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19 Jan 1998

Volume 72, Issue 3, pp. 269-391

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Photochemical and thermal effects in laser irradiated fullerite: From periodic exfoliation to cone formation

P. Milani, C. E. Bottani, A. Parisini, and G. P. Banfi

Appl. Phys. Lett. 72, 293 (1998); http://dx.doi.org/10.1063/1.120716 (3 pages) | Cited 4 times

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We report a characterization of fullerite surface modification by cumulative laser irradiation. We show that the nano- and mesostructure of the transformed material are related and that they depend on the laser wavelength and fluence. Irradiating the sample at 1064 nm we observe periodic exfoliation of the transformed surface which is composed, on a nanometer scale, of a network of graphitic elongated nanoparticles. Under UV irradiation, the nanostructure is characterized by tangled graphene layers and cone formation is observed on a mesoscopic scale. Our observations show that different destabilization mechanisms of C60 produce coalescence pathways towards different nanostructures and mesoscopic morphologies. © 1998 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Ds Laser-beam impact phenomena

Formation of the precursor for diamond growth by in situ direct current glow discharge pretreatment

I. Gouzman, I. Lior, and A. Hoffman

Appl. Phys. Lett. 72, 296 (1998); http://dx.doi.org/10.1063/1.120747 (3 pages) | Cited 23 times

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A direct current (dc) glow discharge—surface interaction process for in situ substrate surface pretreatment, for the promotion of diamond growth on mirror polished Si(100) is reported. A key step of the pretreatment is a generation of a stable dc-glow discharge between a grounded substrate and a positively biased electrode using a CH4/H2 gas mixture. During this stage, no additional gas phase activation by a hot filament is carried out. For subsequent diamond deposition, the dc-glow discharge is switched off and the standard hot filament CVD growth conditions are applied. The nature of the deposits formed by the dc-glow discharge process and after standard diamond deposition conditions, are investigated by Raman spectroscopy and high resolution scanning electron microscopy. It is found that the properties of the films, deposited following the dc-glow discharge pretreatment, strongly depend on the pretreatment conditions: methane concentration, substrate temperature, and pretreatment time. It is suggested that the nature of the diamond precursor formed during the dc-glow discharge pretreatment is similar to that one observed after bias enhanced nucleation process. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology

Phase formation and ferroelectricity of sol-gel derived (Pb, La)TiO3 thin films

Su Jae Lee, Kwang Yong Kang, Seok Kil Han, Min Su Jang, Byung Gyu Chae, Yong Suk Yang, and Seong Hyun Kim

Appl. Phys. Lett. 72, 299 (1998); http://dx.doi.org/10.1063/1.120717 (3 pages) | Cited 34 times

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Ferroelectric lead lanthanum titanate (PLT) thin films with various lanthanum concentration were fabricated by sol-gel spin-on process onto Pt/Ti/SiO2/Si substrates. We investigated the crystal structure, microstructure, and dielectric and ferroelectric properties of PLT films according to lanthanum doping concentration. The films annealed at 600 °C for 30 min have the single perovskite phase having only tetragonal or pseudocubic structure. The film microstructures were changed according to the doping concentration of La. The PLT films showed the typical polarization-electric field hysteresis loops and capacitance-voltage characteristics representing the ferroelectric switching property. The coercive field and remanent polarization decreased due to the phase transformation from ferroelectric to paraelectric phase with increasing La concentration. The effective dielectric constant and the leakage current density increased according to the increase of La content. © 1998 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Fm Switching phenomena
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)

Poole–Frenkel effect assisted emission from deep donor level in chromium doped GaP

R. Ajjel, M. A. Zaidi, S. Alaya, G. Brémond, G. Guillot, and J. C. Bourgoin

Appl. Phys. Lett. 72, 302 (1998); http://dx.doi.org/10.1063/1.120718 (3 pages) | Cited 3 times

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The electrical properties of chromium-related defects in GaP are investigated. Using deep-level transient spectroscopy, a related deep level is observed in p-type GaP exhibiting an activation energy, associated with hole emission, of 0.5 eV. Detailed capacitance transient investigations were undertaken to study the electric field dependence. This emission rate which is found to have a field dependence can be fitted by a Poole–Frenkel model. Evidence is given that the trap is the Cr4+/3+ deep donor level in GaP caused by substitutional Cr on Ga sites. This trap seems to be well adapted to compensate donors for the growth of the semi-insulating GaP. © 1998 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
72.20.Ht High-field and nonlinear effects

Trapping of size-selected Ag clusters at surface steps

S. J. Carroll, K. Seeger, and R. E. Palmer

Appl. Phys. Lett. 72, 305 (1998); http://dx.doi.org/10.1063/1.120719 (3 pages) | Cited 31 times

