APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Nov 2004

Volume 85, Issue 20, pp. 4561-4807

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4768 (2004); http://dx.doi.org/10.1063/1.1818331 (3 pages)

G. Walter, N. Holonyak, M. Feng, and R. Chan
Enlarge Image | Read More
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Clamping effects in the Al2O3(11math0)∕Nb(110)∕Eu(110) epitaxial system

S. Soriano, C. Dufour, K. Dumesnil, J. A. Borchers, and Ph. Mangin

Appl. Phys. Lett. 85, 4636 (2004); http://dx.doi.org/10.1063/1.1821658 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In-plane and out-of-plane lattice parameters of Nb and Eu have been measured as a function of temperature between 10 and 300 K in the Al2O3(11math0)∕Nb(110)∕Eu(110) epitaxial system. It is shown that the Nb lattice is clamped in the growth plane to the sapphire substrate, in the whole temperature range. On its own, the Eu lattice is totally free to expand isotropically above a clamping temperature Tcl, below which in-plane parameters also freeze to an almost constant value. This well-defined clamping temperature strongly depends on the Eu thickness and likely is related to the thermal mobility of interface defects.

Electromigration lifetime and critical void volume

Jun He, Z. Suo, T. N. Marieb, and J. A. Maiz

Appl. Phys. Lett. 85, 4639 (2004); http://dx.doi.org/10.1063/1.1821631 (3 pages) | Cited 10 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study electromigration in copper lines encapsulated in an organosilicate glass. A line fails when a void near the upstream via grows to a critical volume. We calculate the void volume as a function of time. The statistical distribution of the critical volume (DCV) is taken to be independent of testing variables, such as line length and electric current density. By contrast, the distribution of the lifetime (DLT) strongly depends on these testing variables. We deduce the DCV from the experimentally measured DLT. Once deduced, the DCV can predict the DLT under untested conditions.

Spatially resolved measurements of thermal parameters in colloidal suspensions in liquid crystals

F. Mercuri, U. Zammit, and M. Marinelli

Appl. Phys. Lett. 85, 4642 (2004); http://dx.doi.org/10.1063/1.1821655 (3 pages) | Cited 4 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on spatially resolved measurements with a spatial resolution of about 0.1 mm of the transition temperature and of the behavior of the heat capacity, thermal conductivity, and thermal diffusivity over the smectic A–nematic and nematic–isotropic phase transitions in an inhomogeneous aerosil dispersed 8CB liquid crystal. The results were obtained by means of a recently implemented photopyroelectric setup which combines the capability for high temperature resolution measurements with the possibility of visual access in the sample. It is shown that the results relative to different local concentration of particles are consistent with the ones obtained previously on homogeneous samples with different average particle concentration. Finally, the analysis of the local thermal conductivity values has led to an approximate estimate of the local particle concentration in the sample.

Femtosecond real-time pump–probe imaging spectroscopy

Naoki Furukawa, Chad E. Mair, Valeria D. Kleiman, and Jun Takeda

Appl. Phys. Lett. 85, 4645 (2004); http://dx.doi.org/10.1063/1.1823039 (3 pages) | Cited 6 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Real-time pump–probe imaging spectroscopy with femtosecond time resolution is demonstrated. This method allows real-time mapping of frequency- and time-resolved transient absorption of materials at once. We can clearly measure the image of the transient absorption spectra of β-carotene with wide temporal and spectral ranges in a short accumulation time. Since the typical accumulation time is about two orders of magnitude shorter than that by the conventional pump–probe technique, this method becomes a powerful spectroscopic tool to study ultrafast relaxation and dynamics on organic/biochemical materials, which easily undergo photofatigue after many repetitions of the pump–probe sequence.

Bending of dislocations in GaN during epitaxial lateral overgrowth

S. Gradečak, P. Stadelmann, V. Wagner, and M. Ilegems

Appl. Phys. Lett. 85, 4648 (2004); http://dx.doi.org/10.1063/1.1823593 (3 pages) | Cited 20 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Bending of dislocations in GaN during epitaxial lateral overgrowth (ELO) has been experimentally studied using transmission electron microscopy. The orientational dependence of the dislocation energy factor K has been calculated on the basis of anisotropic elasticity theory for different types of perfect dislocation in GaN. Image forces act on dislocations during the growth and dislocations bend to achieve the minimum energy. Bending behavior depends on a dislocation type and we show that the measured bending angles correspond to the calculated energy minima. The results allow us to quantitatively discuss the most advantageous ELO GaN mask direction for the largest dislocation density reduction.

