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13 Aug 2007

Volume 91, Issue 7, Articles (07xxxx)

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Appl. Phys. Lett. 91, 071906 (2007); http://dx.doi.org/10.1063/1.2753092 (3 pages)

Cheng Zhang, Rajiv K. Kalia, Aiichiro Nakano, and Priya Vashishta
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231–261 nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire

Hideki Hirayama, Tohru Yatabe, Norimichi Noguchi, Tomoaki Ohashi, and Norihiko Kamata

Appl. Phys. Lett. 91, 071901 (2007); http://dx.doi.org/10.1063/1.2770662 (3 pages) | Cited 55 times

Online Publication Date: 13 August 2007

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The authors demonstrated AlGaN multiquantum-well (MQW) deep-ultraviolet light-emitting diodes (LEDs) with wavelengths in the range of 231–261 nm, fabricated on low threading dislocation density AlN buffers formed through an ammonia (NH3) pulse-flow multilayer growth technique. The authors obtained a single-peaked operation of the AlGaN-MQW LED with a wavelength of 231 nm, which is the shortest wavelength of AlGaN-based LED on sapphire. The maximum output power and external quantum efficiency of the 261 and 231 nm LEDs were 1.65 mW and 0.23% under room-temperature (RT) continuous-wave (cw) operation, and approximately 5 μW and 0.001% under RT pulsed operation, respectively.
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85.60.Jb Light-emitting devices

First-principles study of the structure, electronic, and optical properties of orthorhombic BiInO3

Chenliang Li, Hai Wang, Biao Wang, and Rui Wang

Appl. Phys. Lett. 91, 071902 (2007); http://dx.doi.org/10.1063/1.2770761 (3 pages) | Cited 10 times

Online Publication Date: 13 August 2007

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The structural, electronic, and optical properties of orthorhombic BiInO3 were investigated in the framework of the density functional theory. The calculated structural parameters are in agreement with the experimental data. The band structure, density of states, and Mulliken charge population are obtained, which indicates that BiInO3 has an indirect band gap of 2.08 eV. Furthermore, its optical properties are also calculated and analyzed in details. It is shown that BiInO3 is a promising dielectric material.
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71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.66.Fn Inorganic compounds
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

1.54 μm photoluminescence from β-FeSi2 as-deposited film

Kensuke Akiyama, Satoru Kaneko, Hiroshi Funakubo, and Masaru Itakura

Appl. Phys. Lett. 91, 071903 (2007); http://dx.doi.org/10.1063/1.2770654 (3 pages) | Cited 12 times

Online Publication Date: 13 August 2007

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The authors succeeded in preparing high-crystal-quality β-FeSi2 as-deposited film emitting a photoluminescence spectrum strong in intensity. The density of the nonradiative center at the interface and in the β-FeSi2 film remained low by depositing a Cu-treated Si layer such as amorphous Si. The recrystallization of the Cu-treated Si layer during β-FeSi2 deposition contributed to improving the β-FeSi2/Si interface and the crystallinity of the β-FeSi2 film.
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78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.35.Ct Interface structure and roughness

Diffusion of nitrogen molecules in amorphous SiO2

Koichi Kajihara, Masahiro Hirano, Yasuyuki Takimoto, Linards Skuja, and Hideo Hosono

Appl. Phys. Lett. 91, 071904 (2007); http://dx.doi.org/10.1063/1.2770796 (3 pages) | Cited 6 times

Online Publication Date: 13 August 2007

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Nitrogen molecules (N2) are incorporated in interstitial voids in amorphous silica (a-SiO2) thermally annealed in N2 atmosphere. The Raman band associated with the infrared N–N stretching mode of interstitial N2 (Q band) is located at ∼ 2325 cm−1 and is shifted to low energy compared to that of N2 molecules in air ( ∼ 2330 cm−1). From depth profiling of the Raman band intensity in the samples thermally annealed at 800, 900, or 1000 °C, the authors determined the diffusion coefficient and solubility of N2 in a-SiO2 as 1.3×10−4±0.5 exp(−1.28±0.1 eV/kT) cm2 s−1 and 7.0×1015±0.5 exp(0.07±0.1 eV/kT) cm−3 atm−1, respectively.
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66.30.-h Diffusion in solids
64.75.-g Phase equilibria
61.72.J- Point defects and defect clusters
61.72.Qq Microscopic defects (voids, inclusions, etc.)
78.30.Hv Other nonmetallic inorganics
81.40.Gh Other heat and thermomechanical treatments

