P.K. Dorhout

Frontiers of high pressure research II: application of high pressure to low-dimensional novel electronic materials

Contributors. Preface. Acknowledgements. Evangelos Anastassakis (1938-2000). Material Synthesis at High Pressures. Stabilization of Unusual Oxidation States of Transition Metals in Oxygen Lattices: Correlations with the Induced Electronic Phenomena G. Demazeau. Synthesis and Properties of Low dimensional F-Element Chalocogenide Compounds P.K. Dorhout, C.R. Evenson, IV. Synthesis and High-Pressure Behavior of C6N9H3*HCl: A graphitic material with a two-dimensional C-N network G.H. Wolf, et al. Plasma Polymerization of Thin Films Using Aniline and p-Xylene Precursors A. Dumitru, et al. Pressure-Induced Phase Transitions. Compressibility, Pressure-Induced Amorphisation and Thermal Collapse of Zeolites G.N. Greaves. Pressure-induced H-transfers in the networks of hydrogen bonds A. Katrusiak. The Light Elements at High Pressure, in Layered Form, and in Combination N.W. Ashcroft. Pressure-induced Phase Transitions in GaSe-, TlGaSe2- and CdGa2S4-type Crystals K.R. Allakhverdiev. Influence of Pressure on the Physical Properties of Chain TlSe-type Crystals K.R. Allakhverdiev, S.S. Ellialtiogammalu. Impendance Spectroscopy at Super High Pressures A.N. Babushkin, et al. Optical Properties of A2CuCl4 Layer Perovskites under Pressure: Structural Correlations F. Rodriguez, et al. The Effect of Pressure-Induced Collapse of Correlation and Hunds Rules on Structure and Electronic Properties of Transition-Metal Compounds M. Paz-Pasternak, et al. Pressure Tuning of Condensation and Ordering of Charge-Transfer Strings H. Cailleau, et al. From Ferroelectric to Quantum Paraelectric: Ktal-xNbxO3(KTN), a Model System G.A.Samara. Molecular Solids Under High Pressures. Quartz like phases in CO2 at very high pressure from ab initio simulations R. Ahuja, et al. Progress in Experimental Studies of Insulator-Metal Transitions at Multimegabar Pressures R.J. Hemley, et al. Solid Oxygen as Low dimensional System by Spectroscopic Studies A. Brodyanski, et al. Evolution of Rotational Spectrum in Solid Hydrogen with Pressure: Implications for Conversion and other Properties M.A. Strzhemechny. An Influence of the Pressure on Metastability of the HCP Phase of Solid Nitrogen B. Kuchta, et al. Semiconductors, 2-D Impurity States, Quantum Dots. X-ray Study of Strain Relaxation in Heteroepitaxial Layers of Semiconductors Annealed under High Hydrostatic Pressure J. Bak-Misiuk. Application of High Temperature-Pressure Treatment for Investigation of Defect Creation in Basic Materials of Modern Micro-electronics: Czochralski Silicon and Solicon Containing Films A. Misiuk. Pressure-induced Phase Transformations in Semiconductors under Contact Loading V. Domnich, Y. Gogotsi. Far-Infrared Spectroscopy of Quasi-2D Impurity States in Semiconductor Nanostructures under High Hydrostatic Pressure B.A. Weinstein, et al. Probing the Effects of Three-Dimensional Confinement on the Electronic Structure of InP under Hydrostatic Pressure C.S. Menoni, et al. Pressure Studies in InGaN/GaN Quantum Wells D. Patel, et al. Superconductivity. What High Pressure Studies Have Taught Us about High-Temperature Superconductivity J.S. Schilling. Anisotropic Low-Dimensional Superconductors Close to an Electronic Topological Transition G.G.N. Angilella, et al. Pressure-Induced Superconducting Phase Separation in Oxygen-Doped La2-xSrxCuO4+&dg

High pressure Brillouin scattering and energy dispersive X-ray diffraction study of (NH4)2ZnCl4

Abstract We have performed a high pressure Brillouin scattering and energy dispersive X-ray diffraction study on (NH 4 ) 2 ZnCl 4 in the temperature range from room temperature to 150°C. At ambient pressure three phase transitions occur in this temperature range. Of special interest are the phase transitions at 91°C and 133°C because an incommensurate phase has been detected in this temperature range. We compare the results of our high pressure Brillouin scattering study with the ones obtained from other studies of the elastic constants. Our results for the anomaly in C 33 observed at the commensurate–incommensurate transition at 133°C at ambient pressure contradict the results of the other Brillouin scattering studies but agree well with the results of an ultrasonic study. This result seems to indicate that critical fluctuations of the order parameter at the phase transition are reduced by pressure. Values of the calculated adiabatic bulk modulus, B S , and the experimentally determined isothermal bulk modulus, B T , for various materials of the A 2 BX 4 family, are compiled and discussed.

High pressure optical and X-ray diffraction studies of two polymorphs of K(RE)P2Se6 (RE = Pr and Tb)

Abstract The results of a high pressure absorption, X-ray diffraction and Raman scattering study indicate a pressure induced phase transition in KTbP 2 Se 6 at about 9.2xa0GPa which is accompanied by a discontinuous jump of the absorption edge of about 0.5xa0eV into the red. The phase transition is also reflected in the Raman spectrum at this pressure. The result of the energy dispersive X-ray diffraction study shows that the high pressure phase above 9.2xa0GPa is also orthorhombic but the b -axis is doubled with respect to the low pressure phase. We propose that the high pressure phase is due to charge transfer from the selenium to the phosphorus accompanied by the formation of a Se–Se bond. We also discuss a model which involves a 4f–5d charge transfer in Tb, leading to the intervalence charge transfer from: Tb 3+ P 4+ →Tb 4+ P 3+ . Studies on KPrP 2 Se 6 did not show a phase transition in this pressure range.

Pressure-induced phonon softening and structural phase transitions in Cs2MoS4

Abstract We report the results of a Raman study on Cs 2 MoS 4 under hydrostatic pressures up to 12 GPa. Two successive phase transitions are observed at 8.0 and 9.7 GPa, respectively. A low frequency phonon mode with a negative pressure shift is seen in the low pressure phase. The results are discussed within the framework of structural phase transitions driven by a soft phonon.

High pressure absorption and Raman study of the quasilinear compound CsCuS6

Abstract We report the results of a combined high pressure absorption and Raman study on CsCuS6. The indirect band gap, Eg, at about 2 eV shifts to lower energy with increasing pressure (55 meV/GPa). The pressure shift is approximately linear up to 17 GPa, the maximum pressure of our study. An extrapolation yields a band closure pressure of about 37 GPa. The Raman spectra of the internal modes are closely related to those of heterocyclic sulphur molecules.

High pressure optical study of KTbP2Se6

Abstract We have observed a pressure induced phase transition in KTbP 2 Se 6 at about 9.2xa0GPa which was accompanied by a discontinuous jump of the absorption edge of about 0.5xa0eV into the red. We have proposed that the high pressure phase is due to charge transfer from the selenium to the phosphorous accompanied by the formation of a Se–Se bond. In order to exclude a model which involves a 4f–5d charge transfer in Tb, leading to the intervalence charge transfer from Tb 3+ P 4+ –Tb 4+ P 3+ ,we have measured the pressure dependence of the luminescence of the crystal field split levels of the Tb-ion. A comparison of the pressure dependence of the luminescence spectra of KTb(MoO 4 ) 2 and KTbP 2 Se 6 shows that such a charge transfer does not occur in KTbP 2 Se 6 .