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15 Dec 1997

Volume 82, Issue 12, pp. 5891-6372

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Analyzing atomic force microscopy images using spectral methods

S. J. Fang, S. Haplepete, W. Chen, C. R. Helms, and Hal Edwards

J. Appl. Phys. 82, 5891 (1997); http://dx.doi.org/10.1063/1.366489 (8 pages) | Cited 42 times

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Various statistical quantities (such as average, peak-to-valley, and root-mean-square roughness) have been applied to characterize surface topography. However, they provide only vertical information. Because spectral analysis provides both lateral and longitudinal information, it is a more informative measurement than all these commonly used statistical quantities. Unfortunately, a standard method to calculate power spectral density (PSD) is not available. For example, the dimensions of PSD are often denoted as either (length)3 or (length)4. This may lead to confusion when utilizing spectral analysis to study surface morphology. In this paper, we will first compare the definitions of PSD commonly used by various authors. Using silicon surface roughness measurements as examples, we will demonstrate the advantages of spectral methods on atomic force microscopic (AFM) image analysis. In this context, we study the effects of typical AFM imaging distortions such as image bow, drift, tip-shape effects, and acoustic noise. As a result, we will provide a procedure to obtain accurate and reproducible AFM measurements. © 1997 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
02.70.Hm Spectral methods

Imaging flaws in magnetically permeable structures using the truncated generalized inverse on leakage fields

A. C. Bruno

J. Appl. Phys. 82, 5899 (1997); http://dx.doi.org/10.1063/1.366490 (8 pages) | Cited 4 times

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In order to image the magnetic source distribution inside a flawed magnetically permeable structure, the truncated generalized inverse and singular value decomposition were used. These techniques were applied to the magnetic flux leakage generated when the structure is magnetized. The leakage field from different flaw shapes was simulated by placing magnetic dipoles at the boundary surfaces, which reduces the flux density in the flawed structure. A criterion to establish the generalized inverse truncation index is proposed, by using the two-dimensional correlation coefficient between the original image and the reconstructed image. Others aspects such as the measurement signal-to-noise ratio, and density of the model source distribution are also discussed. This imaging technique was successfully applied to a number of different model flaw sources. © 1997 American Institute of Physics.
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81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing
07.05.Pj Image processing
42.30.Wb Image reconstruction; tomography

Efficiency enhancement in a Cherenkov laser by a proper permittivity variation

A. Hirata and T. Shiozawa

J. Appl. Phys. 82, 5907 (1997); http://dx.doi.org/10.1063/1.366491 (6 pages) | Cited 5 times

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With the aid of particle simulation, we discuss efficiency enhancement in a single-pass Cherenkov laser by varying the permittivity of a dielectric sheet loaded on a parallel plate waveguide. For the analysis of the problem, a two-dimensional model for the Cherenkov laser is considered which is composed of a planar relativistic electron beam and a parallel plate waveguide, one plate of which is loaded with a dielectric sheet. In order to maintain the synchronism between an electron beam and an electromagnetic wave, the permittivity of the dielectric is properly varied in accordance with the variation in the average velocity of the electron beam. The result of numerical simulation shows that the efficiency of energy transfer from the electron beam to the electromagnetic wave is greatly enhanced by properly varying the permittivity of the dielectric sheet. © 1997 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
41.60.Bq Cherenkov radiation
77.22.Ch Permittivity (dielectric function)

Novel theoretical aspects on photorefractive ultrasonic detection and implementation of a sensor with an optimum sensitivity

Louis-Anne de Montmorillon, Philippe Delaye, Jean-Claude Launay, and Gérald Roosen