Unipolarization of ambipolar organic field effect transistors toward high-impedance complementary metal-oxide-semiconductor circuits

Wataru Takashima, Tsutomu Murasaki, Shuichi Nagamatsu, Takeomi Morita, and Keiichi Kaneto

Appl. Phys. Lett. 91, 071905 (2007); http://dx.doi.org/10.1063/1.2770963 (3 pages) | Cited 11 times

Online Publication Date: 13 August 2007

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Ambipolar organic field effect transistors (OFETs), consisting of a composite of polyhexylthiophene (PHT) and [6,6]-phenyl C61-butylic acid methyl ester (PCBM), was converted into a p- or n-type OFET by insertion of a thin tetracyanoquinodimethane (TCNQ) or tetrathiafluvalene (TTF) buffer layer. The interface in the Au/TCNQ/PHT:PCBM composite transports hole but blocks electron, while the transported carrier was switched to electron with insertion of a TTF layer. The selective transport is probably due to vacuum level matching or temporal doping. High impedance in a complementary metal-oxide-semiconductor inverter was demonstrated with unipolarized ambipolar FETs, resulting in a decrease in the through current.
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85.30.Tv Field effect devices

Hypervelocity impact induced deformation modes in α-alumina

Cheng Zhang, Rajiv K. Kalia, Aiichiro Nakano, and Priya Vashishta

Appl. Phys. Lett. 91, 071906 (2007); http://dx.doi.org/10.1063/1.2753092 (3 pages) | Cited 11 times

Online Publication Date: 13 August 2007

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Hypervelocity impact deformation mechanisms of α-alumina are studied using 540×106 atom molecular dynamics simulation on massively parallel computers. The projectile impact on the (0001) surface of α-alumina at 18 km/s exhibits a fundamentally different symmetry of the deformation patterns from those under lower strain rates. The simulation reveals a sequence of atomistic deformation mechanisms following localized melting and amorphization. These include pyramidal slips, basal slips and twins, rhombohedral twins, and twins along the {0math11}. Some of these deformation patterns are not observed under lower impact velocities.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Mm Grain and twin boundaries
64.70.D- Solid-liquid transitions

Strain-induced single-domain growth of epitaxial SrRuO3 layers on SrTiO3: A high-temperature x-ray diffraction study

Arturas Vailionis, Wolter Siemons, and Gertjan Koster

Appl. Phys. Lett. 91, 071907 (2007); http://dx.doi.org/10.1063/1.2771087 (3 pages) | Cited 6 times

Online Publication Date: 14 August 2007

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Temperature dependent structural phase transitions of SrRuO3 thin films epitaxially grown on SrTiO3(001) single crystal substrates have been studied using high-resolution x-ray diffraction. In contrast to bulk SrRuO3, coherently strained epitaxial layers do not display cubic symmetry up to ∼ 730 °C and remain tetragonal. The cause of this behavior is believed to be the compressive strain in the SrRuO3 layer due to the lattice mismatch with SrTiO3 substrate due to lattice mismatch. The tetragonal symmetry during growth explains the single domain growth on miscut SrTiO3 substrates with step edges running along the [100] or [010] direction.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Fg Pulsed laser ablation deposition
64.70.K- Solid-solid transitions

High-frequency torsional modal testing of a long cylinder by magnetostriction

Seung Hyun Cho, Soon Woo Han, Chan Il Park, and Yoon Young Kim

Appl. Phys. Lett. 91, 071908 (2007); http://dx.doi.org/10.1063/1.2769400 (3 pages) | Cited 4 times

