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1 Jul 1999

Volume 86, Issue 1, pp. 1-709

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GaN: Processing, defects, and devices

S. J. Pearton, J. C. Zolper, R. J. Shul, and F. Ren

J. Appl. Phys. 86, 1 (1999); http://dx.doi.org/10.1063/1.371145 (78 pages) | Cited 714 times

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The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics. © 1999 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
01.30.Rr Surveys and tutorial papers; resource letters
71.20.Nr Semiconductor compounds
61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.65.Cf Surface cleaning, etching, patterning
85.30.Tv Field effect devices
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Jb Light-emitting devices
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Microstructural and nonlinear optical properties of silica–titania sol-gel film doped with PbS quantum dots

A. Martucci, J. Fick, J. Schell, G. Battaglin, and M. Guglielmi

J. Appl. Phys. 86, 79 (1999); http://dx.doi.org/10.1063/1.370702 (9 pages) | Cited 21 times

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Thin silica–titania films doped with different concentration of PbS quantum dots (PbS/oxide molar ratios ranging from 5% to 25%) were fabricated via a sol-gel route. The structural properties were studied by x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering spectrometry. The PbS crystals were found to have a mean diameter in the range 2.3–3.5 nm with narrow size distribution. The resonant nonlinear optical properties were studied by the nonlinear m-line technique and degenerate four-wave mixing. High negative nonlinear refractive indices (n2) were measured at 1.064 μm. Different n2 values were obtained for nanosecond excitation (n2 = 10−7–10−8 cm2/kW) and for picosecond excitation (n2 = 10−9–10−10 cm2/kW). The differences can be explained by saturation effects. Measurements at 532 nm showed n2 values ten times higher than at 1.064 μm. The response time of the nonlinearity for both wavelengths was below 35 ps. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
78.66.-w Optical properties of specific thin films
61.43.Fs Glasses
78.47.-p Spectroscopy of solid state dynamics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Ce Glasses, quartz

X-ray photoemission and photoabsorption of organic electroluminescent materials

R. Treusch, F. J. Himpsel, S. Kakar, L. J. Terminello, C. Heske, T. van Buuren, V. V. Dinh, H. W. Lee, K. Pakbaz, G. Fox, and I. Jiménez

J. Appl. Phys. 86, 88 (1999); http://dx.doi.org/10.1063/1.370703 (6 pages) | Cited 21 times

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Thin films of tris-(8, hydroxyquinoline) aluminum (Alq3) and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) were measured using synchrotron radiation-based core and valence level photoemission and core level photoabsorption to elucidate the element-specific electronic structure of organic electroluminescent materials. The energy level alignment of an Alq3/TPD interface is given for both occupied and unoccupied states. A comparison of freshly evaporated films of Alq3 and TPD with films that have been exposed to intense radiation or oxidative conditions sheds light on possible damage mechanisms of the molecular solid. © 1999 American Institute of Physics.  
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79.60.Dp Adsorbed layers and thin films
78.70.Dm X-ray absorption spectra
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
73.20.At Surface states, band structure, electron density of states
71.20.Rv Polymers and organic compounds
78.60.Fi Electroluminescence