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We have investigated the deposition of size-selected metal clusters (Ag400) onto a stepped graphite surface. The clusters were produced with an inert gas condensation cluster source and were imaged on the surface with a high-resolution scanning electron microscope. For modest cluster deposition energies, cluster aggregation is much more limited at the steps than on the flat terrace regions of the surface, suggesting the possibility of the fabrication of structured arrays (e.g., chains) of size-selected particles. A theoretical analysis of the particle-particle gap size distribution along the step probes the 1D mobility of the particles trapped at the step. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
68.35.Fx Diffusion; interface formation

180° ferroelectric domains in polycrystalline BaTiO3 thin films

In-Tae Kim, Jin Wook Jang, Hyuk-Joon Youn, Chang Hoon Kim, and Kug Sun Hong

Appl. Phys. Lett. 72, 308 (1998); http://dx.doi.org/10.1063/1.120720 (3 pages) | Cited 10 times

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The presence of 180° ferroelectric domains in polycrystalline BaTiO3 thin films has been observed with the aid of transmission electron microscopy. The 180° domain boundary exhibited a curved appearance, and its orientational relationship was demonstrated. It was found that equiaxial grains did not have 180° domain boundaries due to their higher boundary energy. The grain size effect on dielectric constant of polycrystalline BaTiO3 thin films was also discussed in conjunction with 180° ferroelectric domains. © 1998 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films

Alignment of misfit dislocations in the In0.52Al0.48As/InxGa1−xAs/In0.52Al0.48As/InP heterostructure

J. Wu, H. X. Li, T. W. Fan, and Z. G. Wang

Appl. Phys. Lett. 72, 311 (1998); http://dx.doi.org/10.1063/1.120721 (3 pages)

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It was observed with transmission electron microscopy in the In0.52Al0.48As/InxGa1−xAs/In0.52Al0.48As system grown on the (001) InP substrate that misfit dislocation lines deviate 〈110〉 directions at an angle with its value depending on the gallium content. Such an abnormal alignment of misfit dislocations is explained in terms of an alloy effect on the formation of single jogs on misfit dislocations in the interface between the III–V ternary compounds. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.Ct Interface structure and roughness

Formation of BN nanoarches: Possibly the key to cubic boron nitride film growth

C. Collazo-Davila, E. Bengu, C. Leslie, and L. D. Marks

Appl. Phys. Lett. 72, 314 (1998); http://dx.doi.org/10.1063/1.120722 (3 pages) | Cited 20 times

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The formation of epitaxial nanotubes (nanoarches) on the surface of hexagonal BN (h-BN) during electron irradiation is reported. In addition to implications in terms of understanding fullerene based structures, we suggest that these act as the nucleation sites for cubic BN (c-BN) growth and may lead to improved film growth. We also report a strong dependence upon the microscope vacuum, which may be critical in understanding irreproducibility in film growth. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.80.Fe Electron and positron radiation effects
68.55.-a Thin film structure and morphology

Variation of the relative permittivity of charged dielectrics

C. K. Ong, Z. G. Song, K. H. Oh, H. Gong, and C. Le Gressus

Appl. Phys. Lett. 72, 317 (1998); http://dx.doi.org/10.1063/1.120723 (3 pages) | Cited 3 times

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The variation of the relative permittivity of charged dielectrics with trapped charge density has been investigated by a time-resolved current method, in conjunction with a mirror image method employing a scanning electron microscope. The calculation is made by a mathematical expression derived from classical electromagnetic theory. It is found that the relative permittivity of the charged area in the polymethylmethacrylate sample increases with the trapped charge density and saturates at a certain value of the trapped charge density. These observations have been discussed by analogy with the dielectric saturation occurring at a high applied external electric field. © 1998 American Institute of Physics.
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77.84.Jd Polymers; organic compounds
77.22.Ch Permittivity (dielectric function)

Nanometer-scale germanium islands on Si(111) surface windows formed in an ultrathin silicon dioxide film

Alexander A. Shklyaev, Motoshi Shibata, and Masakazu Ichikawa

Appl. Phys. Lett. 72, 320 (1998); http://dx.doi.org/10.1063/1.120724 (3 pages) | Cited 23 times

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Three-dimensional Ge islands between 15 and 200 nm in size were found to grow only on Si(111) surface windows in ultrathin SiO2 film after Ge deposition and subsequent SiO2 decomposition. The size of Ge islands gradually decreased as the Ge thickness decreased. Pseudomorphic two-dimensional Ge layers with the 5×5 structure formed in surrounding areas of the windows. The windows were produced by selective thermal SiO2 decomposition induced by focused electron beam irradiation. These results suggest a new technique for nanometer-scale Ge island fabrication at given points on Si surfaces. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.55.-a Thin film structure and morphology
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Electron-beam damage of C60 films on hydrogen-passivated Si(100)