J. Appl. Phys. 82, 5913 (1997); http://dx.doi.org/10.1063/1.366492 (10 pages) | Cited 14 times

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We here expose theoretical and experimental results on homodyne detection using near-infrared laser sources, at 1.06, 1.32, and 1.55 μm wavelengths. The used photorefractive crystals are two large size CdZnTe:V samples. With speckled beams such as the ones scattered by diffusive objects, we reach a detection limit which, at 1.55 μm, is only 1.6 times above the one obtained with plane waves in a classical interferometer and only 2 and 2.2 times above at 1.32 and 1.06 μm, respectively. It is then demonstrated that the electron–hole competition, which varies enormously between these three wavelengths and gives a nearly zero two-wave-mixing gain at 1.32 μm, does not influence the sensitivity of the system. Moreover, we show that the frequency cutoff of the system is four times higher in the attenuation regime than in the amplification one. © 1997 American Institute of Physics.
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78.20.-e Optical properties of bulk materials and thin films
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.62.-b Laser applications

Temperature-dependence studies of photorefractive effect in a low glass-transition-temperature polymer composite

Bogdan Swedek, Ning Cheng, Yiping Cui, Jaroslaw Zieba, Jeffrey Winiarz, and Paras N. Prasad

J. Appl. Phys. 82, 5923 (1997); http://dx.doi.org/10.1063/1.366493 (9 pages) | Cited 23 times

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The temperature dependence of the photorefractive effect in a polymer composite containing poly(9-vinycarbazole), tricresyl phosphate, buckminsterfullerene, and 4-(N,N- diethylamino)-β-nitrostyrene is presented. The photoconductive, electro-optic and photorefractive properties of the material have been studied in the temperature range of 22–61 °C. An apparent increase of electro-optic modulation with temperature and its eventual saturation is observed. This behavior is attributed to the temperature activated orientational mobility of the second-order nonlinear chromophores. The polarization anisotropy between the p- and s-polarized readouts is consistent with what would be expected on the basis of directly measured effective electro-optic coefficients. By correlating the electro-optic value with the diffraction efficiency, the temperature dependence of the space-charge field is obtained and explained by temperature dependencies of the dark conductivity and the photoconductivity of the material. © 1997 American Institute of Physics.
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42.70.Jk Polymers and organics
78.20.-e Optical properties of bulk materials and thin films
42.65.-k Nonlinear optics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
72.40.+w Photoconduction and photovoltaic effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Jq Electro-optical effects

Attenuation of Love waves in low-loss media

P. Kiełczyński

J. Appl. Phys. 82, 5932 (1997); http://dx.doi.org/10.1063/1.366494 (6 pages) | Cited 6 times

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A theory of Love waves propagating in a viscoelastic surface layer deposited on a perfect elastic substrate was considered. In the case of low losses (ωη44/μB0≪1) an analytical formula relating the attenuation coefficient of the Love wave and the viscoelastic parameters of the waveguide structure was established. This makes it possible to apply the obtained analytical formula in nondestructive testing for determining the rheological parameters of viscoelastic bodies. The established theory of Love waves in viscoelastic media can also be applied in seismology and integrated optics. © 1997 American Institute of Physics.
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62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
62.30.+d Mechanical and elastic waves; vibrations
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
68.35.Gy Mechanical properties; surface strains
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.65.+k Acoustical properties of solids

Kinetics of fluorine atoms in high-density carbon–tetrafluoride plasmas

K. Sasaki, Y. Kawai, C. Suzuki, and K. Kadota

J. Appl. Phys. 82, 5938 (1997); http://dx.doi.org/10.1063/1.366495 (6 pages) | Cited 23 times

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Reaction processes of fluorine (F) atoms in high-density carbon–tetrafluoride (CF4) plasmas were investigated using vacuum ultraviolet absorption spectroscopy. A scaling law nF∝(nenCF4)0.5–0.7 was found experimentally, where nF is the F atom density and ne and nCF4 stand for the electron and parent gas (CF4) densities, respectively. The lifetime measurement in the afterglow showed that the decay curve of the F atom density was composed of two components: a rapid decay in the initial afterglow and an exponential decrease in the late afterglow. The decay time constant in the initial afterglow τ1 satisfied the scaling law τ1∝(nenCF4)−(0.3–0.4), which is a consistent relationship with the scaling law for the F atom density. The two scaling laws and the lifetimes of CFx radicals suggest that the major loss process of F atoms in the initial afterglow is the reaction with CFx radicals (probably, x = 3) on the wall surface. The loss process in the late afterglow was simple diffusion to the wall surface. The surface loss probability of F atoms on the chamber wall was evaluated from the decay time constant in the late afterglow, and was on the order of 10−3. © 1997 American Institute of Physics.
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52.25.Fi Transport properties
32.30.Jc Visible and ultraviolet spectra
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Dg Plasma kinetic equations