Infrared properties of AgGaTe2, a nonlinear optical chalcopyrite semiconductor

M. C. Ohmer, J. T. Goldstein, D. E. Zelmon, A. W. Saxler, S. M. Hegde, J. D. Wolf, P. G. Schunemann, and T. M. Pollak

J. Appl. Phys. 86, 94 (1999); http://dx.doi.org/10.1063/1.370704 (6 pages) | Cited 20 times

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The fundamental optical properties of AgGaTe2, a nonlinear optical semiconductor are reported. These properties include birefringence, indices of refraction, infrared transmission, and the temperature dependence of the band gap. The average index for wavelengths greater than several microns was found to be 3.0. The birefringence was found to be rather large and to range from a near band edge value of 0.038 at 1.3 μm to a value of 0.017 at 15 μm. Additionally, native defect related sub-bandgap absorption, photoluminescence, and electrical transport have been studied in these nominally undoped p-type crystals. An activation energy associated with these defects was determined to be 0.3 eV and the corresponding photoluminescence and absorption data showed, respectively, a broad asymmetric emission band centered at 0.8 eV and two bands at 0.95 and 1.01 eV, the absorption band at 0.95 eV being the most intense. The measured properties were utilized to assess the potential of AgGaTe2 for the wavelength conversion processes of second-harmonic generation and degenerate optical parametric oscillation. It was found that AgGaTe2 will not phase match at room temperature. However, it is estimated that mixed crystals of the form AgGa(Se(1−x))Tex)2 for a Te addition of 19% can exceed the conversion efficiency of AgGaSe2 by more than 100%. © 1999 American Institute of Physics.
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42.70.Mp Nonlinear optical crystals
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.30.Hv Other nonmetallic inorganics
81.05.Hd Other semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Jc Other crystalline inorganic semiconductors
78.20.Fm Birefringence
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr Semiconductor compounds
78.55.Hx Other solid inorganic materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Yj Optical parametric oscillators and amplifiers
71.55.Ht Other nonmetals

Bandwidth enhancement of a shear-force-controlled distance regulation in near-field microscopy

M. Lippitz, M. Schüttler, H. Giessen, M. Born, and W. W. Rühle

J. Appl. Phys. 86, 100 (1999); http://dx.doi.org/10.1063/1.370705 (7 pages) | Cited 5 times

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The distance between sample and probe in a scanning near-field optical microscope is regulated via tracing the shear-force on the tip which is glued to a tuning fork piezo. A lock-in technique is used. We demonstrate that the bandwidth of the control loop is increased if not only amplitude or phase, but a favorable combination of both is used as feedback signal. The enhancement of bandwidth is connected with a reduction of signal-to-noise ratio. The optimum combination of both, bandwidth and signal-to-noise ratio, can be adjusted purely electronically to the specific needs of an experiment. A theoretical model is developed that discloses the relation between the mechanical and electrical properties of the combination of tuning fork and fiber tip. The frequency response of the shear-force detection system is calculated with a numerical simulation based on this model. Experimental frequency response curves are well fitted by these simulations. Our results are especially important for low-temperature scanning microscopy, where the bandwidth enhancement is essential for obtaining a reasonable scanning speed. © 1999 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.10.Pz Instruments for strain, force, and torque
07.05.Dz Control systems
07.68.+m Photography, photographic instruments; xerography

Two-dimensional surface band structure of operating light emitting devices

R. Shikler, T. Meoded, N. Fried, B. Mishori, and Y. Rosenwaks

J. Appl. Phys. 86, 107 (1999); http://dx.doi.org/10.1063/1.370706 (7 pages) | Cited 18 times

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We report on measurements of two-dimensional potential distribution with nanometer spatial resolution of operating light emitting diodes. By measuring the contact potential difference between an atomic force microscope tip and the cleaved surface of the light emitting diode, we were able to measure the device surface potential distribution. These measurements enable us to accurately locate the metallurgical junction of the light emitting device, and to measure the dependence of the built-in voltage on applied external bias. As the device is forward biased, the junction built-in voltage decreases up to flat band conditions, and then inverted. It is shown that the potential distribution across the pn junction is governed by self-absorption of the sub-bandgap diode emission. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.40.Cg Contact resistance, contact potential
73.20.At Surface states, band structure, electron density of states
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Radial plasma flow in a hot anode vacuum arc