Effect of layer thickness on the electrostatic potential in InGaN quantum wells

M. Stevens, A. Bell, M. R. McCartney, F. A. Ponce, H. Marui, and S. Tanaka

Appl. Phys. Lett. 85, 4651 (2004); http://dx.doi.org/10.1063/1.1815376 (3 pages) | Cited 14 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High-resolution electron holography in the transmission electron microscope has the capability to profile the spatial variation of the electrostatic potential in semiconductors, at subnanometer resolution. We have used electron holography to measure the internal electrostatic potential and fields across quantum wells with well thickness ranging from 2 to 10 nm, at a nominal indium concentration of x=0.13. A comparison of field strength versus well width shows a precipitous drop in field strength beyond 6 nm. A close look at the microstructure of the widest well shows additional contrast at the growth interface. An explanation consistent with both observations supports the possibility of compositional fluctuations in combination with strain relaxation at the early stages of growth of the quantum well.

In situ neutron diffraction studies on the elevated-temperature deformation behavior of a TiAl–W alloy

Hahn Choo, Dongyi Seo, Jonathan Beddoes, Mark A. M. Bourke, and Donald W. Brown

Appl. Phys. Lett. 85, 4654 (2004); http://dx.doi.org/10.1063/1.1823043 (3 pages) | Cited 8 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The evolution of elastic lattice strain in a Ti–48Al–2W (at.%) alloy, subjected to (1) quasistatic tensile loading and (2) constant-load tensile creep, was investigated at 1033 K using in situ neutron diffraction. During the quasistatic test to a maximum stress of 435 MPa, a- and c-axes lattice strains increased linearly with a small degree of anisotropy (matha∕mathc≅0.9) up to 200 MPa, followed by a significant redistribution of load above 260 MPa due to the plastic anisotropy. Time-resolved in situ measurements were also performed during the creep at 276 and 327 MPa. The results show that lattice strain evolution during the primary creep is qualitatively similar to the quasistatic case under the current test conditions.

Energy band dispersion in well ordered N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide films

G. N. Gavrila, H. Mendez, T. U. Kampen, D. R. T. Zahn, D. V. Vyalikh, and W. Braun

Appl. Phys. Lett. 85, 4657 (2004); http://dx.doi.org/10.1063/1.1800273 (3 pages) | Cited 22 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electronic properties of well ordered N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic dimide (DiMe-PTCDI) films prepared on sulfur passivated GaAs(001) substrates were studied by means of photoemission spectroscopy. From the photon energy dependence of normal emission spectra an intermolecular energy band dispersion of about 0.2 eV was determined for the highest occupied molecular orbital (HOMO). Simulation of the density of states reveals that the HOMO band has a single π -character. The observed energy band dispersion thus originates from the intermolecular π-π interaction and is modeled using the tight binding model. The analysis provides a value of 0.04 eV for the transfer integral. The inner potential was treated as a fitting parameter such that the expected periodicity of the dispersion in the reciprocal space was obtained.
Show PACS
71.20.Nr Semiconductor compounds
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
back to top
RSS Feeds

Mn diffusion in Ga1−xMnxAs∕GaAs superlattices

A. Mikkelsen, L. Ouattara, H. Davidsson, E. Lundgren, J. Sadowski, and O. Pacherova

Appl. Phys. Lett. 85, 4660 (2004); http://dx.doi.org/10.1063/1.1818338 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ga1−xMnxAs∕GaAs superlattices with Mn concentrations of 1% and 5% in the Ga1−xMnxAs layers and a GaAs spacer thickness of 4 and 60 GaAs monolayers have been studied by cross-sectional scanning tunneling microscopy. By achieving atomic resolution of the superlattices, we observe individual Mn atoms in the Ga1−xMnxAs layers and in the GaAs spacer. We find that about 20% of the total amount of Mn diffuses from the GaMnAs layers into the GaAs spacer layers. Our results can be related to previous measurements of the magnetic properties of short period Ga1−xMnxAs∕GaAs superlattices.

