. Xray peak broadening analysis of zno nanoparticles derived. Rod shape of zno nanoparticles of average particle size 10. The crystal structures shared by zno are wurtzite b4, zinc blende. Ab initio calculations on structural, electronic and optical. Multiple datasets can be concatenated into a single downloadable file by selecting the datasets and then clicking.
Pdf phase formation of hexagonal wurtzite zno through. In this paper, we determine the thermal conductivity of wzno using firstprinciples lattice dynamics and compare it to that of wurtzite. The controllable synthesis of semiconductor nanocrystals is important for exploiting their sizedependent properties in a variety of applications. This structure is a member of the hexagonal crystal system and consists of tetrahedrally coordinated zinc and sulfur atoms that are stacked in an ababababab pattern. In many cases, these structures are the classic structures of crystalline solids, such as the rocksalt structure of the galena group figure 1a, the sphalerite and wurtzite forms of zinc sulphide figures 1b and 1c, or the nickel arsenide structure figure 1e. Zno crystal has a wurtzite structure with c6v symmetry arxiv. In the extreme case u 12 this structure becomes the b k bn structure. With wurtzite zno codoped with b and mg denoted as zno. The chemical prototype is conventionally given as zns, although mineral wurtzite is a multicomponent alloy compound. Subsequently, lattice constant variations and crystal lattice. The zincblende form can be stabilized by growing zno on substrates with cubic lattice structure. Stability of wurtzite, unbuckled wurtzite, and rocksalt. Surface xray diffraction and ab initio calculations h.
Effects of lattice parameters on piezoelectric constants. Zno possesses three different crystallographic phases. The wurtzite structure of zno can be considered to be composed of two. Pdf wurtzite structure in ultrathin zno films on fe110. The vertically aligned, densely packed zno nrs arrays architecture was grown on the. B,mg grown via metalorganic chemical vapor deposition, we have observed that both the bandgap and the conductivity can be widely tunable with the doping levels.
Among the binary oxide semiconductors, zno is the only material with a wurtzitetype structure that has a. Xray diffraction xrd pattern reveals wurtzite structure of zno nanoparticles. Optical and structural properties of zno thin films. However, large discrepancies exist in the literature on the thermal conductivity of wzno.
In a real zno crystal, the wurtzite structure deviates from the ideal arrangement, by changing the ca ratio or the u value. The diffraction patterns revealed that the zno thin films were polycrystalline and have a wurtzite hexagonal structure. The wurtzite structure has a hexagonal unit cell with two. Zno is an inorganic binary compound belonging to the iivi semiconductor material group. On one hand, bandgap engineering on wurtzite zno can be realized through alloying with cubic mgo. Its crystal structure is called the wurtzite crystal structure, to which it lends its name. The lattice constants for several wurtzite structure semiconductors are given in table 9. Raman and photoluminescence properties of zno nanorods with. The wurtzite crystal structure of zno with the lattice parameters a and c indicated in a, and the calculated band structure of zno using the hse hybrid functional in b. The wurtzite structure has a hexagonal unit cell with two lattice parameters a and c. The wurtzite structure may be considered as an hcp structure with a basis of two atoms. Section c is the journal of choice for the rapid publication of articles that highlight interesting research facilitated by the determination, calculation or analysis of. Evolution process of wurtzite zno films on cubic mgo 001.
Wurtzite structure in ultrathin zno films on fe110. Wurtzite zinc oxide has a hexagonal structure space group c6mc with. Pdf electronic structure of zno wurtzite quantum wires. While the zb polymorphs are most stable, methods exist for synthesizing the wztype nanocrystals. It can be considered as being formed by the penetration of two hcp lattices see fig. Stability of wurtzite, unbuckled wurtzite, and rocksalt phases of sic, gan, inn, zno, and cdse under loading of different triaxialities k. We report the bandgap and electronic properties of wurtzite zno doped with elements iia orand iiia, investigated using both theoretical and experimental methods. Synthesis of zno nanocrystals with hexagonal wurtzite. Wurtzite zincoxide wzno is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. Limpijumnong 1school of physics, suranaree university of technology and national synchrotron research center, nakhon ratchasima 30000, thailand 2the george w. Crystal structure, chemical binding, and lattice properties. Zno nrs arrays architecture is hexagonal wurtzite in structure and found highly caxis oriented the length of the zno nrs arrays is 1. We investigated the properties of vibrational modes of the semiconductors such as zno, gan and 6hsic belonging to the wurtzite structure in order to characterize the materials. In our study we calculated the parameters for all the binary wurtzite crystals listed in the structure databases.
The two hcp lattices have the same axis a 3 axis but one of them is displaced with respect to the other. Comparison of the observed patterns with the standard card jcpds no. Sphalerite and wurtzite are both zinc iron sulfides with the same formula, zn, fes. The wurtzite crystal structure has three independent structure parameters, i.
These compounds have recently received considerable attention due to their potential in the semiconductor industry. Wurtzite zincoxide wzno is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is. Band gap and electronic properties of wurtzitestructure. Wurtzite zincoxide w zno is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. Wurtzitetotetragonal structure phase transformation and. Woodruff school of mechanical engineering, georgia. Physikalisches institut, universitatgottingen, tammannstr. Understanding and eliminating these detrimental effects by both experimental and theoretical efforts have attracted much attention in the past decade. These unique nanostructures unambiguously demonstrate that zno. Nanocrystals of zno were prepared by microwave irradiation using zn ii acetate and triethanol amin tea as the starting materials and water as solvent. Structural chemistry is continuing its transition to a journal that publishes exciting science with structural content, in particular, important results relating to the chemical sciences. As most of the group iivi binary compound semiconductors, zno crystallizes both in cubic zinc blende and in hexagonal wurtzite structure.
Zinc oxide zno, which commonly crystallizes in a sta ble wurtzite structure in nature, and its doped compounds with iia e. Zno nanostructures has been observed, which confirms the determinative role of. Wurtzite lattice parameters such as the values of d, the distance between adjacent planes in the miller. Draw wurtzite crystal structure with vesta zno example.
Optical and structural properties of zno thin films fabricated by solgel method ziaul raza khan1, mohd shoeb khan2, mohammad zulfequar1. Three different growth stages were defined during the nanowire growth. The lattice constants for several wurtzite structure semiconductors are given in. Effects of lattice parameters on piezoelectric constants in. With an exciton binding energy of 60 mev and wide direct. Structure wise, the zinc blende structure is more thermodynamically favored, however, because of the wurtzite structures slow construction, both forms of zns can be found. The display shows an idealised unit cell space group p63mc. Wurtzite is the not so common cousin of the much more common mineral, sphalerite. Structural and optical characterization of zno nanoparticles. Usually found as black to dark reddishbrown massive resinous to submetallic material, also as botryoidal banded crusts, and more rarely as hemimorphic pyramidal, or tabular, crystals.
202 464 1218 1152 1038 1129 1181 580 1171 592 136 1250 160 978 238 1281 417 1501 154 450 1042 1312 768 77 1439 602 905 1323 1149 1136 88 1279 379 299 1441 590 587 1436 1239 189