I. I. Beilis, M. Keidar, R. L. Boxman, S. Goldsmith, J. Heberlein, and E. Pfender

J. Appl. Phys. 86, 114 (1999); http://dx.doi.org/10.1063/1.370707 (6 pages) | Cited 15 times

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The free, steady state, two-dimensional radial plasma flow initiated between a pair of disk-shaped electrodes of a hot anode vacuum arc was analyzed in the hydrodynamic approximation. Studies include the influence of the self-magnetic field on the plasma density, velocity, radial spreading of the arc current and potential distribution. The free plasma boundary was calculated by solving the equations for the normal and tangential velocity components at the free boundary. It was found that the plasma significantly expands over a radial distance of about half of the interelectrode gap counted from the electrode edge and the plasma density in the center plane decreases by factor of 2, whereas the density of the fringe current decreases by a factor of 10. The self magnetic field does not influence the plasma flow and current spreading at radial distances larger than the interelectrode gap. The potential distribution is strongly nonsymmetric with respect to the central plane due to the influence of the plasma density gradients on the current spreading. © 1999 American Institute of Physics.
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52.30.-q Plasma dynamics and flow
52.25.-b Plasma properties
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Investigation of dose uniformity on the inner races of bearings treated by plasma immersion ion implantation

Z. M. Zeng, T. K. Kwok, X. B. Tian, B. Y. Tang, and P. K. Chu

J. Appl. Phys. 86, 120 (1999); http://dx.doi.org/10.1063/1.370708 (4 pages) | Cited 25 times

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Plasma immersion ion implantation (PIII) is an effective technique for the surface modification of industrial components possessing an irregular shape. We have recently used PIII to treat a real industrial ball bearing to enhance the surface properties of the race surface on which the balls roll. The implantation dose uniformity along the groove is assessed using theoretical simulation and experiments. The two sets of results agree very well, showing larger doses near the center. However, the highest dose is not observed at the bottom or center of the groove, but rather offset toward the side close to the sample platen when the bearing is placed horizontally. The minimum dose is observed near the edge or corner of the groove and our model indicates that it is due to the more glancing ion incidence as a result of the evolution of the ion sheath near the corner. The dose nonuniformity along the groove surface is about 40% based on our experimental data. © 1999 American Institute of Physics.
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61.82.Bg Metals and alloys
81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.up Other materials

Addressing and sustaining in alternating current coplanar plasma display panels

C. Punset, S. Cany, and J.-P. Boeuf

J. Appl. Phys. 86, 124 (1999); http://dx.doi.org/10.1063/1.370709 (10 pages) | Cited 72 times

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In a coplanar plasma display panel the discharges in each pixel are sustained between two parallel electrodes on the same substrate. A third electrode perpendicular to the sustaining electrodes and placed on a facing substrate is used to address the pixel. A self-consistent two-dimensional model of the microdischarge has been used to simulate and study the addressing and sustaining phases in an alternating current coplanar cell. The formation and decay of the transient plasma during the address and sustain discharge pulses are described. The time evolution of the charges on the dielectric surfaces above each electrode is also discussed and the model is used to derive the voltage margins of the address and sustain regimes. © 1999 American Institute of Physics.  
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07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.
52.75.-d Plasma devices
85.60.Pg Display systems
52.65.-y Plasma simulation
52.80.-s Electric discharges

Self-consistent microwave field and plasma discharge simulations for a moderate pressure hydrogen discharge reactor

K. Hassouni, T. A. Grotjohn, and A. Gicquel

J. Appl. Phys. 86, 134 (1999); http://dx.doi.org/10.1063/1.370710 (18 pages) | Cited 64 times

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A self-consistent two-dimensional model of the electromagnetic field and the plasma in a hydrogen discharge system has been developed and tested in comparison to experimental measurements. The reactor studied is a 25 cm diameter resonant cavity structure operating at 2.45 GHz with a silica belljar of 10 cm diameter and 17 cm height contained within the microwave cavity. The inside of the belljar where the discharge occurs contains a substrate holder of 5 cm diameter that is used to hold substrates for diamond deposition. The electromagnetic field model solves for the microwave fields using a finite difference time-domain solution of Maxwell’s equations. The plasma model is a three energy mode (gas, molecular vibration, and electron) and nine species (H2, H, H(n = 2), H(n = 3), H+, H2+, H3+, H−, electron) model which accounts for non-Boltzmann electron distribution function and has 35 reactions. Simulated characteristics of the reactor in two dimensions include gas temperature, electron temperature, electron density, atomic hydrogen molar fraction, microwave power absorption, and microwave fields. Comparisons of the model are made with close agreement to several experimental measurements including coherent anti-Stokes Raman Spectroscopy measurement of H2 temperature versus position above the substrate, Doppler broadening optical emission spectroscopy (OES) measurements of H temperature versus pressure, actinometry measurements of the relative H atom concentration, Hα OES intensity measurements versus position, and microwave electric field measurements. The parameter range studied includes pressures of 2500–11 000 Pa, microwave powers of 300–2000 W, and three vertical positions of the substrate holder. © 1999 American Institute of Physics.
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52.65.-y Plasma simulation
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
02.70.Bf Finite-difference methods
52.25.-b Plasma properties