Online Publication Date: 14 August 2007

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The torsional modal testing of cylindrical bodies still remains formidable. This is because pure torsional eigenfrequencies typically lying in the kilohertz frequency range are nearly impossible to excite by popular excitation methods. In this study, a torsional modal testing method using a set of magnetostrictive patches, specially arranged permanent magnets, and solenoids is investigated to cover a frequency range of a few kilohertz. The use of magnetostrictive patches for the testing was motivated by torsional wave experiments using the patches, but the use of special magnet configurations was a key to successful modal testing. The developed method was validated with experiments.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
75.80.+q Magnetomechanical effects, magnetostriction

Low-loss optical Er3+-activated glass-ceramics planar waveguides fabricated by bottom-up approach

Y. Jestin, C. Armellini, A. Chiasera, A. Chiappini, M. Ferrari, E. Moser, R. Retoux, and G. C. Righini

Appl. Phys. Lett. 91, 071909 (2007); http://dx.doi.org/10.1063/1.2771537 (3 pages) | Cited 7 times

Online Publication Date: 14 August 2007

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A low-loss optical erbium activated silica-hafnia glass-ceramic planar waveguide was fabricated using a bottom-up approach. Hafnia nanoparticles were first prepared by colloidal route and then mixed in a silica-hafnia:Er3+ sol. The resulting sol was deposited on SiO2 substrate. Analysis of the photoluminescence has demonstrated that erbium ions are embedded in a crystalline phase. A lifetime enhancement of the 4I13/2 metastable level was observed. Losses measurements at 1542 nm highlight a very low attenuation coefficient (0.3 dB/cm) making this nanostructured material suitable for single band waveguide amplifier in the C band of telecommunications.
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42.82.Et Waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Gn Optical waveguides and couplers
42.86.+b Optical workshop techniques

Electric field effect on BiFeO3 single crystal investigated by Raman spectroscopy

M. Cazayous, D. Malka, D. Lebeugle, and D. Colson

Appl. Phys. Lett. 91, 071910 (2007); http://dx.doi.org/10.1063/1.2771380 (3 pages) | Cited 34 times

Online Publication Date: 14 August 2007

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Micro-Raman spectroscopy has been used to study lattice dynamics associated with the ferroelectric domains of a BiFeO3 single crystal at low temperature. The phonon assignment shows a large frequency splitting between the transverse and longitudinal components of the A1 phonon mode related to the Bi–O bonds in contrast with thin films where the splitting is negligible. Applying an external electric field induces frequency shifts of the low energy modes related to the Bi–O bonds. These softenings are due to a tensile stress via the piezoelectric effect. The authors give estimates of the phonon deformation potentials.
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78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
77.65.-j Piezoelectricity and electromechanical effects

Nanoscale thermoelastic probing of megahertz thermal diffusion

Motonobu Tomoda, Oliver B. Wright, and Roberto Li Voti

Appl. Phys. Lett. 91, 071911 (2007); http://dx.doi.org/10.1063/1.2770769 (3 pages) | Cited 1 time

Online Publication Date: 14 August 2007

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The authors demonstrate a method to probe thermal diffusion at megahertz frequencies with nanometer lateral resolution in a thin opaque film on a transparent substrate. They map photothermally induced megahertz surface vibrations in an atomic force microscope using tightly focused optical illumination from the substrate side. By comparison with a theoretical model of the surface displacement field, the authors derive the thermal diffusivity of a thin chromium film on a silica substrate.
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66.30.Xj Thermal diffusivity
68.55.-a Thin film structure and morphology
65.40.-b Thermal properties of crystalline solids

Circular photogalvanic effect of the two-dimensional electron gas in AlxGa1−xN/GaN heterostructures under uniaxial strain

X. W. He, B. Shen, Y. Q. Tang, N. Tang, C. M. Yin, F. J. Xu, Z. J. Yang, G. Y. Zhang, Y. H. Chen, C. G. Tang, and Z. G. Wang

