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1 Mar 2004

Volume 84, Issue 9, pp. 1435-1613

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Appl. Phys. Lett. 84, 1558 (2004); http://dx.doi.org/10.1063/1.1651641 (3 pages)

DongWeon Lee, Adrian Wetzel, Roland Bennewitz, Ernst Meyer, Michel Despont, Peter Vettiger, and Christoph Gerber
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Phase stability of diamond nanocrystals upon pulsed-laser-induced liquid-solid interfacial reaction: Experiments and ab initio calculations

Cheng-Xin Wang, Yu-Hua Yang, Qiu-Xiang Liu, Guo-Wei Yang, Yu-Liang Mao, and Xiao-Hong Yan

Appl. Phys. Lett. 84, 1471 (2004); http://dx.doi.org/10.1063/1.1650917 (3 pages) | Cited 4 times

Online Publication Date: 25 February 2004

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To clarify different phase formations of diamond nanocrystals upon pulsed-laser-induced liquid-solid interfacial reaction (PLIIR), we preformed the first-principles investigation of the total energy of cubic and hexagonal diamond. Interestingly, by a comparison of the structure stabilities of cubic and hexagonal diamond, we found that both cubic and hexagonal structures could form, simultaneously or one by one, upon those processes like as far-from equilibrium growth processes, such as PLIIR, due to the relatively small different of total energies and similar crystalline structures. Eventually, these calculations were in good agreement with the experimental results. © 2004 American Institute of Physics.
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64.70.D- Solid-liquid transitions
52.38.Mf Laser ablation
71.15.Nc Total energy and cohesive energy calculations
61.46.-w Structure of nanoscale materials

Improvement of crystalline silicon surface passivation by hydrogen plasma treatment

I. Martín, M. Vetter, A. Orpella, C. Voz, J. Puigdollers, R. Alcubilla, A. V. Kharchenko, and P. Roca i Cabarrocas

Appl. Phys. Lett. 84, 1474 (2004); http://dx.doi.org/10.1063/1.1647702 (3 pages) | Cited 6 times

Online Publication Date: 25 February 2004

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A completely dry low-temperature process has been developed to passivate 3.3 Ω cm p-type crystalline silicon surface with excellent results. Particularly, we have investigated the use of a hydrogen plasma treatment, just before hydrogenated amorphous silicon carbide (a-SiCx:H) deposition, without breaking the vacuum. We measured effective lifetime, τeff, through a quasi-steady-state photoconductance technique. Experimental results show that hydrogen plasma treatment improves surface passivation compared to classical HF dip. Seff values lower than 19 cm s−1 were achieved using a hydrogen plasma treatment and an a-SiCx:H film deposited at 300 °C. © 2004 American Institute of Physics.
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81.65.Rv Passivation
52.77.Bn Etching and cleaning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Cf Surface cleaning, etching, patterning

Broadband emission and low absorption in microdisks with AlGaAs quantum wells

T. Kipp, K. Petter, Ch. Heyn, D. Heitmann, and C. Schüller

Appl. Phys. Lett. 84, 1477 (2004); http://dx.doi.org/10.1063/1.1651657 (3 pages) | Cited 5 times

Online Publication Date: 25 February 2004

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In microphotoluminescence measurements at room temperature on Al0.2Ga0.8As/Al0.4Ga0.6As multiple quantum well microdisks, we observe a large number of whispering gallery modes in a remarkably broad energy range of about 250 meV. This is in contrast to microdisks containing InGaAs or GaAs quantum wells, where typically only one or two whispering gallery modes are observed, but similar to the behavior of microdisks containing self-organized InAs quantum dots. We conclude that impurity levels below the recombination energy of free electron-hole pairs inside the alloy quantum wells lead to an efficient internal broadband emitter with low absorption. © 2004 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
78.67.De Quantum wells
78.55.Cr III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Mechanism of enhanced luminescence in InxAlyGa1−x−yN quaternary epilayers

C. H. Chen, Y. F. Chen, Z. H. Lan, L. C. Chen, K. H. Chen, H. X. Jiang, and J. Y. Lin

Appl. Phys. Lett. 84, 1480 (2004); http://dx.doi.org/10.1063/1.1650549 (3 pages) | Cited 17 times