Reduction of contact resistance in pentacene thin-film transistors by direct carrier injection into a-few-molecular-layer channel

Nobuhide Yoneya, Makoto Noda, Nobukazu Hirai, Kazumasa Nomoto, Masaru Wada, and Jiro Kasahara

Appl. Phys. Lett. 85, 4663 (2004); http://dx.doi.org/10.1063/1.1814443 (3 pages) | Cited 54 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We found an abrupt reduction of contact resistance, Rc, in pentacene bottom-contact thin-film transistors (TFTs) with Au/Ti source/drain (S/D) electrodes when Ti thickness is below ∼3 nm. Our results suggest that the direct ohmic contact with a few molecular layer channel is a key to reduce the Rc of the S/D electrodes. We propose a Au/self-assembled monolayer electrode structure enabling direct ohmic contact with these few molecular layer channels, and achieved high-performance bottom-contact TFTs with an extrinsic mobility of 1.1 cm2∕V s, an on/off ratio of 106, and a subthreshold swing of 0.3 V/decade.

Memory effect from charge trapping in layered organic structures

Sung Hoon Kang, Todd Crisp, Ioannis Kymissis, and Vladimir Bulović

Appl. Phys. Lett. 85, 4666 (2004); http://dx.doi.org/10.1063/1.1819991 (3 pages) | Cited 26 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate organic light emitting devices (OLEDs) with a charge trap layer that show memory behavior. These OLEDs demonstrate that organic heterojunction structures can controllably trap and release electronic charges. The trap layer is either 5-nm-thick clustered silver islands, or a 10-nm-thick organic laser dye DCM2 ([2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)-ethenyl]-4H-pyran-4-ylidene] propane-dinitrile) doped into TPD (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine). Predictions of the energy band structure indicate that both DCM2 sites and the metal islands can trap charge, consistent with the measured current–voltage characteristics. Trap sites are charged by applying reverse bias over the OLEDs. For devices with DCM2 traps we observe quenching of DCM2 photoluminescence upon charging, which allows us to quantify the charged trap density as approximately 10% of the trap sites or 1018 cm−3. From time resolved measurements we observe that the charge retention time exceeds 2 h.

Silicon doping dependence of highly conductive n-type Al0.7Ga0.3N

K. Zhu, M. L. Nakarmi, K. H. Kim, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 85, 4669 (2004); http://dx.doi.org/10.1063/1.1825055 (3 pages) | Cited 8 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Highly conductive Si-doped n-type Al0.7Ga0.3N alloys were grown by metalorganic chemical vapor deposition on sapphire substrates. Variable temperature Hall-effect measurements have been employed to study the electrical properties for samples with nominal Si dopant concentration (NSi) from 2.6 to 6.8×1019 cm−3. For the sample with NSi=6.0×1019 cm−3, we have achieved n-type resistivity of 0.0075 Ω cm with an electron concentration of 3.3×1019 cm−3 and mobility of 25 cm2∕V s at room temperature. For the same sample, the effective donor (Si) activation energy E0 was determined to be as low as 10 meV. E0 increases to 25 meV as NSi is reduced to 2.6×1019 cm−3, which can be explained by the bandgap renormalization effect. This implies that heavy doping is necessary in high-Al-content AlGaN alloys to bring down the donor activation energy, therefore a higher conductivity.
Show PACS
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.55.Eq III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Electrical conduction properties of n-type Si-doped AlN with high electron mobility (>100 cm2 V−1 s−1)

Yoshitaka Taniyasu, Makoto Kasu, and Toshiki Makimoto

Appl. Phys. Lett. 85, 4672 (2004); http://dx.doi.org/10.1063/1.1824181 (3 pages) | Cited 37 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
For n-type Si-doped AlN, we have obtained an electron mobility and concentration of 125 cm2 V−1 s−1 and 1.75×1015 cm−3 at 300 K, respectively. At 250 K, the mobility reached the maximum of 141 cm2 V−1s−1. To explain the temperature dependence of the mobility, we calculated mobilities limited by specific scattering mechanisms. We found that the mobility is limited by neutral impurity scattering rather than ionized impurity scattering or lattice scattering because of a large donor ionization energy (∼250 meV).
Show PACS
73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
back to top
RSS Feeds

Tunable field imbalance and spin precession in magnetic double layers

Y. Au, R. Sooryakumar, and K. Bussmann

Appl. Phys. Lett. 85, 4675 (2004); http://dx.doi.org/10.1063/1.1818725 (3 pages) | Cited 1 time