Electromagnetic field structure in a weakly collisional inductively coupled plasma

V. A. Godyak and R. B. Piejak

J. Appl. Phys. 82, 5944 (1997); http://dx.doi.org/10.1063/1.366496 (4 pages) | Cited 33 times

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Two-dimensional, phase resolved magnetic probe measurements have been performed in a low pressure inductively coupled cylindrical plasma source driven with a planar coil. The rf electric field and current density distributions determined from these measurements exhibit an abnormal nonmonotonic spatial evolution. Formation of a second current layer, phase bifurcation and a reversal of the rf field phase velocity have been found and are attributed to spatial dispersion of the plasma conductivity due to collisionless electron thermal motion typical of anomalous skin effect. © 1997 American Institute of Physics.
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52.20.Fs Electron collisions
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)

The analysis of background gas heating in direct current sputtering discharges via particle simulation

Vladimir V. Serikov and Kenichi Nanbu

J. Appl. Phys. 82, 5948 (1997); http://dx.doi.org/10.1063/1.366497 (10 pages) | Cited 35 times

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A particle-in-cell/Monte Carlo numerical model has been developed to simulate a direct current discharge self-consistently with the motion and thermalization of both energetic charge-exchange neutrals and sputtered cathode atoms. In the model the charged particle motions are considered in a self-consistent electric field. A one-dimensional glow discharge in Ar has been simulated for the cases of Al and Cu cathode. The background argon gas heating has been predicted, with the temperature rise being larger for the case of Cu cathode which is characterized by a higher sputtering yield than Al. The balance of power input into the gas due to the energetic neutrals, sputtered atoms, and ions is analyzed. The dominant contribution is from energetic neutrals. Comparison of the calculated fluxes of these three species at the cathode surface shows a great contribution of the energetic neutrals into sputtering of the cathode material. The effect of applied voltage has been also investigated. Lastly, the influence of the gas heating on discharge characteristics is discussed. © 1997 American Institute of Physics.
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52.65.Pp Monte Carlo methods
52.65.Rr Particle-in-cell method
52.80.Hc Glow; corona
52.50.Gj Plasma heating by particle beams

Stopping and damage parameters for Monte Carlo simulation of MeV implants in crystalline Si

G. Lulli, E. Albertazzi, M. Bianconi, R. Nipoti, M. Cervera, A. Carnera, and C. Cellini

J. Appl. Phys. 82, 5958 (1997); http://dx.doi.org/10.1063/1.366498 (7 pages) | Cited 19 times

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Semiempirical models of electronic energy loss and damage formation for MeV ions (B, P, As) implanted in silicon at room temperature were investigated through the comparison of measurements with Monte Carlo simulations of both impurity and damage depth distributions. Accurate prediction of dopant profiles in an amorphous target and in a low-dose implanted crystal is achieved by a proper parametrization of well known analytic stopping models. Moreover, to accurately describe the dynamic effects of damage accumulation in medium dose implants, a dependence on ion energy of the efficiency parameter used in the Kinchin–Pease (KP) model must be introduced in the simulation. Such a factor, determined by the fit of the measured integral of defect profiles, is found to decrease for P and As ions with increasing the nuclear energy released to primary recoil atoms, apparently reaching a saturation value of about 0.25. Full cascade simulations show that the increasing fraction of the primary recoils energy spent in electronic processes, not considered in the simple KP approximation, cannot explain the observed trend. While the empirical adjustment of damage efficiency leads to a good agreement between simulated and experimental dopant profiles, a systematic underestimate in the depth position of the peaks of simulated damage distributions is observed, which cannot be accounted for by simple ballistic transport effects. © 1997 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.S- Impurities in crystals
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
85.40.Ry Impurity doping, diffusion and ion implantation technology

