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26 Dec 2005

Volume 87, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 87, 263102 (2005); http://dx.doi.org/10.1063/1.2150278 (3 pages)

Z. Zhong, G. Katsaros, M. Stoffel, G. Costantini, K. Kern, O. G. Schmidt, N. Y. Jin-Phillipp, and G. Bauer
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Initial reaction of hafnium oxide deposited by remote plasma atomic layer deposition method

Youngdo Won, Sangwook Park, Jaehyoung Koo, Seokhoon Kim, Jinwoo Kim, and Hyeongtag Jeon

Appl. Phys. Lett. 87, 262901 (2005); http://dx.doi.org/10.1063/1.2150250 (3 pages) | Cited 16 times

Online Publication Date: 19 December 2005

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A remote plasma atomic layer deposition (RPALD) method has been applied to grow a hafnium oxide thin film on the Si substrate. The deposition process was monitored by in situ XPS and the as-deposited structure and chemical bonding were examined by TEM and XPS. The in situ XPS measurement showed the presence of a hafnium silicate phase at the initial stage of the RPALD process up to the 20th cycle and indicated that no hafnium silicide was formed. The initial hafnium silicate was amorphous and grew to a thickness of approximately 2 nm. Based on these results and model reactions for silicate formation, we proposed an initial growth mechanism that includes adatom migration at nascent step edges. Density functional theory calculations on model compounds indicate that the hafnium silicate is thermodynamically favored over the hafnium silicide by as much as 250 kJ/mol.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.A- Nucleation and growth
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Ultrascaled hafnium silicon oxynitride gate dielectrics with excellent carrier mobility and reliability

M. A. Quevedo-Lopez, S. A. Krishnan, P. D. Kirsch, G. Pant, B. E. Gnade, and R. M. Wallace

Appl. Phys. Lett. 87, 262902 (2005); http://dx.doi.org/10.1063/1.2150586 (3 pages) | Cited 26 times

Online Publication Date: 19 December 2005

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A hafnium silicon oxynitride gate dielectric with a universal channel mobility of ∼ 90% at 1 MV/cm, equivalent oxide thickness of approximately 1 nm, and leakage current 200× less than SiO2 is reported. X-ray photoelectron spectroscopy results suggest that the small peak mobility loss observed in scaled HfSiON may be attributed to increased Si–N bonding near the silicon interface. In accordance with these mobility results, the Si–N:Hf–N bond ratio decreases with increasing HfSiON physical thickness. Threshold voltage instability at 1 nm equivalent oxide thickness is less than 10 mV after a 1000 s stress at 22 MV cm. ΔVTH monotonically increases with HfSiON physical thickness. This is associated with greater crystallization in thicker HfSiON films.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
72.20.Fr Low-field transport and mobility; piezoresistance
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Polarization reversal of ferroelectric small particles: Surface polarization enhancement and bound charges effects

Laurent Baudry

Appl. Phys. Lett. 87, 262903 (2005); http://dx.doi.org/10.1063/1.2151247 (3 pages) | Cited 1 time

Online Publication Date: 19 December 2005

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The polarization reversal mechanism in ferroelectric small particles with surface polarization enhancement has been theoretically investigated. The model based on a thermodynamical approach, in which the bound charges contribution has been included, predicts, as it does for polarization decreases towards the surface, a reversal current curve with one peak. This result is very different from that previously obtained within the uniform electric field approximation for which the current curve exhibited two peaks.
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77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity

Z-contrast and electron energy loss spectroscopy study of passive layer formation at ferroelectric PbTiO3/Pt interfaces

L. F. Fu, S. J. Welz, N. D. Browning, M. Kurasawa, and P. C. McIntyre

Appl. Phys. Lett. 87, 262904 (2005); http://dx.doi.org/10.1063/1.2144279 (3 pages) | Cited 8 times

Online Publication Date: 19 December 2005

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Scanning transmission electron microscopy and electron energy loss spectroscopy have been applied to investigate the possible structural origins of ferroelectric polarization degradation at PbTiO3/Pt interfaces. The microscopic analysis revealed that an amorphous Ti-rich interfacial layer as well as nanometer size precipitates was formed at PbTiO3/Pt interfaces. The interfacial layer appears to form through decomposition of the PbTiO3 film due to a ferroelectric-electrode reaction during Pt deposition. The formation of the interfacial layer and precipitates could contribute to the polarization degradation typically observed for Pt-electroded PbTiO3-based ferroelectric capacitors.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.35.Ct Interface structure and roughness
64.75.-g Phase equilibria
79.20.Uv Electron energy loss spectroscopy

Phase of reflection high-energy electron diffraction oscillations during (Ba,Sr)O epitaxy on Si(100): A marker of Sr barrier integrity

G. J. Norga, C. Marchiori, A. Guiller, J. P. Locquet, Ch. Rossel, H. Siegwart, D. Caimi, J. Fompeyrine, and T. Conard

Appl. Phys. Lett. 87, 262905 (2005); http://dx.doi.org/10.1063/1.2158018 (3 pages) | Cited 13 times