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the manipulation of spin-wave mode profiles by a field imbalance in magnetic double layers produced by the combination of an external field (Hext) and an in-plane spacer layer current-induced Amperian field (Hcur). The magnetizations between layers are tuned from antiparallel to parallel alignment and the associated oscillation amplitudes monitored by Brillouin light scattering. While the results are well accounted for by Maxwell and Landau–Lifshitz equations, a mechanical coupled pendulum analog in a variable unbalanced gravitational acceleration (Δg) provides insight into the underlying physics. It is pointed out that the application of magnetic field pulses of specific strength and duration will lead to direct cross-communication between spin-wave normal modes, a feature unique to the tunable local imbalanced field.

Doping of low-temperature GaAs and GaMnAs with carbon

G. M. Schott, C. Rüster, K. Brunner, C. Gould, G. Schmidt, L. W. Molenkamp, M. Sawicki, R. Jakiela, A. Barcz, and G. Karczewski

Appl. Phys. Lett. 85, 4678 (2004); http://dx.doi.org/10.1063/1.1819522 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The incorporation of carbon in low-temperature (LT) GaAs and GaMnAs layers deposited by molecular-beam epitaxy under various growth conditions has been investigated. The lattice parameter depends on Mn content, C content, and the growth conditions which strongly affect Mn, C, and point defect incorporation. We found optimum growth conditions (Tsub=270 °C, the beam equivalent pressure ratio is 5, growth rate is 0.1 nm∕s) at which high-quality GaMnAs layers with moderate Mn content as well as LT-GaAs layers were deposited, which were efficiently p-doped by carbon. LT GaAs:C revealed the same electrical activation of carbon of about 50% at a high doping level p=5×1019 cm−3 as observed in high-temperature GaAs:C. The Curie temperature as well as the saturation magnetization of GaMnAs decreases with C doping. This suggests a reduced amount of Mn contributing to the ferromagnetic phase in GaMnAs:C.

Thermal effects on the magnetic-field dependence of spin-transfer-induced magnetization reversal

D. Lacour, J. A. Katine, N. Smith, M. J. Carey, and J. R. Childress

Appl. Phys. Lett. 85, 4681 (2004); http://dx.doi.org/10.1063/1.1819516 (3 pages) | Cited 36 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have developed a self-aligned, high-yield process to fabricate current-perpendicular-to-plane giant magnetoresistance (GMR) spin-valve sensors of sub-100-nm dimensions. A pinned synthetic antiferromagnet is used as the reference layer which minimizes dipole coupling to the free layer and field-induced rotation of the reference layer. We find that the critical currents for spin-transfer-induced magnetization reversal of the free layer vary dramatically with relatively small changes in the in-plane magnetic field, in contrast to theoretical predictions based on stability analysis of the Gilbert equations of magnetization dynamics, including Slonczewski-type spin-torque terms. The discrepancy is believed due to thermal fluctuations over the time scale of the measurements. Once thermal fluctuations are taken into account, we find good quantitative agreement between our experimental results and numerical simulations.

Phase separation and magnetic properties of half-metal-type Co2Cr1−xFexAl alloys

K. Kobayashi, R. Y. Umetsu, R. Kainuma, K. Ishida, T. Oyamada, A. Fujita, and K. Fukamichi

Appl. Phys. Lett. 85, 4684 (2004); http://dx.doi.org/10.1063/1.1821654 (3 pages) | Cited 41 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The phase stability and magnetic properties of the half-metal-type Co2Cr1−xFexAl alloy system were investigated. It was found that the occurrence of two-phase separation is unavoidable in a concentration range of less than x=0.4, leading to deviation of the saturation magnetic moments from the generalized Slater–Pauling line. The L21-type phase becomes stable in a concentration range of more than x=0.7, where no half-metallic behaviors are present. Consequently, it is concluded that the most favorable concentration for applications to spintronic devices is located around x=0.4 in Co2Cr1−xFexAl alloys having the B2-type phase.

