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4 Aug 2008

Volume 93, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 93, 051101 (2008); http://dx.doi.org/10.1063/1.2965797 (3 pages)

Mariano A. Zimmler, Jiming Bao, Federico Capasso, Sven Müller, and Carsten Ronning
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Ferroelectric, electrical and magnetic properties of Cr, Mn, Co, Ni, Cu added polycrystalline BiFeO3 films

Hiroshi Naganuma, Jun Miura, and Soichiro Okamura

Appl. Phys. Lett. 93, 052901 (2008); http://dx.doi.org/10.1063/1.2965799 (3 pages) | Cited 49 times

Online Publication Date: 4 August 2008

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Cr, Mn, Co, Ni, and Cu were added to polycrystalline BiFeO3 films, and their influence on the ferroelectric, electrical, and magnetic properties was investigated. All the additives except Ni reduced the leakage current density in the high electric field region. The addition of Cu and Co decreased the coercive field without reducing remanent polarization. The addition of Co caused spontaneous magnetization at room temperature, which exhibited a large coercive field of 16 kOe at 10 K. It was revealed that Co addition suppressed the leakage current density, decreased the electric coercive field, and induced spontaneous magnetization and large magnetic coercivity.
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75.80.+q Magnetomechanical effects, magnetostriction
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.61.Ng Insulators

SmScO3 thin films as an alternative gate dielectric

E. Durğun Özben, J. M. J. Lopes, M. Roeckerath, St. Lenk, B. Holländer, Y. Jia, D. G. Schlom, J. Schubert, and S. Mantl

Appl. Phys. Lett. 93, 052902 (2008); http://dx.doi.org/10.1063/1.2968660 (3 pages) | Cited 12 times

Online Publication Date: 5 August 2008

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Samarium scandate thin films deposited on (100) Si have been investigated structurally and electrically. Rutherford backscattering spectrometry and transmission electron microscopy results show that the films are stoichiometric, amorphous, and smooth. X-ray diffraction analysis indicates that SmScO3 starts to crystallize at 900 °C. Capacitance and leakage current measurements reveal C-V curves with negligible hysteresis, a dielectric constant around 29 for 6 nm thick films, low leakage current densities in the range of 10−7 A/cm2, an effective oxide charge density of ∼ 5×1011 cm−2, and an interface trap density of 4.5×1011 (eV cm2)−1.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.43.Er Other amorphous solids
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)

Low temperature improvement on silicon oxide grown by electron-gun evaporation for resistance memory applications

Chih-Tsung Tsai, Ting-Chang Chang, Po-Tsun Liu, Yi-Li Cheng, and Fon-Shan Huang

Appl. Phys. Lett. 93, 052903 (2008); http://dx.doi.org/10.1063/1.2957655 (3 pages) | Cited 3 times

Online Publication Date: 5 August 2008

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In this work, the supercritical CO2 fluid mixed with cosolvents is introduced to terminate the traps in electron-gun (e-gun) evaporation deposited silicon oxide (SiOx) film at 150 °C. After the proposed treatment, the SiOx film exhibits a lower leakage current and a resistive switching behavior that is controllable by applying proper voltage bias. The change in resistance is over 102 times and the retention time attains to 2×103 s. It is also discovered that the resistive switching behavior seemingly relates to the amount of traps.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.aj Insulators

Band gap engineering for La aluminate dielectrics on Si (100)

Hua Jin, Young Joon Cho, Suhk Kun Oh, Hee Jae Kang, Ju Chul Park, Sung Heo, and Jae Cheol Lee

Appl. Phys. Lett. 93, 052904 (2008); http://dx.doi.org/10.1063/1.2964181 (3 pages) | Cited 6 times

Online Publication Date: 5 August 2008

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La aluminate (La2O3)x(Al2O3)1−x films were grown by atomic layer deposition method, for which the conduction band offset, valence band offset, and band gap were obtained by using x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The valence band offsets were nearly unchanged within the range from 2.23 to 2.37 eV with increasing Al content. The conduction band offsets were changed from 2.40 to 2.86 eV for the above dielectrics. Remarkably, the band gap could be engineered from 5.75 to 6.35 eV by increasing Al content. We also found that La aluminate films have symmetric band profiles.
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71.20.Ps Other inorganic compounds
79.60.Bm Clean metal, semiconductor, and insulator surfaces
77.55.-g Dielectric thin films

Epitaxial growth of aluminum nitride on AlGaN by reactive sputtering at low temperature

C. Duquenne, M. A. Djouadi, P. Y. Tessier, P. Y. Jouan, M. P. Besland, C. Brylinski, R. Aubry, and S. Delage

Appl. Phys. Lett. 93, 052905 (2008); http://dx.doi.org/10.1063/1.2967816 (3 pages) | Cited 6 times

