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3 Jun 2002

Volume 80, Issue 22, pp. 4085-4270

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Stress as a governing parameter to control the crystallization of amorphous silicon films by thermal annealing

Sukti Hazra, Isao Sakata, Mitsuyuki Yamanaka, and Eiichi Suzuki

Appl. Phys. Lett. 80, 4115 (2002); http://dx.doi.org/10.1063/1.1482795 (3 pages) | Cited 3 times

Online Publication Date: 23 May 2002

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We have fabricated nanocrystalline dots by thermal annealing (TA) of thermal chemical-vapor-deposited amorphous silicon (a-Si:H) films. In S. Hazra, I. Sakata, M. Yamanaka, and E. Suzuki, Appl. Phys. Lett. 80, 1159 (2002), we observed that ultrathin a-Si:H films (2–10 nm) are stressed because of the presence of deformed crystallites or paracrystallites. With the increase of thickness, volume fraction of paracrystallites decreased in the films and stress in the films gradually reduced. Therefore, by changing the thickness, we can control the stress in the a-Si:H films and thereby the dimensions (in the range of 5 to 10 nm) as well as volume fractions of nanocrystallites formed by TA. On the other hand, it has been found that relaxed a-Si:H networks form polycrystalline films by TA. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.05.Cy Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
81.40.Gh Other heat and thermomechanical treatments
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots

Interchain interaction and Davydov splitting in polythiophene crystals: An ab initio approach

Giovanni Bussi, Alice Ruini, Elisa Molinari, Marilia J. Caldas, Peter Puschnig, and Claudia Ambrosch-Draxl

Appl. Phys. Lett. 80, 4118 (2002); http://dx.doi.org/10.1063/1.1483905 (3 pages) | Cited 21 times

Online Publication Date: 23 May 2002

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The crystal-induced energy splitting of the lowest excitonic state in polymer crystals, the so-called Davydov splitting Δ, is calculated with a first-principles density-matrix scheme. We show that different crystalline arrangements lead to significant variations in Δ, from below to above the thermal energy kBT at room temperature, with relevant implications on the luminescence efficiency. This is one more piece of evidence supporting the fact that control of interchain interactions and solid-state packing is essential for the design of efficient optical devices. © 2002 American Institute of Physics.
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71.70.Ch Crystal and ligand fields
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
42.70.Jk Polymers and organics
61.41.+e Polymers, elastomers, and plastics
78.55.Kz Solid organic materials
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Stability of interfacial dislocations in (001) silicon surfacial grain boundaries

K. Rousseau, J. L. Rouvière, F. Fournel, and H. Moriceau

Appl. Phys. Lett. 80, 4121 (2002); http://dx.doi.org/10.1063/1.1481957 (3 pages) | Cited 15 times

Online Publication Date: 23 May 2002

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Ultrathin (001) silicon films bonded onto (001) silicon wafers, which form “surfacial grain boundaries” have been investigated by transmission electron microscopy. The samples were obtained by bonding one silicon-on-insulator (SOI) structure with one silicon wafer. After the removal of the SOI substrate, the remaining top thin film was further reduced by a thermal oxidation. Samples with a given film thickness selected in the 200 nm to 10 nm range were obtained. For very thin films, the thinning procedure can induce a mobility of the interfacial dislocations. To keep the interfaces stable, we have replaced the thermal oxidation thinning by a low-temperature chemical etching. © 2002 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Mm Grain and twin boundaries
68.37.Lp Transmission electron microscopy (TEM)
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation

Characteristics of SrS:Cu thin-film electroluminescent device fabricated by pulsed-laser deposition

Jae Young Choe, S. M. Blomquist, and D. C. Morton

Appl. Phys. Lett. 80, 4124 (2002); http://dx.doi.org/10.1063/1.1483925 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2002

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SrS:Cu film was deposited by a pulsed-laser deposition method to fabricate the phosphor film for thin-film electroluminescent (EL) devices. The devices were annealed in dry nitrogen gas to give the characteristic blue emission with a chromaticity coordinate of (0.17, 0.24). The luminance at 100 Hz driving frequency reached 6 cd/cm2 with corresponding transferred charge of 4.1 μC/cm2. The excellent stoichiometry replication of the film from the target being sputtered, pulsed-laser deposition can serve as a convenient method for fabricating high-quality thin-film EL devices of different composition by changing target concentrations. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.15.Fg Pulsed laser ablation deposition
78.66.Nk Insulators
42.79.Wc Optical coatings
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions

Spatially-resolved valence-electron energy-loss spectroscopy of Zr-oxide and Zr-silicate films

Nobuyuki Ikarashi and Kenzo Manabe

Appl. Phys. Lett. 80, 4127 (2002); http://dx.doi.org/10.1063/1.1483130 (3 pages) | Cited 5 times

Online Publication Date: 23 May 2002

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We examined electronic structures in Zr-oxide (ZrO2) and Zr-silicate (ZrxSi1−xO2) films deposited on Si substrates by using valence-electron energy-loss spectroscopy combined with scanning transmission electron microscopy (the electron probe diameter was about 0.3 nm). Our analysis indicated that both valence-electron excitations in ZrO2 and in SiO2 occurred in the ZrxSi1−xO2 films. Therefore, the band gaps in the ZrxSi1−xO2 films should be dominated by an energy gap between O 2p and Zr 4d states. © 2002 American Institute of Physics.
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71.20.Ps Other inorganic compounds
73.20.At Surface states, band structure, electron density of states
77.55.-g Dielectric thin films
79.20.Kz Other electron-impact emission phenomena
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Depth dependence of the tetragonal distortion of a GaN layer on Si(111) studied by Rutherford backscattering/channeling