Model of point-of-use plasma abatement of perfluorinated compounds with an inductively coupled plasma

Ales Fiala, Mark Kiehlbauch, Sergej Mahnovski, and David B. Graves

J. Appl. Phys. 86, 152 (1999); http://dx.doi.org/10.1063/1.370711 (11 pages) | Cited 17 times

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Point-of-use plasma abatement (PPA) has been proposed as one way to eliminate perfluorinated compound (PFC) emission from various tools used in integrated circuit manufacturing. PPA employs a high density plasma between the process tool turbomolecular pump and the backing pump. Oxygen is added to the process tool effluent upstream of the PPA tool. The mixture of oxygen and PFC-containing tool effluent enters the PPA tool and the PFCs are converted to products that can be scrubbed downstream of the backing pump. In this article, we present a model for the PPA tool operation, illustrating the principles with a mixture of C2F6/O2. A plasma model is coupled to a neutral transport and reaction model, including electron-impact molecular dissociation and subsequent gas phase chemistry. © 1999 American Institute of Physics.
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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
81.65.Cf Surface cleaning, etching, patterning
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Effects of plasma power on the epitaxial growth of (Ba0.48Sr0.52)TiO3 thin film

U. C. Oh, T. S. Kang, K. H. Park, and Jung Ho Je

J. Appl. Phys. 86, 163 (1999); http://dx.doi.org/10.1063/1.370712 (5 pages) | Cited 3 times

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We studied the effects of plasma power on the epitaxial behavior of (Ba0.48Sr0.52)TiO3 (BST) film growth on MgO (001) substrates using synchrotron x-ray scattering experiments. The BST films were grown on MgO (001) by magnetron sputtering at sputtering powers up to 3 W/cm2. We found that stress in the epitaxial BST films grown at lower powers was mainly induced by lattice mismatch, but in films grown at higher powers, it was primarily intrinsic stress. The films grown at higher powers were much more strained and exhibited better epitaxial quality. This study suggests that it is feasible to control the epitaxial quality of BST films just by varying the plasma power in magnetron sputtering. © 1999 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Cd Deposition by sputtering
77.80.-e Ferroelectricity and antiferroelectricity
77.55.-g Dielectric thin films
78.70.Ck X-ray scattering
61.05.cf X-ray scattering (including small-angle scattering)
68.60.Bs Mechanical and acoustical properties

Influence of the spatial laser intensity distribution on laser nitriding of iron

F. Landry, K.-P. Lieb, and P. Schaaf

J. Appl. Phys. 86, 168 (1999); http://dx.doi.org/10.1063/1.370713 (11 pages) | Cited 25 times

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Laser nitriding of iron and other metals is governed by the complicated interplay of the laser–plasma–solid interactions which lead to a superposition of several mechanisms. This work reports on the drastic influence of the spatial laser intensity distribution on the nitriding process. The effects of the lateral laser intensity on the nitrogen lateral and depth profiles, the phase formation, the surface topology, and the microhardness are revealed by resonant nuclear reaction analysis, Mössbauer spectroscopy, surface profilometry, and nanoindentation. Homogeneous laser beams lead to a strong reduction or almost the absence of the piston mechanism, thus confining the nitriding and the transport processes to the laser spot and avoiding the fallout. The details are discussed in relation to the results obtained for the raw-beam irradiations. Much higher nitrogen saturation concentrations can be achieved with a homogenized beam, but the surface hardness and the hardening depth are lower than in the case of irradiation with the raw beam. The ϵ nitride is only found for raw-beam irradiation. © 1999 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.82.Bg Metals and alloys
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
76.80.+y Mössbauer effect; other γ-ray spectroscopy
62.20.M- Structural failure of materials