Online Publication Date: 5 August 2008

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We report the synthesis of 1 μm thick single crystalline aluminum nitride films by dc magnetron sputtering on AlGaN/GaN layer grown on sapphire substrate at low temperature (substrate temperature <250 °C). The microstructure of c-axis oriented AlN films deposited on Si (100) and AlGaN ⟨0001⟩ substrates was studied by x-ray diffraction, selected area electron diffraction, and transmission electron microscopy. The optimization of process parameters, involving low energetic ion bombardment on film surface (20–30 eV) during the growth, leads to an increase in the surface mobility and thus promotes AlN epitaxial growth on AlGaN substrate at 250 °C.
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81.05.Ea III-V semiconductors
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
68.37.Lp Transmission electron microscopy (TEM)

A multiferroic ceramic with perovskite structure: (La0.5Bi0.5)(Mn0.5Fe0.5)O3.09

Asish K. Kundu, R. Ranjith, B. Kundys, N. Nguyen, V Caignaert, V Pralong, W. Prellier, and B. Raveau

Appl. Phys. Lett. 93, 052906 (2008); http://dx.doi.org/10.1063/1.2961022 (3 pages) | Cited 12 times

Online Publication Date: 5 August 2008

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An ABO3 perovskite multiferroic, where the B-site cation is responsible for the magnetic properties and the A-site cation with lone pair electron is responsible for the ferroelectric properties, was synthesized with the composition (La0.5Bi0.5)(Mn0.5Fe0.5)O3.09 at normal conditions. This oxide exhibits a ferromagnetic transition around 240 K with a well defined hysteresis loop, and a significant reversible remnant polarization below 67 K similar to ferroelectric behavior. The magnetic interaction is interpreted by the ferromagnetic Fe3+–O–Mn3+ and antiferromagnetic Fe3+(Mn3+)–O–Fe3+(Mn3+) interactions competed with each other, whereas the ferroelectricity is predominantly due to the polar nature introduced by the 6 s2 lone pair of Bi3+ cations.
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75.80.+q Magnetomechanical effects, magnetostriction
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effects of hydrogen anneals on oxygen deficient SrTiO3−x single crystals

Bharat Jalan, Roman Engel-Herbert, Thomas E. Mates, and Susanne Stemmer

Appl. Phys. Lett. 93, 052907 (2008); http://dx.doi.org/10.1063/1.2969037 (3 pages) | Cited 11 times

Online Publication Date: 6 August 2008

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The influence of hydrogen gas anneals on the electrical properties of nominally undoped, oxygen-deficient SrTiO3−x single crystals was investigated. Titanium getter layers and vacuum anneals were used to obtain oxygen-deficient SrTiO3−x with a low electrical resistivity. These crystals showed an optical absorption peak at 2.92 eV and strong midinfrared absorption. Subsequent anneals at 800 °C in forming gas, which contained 10% hydrogen, returned the crystals into the insulating, transparent state. The mechanisms by which hydrogen anneals can compensate for the effects of oxygen vacancies in SrTiO3−x are discussed. The results show that forming gas anneals of stoichiometric SrTiO3 can lead to complex electrical conduction behavior.
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72.80.Sk Insulators
61.66.Bi Elemental solids
61.66.Dk Alloys
78.30.Hv Other nonmetallic inorganics

Effect of ruthenium oxide electrode on the resistive switching of Nb-doped strontium titanate

Musarrat Hasan, Rui Dong, H. J. Choi, D. S. Lee, D.-J. Seong, M. B. Pyun, and Hyunsang Hwang

Appl. Phys. Lett. 93, 052908 (2008); http://dx.doi.org/10.1063/1.2969052 (3 pages) | Cited 8 times

Online Publication Date: 6 August 2008

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We studied resistance switching characteristics of ruthenium oxide (RuOx)/niobium-doped strontium titanate (Nb:STO) contact. With increasing oxygen content of oxide electrode, the resistance window was improved. The switching speed of RuOx electrode also showed improvement compared to platinum (Pt) electrode. The RuOx film contains amorphous phase and also forms an interface oxide layer at the RuOx/Nb:STO contact, which suggests defect generation near the interface. Additionally, the interface reaction disturbs the crystalline orientation of Nb:STO. These defect sites facilitate switching properties by easy drift of current and oxygen ion and also by modulation of barrier height.
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73.40.-c Electronic transport in interface structures
68.35.Ct Interface structure and roughness

Characterization of laser-transferred bismuth ferrite lead titanate ferroelectric thick films

Tim P. Comyn, Tanusri Chakraborty, Robert E. Miles, and Steven J. Milne

Appl. Phys. Lett. 93, 052909 (2008); http://dx.doi.org/10.1063/1.2969288 (3 pages) | Cited 2 times

Online Publication Date: 7 August 2008

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Thick films of 0.7BiFeO3–0.3PbTiO3 have been deposited on sapphire substrates by tape casting and sintering at 1000 °C. Films 20 μm in thickness were released from the fabrication substrate using KrF pulsed laser radiation, and epoxy bonded to platinized silicon substrates in order to demonstrate the low-temperature integration possibilities of xBiFeO3–(1−x)PbTiO3 films. Despite structural changes at the laser-released film interface, strain-electric field loops are typical of a ferroelectric, showing an ultimate strain of 0.09%. X-ray diffraction and scanning electron microscopy observations suggest that interfacial melting and migration of Bi2O3 is involved in the lift-off process.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.60.Bs Mechanical and acoustical properties