Ion mass and temperature dependence of damage production in ion implanted InP

E. Wendler, T. Opfermann, and P. I. Gaiduk

J. Appl. Phys. 82, 5965 (1997); http://dx.doi.org/10.1063/1.366499 (11 pages) | Cited 23 times

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Ion beam induced damaging and amorphization of crystalline InP is investigated. 100 keV B+, 300 keV Si+, 200 keV Ar+ and 600 keV Se+ ions are implanted into 〈100〉 InP at temperatures ranging from 80 K to 420 K. The implanted layers are analyzed using Rutherford backscattering spectrometry in channeling configuration, cross section transmission electron microscopy and optical spectroscopy in the sub-gap frequency region. The temperature dependence of damage production can be represented assuming a thermally stimulated defect diffusion within the primary collision cascades, resulting in a shrinkage of the remaining defect clusters. At a critical temperature T∞ these clusters dissolve completely and only point defect complexes nucleate. Then, amorphization occurs only at very large ion fluences ( ≈ 1016cm−2) and the process seems to be influenced by the high amount of implanted ions. A defect band forms around the projected range of the implanted ions, which may act as a diffusion barrier for point defects. The range of T∞ from ≈ 350 K for B+ and ≈ 420 K for Se+ ions corresponds to the annealing stage II of defects in InP, which can be related to the mobility of phosphorous interstitials. This indicates that phosphorous interstitials play an important role during ion irradiation of InP. © 1997 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.43.Dq Amorphous semiconductors, metals, and alloys
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
66.30.J- Diffusion of impurities

Vibrational local modes of a-SiO2:H and variation of local modes in different local environments

Shu-Ya Lin

J. Appl. Phys. 82, 5976 (1997); http://dx.doi.org/10.1063/1.366488 (7 pages) | Cited 9 times

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The vibrational densities of states for the SiO2 Bethe lattices of different Si–O–Si angles and various local bonding structures in a-SiO2:H are calculated. It is found that the Si–O–Si bond-stretching mode shifts to a higher frequency and the bond-bending mode shifts to a lower frequency when the Si–O–Si bond angle increases. The SiH bond-bending mode lies at 876 cm−1 and there is an additional mode, which comes from the coupled motions of SiH and Si–O–Si bonds, at a lower frequency. This mode is not revealed by experiments. The Si-dangling bond has minor effects to the vibrational spectrum of the a-SiO2. The Si–O bond-stretching mode, of the O atom with dangling bond, shifts to a much lower 950 cm−1 compared to the 1200 cm−1 of the Si–O–Si bond-stretching mode of bulk SiO2. The Si–OH bond-stretching mode has a peak at 932 cm−1 which is slightly less than that of the Si–O bond of the dangling O atom. Under thermal annealing, some H atoms will evolve and the O atom will become a dangling atom or form a Si–O–Si bond with the other Si atom. The Si–Si bond gives an additional Si–Si vibrational mode at 464 cm−1 in the spectrum. © 1997 American Institute of Physics.
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63.50.-x Vibrational states in disordered systems

Internal friction and dislocation collective pinning in disordered quenched solid solutions

G. D’Anna, W. Benoit, and V. M. Vinokur

J. Appl. Phys. 82, 5983 (1997); http://dx.doi.org/10.1063/1.366463 (8 pages) | Cited 14 times

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We introduce the collective pinning of dislocations in disordered quenched solid solutions and calculate the macroscopic mechanical response to a small dc or ac applied stress. This work is a generalization of the Granato–Lücke string model, able to describe self-consistently short and long range dislocation motion. Under dc applied stress the long distance dislocation creep has at the microscopic level avalanche features, which result in a macroscopic nonlinear “glassy” velocity-stress characteristic. Under ac conditions the model predicts, in addition to the anelastic internal friction relaxation in the high frequency regime, a linear internal friction background which remains amplitude-independent down to a crossover frequency to a strongly nonlinear internal friction regime. © 1997 American Institute of Physics.
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61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.Hg Creep

