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9 Oct 2000

Volume 77, Issue 15, pp. 2271-2423

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Yttrium silicate formation on silicon: Effect of silicon preoxidation and nitridation on interface reaction kinetics

J. J. Chambers and G. N. Parsons

Appl. Phys. Lett. 77, 2385 (2000); http://dx.doi.org/10.1063/1.1316073 (3 pages) | Cited 51 times

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The effects of oxygen and nitrogen pretreatments on interface reaction kinetics during yttrium silicate formation on silicon are described. X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) are used to determine chemical bonding and composition of films formed by oxidation of yttrium deposited on silicon. Capacitance–voltage testing is used to determine the quality of the dielectric and the electrical thickness. The effect of ultrathin silicon oxide, nitrided oxide, and nitrided silicon interfaces on metal oxidation kinetics is also described. When yttrium is deposited on clean silicon and oxidized, XPS and MEIS indicate significant mixing of the metal and the silicon, resulting in a film with Y–O–Si bonding and composition close to yttrium orthosilicate (Y2O3⋅SiO2). A thin (∼10 Å) in situ preoxidation step is not sufficient to impede the metal/silicon reaction, whereas a nitrided silicon interface significantly reduces the silicon consumption rate, and the resulting film is close to Y2O3. The mechanisms described for yttrium are expected to occur in a variety of oxide and silicate deposition processes of interest for high-k dielectrics. Therefore, in addition to thermodynamic stability, understanding the relative rates of elementary reaction steps in film formation is critical to control composition and structure at the dielectric/Si interface. © 2000 American Institute of Physics.
Show PACS
81.65.Mq Oxidation
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.05.Cy Elemental semiconductors
61.50.Lt Crystal binding; cohesive energy
68.55.-a Thin film structure and morphology
82.20.-w Chemical kinetics and dynamics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Dp Adsorbed layers and thin films
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Ct Interface structure and roughness
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Enhanced-response pyroelectric heterostructures

C. Wesley Tipton, K. Kirchner, R. Godfrey, M. Cardenas, S. Aggarwal, H. Li, and R. Ramesh

Appl. Phys. Lett. 77, 2388 (2000); http://dx.doi.org/10.1063/1.1316774 (3 pages) | Cited 5 times

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We have observed enhanced pyroelectric responses in sub-100 nm, epitaxial Pb–Zr–Ti–O films contacted with conducting perovskite oxide top and bottom electrodes. These enhancements are obtained in capacitors where the bottom electrode is processed under reducing conditions. This leads to an asymmetric, temperature-dependent internal electric field that is produced within the ferroelectric capacitor and manifests itself as a strongly shifted ferroelectric hysteresis loop. Because the shifted coercive voltage lies near the unbiased operating point, the pyroelectric film has a large value of dP/dE. The product (dP/dE)/(dE/dT) gives rise to an enhanced pyroelectric response. Our data show that a 10–30 times increase in the pyroelectric response can be obtained over symmetric devices, with a concomitant improvement of the sensing figure-of-merit by three times. © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.70.+a Pyroelectric and electrocaloric effects
84.32.Tt Capacitors
77.80.Dj Domain structure; hysteresis

Subsecond relaxation of internal field after polarization reversal in congruent LiNbO3 and LiTaO3 crystals

Jung Hoon Ro and Myoungsik Cha

Appl. Phys. Lett. 77, 2391 (2000); http://dx.doi.org/10.1063/1.1316781 (3 pages) | Cited 16 times

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We developed an experimental method for measuring subsecond temporal evolution of the internal field after polarization reversal in ferroelectric crystals, congruent LiNbO3 and LiTaO3 crystals. In each crystal the internal field exhibited two distinct relaxations, suggesting that they originate from two different types of defects. The fast one decays in subsecond range while the slow one lasts over days at room temperature. The subsecond relaxation could be fit to a stretched exponential. This method can be applied to other ferroelectric crystals to investigate the properties of defects. © 2000 American Institute of Physics.
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77.22.Ej Polarization and depolarization
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
71.70.Ch Crystal and ligand fields
77.80.-e Ferroelectricity and antiferroelectricity
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