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6 Jun 2011

Volume 98, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 98, 233101 (2011); http://dx.doi.org/10.1063/1.3597211 (3 pages)

Yu-Jung Lu (呂宥蓉), Hon-Way Lin (林弘偉), Hung-Ying Chen (陳虹穎), Yu-Chen Yang (楊右丞), and Shangjr Gwo (果尚志)
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Reduction in thermal boundary conductance due to proton implantation in silicon and sapphire

Patrick E. Hopkins, Khalid Hattar, Thomas Beechem, Jon F. Ihlefeld, Douglas L. Medlin, and Edward S. Piekos

Appl. Phys. Lett. 98, 231901 (2011); http://dx.doi.org/10.1063/1.3592822 (3 pages) | Cited 2 times

Online Publication Date: 6 June 2011

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We measure the thermal boundary conductance across Al/Si and Al/Al2O3 interfaces that are subjected to varying doses of proton ion implantation with time domain thermoreflectance. The proton irradiation creates a major reduction in the thermal boundary conductance that is much greater than the corresponding decrease in the thermal conductivities of both the Si and Al2O3 substrates into which the ions were implanted. Specifically, the thermal boundary conductances decrease by over an order of magnitude, indicating that proton irradiation presents a unique method to systematically decrease the thermal boundary conductance at solid interfaces.
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61.72.up Other materials
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
66.70.Df Metals, alloys, and semiconductors
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
78.20.N- Thermo-optic effects

The surface boundary conditions in GaN/AlGaN/GaN transistor heterostructures

M. Gladysiewicz, R. Kudrawiec, J. Misiewicz, G. Cywinski, M. Siekacz, P. Wolny, and C. Skierbiszewski

Appl. Phys. Lett. 98, 231902 (2011); http://dx.doi.org/10.1063/1.3592801 (3 pages) | Cited 5 times

Online Publication Date: 7 June 2011

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The distribution of electric field in GaN(cap)/AlGaN/GaN(buffer) transistor heterostructures with various AlGaN layer thicknesses (10, 20, and 30 nm) has been studied by contactless electroreflectance and compared with theoretical calculations performed for various positions of the Fermi-level on GaN surface. For the three samples the best agreement between experimental data and theoretical calculations has been found at the same position of the Fermi-level on GaN surface (i.e., 0.55±0.05 eV below the conduction band). It means that the Fermi-level is pinned on GaN surface and this pinning can be treated as the boundary condition for the distribution of polarization-related fields in this heterostructure.
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85.30.-z Semiconductor devices

Induced magnetic anisotropy in lifted (Ga,Mn)As thin films

F. Greullet, L. Ebel, F. Münzhuber, S. Mark, G. V. Astakhov, T. Kießling, C. Schumacher, C. Gould, K. Brunner, W. Ossau, and L. W. Molenkamp

Appl. Phys. Lett. 98, 231903 (2011); http://dx.doi.org/10.1063/1.3597301 (3 pages)

Online Publication Date: 7 June 2011

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We demonstrate the ability to release the growth-induced strain in (Ga,Mn)As layers and (In,Ga)As/(Ga,Mn)As bilayers by lifting them from the GaAs substrate. The lifted (bi)layers are then deposited back onto various substrates. The change in strain before and after processing has been studied by means of x-ray diffraction. Magnetic characterization demonstrates the efficiency of our lift-off process to reorient the magnetization to the direction normal to the layer plane.
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75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Surface damage on diamond membranes fabricated by ion implantation and lift-off

V. S. Drumm, A. D. C. Alves, B. A. Fairchild, K. Ganesan, J. C. McCallum, D. N. Jamieson, S. Prawer, S. Rubanov, R. Kalish, and L. C. Feldman

Appl. Phys. Lett. 98, 231904 (2011); http://dx.doi.org/10.1063/1.3597223 (3 pages) | Cited 4 times