Flexible boundary condition for a moving dislocation

K. Ohsawa and E. Kuramoto

J. Appl. Phys. 86, 179 (1999); http://dx.doi.org/10.1063/1.370714 (7 pages) | Cited 3 times

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It is well known that a boundary condition usually affects the result of the computer simulation of defects, especially extended defects like a straight dislocation, where the model size dependence of the result is sometimes observed. In order to solve this problem, a flexible boundary condition is developed for the simulation of a moving dislocation by applying the Lagrange principle in the present study. Under the flexible boundary condition described here, various properties of a screw dislocation, i.e., stable core structure, Peierls stress and glide property, are calculated in a square lattice and the model size dependence of the result is hardly obtained over a wide range. Contrary to the present flexible boundary condition, explicit size dependence is observed in the case of a rigid boundary condition due to a strong image force from the boundary. It is observed, however, that the result tends to approach that obtained in the above flexible boundary model as the size of the model lattice increases. Unfortunately, in the case of a screw dislocation with higher Peierls stress than 10−2G, the flexible boundary condition is not available, because lattice vibrations with a high frequency are emitted from the dislocation line during glide motion and the boundary cannot respond to these waves. © 1999 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
61.72.Bb Theories and models of crystal defects
66.30.Lw Diffusion of other defects

Scanning electron microscopy study of carbon nanotubes heated at high temperatures in air

Xuekun Lu, Kevin D. Ausman, Richard D. Piner, and Rodney S. Ruoff

J. Appl. Phys. 86, 186 (1999); http://dx.doi.org/10.1063/1.370715 (4 pages) | Cited 7 times

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Multiwalled carbon nanotubes (MWNTs) were dispersed in 2-butanol and dropped onto a V-ridge, lithographically patterned Si substrate that was coated with a thin layer of gold. These MWNTs were shown by scanning electron microscopy (SEM) to conform to the V-ridge surface topology at room temperature, which is thus useful for introducing kinks (at the apex of the V-ridge and the bottom of the trenches between V ridges). The substrate-supported MWNTs were then heated in air at temperatures from 673 to 1173 K for varying exposure times and were monitored with SEM. A 122 kJ mol−1 activation energy for complete oxidation was obtained, and preferential oxidation at kink sites was observed on some MWNTs at high temperatures. The dominant mode of oxidation was either thinning of the walls of the MWNTs or sequential oxidation of the component tubes in bundles. Some MWNTs, which at room temperature conformed to the V-ridge surface topology, detached (“sprang” away) from the substrate surface, demonstrating that the MWNTs are under tensile stress, but are held to the surface by van der Waals attractive forces, which can be overcome by exposure to higher temperatures. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Mq Oxidation

Characterization of vacancies in as-grown and electron irradiated α-quartz by means of positron annihilation

S. Dannefaer, T. Bretagnon, and D. Craigen

J. Appl. Phys. 86, 190 (1999); http://dx.doi.org/10.1063/1.370716 (8 pages) | Cited 1 time

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Synthetic α-quartz is shown to contain a significant concentration (several ppm) of vacancies. The major concentration of vacancies is suggested to be in the form of divacancies, giving rise to a positron lifetime of 285±5 ps, but in addition, there is a much smaller concentration of large vacancy clusters that are observable only after electron irradiation, whereupon they give rise to a positron lifetime close to 425 ps. Annealing between 900 and 1000 °C causes disappearance of divacancies and formation of vacancy clusters giving rise to a positron lifetime close to 300 ps. Above ∼ 950 °C positronium is formed with an exceptionally long lifetime (3–5 ns) ascribable to the formation of an amorphous phase connected with the thermal instability of β-quartz. Electron irradiation (2.3 MeV at 8 °C) gave rise to a 250±5 ps lifetime component interpreted to signify formation of neutral monovacancies, V0 and/or VSi. Their introduction rate is nonlinear, decreasing abruptly by a factor of ∼5 above a dose of 1×1017 e/cm2, an effect which is ascribed to the removal of irradiation-produced vacancy-interstitial complexes by means of electron-hole recombination during the irradiation. © 1999 American Institute of Physics.
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61.80.Fe Electron and positron radiation effects
61.82.Ms Insulators
61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation

