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5 Nov 2001

Volume 79, Issue 19, pp. 3017-3198

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Polarity dependence of defect generation in ultrathin SiO2/ZrO2 gate dielectric stacks

M. Houssa, V. V. Afanas’ev, A. Stesmans, and M. M. Heyns

Appl. Phys. Lett. 79, 3134 (2001); http://dx.doi.org/10.1063/1.1415401 (3 pages) | Cited 19 times

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The generation of defects during the injection of charge carriers in metal–oxide–semiconductor capacitors with ultrathin SiON/ZrO2 gate stacks is investigated. A polarity dependence for the defect generation is revealed. It is shown that this polarity effect is inconsistent with the predictions of the anode–hole injection model, but can be explained by assuming the release of hydrogen close to the SiON/ZrO2 interface, followed by its transport and trapping in the gate dielectric, resulting in the generation of hydrogen-induced positive charge and bulk neutral traps. © 2001 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Fatigue-free samarium-modified bismuth titanate (Bi4−xSmxTi3O12) film capacitors having large spontaneous polarizations

Uong Chon, Ki-Bum Kim, Hyun M. Jang, and Gyu-Chul Yi

Appl. Phys. Lett. 79, 3137 (2001); http://dx.doi.org/10.1063/1.1415353 (3 pages) | Cited 93 times

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Fatigue-free and highly c-axis oriented Bi3.15Sm0.85Ti3O12 (BSmT) thin films were grown on Pt/TiO2/SiO2/Si(100) substrates using the method of metalorganic sol decomposition. The BSmT film capacitor with a top Pt electrode showed significantly improved values of the remanent polarization (2Pr) and the nonvolatile charge as compared to those of the Bi4−xLaxTi3O12 (x = 0.75) film capacitor, recently known as the most promising candidate for nonvolatile memories. The 2Pr value of the BSmT capacitor was 49 μC/cm2 at an applied voltage of 10 V while the net nonvolatile switching charge was as high as 20 μC/cm2 and remained essentially constant up to 4.5×1010 read/write switching cycles at a frequency of 1 MHz. In addition to these, the capacitor demonstrated excellent charge–retention characteristics with its sensing margin of 17 μC/cm2 and a strong resistance against the imprinting failure. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.Gk Non-volatile ferroelectric memories
84.32.Tt Capacitors
77.22.Ej Polarization and depolarization

Correlation between the dielectric constant and porosity of nanoporous silica thin films deposited by the gas evaporation technique

J. J. Si, H. Ono, K. Uchida, S. Nozaki, H. Morisaki, and N. Itoh

Appl. Phys. Lett. 79, 3140 (2001); http://dx.doi.org/10.1063/1.1415042 (3 pages) | Cited 16 times

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Nanoporous silica thin films with low dielectric constants were deposited by gas evaporation of SiO2 nanoparticles in an argon atmosphere. With increasing gas pressure during the evaporation, the dielectric constant decreases, while the porosity increases. The correlation between the dielectric constant and porosity is well modeled by a serial connection of two capacitors, one with air and the other with SiO2 as the dielectric medium. This suggests that the dielectric constant of the nanoporous silica thin film using the gas evaporation technique is more effectively lowered by forming “uniformly” distributed voids of closed gaps than those of the nanoporous silica films with pores extending from the back to front surface. Therefore, the former nanoporous silica thin film requires less porosity to obtain a low dielectric constant and is regarded as an ideal low-k material. © 2001 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
61.43.Gt Powders, porous materials
81.05.Rm Porous materials; granular materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.43.Vx Thermal desorption

Oxidation states in scanning-probe-induced Si3N4 to SiOx conversion studied by scanning photoemission microscopy

R. Klauser, I.-H. Hong, H.-J. Su, T. T. Chen, S. Gwo, S.-C. Wang, T. J. Chuang, and V. A. Gritsenko

Appl. Phys. Lett. 79, 3143 (2001); http://dx.doi.org/10.1063/1.1415415 (3 pages) | Cited 17 times