Online Publication Date: 25 February 2004

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We report firm evidence for the underlying mechanism of the enhanced luminescence in InxAlyGa1−x−yN quaternary epilayers. Photoluminescence, Raman scattering, field emission scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS), and cathodoluminescence (CL) measurements have been employed to study the correlation between optical and structural properties in these alloys. The phonon replica structures accompanying luminescence line, InGaN-related phonon modes in Raman spectra, SEM images, element composition analysis by EDS, and localized CL spectra provide the evidence to show that the existence of InGaN-like nanoclusters is responsible for the enhanced luminescence in InxAlyGa1−x−yN quaternary alloys. Our result therefore gives an excellent demonstration showing that because of the existence of nanoclusters a very defective alloy can exhibit a strong emission even at room temperature. © 2004 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
78.60.Hk Cathodoluminescence, ionoluminescence
61.66.Fn Inorganic compounds
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Pulsed-electron-beam deposition of transparent conducting SnO2 films and study of their properties

R. J. Choudhary, S. B. Ogale, S. R. Shinde, V. N. Kulkarni, T. Venkatesan, K. S. Harshavardhan, M. Strikovski, and B. Hannoyer

Appl. Phys. Lett. 84, 1483 (2004); http://dx.doi.org/10.1063/1.1651326 (3 pages) | Cited 30 times

Online Publication Date: 25 February 2004

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Transparent conducting films of SnO2 are grown on single-crystal R-Al2O3 substrates by the pulsed electron beam deposition (PED) technique, and their electrical, optical, and microstructural properties are compared with the films grown by pulsed-laser deposition (PLD). In PED, the pulsed electron beam used for ablation is generated by a channel-spark system with discharge voltage of 12 kV, current ∼1 kA, and pulse duration of ∼100 ns. The PED films are highly oriented, show good epitaxy, and are highly transparent with transmittance of ∼80% in the visible and IR range. The measured band gap is close to 3.9 eV. It is shown that the PED film properties compare well with those of PLD films, with the 119Sn Mossbauer spectroscopy showing comparable local environments in the two. © 2004 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.66.Nk Insulators
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Influence of layer thickness on the formation of In vacancies in InN grown by molecular beam epitaxy

J. Oila, A. Kemppinen, A. Laakso, K. Saarinen, W. Egger, L. Liszkay, P. Sperr, H. Lu, and W. J. Schaff

Appl. Phys. Lett. 84, 1486 (2004); http://dx.doi.org/10.1063/1.1651327 (3 pages) | Cited 23 times

Online Publication Date: 25 February 2004

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We have used a low-energy positron beam to identify In vacancies in InN layers grown on Al2O3 by molecular beam epitaxy. Their concentration decreases from ∼ 5×1018 to below 1016 cm−3 with increasing layer thickness (120–800 nm). The decrease in the vacancy concentration coincides with the increase in the electron Hall mobility, suggesting that In vacancies act as electron scattering centers. © 2004 American Institute of Physics.
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61.72.J- Point defects and defect clusters
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Epitaxial GaN1−yAsy layers with high As content grown by metalorganic vapor phase epitaxy and their band gap energy

Akitaka Kimura, C. A. Paulson, H. F. Tang, and T. F. Kuech

Appl. Phys. Lett. 84, 1489 (2004); http://dx.doi.org/10.1063/1.1652232 (3 pages) | Cited 13 times

Online Publication Date: 25 February 2004

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GaN1−yAsy epitaxial alloy samples with [N]≫[As] were grown by metalorganic vapor phase epitaxy. The range of As content achieved, up to y = 0.067, greatly extends the range of achievable As levels to values that are well within the miscibility gap of the GaN–GaAs system. The single-phase epitaxial nature of the alloy samples was confirmed by x-ray diffraction. The As-content dependence of the band gap was determined by optical absorption measurements. A highly-bowed bandgap was observed as a function of the As content, and a refined value of the bowing parameter of 16.9±1.1 eV was determined. © 2004 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Ea III-V semiconductors

Comparative study of defect energetics in HfO2 and SiO2

W. L. Scopel, Antônio J. R. da Silva, W. Orellana, and A. Fazzio

Appl. Phys. Lett. 84, 1492 (2004); http://dx.doi.org/10.1063/1.1650874 (3 pages) | Cited 52 times

Online Publication Date: 25 February 2004

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We perform ab initio calculations, based on density functional theory, for substitutional and vacancy defects in the monoclinic hafnium oxide (m-HfO2) and α-quartz (SiO2). The neutral oxygen vacancies and substitutional Si and Hf defects in HfO2 and SiO2, respectively, are investigated. Our calculations show that, for a large range of Hf chemical potential, Si substitutional defects are most likely to form in HfO2, leading to the formation of a silicate layer at the HfO2/Si interface. We also find that it is energetically more favorable to form oxygen vacancies in SiO2 than in HfO2, which implies that oxygen-deficient HfO2 grown on top of SiO2 will consume oxygen from the SiO2. © 2004 American Institute of Physics.
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61.72.J- Point defects and defect clusters
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
65.40.G- Other thermodynamical quantities
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