Stress/strain dependence of ac loss and critical current of Bi2Sr2Ca2Cu3O10 reinforced tape

Guo Min Zhang, Justin Schwartz, P. V. P. S. S. Sastry, Liang Zhen Lin, Li Ye Xiao, and Yun Jia Yu

Appl. Phys. Lett. 85, 4687 (2004); http://dx.doi.org/10.1063/1.1819995 (3 pages) | Cited 2 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The critical current and ac loss of a stainless steel reinforced Bi2Sr2Ca2Cu3O10 composite superconducting tape were measured under tensile stress/strain at 77 K. By use of the definition of irreversible strain, a formula describing the variation of the critical current with strain was proposed. A relationship between ac loss and tensile strain was developed from Norris’ formula and the critical current–strain relation. It is shown that the experimental results agree well with the values calculated from our formulas.
Show PACS
84.71.Mn Superconducting wires, fibers, and tapes
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.Ld Mechanical and acoustical properties, elasticity, and ultrasonic attenuation
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Applied field Mössbauer study of shape anisotropy in Fe nanowire arrays

Qing-feng Zhan, Wei He, Xiao Ma, Ya-qiong Liang, Zhi-qi Kou, Nai-li Di, and Zhao-hua Cheng

Appl. Phys. Lett. 85, 4690 (2004); http://dx.doi.org/10.1063/1.1827330 (3 pages) | Cited 11 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In order to investigate the magnetic anisotropy of Fe nanowire arrays from microscopic point of view, 57Fe Mössbauer spectra were measured at various magnetic fields along and perpendicular to the nanowire axis, respectively. On the basis of the absorption intensities of the second and the fifth lines of sextet, the orientation of Fe magnetic moments can be detected. It was found that the shape anisotropy dominates the overall magnetic anisotropy in the Fe nanowires. Furthermore, the longitudinal and transverse demagnetizing fields of Fe nanowire, respectively, were deduced from the effective hyperfine field at 57Fe nuclei as a function of applied field. The chain-of-spheres model in conjunction with symmetric fanning mechanism was adopted to interpret the domain structure and the parallel coercivity of magnetic nanowire arrays.
Show PACS
75.50.Bb Fe and its alloys
75.50.Vv High coercivity materials
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Characterization of single magnetic particles with InAs quantum-well Hall devices

G. Landry, M. M. Miller, B. R. Bennett, M. Johnson, and V. Smolyaninova

Appl. Phys. Lett. 85, 4693 (2004); http://dx.doi.org/10.1063/1.1827328 (3 pages) | Cited 15 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have measured the magnetic dipolar field from individual micron-sized spherical ferromagnetic particles. The particles were positioned using an atomic force microscope and measured using submicron Hall sensors fabricated from an InAs single-quantum-well heterostructure with lateral dimensions of 0.5–2.5 μm. The magnetic moment of individual particles has been measured, verifying their dipolar moment. We also demonstrate a scaling rule for the detection of individual particles which is relevant to the design of biosensors.
Show PACS
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
back to top
RSS Feeds

Microwave characterization of (Pb,La)TiO3 thin films integrated on ZrO2∕SiO2∕Si wafers by sol-gel techniques

Z. T. Song, Y. Wang, H. L. W. Chan, C. L. Choy, and S. L. Feng

Appl. Phys. Lett. 85, 4696 (2004); http://dx.doi.org/10.1063/1.1823038 (3 pages) | Cited 6 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Polycrystalline perovskite lead lanthanum titanate (PLT) thin films were prepared by a sol-gel method on ZrO2∕SiO2∕Si substrates. The structure of the films was studied by x-ray diffraction and scanning electron microscopy, and the microwave dielectric properties characterized on a network analyzer. A strong dependence of the dielectric constant of PLT films and, correspondingly, the resonance frequency of PLT-based interdigital capacitor on the sample preparation conditions were observed. They resulted from the structural transformation of PLT from a layered structure to a uniform film as the annealing temperature was raised from 550 to 700 °C, suggesting a possible way to modify the device performance by controlling the layered structure of the ferroelectric film.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
81.40.Gh Other heat and thermomechanical treatments
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Film and interface layer properties of ultraviolet-ozone oxidized hafnia and zirconia gate dielectrics on silicon substrates