Temperature dependence of the properties of heteroepitaxial Y2O3 films grown on Si by ion assisted evaporation

M.-H. Cho, D.-H. Ko, K. Jeong, I. W. Lyo, S. W. Whangbo, H. B. Kim, S. C. Choi, J. H. Song, S. J. Cho, and C. N. Whang

J. Appl. Phys. 86, 198 (1999); http://dx.doi.org/10.1063/1.370717 (7 pages) | Cited 11 times

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Heteroepitaxial Y2O3 films were grown on an Si(111) substrate by ion assisted evaporation in an ultrahigh vacuum, and their properties such as crystallinity, film stress, and morphological change were investigated using the various measurement methods. The crystallinity was assessed by x-ray diffraction (XRD) and reflection high-energy electron diffraction. Interface crystallinity was also examined by Rutherford backscattering spectroscopy (RBS) channeling and transmission electron microscopy. The strain of the films was measured by RBS channeling and XRD. Surface and interface morphological characteristics were observed by atomic force microscopy and x-ray scattering method. By comparing the interface with the surface characteristics, we can conclude that many defects at the interface region were generated by interface interaction between the yttrium metal and Si substrate. Moreover, the film quality dominantly depended on the deposition temperature. The crystallinity was greatly improved and the surface roughness was drastically decreased in the temperature range 500–600 °C. On the other hand, in the temperature range 600–700 °C, the compressive stress and film density were further increased, and the island size decreased. Also, the shape of the surface islands was transformed from elliptical to triangular. The film stress was found primarily at the interface area because of the interaction between yttrium and Si substrate. © 1999 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
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness

Charge trapping and defect segregation in quartz

M. A. Stevens Kalceff, G. J. Thorogood, and K. T. Short

J. Appl. Phys. 86, 205 (1999); http://dx.doi.org/10.1063/1.370718 (4 pages) | Cited 18 times

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Irradiation induced charging of wide band gap materials may significantly influence the development of radiation damage and associated defect migration. Charge trapped at irradiation induced and/or pre-existing defects induces a localized electric field within the irradiated volume of specimen. The powerful combination of cathodoluminescence microanalysis and electric force microscopy allows direct monitoring of the development of the irradiation induced charge distribution and its effect on the microscopic spatial segregation of defects. These techniques have been used to demonstrate the important influence of the induced local field on the microscopic defect structure of quartz. © 1999 American Institute of Physics.
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61.80.Fe Electron and positron radiation effects
61.82.Ms Insulators
64.75.-g Phase equilibria
78.60.Hk Cathodoluminescence, ionoluminescence
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Near edge x-ray absorption fine structure characterization of polycrystalline GaN grown by nitridation of GaAs (001)