Field-induced soft mode hardening in SrTiO3/DyScO3 multilayers

P. Kužel, C. Kadlec, F. Kadlec, J. Schubert, and G. Panaitov

Appl. Phys. Lett. 93, 052910 (2008); http://dx.doi.org/10.1063/1.2967336 (3 pages) | Cited 6 times

Online Publication Date: 7 August 2008

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We investigate a SrTiO3/DyScO3 epitaxial multilayer with four 50-nm-thick layers of each compound deposited on DyScO3 substrate by pulsed laser deposition. The spectra of SrTiO3 obtained using time-domain terahertz spectroscopy at room temperature with and without electrical bias are explained by the ferroelectric soft mode coupled to a silent central peak, where the bare soft mode frequency is the only field-dependent parameter. We show that terahertz and subterahertz properties of the layers are determined solely by a tremendous hardening of the soft mode with increasing field. We demonstrate that our structure induces more than 40% modulation of the transmitted terahertz power in a broad frequency range of 0.65–1.15 THz at 140 V (93 kV/cm) bias.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.55.-g Dielectric thin films
78.70.Gq Microwave and radio-frequency interactions
81.15.Fg Pulsed laser ablation deposition

Pre-atomic layer deposition surface cleaning and chemical passivation of (100) In0.2Ga0.8As and deposition of ultrathin Al2O3 gate insulators

Byungha Shin, Donghun Choi, James S. Harris, and Paul C. McIntyre

Appl. Phys. Lett. 93, 052911 (2008); http://dx.doi.org/10.1063/1.2966357 (3 pages) | Cited 27 times

Online Publication Date: 8 August 2008

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We have developed and tested the efficacy of a method for pre-atomic layer deposition (ALD) surface preparation that removes native oxides from the (100) In0.2Ga0.8As surface and provides a clean starting surface for ALD of ultrathin Al2O3 layers. Successive wet etching by aqueous HCl and NH4(OH) solutions and in situ pre-ALD thermal desorption of residual elemental As were performed. Photoelectron spectra obtained after ALD of Al2O3 on In0.2Ga0.8As prepared by this method revealed that the interface was free of In, Ga, and As oxides. The resultant metal-oxide-semiconductor capacitors with Pt electrodes exhibited capacitance-derived equivalent oxide thicknesses as small as 1.8 nm.
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81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
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.)
68.55.aj Insulators
84.32.Tt Capacitors

Design and simulation of planar electro-optic switches in ferroelectrics

Mahesh Krishnamurthi, Lili Tian, and Venkatraman Gopalan

Appl. Phys. Lett. 93, 052912 (2008); http://dx.doi.org/10.1063/1.2967469 (3 pages) | Cited 3 times

Online Publication Date: 8 August 2008

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Conceptual design and numerical simulation of two polarization dependent planar optical switches based on the electro-optic effect in ferroelectrics operating at 1.55 μm wavelength are presented. The first design is a 3×3 optical switch based entirely on electro-optic beam steering (prism) elements and ion-exchanged lenses for collimation. The second design is a 1×N optical switch based on a combination of electro-optic beam steering and electro-optic focusing (lens) elements. The scalability of this device has been improved by compensating the in-plane divergence of the laser. Analytical expressions for the dependence of scalability are presented.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Bh Lenses, prisms and mirrors
42.15.Eq Optical system design
42.70.-a Optical materials
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Large pyroelectric effect in undoped epitaxial Pb(Zr,Ti)O3 thin films on SrTiO3 substrates

Bo Xiao, Vitaliy Avrutin, Huiyong Liu, Ümit Özgür, Hadis Morkoç, and Changzhi Lu

Appl. Phys. Lett. 93, 052913 (2008); http://dx.doi.org/10.1063/1.2969778 (3 pages) | Cited 5 times

Online Publication Date: 8 August 2008

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We have studied pyroelectric and ferroelectric properties of Pb(Zr,Ti)O3 thin films grown epitaxially on SrTiO3(001) substrates by rf magnetron sputtering. The pyroelectric coefficient was measured in the temperature range from 280 to 370 K using the Byer–Roundy method. Values as high as 48 nC/cm2 K have been obtained at 300 K. The PZT thin films exhibited a remanent polarization of 45–58 μC/cm2. The improved pyroelectric coefficient was attributed to a high crystalline quality of the films, as revealed by x-ray diffraction that showed only (001)-oriented perovskite PZT phase and a ω-rocking curve full width at half maximum value as low as 4.2 arc min for 300 nm thick films.
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77.55.-g Dielectric thin films
77.70.+a Pyroelectric and electrocaloric effects
77.80.-e Ferroelectricity and antiferroelectricity
77.65.-j Piezoelectricity and electromechanical effects
81.15.Cd Deposition by sputtering
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