David Chi and Paul C. McIntyre

Appl. Phys. Lett. 85, 4699 (2004); http://dx.doi.org/10.1063/1.1814799 (3 pages) | Cited 14 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the use of ultraviolet-ozone (UVO) oxidation of thin film hafnium and zirconium to fabricate high-dielectric constant (high-k) gate oxides with chemically modified silicon dioxide-based interface layers on silicon (100) substrates. Using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy, the oxidation state and thickness of the interfacial layer are characterized before and after UVO exposure. Reduction of the chemical oxide followed by reoxidation is observed. The reoxidized silicon is found to be substoichiometric. Thickness series fabricated by repeating the UVO process multiple times for the same substrate indicate a constant interface layer thickness. Inverse capacitance density versus physical thickness plots were used to determine that the dielectric constants for the UVO HfO2 and UVO ZrO2 are 17.3 and 24.8, respectively.
Show PACS
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
81.65.Mq Oxidation
61.66.Bi Elemental solids
61.66.Dk Alloys
78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
79.60.Dp Adsorbed layers and thin films
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Lp Transmission electron microscopy (TEM)

Dielectric properties of epitaxial Ba0.6Sr0.4TiO3 films on SiO2∕Si using biaxially oriented ion-beam-assisted-deposited MgO as templates

B. S. Kang, Jang-Sik Lee, L. Stan, J.-K. Lee, R. F. DePaula, P. N. Arendt, M. Nastasi, and Q. X. Jia

Appl. Phys. Lett. 85, 4702 (2004); http://dx.doi.org/10.1063/1.1812573 (3 pages) | Cited 12 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have epitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on SiO2∕Si substrates using pulsed laser deposition by introducing biaxially oriented ion-beam-assisted-deposited MgO as templates. The structural properties of the BST films were strongly affected by the crystallinity of the templates. The dielectric loss of the BST film was found to decrease as its in-plane texture alignment was improved. As a result, a relatively larger figure of merit K value, defined as tunability∕loss, was obtained for the films with better in-plane crystallinity. The K factor ranged between 7.5 and 3.5 when the in-plane alignment of the MgO templates was varied from 5.0° to 10.5°. This work demonstrates that the crystalline quality of the template layers plays a critical role in monolithic integration of BST with SiO2∕Si for frequency agile devices.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
77.22.Gm Dielectric loss and relaxation
81.15.Fg Pulsed laser ablation deposition

High tunability (Ba,Sr)TiO3 thin films grown on atomic layer deposited TiO2 and Ta2O5 buffer layers

Il-Doo Kim, Harry L. Tuller, Hyun-Suk Kim, and Jin-Seong Park

Appl. Phys. Lett. 85, 4705 (2004); http://dx.doi.org/10.1063/1.1821656 (3 pages) | Cited 37 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this letter, we report on increased tunability of Ba0.6Sr0.4TiO3 (BST) thin films by use of Ta2O5 and TiO2 films as buffer layers between BST and Si substrates. Ta2O5 and TiO2 buffer layers were grown by atomic layer deposition (ALD) onto Si substrates followed by pulsed laser deposition of Ba0.6Sr0.4TiO3 thin films onto the buffer layers. The randomly oriented BST films deposited on TiO2∕Si substrates exhibited a broader grain size distribution than the (110) textured BST films grown on Ta2O5∕Si substrates. At an applied voltage of 10 V, the BST films grown on Ta2O5∕Si and TiO2∕Si substrates showed much enhanced tunability values of 53.1% and 72.9%, respectively, as compared to the 20.7% value obtained with BST films grown on MgO single crystal substrates. Successful integration of BST low voltage microwave tunable devices onto Si substrates thus appears possible with the aid of ALD grown Ta2O5 or TiO2 buffer layers.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)

Interface-related thickness dependence of the tunability in BaSrTiO3 thin films

U. Ellerkmann, R. Liedtke, U. Boettger, and R. Waser

Appl. Phys. Lett. 85, 4708 (2004); http://dx.doi.org/10.1063/1.1824173 (3 pages) | Cited 14 times

Online Publication Date: 16 November 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The thickness dependence of the tunability of Ba0.7Sr0.3TiO3 thin films is investigated. The capacitance–voltage curves, revealing the tunability of the films with thickness from 30 to 370 nm, show a strong thickness dependence. This is attributed to a bias-independent interface capacity. The interface suppresses the permittivity of the film with increasing influence for decreasing film thickness, whereas the tunability of the bulk of the film remains constant. Calculations are performed from a thermodynamic model based on the Landau–Ginzburg–Devonshire theory leading to the assumption of the bias-independent interface capacity. The bias dependence of the bulk of the films derived from measurement data are in very good agreement with the theoretically derived values.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close