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8 Jul 2002

Volume 81, Issue 2, pp. 187-387

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Structure and bonding in a cubic phase of SiAlON derived from the cubic spinel phase of Si3N4

Lizhi Ouyang and W. Y. Ching

Appl. Phys. Lett. 81, 229 (2002); http://dx.doi.org/10.1063/1.1491004 (3 pages) | Cited 11 times

Online Publication Date: 27 June 2002

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The structure and electronic bonding in the spinel SiAlON (Si6−zAlzOzN8−z, z = 1) derived from the cubic c-Si3N4 are studied by a first-principles density functional method. Al prefers the octahedral site of the spinel lattice. The small energy difference between the four possible structural configurations indicates that the real SiAlON may be a random solid solution. The lowest energy configuration of c-Si5AlON7 is a semiconductor with a direct LDA band gap of 2.29 eV. © 2002 American Institute of Physics.
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61.66.Fn Inorganic compounds
61.50.Lt Crystal binding; cohesive energy
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
71.15.-m Methods of electronic structure calculations

Different pressure coefficients of the light emission in cubic and hexagonal InGaN/GaN quantum wells

T. Suski, H. Teisseyre, S. P. Łepkowski, P. Perlin, T. Kitamura, Y. Ishida, H. Okumura, and S. F. Chichibu

Appl. Phys. Lett. 81, 232 (2002); http://dx.doi.org/10.1063/1.1490400 (3 pages) | Cited 6 times

Online Publication Date: 27 June 2002

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We have studied the influence of hydrostatic pressure on the light emission from cubic In0.1Ga0.9N. A qualitative difference between pressure dependence of photoluminescence peak energies for cubic and wurtzite symmetry InGaN/GaN quantum wells (QWs) was found. Cubic samples revealed magnitude of dEE/dP of 26–30 meV/GPa, practically independent of the QW width. Previous studies of the hexagonal InGaN/GaN structures showed that with increasing QW width dEE/dP changed between about 30 meV/GPa and 0 meV/GPa. This different behavior of two types of QWs can be explained by the lack of built-in electric field (along growth direction) in case of cubic structures. To describe pressure evolution of the optical transitions in cubic InGaN/GaN QWs and thick epitaxial layer, we use a simple k×p model based on the linear theory of elasticity. To reproduce the experimental data, it is necessary to invoke presence of In-rich fluctuations in the cubic In0.1Ga0.9N samples. © 2002 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.40.Fy Semiconductors

Systematic examination of carrier polarity in composition spread ZnO thin films codoped with Ga and N

A. Tsukazaki, H. Saito, K. Tamura, M. Ohtani, H. Koinuma, M. Sumiya, S. Fuke, T. Fukumura, and M. Kawasaki

Appl. Phys. Lett. 81, 235 (2002); http://dx.doi.org/10.1063/1.1491294 (3 pages) | Cited 55 times

Online Publication Date: 27 June 2002

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We have grown high-crystallinity ZnO thin films on lattice-matched ScAlMgO4 substrates by pulsed-laser deposition with doping donor (Ga) and acceptor (N) simultaneously. Alternating ablation of ceramics with concentrated Ga addition and highly pure single crystal targets yielded in a controlled Ga concentration (CGa) in a wide range of 1018–1020 cm−3 with minimal contamination of undesired impurities such as Al and Si. The use of the originally developed temperature-gradient method, where controlled and continuous gradient of the growth temperature is given to the single substrate with a range of about 50–200 °C, results in a continuous spread of N concentration (CN) in a controlled fashion. Therefore, the ratio of CN/CGa can be varied continuously in a wide range for each film, assuring that a region satisfying p-type codoping condition predicted by T. Yamamoto and H. K. Yoshida [Jpn. J. Appl. Phys., Part 2 38, L166 (1999)] is included in the sample. The electrical properties were measured for over thousand specimens of lithographically patterned Hall bars without observing any sign of p-type conduction. © 2002 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.05.Dz II-VI semiconductors
73.61.Ga II-VI semiconductors
71.55.Gs II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Fg Pulsed laser ablation deposition
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

(Zr,Ti)O2 interface structure in ZrO2–TiO2 nanolaminates with ultrathin periodicity

C. R. Aita, J. D. DeLoach, and V. V. Yakovlev

Appl. Phys. Lett. 81, 238 (2002); http://dx.doi.org/10.1063/1.1492013 (3 pages) | Cited 11 times

Online Publication Date: 27 June 2002

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A mixed cation interfacial structure in ZrO2–TiO2 nanolaminate films with ultrathin bilayer periodicity grown by sputter deposition at 297 K was identified by x-ray diffraction and nonresonant Raman spectroscopy. This structure consists of an amorphous phase at a ZrO2-on-TiO2 bilayer interface, followed by an extensive crystalline monoclinic (Zr,Ti)O2 solid solution predicted by Vegard’s law. Monoclinic (Zr,Ti)O2 has previously been reported only once, in bulk powder of a single composition (ZrTiO4) at high pressure. Its stabilization in the nanolaminates is explained by the Gibbs–Thomson effect. This complex interfacial structure is shown to be a means of accommodating chemical mixing in the absence of a driving force for heteroepitaxy. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
81.15.Cd Deposition by sputtering
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators

From nucleation to coalescence of Cu2O islands during in situ oxidation of Cu(001)

J. C. Yang, D. Evan, and L. Tropia

Appl. Phys. Lett. 81, 241 (2002); http://dx.doi.org/10.1063/1.1492007 (3 pages) | Cited 21 times