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The biased conductive probe of an atomic force microscope can induce local oxidation in ambience for converting silicon nitride films to silicon oxides with high reaction rate. Spatially resolved photoemission analysis with submicron resolution has been utilized to study the oxidation states of converted silicon oxide patterns in comparison with the surrounding Si3N4 layer. The core level shift of the Si 2p photoelectron peak and the spectral features in the valence band reveal a complete conversion of silicon nitride to silicon oxide at a bias voltage of 10 V, with no remaining nitrogen left. The major oxide is SiO2. The observed oxidation states of Si4+, Si3+, and Si2+ show a gradient depth distribution indicating excess silicon in the layer. © 2001 American Institute of Physics.
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81.65.Mq Oxidation
81.16.Ta Atom manipulation

Polarization reversal in congruent and stoichiometric lithium tantalate

V. Ya. Shur, E. V. Nikolaeva, E. I. Shishkin, V. L. Kozhevnikov, A. P. Chernykh, K. Terabe, and K. Kitamura

Appl. Phys. Lett. 79, 3146 (2001); http://dx.doi.org/10.1063/1.1416471 (3 pages) | Cited 24 times

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Switching kinetics has been compared in congruent (CLT) and stoichiometric (SLT) lithium tantalate by simultaneous recording of instantaneous domain patterns and switching current. A mechanism of fast domain kinetics in CLT driven by domain merging was revealed. The important information about the domain kinetics has been obtained by the statistical analysis of current noise in SLT. A model of jerky domain wall motion is proposed. © 2001 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena

Oxidation states of titanium in bulk barium titanates and in (100) fiber-textured (BaxSr1−x)Ti1+yO3+z thin films

S. Stemmer, T. Höche, R. Keding, C. Rüssel, R. Schneider, N. D. Browning, S. K. Streiffer, and H.-J. Kleebe

Appl. Phys. Lett. 79, 3149 (2001); http://dx.doi.org/10.1063/1.1418036 (3 pages) | Cited 2 times

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Chemical shifts of titanium L edges and oxygen K edges in electron energy-loss spectroscopy in transmission electron microscopy were used to detect valence state reduction of Ti in bulk barium titanates, used as reference materials, and in (BaxSr1−x)Ti1+yO3+z (BST) thin films grown with excess Ti. A hollandite-type Ba titanate, containing Ti with an average valence state of approximately 3.7 in octahedral coordination, showed large chemical shifts relative to rutile TiO2 and BaTiO3, containing only Ti4+. In BST, chemical shifts relative to BaTiO3 were measured from grain interiors of columnar films with different amounts of excess Ti. We found that shifts, corresponding to an average valence state of Ti smaller than nominal 4+, increase with increasing amounts of excess Ti in the films. The results show that at least some amount of excess Ti is accommodated in these films by a defect mechanism that requires a reduction of the average valence state of Ti. © 2001 American Institute of Physics.
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71.28.+d Narrow-band systems; intermediate-valence solids
61.66.Bi Elemental solids
61.66.Dk Alloys
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.37.Lp Transmission electron microscopy (TEM)
79.20.Uv Electron energy loss spectroscopy

Nanometer spot allocation for Raman spectroscopy on ferroelectrics by polarization and piezoresponse force microscopy

G. Tarrach, P. Lagos L., R. Hermans Z., F. Schlaphof, Ch. Loppacher, and L. M. Eng

Appl. Phys. Lett. 79, 3152 (2001); http://dx.doi.org/10.1063/1.1414292 (3 pages) | Cited 10 times

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We report the 100% correlation between polarized light microscopy (PLM), piezoresponse force microscopy (PFM), and micro-Raman spectroscopy when investigating domain-rich ferroelectric systems. In order to allocate the desired spot on a submicrometer scale, both PLM and PFM were combined to elucidate the effective three-dimensional ferroelectric domain distribution. With PFM we observe spike-like a and c domains well inside extended a and c-polarized areas, which were not conclusive with PLM. The knowledge on such a domain distribution is essential when addressing quantitative micro-Raman spectroscopy. In addition, we show the unambiguous differentiation between a and c domains on the submicrometer scale using the B2 mode of lattice vibrations. © 2001 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
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