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T. C. Huang

Bio: T. C. Huang is an academic researcher from IBM. The author has contributed to research in topics: Materials science & Microstructure. The author has an hindex of 13, co-authored 17 publications receiving 1723 citations.

Papers
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Journal ArticleDOI
TL;DR: These data are interpreted to demonstrate that the (Cu-O) charge in the sheets largely determines T/sub c/ and that the varying oxygen content and the chains merely provide an insulating reservoir of charge.
Abstract: A series of new $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$-like materials are reported in which the oxygen content and the average [Cu-O] charge (or Cu valence) are separately varied over a wide range. We find a distinct boundary between samples showing anomalous insulating behavior and those with high ${T}_{c}$. These data are interpreted to demonstrate that the [Cu-O] charge in the sheets largely determines ${T}_{c}$ and that the variable oxygen content and the chains merely provide an insulating reservoir of charge.

467 citations

Journal ArticleDOI
TL;DR: A search for changes in physical properties at the values of {ital x} where {ital T}{sub {ital c}} is observed to change its behavior is reported, suggesting that no major electronic changes occur.
Abstract: In the system ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_{4}$, as x and p (the [${\mathrm{CuO}}_{2}$${]}^{\mathrm{p}\mathrm{\ensuremath{-}}2}$ charge) are increased, the superconducting transition temperature first increases, then peaks becoming nonsuperconducting for x\ensuremath{\gtrsim}026 We report here a search for changes in physical properties at the values of x where ${T}_{c}$ is observed to change its behavior The in-plane lattice constants and the normal resistivity both show a continued monotonic decrease over this entire region, suggesting that no major electronic changes occur The tetragonal-to-orthorhombic transition temperature ${T}_{s}$ also decreases with increasing x and becomes unobservable for x\ensuremath{\gtrsim}019, suggesting that this structural transition itself is unrelated to the disappearance of superconductivity that occurs at higher doping levels The magnetic spin susceptibility ${\ensuremath{\chi}}_{\mathrm{spin}(\mathrm{T}}$) generally rises gradually with increasing doping (reflecting decreasing spin-spin interactions), reaches a maximum near x\ensuremath{\sim}025, and then decreases There is a weak peak in ${\ensuremath{\chi}}_{\mathrm{spin}(\mathrm{T}}$) as a function of temperature at T=${T}_{\mathrm{max}}$ As a function of increasing x,${T}_{\mathrm{max}}$ falls to zero near x\ensuremath{\sim}025 These two observations might be related to the disappearance of superconductivity, since all three occur near the same value of Sr content x

239 citations

Journal ArticleDOI
Stuart S. P. Parkin1, V. Y. Lee1, A. I. Nazzal1, R. Savoy1, T. C. Huang1, G. Gorman1, Robert Beyers1 
TL;DR: Variations in the transition temperatures in the double- and triple-CuO/sub 2/-layer compounds are observed to correlate with increased densities of intergrowths of related structures.
Abstract: We describe the structures and superconducting properties of six compounds in the Tl-Ca-Ba-Cu-O system of the general form, Tl/sub m/Ca/sub inr-1/Ba/sub 2/Cu/sub n/O/sub 2(//sub n//sub +1)+//sub m/, where m = 1 or 2 and n = 1, 2, or 3. One of these compounds displays the highest known superconducting transition temperature, T/sub c/approx. =125 K. The structures of these compounds consist of copper perovskitelike blocks containing 1, 2, or 3 CuO/sub 2/ planes separated by one or two Tl-O layers and thus form a model family of structures in which both the size and separation of the copper oxide blocks can be independently varied. The superconducting transition temperature increase with the number of CuO/sub 2/ planes in the perovskitelike block for both the Tl-O monolayer and bilayer compounds. For each pair of compounds (m = 1,2) with the same number of CuO/sub 2/ planes (same n), the transition temperatures are similar but are consistently 15--20 K lower in the material with single Tl-O layers. Variations in the transition temperatures in the double- and triple-CuO/sub 2/-layer compounds are observed to correlate with increased densities of intergrowths of related structures.

224 citations

Journal ArticleDOI
Jerry B. Torrance1, Yasuhiro Tokura, S.J. LaPlaca1, T. C. Huang1, R. J. Savoy1, A. I. Nazzal1 
TL;DR: In this paper, the structures of two new superconductors were determined from their X-ray powder diffraction patterns, which are members of a new structural type: intergrowths of two BiO sheets with n (n = 1,2,3…) copper oxide perovskite-like layers.

164 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of argon ion bombardment on the microstructure of several tens of nanometers thick Ag films was analyzed by x-ray powder diffraction method, which showed that Ar ion bombardment not only influenced the film growth process but had a significant effect on the structure of the resulting films.
Abstract: The effect of argon ion bombardment, during deposition on the microstructure of several tens of nanometers thick Ag films, has been studied. The structure of the Ag films was analyzed by x‐ray powder diffraction method. Results show that Ar ion bombardment not only influenced the film growth process but had a significant effect on the structure of the resulting films. In comparison to an evaporated thin Ag film, our films showed much less [111] preferred orientation and a lattice expansion normal to the film surface instead of contraction, with compressive rather than tensile surface strain and plane stress. We also observed much smaller grain sizes, and higher twin fault probabilities, microstrains and dislocation densities. These structural parameters varied systematically with the normalized energy En, that is, the energy deposited by incident energetic Ar+ at the film surface per arriving Ag atom; at first rapidly, then leveling off when En≥42% eV/Ag atom. Preferential orientation is believed to be dependent on film thickness as well as on En. Unlike other parameters, twin fault probability increased to a maximum at En=20 eV/Ag atom and then decreased as En increased further due to self‐annealing during deposition.