M. Lübbe, P. R. Bressler, W. Braun, T. U. Kampen, and D. R. T. Zahn

J. Appl. Phys. 86, 209 (1999); http://dx.doi.org/10.1063/1.370791 (5 pages) | Cited 9 times

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The phase composition and microcrystalline structure of thin gallium nitride (GaN) grown by nitridation of (001) oriented gallium arsenide (GaAs) was investigated by near edge x-ray absorption fine structure (NEXAFS) spectroscopy. The GaN layer was grown by the interaction of atomic nitrogen produced by a rf-plasma source with the clean GaAs surface at a temperature of 700 °C. In this way a GaN film thickness of ≈100 Å was obtained after 6 h of nitridation. Using surface sensitive NEXAFS at the nitrogen K edge, the partial nitrogen p density of states was determined. Comparing the data to reference spectra of hexagonal and cubic GaN, the amount of cubic GaN in the nitrided film was estimated to be 20%–25%. Varying the angle of polarization of the synchrotron radiation with respect to the sample surface, the geometric anisotropy of the GaN film, and thus its crystalline structure, was probed, providing information on the orientation of the GaN microcrystallites. The results from the polarization dependent measurements suggest that the c axes of the hexagonal GaN crystallites in the film are mainly oriented parallel to the (001) direction of the GaAs substrate. The c axes of roughly 45% of the crystallites are tilted by 90° and lie parallel to the surface plane. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.70.Dm X-ray absorption spectra
81.05.Ea III-V semiconductors
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
71.20.Nr Semiconductor compounds

Migration energy for the silicon self-interstitial

Anders Hallén, Niclas Keskitalo, Lalita Josyula, and Bengt G. Svensson

J. Appl. Phys. 86, 214 (1999); http://dx.doi.org/10.1063/1.370719 (3 pages) | Cited 16 times

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The generation of vacancy-related point defects in low dose 1.3 MeV proton irradiated high purity silicon has been investigated. The dose rate was varied to give a total dose of 5×109 cm−2 at irradiation temperatures from 70 to 295 K. The inverse dose rate effect, i.e., a decrease in the production of room temperature stable vacancy related defects for increasing dose rates, is also shown to be thermally activated and involve long range migration of the silicon self-interstitial. The inverse dose rate effect is utilized to obtain a value of 0.065±0.015 eV for the migration energy of the Si interstitial at room temperature and below. This is an experimental estimate of the interstitial migration energy and the low value suggests that ionization enhanced diffusion is important for the motion of Si interstitials. © 1999 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects

Deep level analysis of radiation-induced defects in Si crystals and solar cells

Masafumi Yamaguchi, Aurangzeb Khan, Stephen J. Taylor, Koshi Ando, Tsutomu Yamaguchi, Sumio Matsuda, and Takashi Aburaya

J. Appl. Phys. 86, 217 (1999); http://dx.doi.org/10.1063/1.370698 (7 pages) | Cited 15 times

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Deep level transient spectroscopy (DLTS) analysis of radiation-induced defects in p-type Si crystals and solar cells has been carried out to clarify the mechanism of the anomalous degradation of Si n+–p–p+ structure space cells induced by high-energy, high-fluence electron/proton irradiations. A large concentration of a minority-carrier trap with an activation energy of about 0.18 eV has been observed in irradiated p-Si using DLTS measurements, as well as the majority-carrier traps at around Ev+0.18 eV and Ev+0.36 eV, Correlations between DLTS data and solar-cell properties for irradiated and annealed Si diodes and solar cells have shown that type conversion of p-Si base layer from p-type to n-type is found to be mainly caused by introduction of the 0.18 eV minority-carrier trap center, that is, this center acts as a deep-donor center. The Ev+0.36 eV majority-carrier trap center is thought to also act as a recombination center that decreases minority-carrier lifetime (diffusion length). Moreover, origins of radiation-induced defects in heavily irradiated p-Si and generation of deep-donor defect has also been discussed. © 1999 American Institute of Physics.
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71.55.Cn Elemental semiconductors
84.60.Jt Photoelectric conversion
72.80.Cw Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.80.Jh Ion radiation effects
61.80.Fe Electron and positron radiation effects
61.72.Cc Kinetics of defect formation and annealing

Residual stress distribution in the direction of the film normal in thin diamond films