Appl. Phys. Lett. 91, 071912 (2007); http://dx.doi.org/10.1063/1.2768918 (3 pages) | Cited 20 times

Online Publication Date: 15 August 2007

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The circular photogalvanic effect (CPGE) of the two-dimensional electron gas (2DEG) in Al0.25Ga0.75N/GaN heterostructures induced by infrared radiation has been investigated under uniaxial strain. The observed photocurrent consists of the superposition of the CPGE and the linear photogalvanic effect currents, both of which are up to 10−2 nA. The amplitude of the CPGE current increases linearly with additional strain and is enhanced by 18.6% with a strain of 2.2×10−3. Based on the experimental results, the contribution of bulk-inversion asymmetry (BIA) and structure-inversion asymmetry (SIA) spin splitting of the 2DEG to the CPGE current in the heterostructures is separated, and the ratio of SIA and BIA terms is estimated to be about 13.2, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at AlxGa1−xN/GaN heterointerfaces.
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73.63.Hs Quantum wells
72.40.+w Photoconduction and photovoltaic effects
68.65.Fg Quantum wells
73.21.Fg Quantum wells

Variable temperature Raman microscopy as a nanometrology tool for graphene layers and graphene-based devices

I. Calizo, F. Miao, W. Bao, C. N. Lau, and A. A. Balandin

Appl. Phys. Lett. 91, 071913 (2007); http://dx.doi.org/10.1063/1.2771379 (3 pages) | Cited 59 times

Online Publication Date: 15 August 2007

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Raman microscopy of graphene was carried out over the temperature range from 83 to 373 K. The number of layers was independently confirmed by the quantum Hall measurements and atomic force microscopy. The values of the temperature coefficients for the G and 2D-band frequencies extracted from Raman spectra of the single-layer graphene are −(1.6±0.2)×10−2 cm−1/K and −(3.4±0.4)×10−2 cm−1/K, respectively. The G peak temperature coefficients of the bilayer graphene and bulk graphite are −(1.5±0.06)×10−2 cm−1/K and −(1.1±0.04)×10−2 cm−1/K, respectively. The results are important for the application of Raman microscopy as a nanometrology tool for the graphene-based devices operating at various temperatures.
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07.60.Pb Conventional optical microscopes
78.30.Hv Other nonmetallic inorganics

Enhanced 1.5 μm emission and simultaneously suppressed green upconversion emission in Er:LiNbO3 crystals heavily codoped with MgO

Liang Sun, Ai-Hua Li, Feng-Yun Guo, Qiang Lü, Yu-Heng Xu, and Lian-Cheng Zhao

Appl. Phys. Lett. 91, 071914 (2007); http://dx.doi.org/10.1063/1.2769749 (3 pages) | Cited 15 times

Online Publication Date: 15 August 2007

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Enhanced 1.5 μm emission and simultaneously suppressed green upconversion emission was observed for Er(1.0 mol %):LiNbO3 crystals codoped with 8 mol % MgO. The heavy MgO codoping results in the lengthening of the 1.5 μm emission by 11.7%. Time-resolved spectroscopy study shows that the decay trace of the green upconversion emission of the Er/Mg codoped crystal is obviously nonexponential. These spectroscopic characteristics are associated with the lower concentration of the cluster sites of Er3+ ion, the higher nonradiative energy transfer upconversion probability, and the lower OH− content in the crystal.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
61.72.up Other materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
42.70.-a Optical materials

Configuration of the misfit dislocation networks in uncapped and capped InN quantum dots

J. G. Lozano, A. M. Sánchez, R. García, D. González, M. Herrera, N. D. Browning, S. Ruffenach, and O. Briot

Appl. Phys. Lett. 91, 071915 (2007); http://dx.doi.org/10.1063/1.2770776 (3 pages) | Cited 7 times

Online Publication Date: 15 August 2007

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A transmission electron microscopy study of the misfit dislocation (MD) networks between InN quantum dots (QDs) and GaN substrate/capping layer is presented. Applying the geometric phase algorithm in planar-view orientation, a complete characterization of the first interface shows a set of three families of 60° MDs lying along the three 〈11math0〉 directions without node formation. The growth of a GaN capping layer decreases the plastic relaxation degree of the InN QDs by a rearrangement of the MDs. The full relaxation of the capping layer suggest that no changes will occur in the QD strain state during later growths.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