M. F. Wu, ChangChun Chen, DeZhang Zhu, Shengqiang Zhou, A. Vantomme, G. Langouche, B. S. Zhang, and Hui Yang

Appl. Phys. Lett. 80, 4130 (2002); http://dx.doi.org/10.1063/1.1483389 (3 pages) | Cited 14 times

Online Publication Date: 23 May 2002

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Rutherford backscattering and channeling have been used to characterize the structure of a GaN layer grown on a Si(111) substrate. The results show that a 1.26 μm GaN epitaxial layer with a rather abrupt interface and a good crystalline quality (χmin = 3.4%) can be grown on a Si(111) substrate. Using the channeling angular scan around an off-normal 〈1math13〉 axis in the {10math0} plane of the GaN layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, can be determined. Moreover, the depth dependence of the eT can be obtained using this technique. A fully relaxed (eT = 0) GaN layer for a thickness <2.8 μm is expected. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Three-dimensional self-assembly by ice crystallization

Sang Hyuk Im and O Ok Park

Appl. Phys. Lett. 80, 4133 (2002); http://dx.doi.org/10.1063/1.1483385 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2002

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Three-dimensional self-assembly of colloidal particles by ice crystallization is observed in a water based-colloidal suspension. When water containing polystyrene beads freezes and is crystalized into ice, the polystyrene beads are extruded outward from the ice regions. Consequently, the concentration of polystyrene beads increases rapidly and they are assembled together into a regular structure. As ice crystallization proceeds, a color appears abruptly. This indicates that the polystyrene beads have been assembled three dimensionally. The generated three-dimensional structure is confirmed by scanning electron microscopy images and the existance of a photonic band gap measured by an ultraviolet-visible spectrophotometer. The sample fabricated by this method is compared with a sample made by conventional vertical deposition. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
64.70.D- Solid-liquid transitions
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
07.60.Dq Photometers, radiometers, and colorimeters
07.60.Rd Visible and ultraviolet spectrometers

Comparison of nitrogen compositions in the as-grown GaNxAs1−x on GaAs measured by high-resolution x-ray diffraction and secondary-ion mass spectroscopy

W. J. Fan, S. F. Yoon, T. K. Ng, S. Z. Wang, W. K. Loke, R. Liu, and A. Wee

Appl. Phys. Lett. 80, 4136 (2002); http://dx.doi.org/10.1063/1.1483913 (3 pages) | Cited 44 times

Online Publication Date: 23 May 2002

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High-resolution x-ray diffraction (HRXRD) and secondary-ion mass spectroscopy were used to measure the N compositions of a series of as-grown GaNAs samples grown by solid-source molecular-beam epitaxy. We found that N compositions measured by the two methods agree well at lower N compositions (x<3%), and deviate at larger N compositions (x>3%). The HRXRD measurement by using Vegard’s law to extract the lattice constant of GaNAs, underestimates N composition at larger N compositions. We found that the underestimation is up to 14.3% at the x = 4.2%. In order to explain the deviation, a model for analyzing the correlation between lattice parameters and point defects in the epilayer was carried out. © 2002 American Institute of Physics.
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68.55.Nq Composition and phase identification
61.05.cp X-ray diffraction
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Suppression of phase segregation during molecular-beam epitaxial growth of GaMnN using nitrogen–hydrogen plasma

Y. Cui and L. Li

Appl. Phys. Lett. 80, 4139 (2002); http://dx.doi.org/10.1063/1.1483387 (3 pages) | Cited 23 times

Online Publication Date: 23 May 2002

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Epitaxial growth of GaMnN by electron-cyclotron-resonance plasma-assisted molecular-beam epitaxy using nitrogen–hydrogen plasma was studied by reflection high-energy electron diffraction, scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. The electron diffraction pattern changed from streaky to spotty when hydrogen was added to the nitrogen plasma, indicating that the effective group V/III ratio was increased. Films grown with nitrogen plasma are phase segregated into GaN and manganese nitrides. In contrast, when nitrogen–hydrogen plasma was used, the films are single phase Ga1−xMnxN, and x can be as high as 0.06. These results indicate that phase segregation can be suppressed by adding hydrogen to the nitrogen plasma during growth. © 2002 American Institute of Physics.
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81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria
75.50.Pp Magnetic semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
61.66.Bi Elemental solids
61.66.Dk Alloys

Role of substrate in the pseudomorphic stabilization of rocksalt-type AlN phase in AlN/TiN superlattices

V. Pankov, M. Evstigneev, and R. H. Prince

Appl. Phys. Lett. 80, 4142 (2002); http://dx.doi.org/10.1063/1.1482798 (3 pages) | Cited 10 times

Online Publication Date: 23 May 2002

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The nonequilibrium B1 (rocksalt-type) AlN phase was successfully stabilized in stress-free AlN/TiN superlattices prepared by room-temperature pulsed laser deposition on thin film amorphous carbon substrates. The coatings displayed the same properties as reported for multilayers grown on thick crystalline substrates; namely, the existence of a critical thickness of AlN (about 1 nm for the present study) below which AlN crystallizes in the B1–AlN phase. Exceeding this value lead to AlN crystallization in its equilibrium hexagonal wurtzite-type structure, accompanied by considerable degradation of coating crystallinity due to the loss of coherent epitaxial growth of alternating TiN and AlN layers in the coating. It is concluded that neither an orientational effect of the substrate nor its stress-sustaining ability is required to provide a pseudomorphic stabilization of the nonequilibrium B1–AlN phase in AlN/TiN multilayered coatings. © 2002 American Institute of Physics.
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68.65.Cd Superlattices
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
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