Reliability analysis for encapsulated interconnect lines under dc and pulsed dc current using a continuum electromigration transport model

J. J. Clement

J. Appl. Phys. 82, 5991 (1997); http://dx.doi.org/10.1063/1.366464 (10 pages) | Cited 19 times

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The origins of two types of electromigration failure models are explored starting with the basic transport differential equations including the effects of electromigration-induced mechanical stress. We compare the results of a nucleation model, in which failure is determined by the time required to build up a critical stress or a critical vacancy concentration at a site of atomic flux divergence, with a void-growth model, in which failure is linked to the growth of a void to a critical size. Two particular applications of the model are investigated, and the results are shown to be in good agreement with available experimental data. In one example, the effect of the presence of a field-free reservoir region extending beyond the current-carrying region of the line is compared to the case without such a field-free extension. In the other, the effects under pulsed dc current stress are examined in comparison to dc current. Possible applications of this model to design verification are also discussed. © 1997 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.J- Point defects and defect clusters
61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Qa Electromigration

Growth kinetics of intermediate compounds at a planar solid-solid or solid-liquid interface by diffusion mechanisms

André Coulet, Karine Bouche, Francis Marinelli, and Francoise Barbier

J. Appl. Phys. 82, 6001 (1997); http://dx.doi.org/10.1063/1.366465 (7 pages) | Cited 1 time

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A diffusional model of interface displacement kinetics is proposed for the growth of n intermediate compounds at an initially planar interface between two semi-infinite phases. The model is based on the solution of Fick’s equations with the restrictive assumptions of simultaneous growth of n intermediate phases, unidirectional diffusion flow, and local equilibrium conditions. The velocity of each interface follows the parabolic law and the (n+1) kinetic coefficients are expressed as a function of boundary concentrations and diffusion coefficients of all the phases via (n+1) nonlinear equations. A parametric study of the kinetic coefficients, corresponding to realistic situations of initial solid-solid or solid-liquid interface, is developed for systems with one or two intermediate layers. If two interacting initial phases α and β are such that the chemical diffusion coefficient Dα (in α) is smaller than Dβ (in β), it is found that the interface velocities are enhanced by: (a) increases in Dβ, (b) increases in the solubility limit in β, and (c) reduced miscibility gaps at the interfaces. Moreover, the widths of the intermediate layers are increased by: (a) decreases in Dβ and (b) increases in the diffusion coefficients and solubility limits in these intermediate phases. © 1997 American Institute of Physics.
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68.35.Fx Diffusion; interface formation

Microstructural study of Mg-doped p-type GaN: Correlation between high-resolution electron microscopy and Raman spectroscopy

S.-C. Y. Tsen, David J. Smith, K. T. Tsen, W. Kim, and H. Morkoç

J. Appl. Phys. 82, 6008 (1997); http://dx.doi.org/10.1063/1.366466 (4 pages) | Cited 9 times

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A series of Mg-doped GaN films ( ∼ 1–1.3 μm) grown by reactive molecular beam epitaxy at substrate temperatures of 750 and 800 °C has been studied by high-resolution electron microscopy (HREM) and Raman spectroscopy. Stacking defects parallel to the substrate surface were observed in samples grown on sapphire substrates at 750 °C with AlN buffer layers (60–70 nm) at low Mg concentration. A transition region with mixed zinc-blende cubic (c) and wurtzite hexagonal (h) phases having the relative orientations of (111)c//(00.1)h and (1math0)c//(10.0)h was observed for increased Mg concentration. The top surfaces of highly doped samples were rough and assumed a completely zinc-blende phase with some inclined stacking faults. Samples grown with a Mg cell temperature of 350 °C and high doping levels were highly disordered with many small crystals having inclined stacking faults, microtwins, and defective wurtzite and zinc-blende phases. Correlation between HREM and Raman scattering results points towards the presence of compressive lattice distortion along the growth direction which might be attributable to structural defects. The films grown at 800 °C had better quality with less observable defects and less yellow luminescence than samples grown at 750 °C. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Strain effects in CdTe/Si heterostructures