High-throughput screening of combinatorial materials libraries by high-energy x-ray diffraction

Dmitry A. Kukuruznyak, Harald Reichert, John Okasinski, Helmut Dosch, Toyohiro Chikyow, John Daniels, and Veijo Honkimäki

Appl. Phys. Lett. 91, 071916 (2007); http://dx.doi.org/10.1063/1.2771539 (3 pages) | Cited 2 times

Online Publication Date: 16 August 2007

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The authors introduce a method for high-throughput structural characterization of composition-spread thin-film libraries using high-energy x-ray beams in transmission geometry. Scanning the composition-spread film with the x-ray beam yields texture, and in case of polycrystalline spreads, crystal structure maps. In addition, regions with single-crystalline or epitaxial films can be readily identified and further characterized by tilting the sample and taking additional diffraction patterns at selected angles. The authors describe the application of this techniques to the ternary oxide system CeO2–Al2O3–HfO2.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)

Sense determination of micropipes via grazing-incidence synchrotron white beam x-ray topography in 4H silicon carbide

Y. Chen, G. Dhanaraj, M. Dudley, E. K. Sanchez, and M. F. MacMillan

Appl. Phys. Lett. 91, 071917 (2007); http://dx.doi.org/10.1063/1.2772190 (3 pages) | Cited 6 times

Online Publication Date: 16 August 2007

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Computer modeling using the ray-tracing method has been used to simulate the grazing-incidence x-ray topographic images of micropipes in 4H silicon carbide recorded using the pyramidal (11−28) reflection. Simulation results indicate that the images of micropipes appear as white features of roughly elliptical shape, canted to one side or other of the g vector depending on the dislocation sense. Observed images compare well with the simulations, demonstrating that the direction of cant provides a simple, nondestructive, and reliable way to reveal the senses of micropipes. Sense assignment has been validated using back-reflection reticulography.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology

Relaxation and dephasing of the intersubband transitions in n-type InAs/AlSb multi quantum wells

S. Menzel, E. A. Zibik, D. G. Revin, J. W. Cockburn, J. Devenson, R. Teissier, and A. N. Baranov

Appl. Phys. Lett. 91, 071918 (2007); http://dx.doi.org/10.1063/1.2769948 (3 pages) | Cited 1 time

Online Publication Date: 16 August 2007

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Intersubband electron relaxation and dephasing has been studied in InAs/AlSb multi quantum wells using time resolved femtosecond spectroscopy. The authors have measured a relaxation time T1 of 3 ps at T = 300 K (and 4.6 ps at T = 10 K) for a transition energy of 260 meV, which is in good agreement with our calculations. A dephasing time T2 of ∼ 320 fs for optically excited electrons in the second subband was measured which determines the homogeneous broadening ( ∼ 4.1 meV) of the absorption line.
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78.67.De Quantum wells
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics
73.63.Hs Quantum wells

In situ mechanical characterization of polymers with the association of three optical techniques

Stéphane André, Christophe Baravian, Norbert Renault, and Christian Cunat

Appl. Phys. Lett. 91, 071919 (2007); http://dx.doi.org/10.1063/1.2768627 (3 pages) | Cited 3 times

Online Publication Date: 17 August 2007

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A combination of three optical techniques is presented for in situ monitoring of macroscopic and microscopic variables characterizing the deformation of polymers. A video extensometer allows for the monitoring of true stress and strain. An infrared imager along with an appropriate mathematical algorithm allows for the determination of the energies that are converted into heat during the whole test. This makes possible a quantification of thermomechanical couplings revealing structural effects at microscopic scales. Finally, incoherent steady light transport is used to produce images of backscattered intensities. A physical model enables the authors to follow damaging processes occurring at microscopic scales.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
07.10.Pz Instruments for strain, force, and torque