Online Publication Date: 21 December 2005

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We use the reflection high-energy electron diffraction oscillation phase shift to monitor the stability of the Sr barrier, prepared by exposure of Si(100) to Sr at high temperatures, in situ during molecular beam epitaxy growth of (Ba,Sr)O on Si(100). Our results confirm that the deposition of additional metallic Sr at low temperature is essential for preventing the incorporation of the Sr termination layer in the (Ba,Sr)O layer during its growth, and for obtaining monolayer thin (Ba,Sr)O layers with good crystallinity and minimal density of interfacial Si–O bonds on Si(100).
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.65.Mq Oxidation

Characteristics of HfO2–Al2O3 laminate films containing incorporated N as a function of stack structure and annealing temperature

M.-H. Cho, K. B. Chung, C. N. Whang, D.-H. Ko, and H. S. Kim

Appl. Phys. Lett. 87, 262906 (2005); http://dx.doi.org/10.1063/1.2147718 (3 pages) | Cited 2 times

Online Publication Date: 23 December 2005

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The properties of Al2O3–HfO2 laminated films with incorporated N were investigated as a function of stack structure and annealing temperature by high-resolution x-ray photoelectron spectroscopy, and medium energy ion scattering (MEIS). The MEIS results indicate that the diffusion of Si from the Si substrate into film increased in the case where a film with a buffer layer of Al2O3 was present during the annealing at temperatures up to 800 °C, while it led to a relative suppression in a film with a HfO2 buffer layer. The incorporation of N was gradually increased in the film with a buffer layer of Al2O3 on Si with annealing temperature, while the increase was abrupt in the film with a buffer layer of HfO2 on Si at an annealing temperature of 900 °C. The N incorporated into the film was very unstable, resulting in out diffusion from the film after an additional annealing treatment.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.84.Lf Composite materials
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
79.60.-i Photoemission and photoelectron spectra
66.30.J- Diffusion of impurities

Larger polarization and weak ferromagnetism in quenched BiFeO3 ceramics with a distorted rhombohedral crystal structure

S. T. Zhang, M. H. Lu, D. Wu, Y. F. Chen, and N. B. Ming

Appl. Phys. Lett. 87, 262907 (2005); http://dx.doi.org/10.1063/1.2147719 (3 pages) | Cited 95 times

Online Publication Date: 28 December 2005

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Single-phase insulating BiFeO3 ceramics have been synthesized by a simple but effective method that conventional solid state reaction is followed immediately by quenching processing. At room temperature, the ceramics show a metastable, distorted rhombohedral phase and the refined structure parameters are presented based on x-ray diffraction. It is revealed that the formations of Fe2+ and oxygen deficiency are greatly suppressed by the quenching processing. A well-saturated ferroelectric hysteresis loop with a large remnant polarization (2Pr = 23.5 μC/cm2) is observed with an applied field of 155 kV/cm. Temperature-dependent magnetic property is investigated and weak ferromagnetism with a remnant magnetization of 4×10−6 μB/Fe at 10 K is established. These results may have implications for further studies on multiferroics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Gh Other heat and thermomechanical treatments

Excellent frequency dispersion of thin gadolinium oxide high-k gate dielectrics

Tung-Ming Pan, Chao-Sung Liao, Hui-Hsin Hsu, Chun-Lin Chen, Jian-Der Lee, Kuan-Ti Wang, and Jer-Chyi Wang

Appl. Phys. Lett. 87, 262908 (2005); http://dx.doi.org/10.1063/1.2152107 (3 pages) | Cited 29 times

Online Publication Date: 28 December 2005

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In this letter, we reported a high-k gadolinium oxide (Gd2O3) gate dielectric formed by reactive rf sputtering. It is found that the Gd2O3 gate dielectric film exhibits excellent electrical properties such as low leakage current density, high breakdown voltage, and almost no hysteresis and frequency dispersion in C‐V curves comparable to that of HfO2 film. This indicates that postprocessing treatments can reduce a large amount of interface trap and can passivate a large amount of trapped charge at defect sites.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis

Thermal stability of low dielectric constant porous silica films

L. Esposito, G. Ottaviani, E. Carollo, and M. Bacchetta

Appl. Phys. Lett. 87, 262909 (2005); http://dx.doi.org/10.1063/1.2159093 (3 pages) | Cited 2 times

Online Publication Date: 28 December 2005

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Thermal stability of porous-silica-based low dielectric constant, k, material deposited by chemical vapor deposition has been investigated in a wide temperature range. The films as-deposited and after heat treatments up to 600 °C have Si1O1.6C1.4H2.3 composition, permittivity k ≈ 2.8, and porosity h ≈ 0.25. A skeleton of silicon dioxide and empty pores justifies the permittivity and porosity values. Permeation experiments with deuterated water vapor indicate that pores are interconnected. At 700 °C, the film has Si1O1.6C1.4H1.4 composition, k ≈ 2.4, and h ≈ 0.21. Bonds with lower polarizability could be responsible for the decrease of k. Above 800 °C, carbon segregation and nanoclusters formation occur.
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68.60.Dv Thermal stability; thermal effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Gh Other heat and thermomechanical treatments
77.22.Ej Polarization and depolarization
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