M. S. Han, T. W. Kang, J. H. Leem, M. H. Lee, K. J. Kim, and T. W. Kim

J. Appl. Phys. 82, 6012 (1997); http://dx.doi.org/10.1063/1.366467 (4 pages) | Cited 2 times

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Photoluminescence (PL) and spectroscopic ellipsometry measurements on CdTe/Si strained heterostructures grown by molecular beam epitaxy were carried out to investigate the effect of the strain and the dependence of the strain on the Si tilted substrates. The results of the PL spectra showed that the relative intensity ratio between the peak at 1.452 eV and the bound-exciton peak for the CdTe epilayer grown on the Si (100) 1° tilted substrate had a minimum value and that the strain for the CdTe epilayer grown on the Si (100) 8° tilted substrate had a minimum value. When rapid thermal annealing (RTA) was performed at 55 °C, the PL spectra showed that the relative intensity ratio between the peak at 1.452 eV and that at 1.574 eV for the CdTe epilayer grown on the Si (100) 8° tilted substrate had a minimum value and that the strain for the CdTe epilayer grown on the Si (100) 1° tilted substrate had a minimum value. Spectroscopic ellipsometry measurements showed that the spectrum of the dielectric constant of the CdTe epilayer grown on the Si (100) 8° tilted substrate is similar to that of the CdTe bulk. These results indicate that the strains in the CdTe layers grown on Si substrates are strongly dependent on the Si substrate orientation and that the crystallinity of the CdTe epitaxial layer grown on the Si substrate is remarkably improved by RTA. © 1997 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.66.Hf II-VI semiconductors
78.55.Ap Elemental semiconductors
78.55.Et II-VI semiconductors
62.20.F- Deformation and plasticity
68.35.Gy Mechanical properties; surface strains
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
77.22.Ch Permittivity (dielectric function)

Characterization and modelling of the strain fields associated with InGaAs layers on V-grooved InP substrates

A. Gupta, G. C. Weatherly, Daniel T. Cassidy, and D. M. Bruce

J. Appl. Phys. 82, 6016 (1997); http://dx.doi.org/10.1063/1.366468 (8 pages) | Cited 3 times

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A series of lattice-matched or compressively strained InGaAs layers were grown by gas source molecular beam epitaxy on V grooved InP substrates, with grooves bounded by {211}A or {111}B facets. The stress field associated with the layers was measured by the degree of polarization technique, and compared to the predictions of analytical or finite element models. Good agreement was found for the {211}A V grooves, but both the nominally lattice-matched and compressively strained layers grown on {111}B  V grooves displayed similar degree of polarization maps. Analytical electron microscopy demonstrated that the {211}A  V-groove samples had the targeted composition, but the {111}B  samples showed much higher In/Ga ratios at the bottom of the groove than the expected values. Indium enrichment at the bottom of the groove led to defect formation there, and left the V groove of both the lattice-matched and compressively strained samples under a net compressive force. © 1997 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
02.70.Dh Finite-element and Galerkin methods
82.80.-d Chemical analysis and related physical methods of analysis
61.72.-y Defects and impurities in crystals; microstructure

Stress-induced formation of high-density amorphous carbon thin films

J. Schwan, S. Ulrich, T. Theel, H. Roth, H. Ehrhardt, P. Becker, and S. R. P. Silva

J. Appl. Phys. 82, 6024 (1997); http://dx.doi.org/10.1063/1.366469 (7 pages) | Cited 54 times

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Amorphous carbon films with high sp3 content were deposited by magnetron sputtering and intense argon ion plating. Above a compressive stress of 13 GPa a strong increase of the density of the carbon films is observed. We explain the increase of density by a stress-induced phase transition of sp2 configured carbon to sp3 configured carbon. Preferential sputtering of the sp2 component in the carbon films plays a minor role compared to the sp2⇒sp3 transition at high compressive stress formed during the deposition process. Transmission electron microscopy shows evidence of graphitic regions in the magnetron sputtered/Ar plated amorphous carbon thin films. Differences in the microstructure of the tetrahedral amorphous carbon (ta–C) films deposited by filtered arc and mass selected ion beam; and those films deposited using magnetron sputtering combined with intense ion plating can be used to explain the different electronic and optical properties of both kinds of ta–C films. © 1997 American Institute of Physics.
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61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Cd Deposition by sputtering
81.15.Jj Ion and electron beam-assisted deposition; ion plating
79.20.Kz Other electron-impact emission phenomena
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
62.20.-x Mechanical properties of solids
78.66.Nk Insulators