Online Publication Date: 27 June 2002

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The nucleation, growth, and coalescence of Cu2O islands due to oxidation of Cu(001) films were visualized by in situ ultrahigh-vacuum transmission electron microscopy. We have previously demonstrated that the nucleation and initial growth of copper oxides is dominated by oxygen surface diffusion. These surface models have been extended to quantitatively represent the coalescence behavior of copper oxidation in the framework of the Johnson–Mehl–Avrami–Kolmogorov theory. An excellent agreement exists between the experimental data of nucleation to coalescence with the surface model. The implication could be an alternate paradigm for passivation and oxidation, since classic theories assume uniform film growth. © 2002 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
81.65.Mq Oxidation
68.35.Fx Diffusion; interface formation

Evidence of noble metal diffusion in polymers at room temperature and its retardation by a chromium barrier

A. Thran, T. Strunskus, V. Zaporojtchenko, and F. Faupel

Appl. Phys. Lett. 81, 244 (2002); http://dx.doi.org/10.1063/1.1491609 (3 pages) | Cited 11 times

Online Publication Date: 27 June 2002

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Recent applications of organic low-k dielectrics in microelectronics have stimulated many investigations of metal diffusion in polymers. Here we report results from radiotracer measurements of 110mAg diffusion in trimethylcyclohexane polycarbonate. Serial sectioning was carried out with 190 eV krypton ions in and opposite to the diffusion direction to rule out sputtering artifacts. Ag was found to be strongly immobilized by self aggregation. In contrast to earlier reports, however, trace amounts of Ag were clearly seen to diffuse into the polymer even at room temperature. A chromium film of only one tenth of a monolayer turned out to be an effective diffusion barrier. © 2002 American Institute of Physics.
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68.60.Wm Other nonelectronic physical properties
61.41.+e Polymers, elastomers, and plastics
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation

Phase-sensitive second-harmonic microscopy reveals polarity of topologically centrosymmetric molecular crystals

S. Kluge, F. Budde, I. Dohnke, P. Rechsteiner, and J. Hulliger

Appl. Phys. Lett. 81, 247 (2002); http://dx.doi.org/10.1063/1.1492850 (3 pages) | Cited 11 times

Online Publication Date: 27 June 2002

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Phase-sensitive second-harmonic microscopy is applied to reveal grow-in polarity in topologically centrosymmetric crystals of 4-chloro-4′-nitrostilben. As predicted by the Markow model of layer-by-layer polarity formation, growth along + and −b-direction in P21/c is producing optical nonlinearity in both sectors associated with the b axis. Present experiments show that formation of a pyroelectric symmetry class is a stochastic property of molecular crystals grown from dipolar compounds and near to thermodynamic equilibrium. © 2002 American Institute of Physics.
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77.70.+a Pyroelectric and electrocaloric effects
61.66.Hq Organic compounds
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Optical properties of gallium oxide thin films

M. Rebien, W. Henrion, M. Hong, J. P. Mannaerts, and M. Fleischer

Appl. Phys. Lett. 81, 250 (2002); http://dx.doi.org/10.1063/1.1491613 (3 pages) | Cited 42 times

Online Publication Date: 27 June 2002

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The optical functions of β-Ga2O3 thin films have been determined by ellipsometry from 0.74–5 eV. Several electron-beam evaporated and rf magnetron sputtered films of different thicknesses were investigated using a multisample technique. Refractive index values comparable to those of bulk material are found. Cauchy dispersion model fits yield a high-frequency dielectric constant ϵ∞ of 3.57. Above 4.7 eV a direct absorption edge is observed. © 2002 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators

Visible photoluminescence in amorphous ABO3 perovskites

P. S. Pizani, H. C. Basso, F. Lanciotti, T. M. Boschi, F. M. Pontes, E. Longo, and E. R. Leite

Appl. Phys. Lett. 81, 253 (2002); http://dx.doi.org/10.1063/1.1494464 (3 pages) | Cited 21 times

Online Publication Date: 27 June 2002

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The photoluminescence observed in ABO3 type perovskite in their highly structural disordered state can be explained by a model in which is assumed a distribution of electronic states localized within the energy band gap coupled to lattice local vibrational states. The model fits very well the experimental results and indicates that photoluminescence in the visible region can be considered as a general behavior of disordered solids. © 2002 American Institute of Physics.
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78.55.-m Photoluminescence, properties and materials
71.55.Jv Disordered structures; amorphous and glassy solids
63.50.-x Vibrational states in disordered systems

Band anticrossing in dilute InNxSb1−x

B. N. Murdin, A. R. Adams, P. Murzyn, C. R. Pidgeon, I. V. Bradley, J.-P. R. Wells, Y. H. Matsuda, N. Miura, T. Burke, and A. D. Johnson

Appl. Phys. Lett. 81, 256 (2002); http://dx.doi.org/10.1063/1.1493663 (3 pages) | Cited 24 times

Online Publication Date: 27 June 2002

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Dilute nitrogen alloys of InSb exhibit extremely strong band gap bowing with nitrogen composition that has been associated with anticrossing between the localized resonant states of the nitrogen within the conduction band and the extended states of the conduction band itself. This also results in the conduction band dispersion having an enhanced nonparabolicity. We have measured the electron effective mass near the anticrossing by cyclotron resonance in InNxSb1−x alloys with absorption edge near 15 μm, using pulsed fields up to 150 T. The results directly demonstrate the band anticrossing and quantitatively confirm the increase of effective mass versus x predicted for InNxSb1−x by a tight binding calculation for low nitrogen concentration (x<0.01). © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
76.40.+b Diamagnetic and cyclotron resonances
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
78.20.Ls Magneto-optical effects
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