Online Publication Date: 8 June 2011

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Thin membranes with excellent optical properties are essential elements in diamond based photonic systems. Due to the chemical inertness of diamond, ion beam processing must be employed to carve photonic structures. One method to realize such membranes is ion-implantation graphitization followed by chemical removal of the sacrificial graphite. The interface revealed when the sacrificial layer is removed has interesting properties. To investigate this interface, we employed the surface sensitive technique of grazing angle channeled Rutherford backscattering spectroscopy. Even after high temperature annealing and chemical etching a thin layer of damaged diamond remains, however, it is removed by hydrogen plasma exposure.
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81.65.Cf Surface cleaning, etching, patterning
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.05.Np Atom, molecule, and ion scattering (for structure determination only)
52.77.Dq Plasma-based ion implantation and deposition
61.72.Cc Kinetics of defect formation and annealing

In situ synchrotron based x-ray fluorescence and scattering measurements during atomic layer deposition: Initial growth of HfO2 on Si and Ge substrates

K. Devloo-Casier, J. Dendooven, K. F. Ludwig, G. Lekens, J. D’Haen, and C. Detavernier

Appl. Phys. Lett. 98, 231905 (2011); http://dx.doi.org/10.1063/1.3598433 (3 pages) | Cited 3 times

Online Publication Date: 8 June 2011

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The initial growth of HfO2 was studied by means of synchrotron based in situ x-ray fluorescence (XRF) and grazing incidence small angle x-ray scattering (GISAXS). HfO2 was deposited by atomic layer deposition (ALD) using tetrakis(ethylmethylamino)hafnium and H2O on both oxidized and H-terminated Si and Ge surfaces. XRF quantifies the amount of deposited material during each ALD cycle and shows an inhibition period on H-terminated substrates. No inhibition period is observed on oxidized substrates. The evolution of film roughness was monitored using GISAXS. A correlation is found between the inhibition period and the onset of surface roughness.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.70.Ck X-ray scattering
78.70.En X-ray emission spectra and fluorescence
78.55.Hx Other solid inorganic materials
68.55.aj Insulators
81.65.Mq Oxidation

Medium-range icosahedral order in quasicrystal-forming Zr2Pd binary metallic glass

Li Huang, X. W. Fang, C. Z. Wang, M. J. Kramer, Z. J. Ding, and K. M. Ho

Appl. Phys. Lett. 98, 231906 (2011); http://dx.doi.org/10.1063/1.3597302 (3 pages) | Cited 4 times

Online Publication Date: 9 June 2011

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Medium-range order in Zr2Pd metallic glass was studied using a combination of x-ray diffraction experiment and atomistic simulations. We show that, in contrast to earlier experimental interpretations, the icosahedral-like polyhedron is centered around Pd, rather than Zr. Furthermore, we find that the ordered icosahedral packing around Pd extends to the third shell in the way similar to that in the Bergman-type clusters. The existence of Bergman-type clusters sheds interesting light into the formation of nanoquasicrystal phase during crystallization process of Zr2Pd metallic glass.
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61.43.Fs Glasses
61.44.Br Quasicrystals
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.23.Ft Quasicrystals
81.05.Kf Glasses (including metallic glasses)
64.70.dg Crystallization of specific substances

Effect of doping on global and local order in crystalline GeTe

Xavier Biquard, Milos Krbal, Alexander V. Kolobov, Paul Fons, Robert E. Simpson, Bérangère Hyot, Bernard André, Junji Tominaga, and Tomoya Uruga

Appl. Phys. Lett. 98, 231907 (2011); http://dx.doi.org/10.1063/1.3598384 (3 pages) | Cited 2 times

Online Publication Date: 9 June 2011

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Effect of nitrogen and carbon doping on the structure of GeTe has been investigated using x-ray diffraction and extended x-ray absorption fine structure (EXAFS) spectroscopies. While Bragg diffraction which probes the global structure exhibits a clear transition upon doping from the rhombohedral phase to the cubic (rocksalt) phase, the local structure probed by EXAFS remains rhombohedrally distorted across the compositions studied. The apparent inconsistency between the results of the two techniques used is attributed to disordering upon doping and the resulting order-disorder transition that is “seen” by site-averaging diffraction as a displacive rhombohedral-to-cubic transition.
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61.72.U- Doping and impurity implantation
78.70.Dm X-ray absorption spectra
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
64.60.Cn Order-disorder transformations

Ultrathin (1×2)-Sn layer on GaAs(100) and InAs(100) substrates: A catalyst for removal of amorphous surface oxides

P. Laukkanen, M. P. J. Punkkinen, J. Lång, M. Tuominen, M. Kuzmin, V. Tuominen, J. Dahl, J. Adell, J. Sadowski, J. Kanski, V. Polojärvi, J. Pakarinen, K. Kokko, M. Guina, M. Pessa, et al.