Reconstructed (881) Si surface structure observed by scanning tunneling microscopy

Tsutomu Kawamura, Shiro Kojima, and Tomohide Kanzawa

J. Appl. Phys. 82, 6031 (1997); http://dx.doi.org/10.1063/1.366548 (6 pages) | Cited 2 times

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The high-index (881) surface has been studied by ultra-high-vacuum scanning tunneling microscopy (STM). Reconstruction of the (881) Si surface was found to occur, as evident from the appearance of a number of different characteristic patterns in the STM image, including various kinds of terraces, step walls, and kinks. A typical terrace had, on average, a (7×2) reconstruction. The step walls consisted of several split lattices. Their multiple reciprocal networks and their relationship to the step walls has been analyzed. The kinks were found to consist of one-dimensional long-period superlattices. The reason for the disorder is discussed in terms of the relationship between the effective dangling-bond density and the periodic bond chain vector approximation. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Scanning tunneling microscopy and atomic force microscopy study of graphite defects produced by bombarding with highly charged ions

Kozo Mochiji, Seiji Yamamoto, Hiroshi Shimizu, Shunsuke Ohtani, Takashi Seguchi, and Nobuo Kobayashi

J. Appl. Phys. 82, 6037 (1997); http://dx.doi.org/10.1063/1.366470 (4 pages) | Cited 31 times

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The defects produced on a graphite surface by single ion impact using highly charged Ar ions (charge state q ⩽ 8) is investigated by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The defect looks like a protrusion in the STM image, while it is flat in the AFM image. From these two contrasting images, the defects are considered to be due to the increase in the local charge density of state at the surface caused by carbon atom sputtering. The average value for the defect size increases remarkably with the charge state of incident Ar ions. This is explained by the enhancement of potential sputtering due to the Coulomb repulsion between surface holes which are generated by the neutralization of highly charged Ar ions. © 1997 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.72.-y Defects and impurities in crystals; microstructure
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Investigation of substrate-dependent nucleation of plasma-deposited microcrystalline silicon on glass and silicon substrates using atomic force microscopy

L. L. Smith, E. Srinivasan, and G. N. Parsons

J. Appl. Phys. 82, 6041 (1997); http://dx.doi.org/10.1063/1.366471 (6 pages) | Cited 7 times

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In order to define mechanisms for pulsed-gas plasma enhanced substrate-selective deposition of silicon, the initial stages of microcrystalline silicon (μc-Si) growth by plasma enhanced chemical vapor deposition on both c-Si and glass substrates were investigated by means of atomic force microscopy (AFM) and reflective high energy electron diffraction (RHEED). Differences in initial substrate morphology were reflected in significant differences in film surface morphology in the early stages of growth. AFM images and rms roughness measurements indicated that the initial growth on the c-Si substrate was three dimensional in character. On glass, the initial Si deposits were much more irregular in shape and the tallest features extended over wider areas than the initial deposits on c-Si. The character of the initial growth on glass was partly obscured by the roughness of the substrate, but the appearance of the initial Si deposits suggested a flatter and more two-dimensional character on glass than on c-Si. As the Si deposition progressed, the films on the different substrates developed similar morphology with increasing thickness. On the c-Si substrate, surface coverage was nearly complete at 50 Å. RHEED analysis of the films grown on c-Si revealed the presence of amorphous structure in the early stages of film growth, which began to transition to a randomly oriented μc-Si structure after 40–50 Å of growth. Observed differences in nucleation affirm and clarify proposed mechanisms and limitations for plasma enhanced selective μc-Si deposition. © 1997 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Simulations of sputtering induced roughening and formation of surface topography in deposition of amorphous diamond films with mass separated kiloelectronvolt ion beams

