The new perovskite PbVO 3 was synthesized under high-temperature and high-pressure conditions. Its crystal structure (a ) 3.80005(6) Å, c ) 4.6703(1) Å, Z ) 1, S.G. P4mm) contains isolated layers of corner-shared VO 5 pyramids, which are formed instead of octahedra due to a strong tetragonal distortion (c/a ) 1.23). The lead atom is shifted out of the center of the unit cell toward one of two [VO 2 ]-layers due to the influence of the lone pair. This new perovskite exhibits a semiconductor-like F(T) dependence down to 2 K. This behavior can be qualitatively explained by taking into account strong electron correlations in electronic structure calculations.

A series of In2O3 thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature. The amorphous-to-crystalline transition and the structure of amorphous In2O3 were investigated by grazing angle X-ray diffraction (GIXRD), Hall transport measurement, high resolution transmission electron microscopy (HRTEM), electron diffraction, extended X-ray absorption fine structure (EXAFS), and ab initio molecular dynamics (MD) liquid-quench simulation. On the basis of excellent agreement between the EXAFS and MD results, a model of the amorphous oxide structure as a network of InOx polyhedra was constructed. Mechanisms for the transport properties observed in the crystalline, amorphous-to-crystalline, and amorphous deposition regions are presented, highlighting a unique structure–property relationship.

conductivity. [1] Following the discovery of SnO 2 with a similar unique combination of properties, [2] several patents were filed in the 1940s to employ TCOs as antistatic coatings and transparent heaters-long before the discovery of the now well-known Sn-doped In 2 O 3 (ITO) and Al-doped ZnO, [3] widely employed as flat panel display electrodes in the past decades. Despite great technological demand for TCOs [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and extensive experimental efforts to improve the conductivity via impurity doping, [21,22] to tune the work function and carrier concentration via cation composition, [23][24][25][26][27][28] to achieve two-dimensional transport via heterointerfaces, [29] and to p-dope the oxides toward active layers of transparent electronics, [30][31][32] theoretical understanding of these fascinating materials has lagged behind significantly. The first electronic band structure of ITO was calculated in 2001; [33] the role of native defects in prototype TCOs was understood after 2002; [34][35][36][37] the properties of multi-cation TCOs were first considered in 2004 [37][38][39][40][41][42] followed by modeling of novel TCO hosts [43,44] and spin-dependent transport in transition-metal-doped TCOs; [45] the nature of the band gap in In 2 O 3 was clarified in 2008; [46] and a first highthroughput search for p-type TCOs was performed in 2013. [47] Complex oxides that consist of multiple post-transition metals, such as InGaZnO 4 , have recently become competitive with silicon as the active transistor layer to drive arrays of pixels in large area displays. [9,[13][14][15][16][17][18][19]24] As the billion-dollar display industry moves forward, the amorphous phase of the complex oxides is favored both for flexible and high-resolution display applications. [13][14][15][16][48][49][50][51][52][53][54][55][56][57][58][59] The unique properties of AOSs were first demonstrated in 1990, [60] and the research area has been growing exponentially since then. Unlike Si-based semiconductors, AOSs were shown to exhibit optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts. [48][49][50][51][52][53][54][55][56][57][58] Table 1 summarizes the key physical properties of best-performing crystalline TCOs and AOSs; the differences (or the lack thereof) between the two will be discussed in detail in the respective sections below.

The electronic properties of single-and multi-cation transparent conducting oxides (TCOs) are investigated using first-principles density functional approach. A detailed comparison of the electronic band structure of stoichiometric and oxygen deficient In2O3, α-and β-Ga2O3, rock salt and wurtzite ZnO, and layered InGaZnO4 reveals the role of the following factors which govern the transport and optical properties of these TCO materials: (i) the crystal symmetry of the oxides, including both the oxygen coordination and the long-range structural anisotropy; (ii) the electronic configuration of the cation(s), specifically, the type of orbital(s) -s, p or d -which form the conduction band; and (iii) the strength of the hybridization between the cation's states and the p-states of the neighboring oxygen atoms. The results not only explain the experimentally observed trends in the electrical conductivity in the single-cation TCO, but also demonstrate that multicomponent oxides may offer a way to overcome the electron localization bottleneck which limits the charge transport in widebandgap main-group metal oxides. Further, the advantages of aliovalent substitutional doping -an alternative route to generate carriers in a TCO host -are outlined based on the electronic band structure calculations of Sn, Ga, Ti and Zr-doped InGaZnO4. We show that the transition metal dopants offer a possibility to improve conductivity without compromising the optical transmittance.

First principles FLMTO-GGA electronic structure calculations of the new medium-T C superconductor (MTSC) M gB 2 and related diborides indicate that superconductivity in these compounds is related to the the existence of p x,y -band holes at the Γ point. Based on these calculations, we explain the absence of medium-T C superconductivity for BeB 2 , AlB 2 ScB 2 and Y B 2 . The simulation of a number of M gB 2 -based ternary systems using a supercell approach demonstrates that (i) the electron doping of M gB 2 (i.e., M gB 2−y X y with X = Be, C, N, O) and the creation of isoelectronic defects in the boron sublattice (nonstoichiometric M gB y<2 ) are not favorable for superconductivity, and (ii) a possible way of searching for similar MTSC should be via hole doping of M gB 2 (i.e., M g 1−x M x B 2 with M = Be, Ca, Li, N a, Cu, Zn) or CaB 2 or via creating layered superstructures of the M gB 2 /CaB 2 type. A recent report of superconductivity in Cu doped M gB 2 supports this view.

Results of extensive density-functional studies provide direct evidence that Cr atoms in Cr:GaN have a strong tendency to form embedded clusters, occupying Ga sites. Significantly, for larger than 2-Cr-atom clusters, states containing antiferromagnetic coupling with net spin in the range 0.06-1.47 muB/Cr are favored. We propose a picture where various configurations coexist and the statistical distribution and associated magnetism will depend sensitively on the growth details. Such a view may elucidate many puzzling observations related to the structural and magnetic properties of III-N and other dilute semiconductors.

A series of yttrium-doped CdO (CYO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates at 410 degrees C by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties have been investigated. XRD data reveal that all as-deposited CYO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CYO thin films exhibit excellent optical transparency, with an average transmittance of >80% in the visible range. Y doping widens the optical band gap from 2.86 to 3.27 eV via a Burstein-Moss shift. Room temperature thin film conductivities of 8,540 and 17,800 S/cm on glass and MgO(100), respectively, are obtained at an optimum Y doping level of 1.2-1.3%. Finally, electronic band structure calculations are carried out to systematically compare the structural, electronic, and optical properties of the In-, Sc-, and Y-doped CdO systems. Both experimental and theoretical results reveal that dopant ionic radius and electronic structure have a significant influence on the CdO-based TCO crystal and band structure: (1) lattice parameters contract as a function of dopant ionic radii in the order Y (1.09 A) < In (0.94 A) < Sc (0.89 A); (2) the carrier mobilities and doping efficiencies decrease in the order In > Y > Sc; (3) the dopant d state has substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.

First-principles band structure investigations of the electronic, optical and magnetic properties of Mo-doped In2O3 reveal the vital role of magnetic interactions in determining both the electrical conductivity and the Burstein-Moss shift which governs optical absorption. We demonstrate the advantages of the transition metal doping which results in smaller effective mass, larger fundamental band gap and better overall optical transmission in the visible -as compared to commercial Sndoped In2O3. Similar behavior is expected upon doping with other transition metals opening up an avenue for the family of efficient transparent conductors mediated by magnetic interactions. PACS number(s): 71.20.-b