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

J. Appl. Phys. 86, 224 (1999); http://dx.doi.org/10.1063/1.370720 (6 pages) | Cited 11 times

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The residual stress distribution in the direction of the film normal in thin diamond films deposited on Si substrate has been evaluated together with the distribution of Young’s modulus. The films were deposited on the substrate by the microwave chemical vapor deposition method. It has been observed that the curvature of the diamond films delaminated from the Si substrate is functionally dependent on the film thickness. Young’s modulus, which has been estimated by the film bending test in conjunction with a finite element method of analysis, appears to be gradually decreasing towards the adhesion interface. On the basis of detailed measurement of curvature and with the aid of Raman spectroscopy, the residual strain distribution in the film has been evaluated. Although the average intrinsic stress was tensile as reported earlier, we have found that a huge compression concentrates in the very small region near the adhesion interface. This finding shows evidence that something happens on the interface, which is absolutely different from the subsequent process of film growth. © 1999 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
68.35.Gy Mechanical properties; surface strains
02.70.Dh Finite-element and Galerkin methods

Electron diffraction from polycrystalline materials showing stress induced preferred orientation

D. R. McKenzie and M. M. M. Bilek

J. Appl. Phys. 86, 230 (1999); http://dx.doi.org/10.1063/1.370721 (7 pages) | Cited 24 times

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The Gibbs free energy as generalized by J. F. Nye [Physical Properties of Crystals (Clarendon Press, Oxford, 1957), p. 179] is minimized in thermodynamic systems held at constant temperature and constant stress. This function is orientation dependent in all crystal systems in stress fields which are not purely hydrostatic. There are situations in which preferred orientation arises as a result of the synthesis of materials under impressed stress conditions such as thin film growth under ion bombardment and the pressing of powders into solids. Here, we derive the orientational constraints for cubic crystals which result from growth under a general biaxial stress field. The sign of the expression δ = s11−s12−½s44 determines the behavior of a cubic crystal. Electron diffraction patterns of face-centered-cubic specimens with both positive and negative values of δ are calculated using a program in MATLAB and displayed in a form suitable for direct comparison with experiment. The use of a biaxial stress with unequal principal components for producing highly oriented polycrystalline material is discussed. In the case of δ positive, as occurs in silicon, the preferred orientation is simply an alignment of the 〈100〉 directions along the principal stresses. For δ negative, as occurs in titanium nitride, the preferred orientation depends on the ratio of the principal stresses and low index directions are aligned with the principal stresses only when the principal stresses are either equal or one of them is zero. In the general case, arc-like diffraction patterns are produced. The results of a calculation of a diffraction pattern from a cross-sectional TiN film are compared with diffraction patterns reported by L. Hultman et al. [J. Appl. Phys. 78, 5395 (1995)] and show good agreement. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
65.20.-w Thermal properties of liquids
65.40.gd Entropy
68.60.Dv Thermal stability; thermal effects

Carbon clustering kinetics in detonation wave propagation

J. A. Viecelli and F. H. Ree

J. Appl. Phys. 86, 237 (1999); http://dx.doi.org/10.1063/1.370722 (12 pages) | Cited 10 times

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Much of the nonideality of insensitive carbon rich explosives such as TATB is thought to be caused by a late-time slow release of energy associated with diffusion limited growth of carbon clusters. We have adapted Shaw and Johnson’s approximate analytic solution of the Smoluchowski rate equations for the evolution of the cluster size distribution function for use in hydrodynamic calculations and in Wood and Kirkwood approximate theory for the detonation velocity-curvature relationship. Solutions for the effect of carbon cluster growth on the structure of the reaction zone are obtained, and the results are compared with available experimental data. © 1999 American Institute of Physics.
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82.30.Nr Association, addition, insertion, cluster formation
36.40.Jn Reactivity of clusters
82.20.Hf Product distribution
82.33.Vx Reactions in flames, combustion, and explosions
47.40.Nm Shock wave interactions and shock effects

Strain characterization of polycrystalline diamond and silicon systems

E. Anastassakis

J. Appl. Phys. 86, 249 (1999); http://dx.doi.org/10.1063/1.370723 (10 pages) | Cited 23 times

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The phonon deformation potentials of polycrystalline diamond and silicon, derived through the Voigt–Reuss–Hill averaging technique, are used to establish the systematics of strain characterization of polycrystalline films, considering all possible stress configurations. The results are compared to Raman data from the literature. © 1999 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.-x Mechanical properties of solids
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
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