I. Koponen, O.-P. Sievänen, M. Hautala, and M. Hakovirta

J. Appl. Phys. 82, 6047 (1997); http://dx.doi.org/10.1063/1.366472 (9 pages) | Cited 3 times

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Atomic scale simulations are performed for ion bombardment induced roughening of amorphous diamond films in a process where deposition is done by using kiloelectronvolt mass separated ion beams operated in the upper limit of practical deposition energies up to 20 keV. Resulting surfaces are shown to be self-affine and they have low surface roughness. The experimentally observed extremely low roughness is obtained when moderate surface relaxation within the distance of next nearest neighbors is taken into account in simulations. It is found that there is also another mechanism, originating from the ballistic movement of redeposited atoms, which can maintain the eroding surfaces smooth. High-energy, off-normal deposition is shown to lead in pattern formation on a mesoscopic scale. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
61.80.Jh Ion radiation effects
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.55.-a Thin film structure and morphology
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Fracture toughness estimation of thin chemical vapor deposition diamond films based on the spontaneous fracture behavior on quartz glass substrates

Shoji Kamiya, Masaki Sato, Masumi Saka, and Hiroyuki Abé

J. Appl. Phys. 82, 6056 (1997); http://dx.doi.org/10.1063/1.366473 (6 pages) | Cited 3 times

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This article is on the experimental estimation of the fracture toughness of thin diamond film deposited by the microwave plasma chemical vapor deposition method on a quartz glass substrate. Because of their differences in the coefficient of thermal expansion, diamond films on a quartz glass substrate suffer tensile stress at room temperature and show various kinds of spontaneous fracture behavior, reflecting the mechanical properties of the films. On the basis of detailed observation of cracking patterns and also measuring the residual stress with the aid of Raman spectroscopy, the fracture toughness of the film having thickness of around 1 μm has been estimated here satisfactorily without the help of any difficult microscopic experiment. The fracture toughness of the film of thickness 0.35 μm is found to be around half of that obtained with much thicker films. © 1997 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.ub Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
62.20.M- Structural failure of materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
65.40.De Thermal expansion; thermomechanical effects
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators

Effects of H coverage on Ge segregation during Si1−xGex gas-source molecular beam epitaxy

H. Kim, N. Taylor, J. R. Abelson, and J. E. Greene

J. Appl. Phys. 82, 6062 (1997); http://dx.doi.org/10.1063/1.366474 (5 pages) | Cited 23 times

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The effects of H coverage θH on Ge segregation during Si1−xGex gas-source molecular beam epitaxy (GS-MBE) were investigated using D2 temperature programmed desorption (TPD). Si1−xGex films with x = 0.01–0.30 were grown from Si2H6/Ge2H6 mixtures at Ts = 450–800 °C, held at the growth temperature for 30 s, cooled to <200 °C, and then exposed to atomic deuterium until saturation coverage. D2 TPD spectra were fit using four peaks corresponding, in order of decreasing activation energy, to desorption from Si monodeuteride, Ge–Si mixed-dimer monodeuterides, Si dideuteride, and Ge monodeuteride. Steady-state Ge surface coverages were determined from the TPD data as a function of Ts and x. In contrast to solid-source MBE films grown in this temperature regime, Ge segregation during GS-MBE decreases with decreasing Ts due to the increasing H coverage. The results were well described by a model accounting for the Si/Ge site exchange and θH. The Ge segregation enthalpy varies from −0.28 eV at Ts ≥ 800 °C, where the steady-state hydrogen coverage θH approaches zero, to −0.10 eV at Ts ⩽ 450 °C, where θH is nearly saturated. © 1997 American Institute of Physics.
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81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
64.75.-g Phase equilibria
68.55.-a Thin film structure and morphology
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
65.20.-w Thermal properties of liquids
65.40.gd Entropy
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