160 citations


Cited by
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TL;DR: In this paper, a review of the results of the density-functional type of electronic structure calculations is presented, and their results are compared with the relevant experimental data, showing that the important electronic states are dominated by the copper and oxygen orbitals, with strong hybridization between them.
Abstract: Since the discovery of superconductivity above 30 K by Bednorz and M\"uller in the La copper oxide system, the critical temperature has been raised to 90 K in Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ and to 110 and 125 K in Bi-based and Tl-based copper oxides, respectively. In the two years since this Nobel-prize-winning discovery, a large number of electronic structure calculations have been carried out as a first step in understanding the electronic properties of these materials. In this paper these calculations (mostly of the density-functional type) are gathered and reviewed, and their results are compared with the relevant experimental data. The picture that emerges is one in which the important electronic states are dominated by the copper $d$ and oxygen $p$ orbitals, with strong hybridization between them. Photon, electron, and positron spectroscopies provide important information about the electronic states, and comparison with electronic structure calculations indicates that, while many features can be interpreted in terms of existing calculations, self-energy corrections ("correlations") are important for a more detailed understanding. The antiferromagnetism that occurs in some regions of the phase diagram poses a particularly challenging problem for any detailed theory. The study of structural stability, lattice dynamics, and electron-phonon coupling in the copper oxides is also discussed. Finally, a brief review is given of the attempts so far to identify interaction constants appropriate for a model Hamiltonian treatment of many-body interactions in these materials.

988 citations

Journal ArticleDOI
01 Mar 1993-Nature
TL;DR: In this article, the same authors reported the synthesis of the related compound HgBa2CuO4+δ (Hg-1201), with only one CuO2 layer per unit cell, and showed that it is superconducting below 94 K.
Abstract: FOLLOWING the discovery1 of high-transition-temperature (high-Tc) superconductivity in doped La2CuO4, several families of related compounds have been discovered which have layers of CuO2 as the essential requirement for superconductivity: the highest transition temperatures so far have been found for thallium-bearing compounds2. Recently the mercury-bearing compound HgBa2Rcu2O6+δ (Hg-1212) was synthesized3 (where R is a rare-earth element), with a structure similar to the thallium-bearing superconductor TlBa2CaCu2O7 (Tl-1212), which has one T1O layer and two CuO2 layers per unit cell, and a Tc of 85 K (ref. 2). But in spite of its resemblance to Tl-1212, Hg-1212 was found not to be superconducting. Here we report the synthesis of the related compound HgBa2CuO4+δ (Hg-1201), with only one CuO2 layer per unit cell, and show that it is superconducting below 94 K. Its structure is similar to that of Tl-1201 (which has a Tc of < 10 K)4, but its transition temperature is considerably higher. The availability of a material with high Tc but only a single metal oxide (HgO) layer may be important for technological applications, as it seems that a smaller spacing between CuO2 planes leads to better superconducting properties in a magnetic field5.

919 citations

Journal ArticleDOI
TL;DR: In this paper, annealing results for several Tl-superconductors in the series Tlm(Ba, Sr)2Can−1CunO2n+m+2+δ, for both m=1 and 2, revealing two general results for this class of Bi or TI superconductors: (1) effects on Tc due to labile oxygen occur for all m=2 compounds but are absent in m = 1 compounds with Sr.
Abstract: We have previously shown that Tc for Bi2 (Sr, Ca)n+1CunO2n+4+δ (n=1, 2 and 3) varies with oxygen stoichiometry δ determined by annealing in a variety of oxygen partial pressures and temperatures. Annealing results are now also presented for several Tl-superconductors in the series Tlm(Ba, Sr)2Can−1CunO2n+m+2+δ, for both m=1 and 2, revealing two general results for this class of Bi or TI superconductors: (1) effects on Tc due to labile oxygen occur for all m=2 compounds but are absent in m = 1 compounds with Sr. m=1 compounds with Ba do have variable oxygen but the effects on the c-axis are the opposite to m=2 compounds. This suggests for the latter that the labile oxygen resides in interstitial sites within the Bi2O2 or Tl2O2 bi layers; (2) the hole concentration per Cu decreases in progressing from n = 1 to 2 to 3 in either class so that the parent n = 3 and n = 2 compounds lie respectively on the low- and high-hole concentration sides of the peak in Tc while the n = 1 compounds extend out into the non-superconducting domain at very high hole concentration.

712 citations

Journal ArticleDOI
TL;DR: In this article, a combined theoretical and experimental approach has been used to study nanoscale CoFe/Cu/CoFe multilayer films grown by sputter deposition, and a novel deposition technique is proposed which reduces both interfacial mixing and Fe depletion by controlling the incident adatom energies.

644 citations

Journal ArticleDOI
Henry Windischmann1
TL;DR: A review of the sputtered film stress literature shows that the intrinsic stress can be tensile or compressive depending on the energetics of the deposition process as discussed by the authors, and extensive experimental evidence show a direct link between the particle flux and energy striking the condensing film, which determines the nature and magnitude of the stress.
Abstract: A review of the sputtered film stress literature shows that the intrinsic stress can be tensile or compressive depending on the energetics of the deposition process. Modeling studies of film growth and extensive experimental evidence show a direct link between the energetics of the deposition process and film microstructure, which in turn determines the nature and magnitude of the stress. The fundamental quantities are the particle flux and energy striking the condensing film, which are a function of many process parameters such as pressure (discharge voltage), target/sputtering gas mass ratio, cathode shape, bias voltage, and substrate orientation. Tensile stress is generally observed in zone 1-type, porous films and is explained in terms of the grain boundary relaxation model, whereas compressive stress, observed in zone T-type, dense films, is interpreted in terms of the atomic peening mechanism. Modeling of the atomic peening mechanism and experimental data indicate that the normalized moment...

584 citations