Michael R. C. Hunt, Jens Schmidt, and Richard E. Palmer

Appl. Phys. Lett. 72, 323 (1998); http://dx.doi.org/10.1063/1.120725 (3 pages) | Cited 8 times

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We report the effects of medium-energy (3.5 keV) electron-beam irradiation of C60 films between 1 and 4 ML thick grown on Si(100) 2×1-H studied by high-resolution electron energy-loss spectroscopy. Electron irradiation leads primarily to molecular fragmentation. Initially, molecular fragments are discrete, and saturated with hydrogen, but continued irradiation leads to the formation of a disordered material with a graphitic local structure. Experiments performed on a single monolayer of C60 show that under irradiation, fragments can bond to the substrate via displacement or desorption of the hydrogen atoms bonded to the Si substrate. © 1998 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
61.80.Fe Electron and positron radiation effects
79.20.Kz Other electron-impact emission phenomena
61.82.Pv Polymers, organic compounds

Linewidth and underlayer influence on texture in submicrometer-wide Al and AlCu lines

J. L. Hurd, K. P. Rodbell, L. M. Gignac, L. A. Clevenger, R. C. Iggulden, R. F. Schnabel, S. J. Weber, and N. H. Schmidt

Appl. Phys. Lett. 72, 326 (1998); http://dx.doi.org/10.1063/1.120726 (3 pages) | Cited 9 times

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The local texture in three types of patterned, thin-film, Al and AlCu interconnections on Si semiconductor devices is investigated by electron backscatter diffraction. Two types of standard planar metal structures were investigated: (1) blanket Al and (2) blanket Al–0.5 wt % Cu on TiN/Ti underlayers. Both were deposited on amorphous SiO2 substrates followed by reactive ion etching to define 0.45–10 μm wide lines and >10×10 μm2 pads. Damascene structures were also investigated in which Al–0.5 wt % Cu films were deposited into preformed Ti-lined amorphous SiO2 trenches, 0.3–5.0 μm wide by 0.4 μm deep, followed by chemical–mechanical polishing to remove the metal overburden. For these three types of structures, distinctly different behaviors were observed: the two planar metal samples exhibited either little change or a large increase in their (111) fiber texture strength with decreasing linewidth, while the damascene samples showed a marked decrease in the (111) fiber texture with decreasing linewidth and feature size. In addition, a novel trimodal (111) texture distribution was found in 0.3 μm wide damascene lines in which appreciable TiAl3 formed. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.65.Cf Surface cleaning, etching, patterning
81.65.Ps Polishing, grinding, surface finishing
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Determination of the unified surface-anchoring energy of a nematic liquid crystal on a polymer substrate

Akihiko Sugimura, Tetsuo Miyamoto, Makoto Tsuji, and Michiyoshi Kuze

Appl. Phys. Lett. 72, 329 (1998); http://dx.doi.org/10.1063/1.120727 (3 pages) | Cited 27 times

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A saturation voltage method is described for determining the unified surface-anchoring energy, which has been proposed theoretically by Sugimura and co-workers [Phys. Rev. E, 52, 681 (1995)], at the interface of nematic (4-pentyl-4′-cyanobiphenyl) and its alignment layer (polyvinyl cinnamate). The method proposed can be employed as a standard measure of this energy without any additional numerical calculation. A conventional measurement method of an optical retardation from a liquid crystal slab is used to estimate the saturation voltage. © 1998 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Dielectric property of (TiO2)x−(Ta2O5)1−x thin films

J.-Y. Gan, Y. C. Chang, and T. B. Wu

Appl. Phys. Lett. 72, 332 (1998); http://dx.doi.org/10.1063/1.120746 (3 pages) | Cited 31 times

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(TiO2)x−(Ta2O5)1−x thin films were prepared with radio-frequency magnetron sputtering deposition in this study. The dielectric constant measured from these films appears to critically depend on the amount of TiO2 incorporated into the film and post-anneal condition. The composition dependence was found similar to that reported on (TiO2)x−(Ta2O5)1−x bulk. The highest value of dielectric constant is about 55 for a TiO2 content of 8% and annealing at 800 °C. Compared to pure Ta2O5 thin films, significant enhancement in dielectric constant is obtained by adding small quantity of TiO2. © 1998 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
81.15.Cd Deposition by sputtering
77.22.Ch Permittivity (dielectric function)
61.66.Bi Elemental solids
61.66.Dk Alloys
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.55.Nq Composition and phase identification
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