Appl. Phys. Lett. 98, 231908 (2011); http://dx.doi.org/10.1063/1.3596702 (3 pages)

Online Publication Date: 10 June 2011

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Amorphous surface oxides of III–V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs(100) and InAs(100) surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure results in the initial well-defined Sn-stabilized (1×2) surface even for samples exposed to air for a prolonged time. Based on ab initio calculations we propose that the phenomenon is due to indirect and direct effects of Sn. The Sn-induced surface composition weakens oxygen adsorption.
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68.43.Mn Adsorption kinetics
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Gh Other heat and thermomechanical treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Nr Desorption kinetics
68.35.Dv Composition, segregation; defects and impurities

Enhancement of the magneto-optical performance of Sr(Ti0.6−xGaxFe0.4)O3 perovskite films by Ga substitution

Peng Jiang, Lei Bi, Dong Hun Kim, G. F. Dionne, and C. A. Ross

Appl. Phys. Lett. 98, 231909 (2011); http://dx.doi.org/10.1063/1.3595337 (3 pages) | Cited 2 times

Online Publication Date: 10 June 2011

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Epitaxial films of ferromagnetic single-phase perovskite (Ti0.6−xGaxFe0.4)O3 (x ≤ 0.6) were grown on (001) oriented (La,Sr)(Al,Ta)O3 substrates by pulsed laser deposition. The films had an out-of-plane magnetic easy axis which is attributed to magnetoelastic effects. Ga lowered the optical absorption of the film, the Faraday rotation, and the magnetization but increased the magneto-optical figure of merit. The figure of merit for x = 0.4 was 3.5±0.3 deg/dB, at least approximately three times greater than the value at x = 0, and the optical loss at 1550 nm wavelength was 0.012–0.015 dB/μm.
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78.20.Ls Magneto-optical effects
78.66.Nk Insulators
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.80.+q Magnetomechanical effects, magnetostriction
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Phase change behavior in titanium-doped Ge2Sb2Te5 films

S. J. Wei, H. F. Zhu, K. Chen, D. Xu, J. Li, F. X. Gan, X. Zhang, Y. J. Xia, and G. H. Li

Appl. Phys. Lett. 98, 231910 (2011); http://dx.doi.org/10.1063/1.3597617 (3 pages) | Cited 5 times

Online Publication Date: 10 June 2011

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The titanium-doped Ge2Sb2Te5 films were deposited on Si(100) substrates by comagnetron sputtering method. The titanium concentrations in those films were determined by x-ray photoelectron spectroscopy. The influence of Ti doping upon phase change characteristics of the samples has been investigated by x-ray diffraction and a temperature-regulable UVISEL™ typed spectroscopic ellipsometry. With the augmentation of Ti doping concentration, the crystalline temperatures of the films went up while annealing, and the face-centered-cubic phase of them had high thermal stability because of the bond making between Ti and Te elements partly.
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68.55.ag Semiconductors
61.72.Cc Kinetics of defect formation and annealing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Determination of the anisotropic elastic properties of Ge1Sb2Te4

Arnaud Marmier, Krisztian Kohary, and C. David Wright

Appl. Phys. Lett. 98, 231911 (2011); http://dx.doi.org/10.1063/1.3598934 (3 pages) | Cited 1 time

Online Publication Date: 10 June 2011

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The elastic properties of Ge–Sb–Te (GST) alloys are important for phase-change devices (such as CD-RW, DVD-RW, Blu-ray, or phase-change random access memory) because the transition between the crystalline and amorphous phases involves a volume change accommodated by a strain estimated to be between 150 MPa and 10 GPa. However, the elastic properties of GST alloys are poorly characterized and the experimental and theoretical values show large discrepancies. We carry out a careful analysis of the elastic properties of a model system, crystalline Ge1Sb2Te4, using density functional theory and elastic anisotropy considerations. We show that Ge1Sb2Te4 exhibits significant anisotropy in its elastic properties.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.kg Semiconductors
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