Room-temperature spin-oriented photocurrent under near-infrared irradiation and comparison of optical means with Shubnikov de-Haas measurements in AlxGa1−xN/GaN heterostructures

Y. Q. Tang, B. Shen, X. W. He, K. Han, N. Tang, W. H. Chen, Z. J. Yang, G. Y. Zhang, Y. H. Chen, C. G. Tang, Z. G. Wang, K. S. Cho, and Y. F. Chen

Appl. Phys. Lett. 91, 071920 (2007); http://dx.doi.org/10.1063/1.2770659 (3 pages) | Cited 8 times

Online Publication Date: 17 August 2007

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The admixture of linear and circular photogalvanic effects and (CPGEs) in AlxGa1−xN/GaN heterostructures has been investigated quantitatively by near-infrared irradiation at room temperature. The spin-based photocurrent that the authors have observed solidly indicates the sizable spin-orbital interaction of the two-dimensional electron gas in the heterostructures. Further analysis shows consistency between studies by optical and magnetic (Shubnikov de-Haas) measurements on the spin-orbital coupling effects among different AlxGa1−xN/GaN heterostructures, indicating that the CPGE measurement is a good way to investigate the spin splitting and the spin polarization in semiconductors.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.25.Dc Spin polarized transport in semiconductors
72.40.+w Photoconduction and photovoltaic effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Quenching of surface-exciton emission from ZnO nanocombs by plasma immersion ion implantation

Y. Yang, B. K. Tay, X. W. Sun, J. Y. Sze, Z. J. Han, J. X. Wang, X. H. Zhang, Y. B. Li, and S. Zhang

Appl. Phys. Lett. 91, 071921 (2007); http://dx.doi.org/10.1063/1.2772668 (3 pages) | Cited 17 times

Online Publication Date: 17 August 2007

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Surface modification of ZnO nanocombs was performed through a Ti plasma immersion ion implantation (PIII) with low bias voltages ranging from 0 to 5 kV to quench surface-originated exciton emission. The ion energy dependent surface modification on ZnO was investigated using transmission electron microscopy and temperature-dependent photoluminescence (PL). The surface exciton (SX) was clearly identified for the as-grown sample at 4.5 K, and complete quenching was observed for sample treated with 5 kV PIII due to surface state passivation. The SX related surface states were located within 5 nm in depth from the surface corresponding to the implantation depth of 5 kV PIII. Room-temperature PL enhancement of these surface-modified ZnO nanocombs was observed and discussed. The results show that PIII can become a viable technique for nanostructure surface passivation.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.05.Dz II-VI semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
71.35.-y Excitons and related phenomena
61.72.uj III-V and II-VI semiconductors
52.77.Dq Plasma-based ion implantation and deposition

Adsorption-controlled molecular-beam epitaxial growth of BiFeO3

J. F. Ihlefeld, A. Kumar, V. Gopalan, D. G. Schlom, Y. B. Chen, X. Q. Pan, T. Heeg, J. Schubert, X. Ke, P. Schiffer, J. Orenstein, L. W. Martin, Y. H. Chu, and R. Ramesh

Appl. Phys. Lett. 91, 071922 (2007); http://dx.doi.org/10.1063/1.2767771 (3 pages) | Cited 19 times

Online Publication Date: 17 August 2007

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BiFeO3 thin films have been deposited on (111) SrTiO3 single crystal substrates by reactive molecular-beam epitaxy in an adsorption-controlled growth regime. This is achieved by supplying a bismuth overpressure and utilizing the differential vapor pressures between bismuth oxides and BiFeO3 to control stoichiometry. Four-circle x-ray diffraction reveals phase-pure, untwinned, epitaxial, (0001)-oriented films with rocking curve full width at half maximum values as narrow as 25 arc sec (0.007°). Second harmonic generation polar plots combined with diffraction establish the crystallographic point group of these untwinned epitaxial films to be 3m at room temperature.
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68.55.A- Nucleation and growth
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
75.50.Ee Antiferromagnetics
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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