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1 Sep 1998

Volume 84, Issue 5, pp. 2371-2982

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Mechanism of topography formation during CO2 laser texturing of silicate glasses

Ted D. Bennett, Douglas J. Krajnovich, Lei Li, and Dujiang Wan

J. Appl. Phys. 84, 2897 (1998); http://dx.doi.org/10.1063/1.368396 (9 pages) | Cited 18 times

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A theoretical picture is advanced to explain experimental results of CO2 laser texturing of silicate glasses. Common characteristics among several glass types are found that corroborate observations made by other investigators and establish features of glass laser texture. The principal experimental results include increasing bump height with pulse energy (above some threshold); bump width scales with the bump height; annealing, before or after laser texture, reduces bump heights; and finally, further growth in bump height occurs with a finite number of laser pulses subsequent to the first. Explanations for these results have been unified in terms of a “fictive temperature map” that relates microstructure to the thermal history of the glass. On this map, the glass transition temperature identifies a fictive temperature at which the rate of change of temperature is comparable to the rate of change of the microstructure. Therefore, the time scale imposed by the laser pulse can elevate the transition temperature of the glass, making accessible high fictive temperatures to the heat affected zone. As a result of this description we can offer explanations to important characteristics of glass laser texturing, perhaps most notably the nonlinear threshold dependence of bump height on pulse energy. We can also explain the observed bump growth with multiple laser pulses, the effect of chemical strengthening, and the effect of annealing before or after laser texturing. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Ds Laser-beam impact phenomena
61.82.Ms Insulators
61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.72.Cc Kinetics of defect formation and annealing

Surfactant effect of Sb on the growth of (111) orientated fullerene thin films

J. G. Hou, Wentao Xu, Wang Haiqian, and Yang Li

J. Appl. Phys. 84, 2906 (1998); http://dx.doi.org/10.1063/1.368445 (3 pages) | Cited 4 times

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We report a method for the growth of C60 single crystal thin films using Sb as the surfactant. It is found that the growth mechanism of C60 thin films on the substrates of (001) NaCl was significantly affected by the thin layer of Sb when the substrate temperature is 160 °C. (111) orientated C60 single crystal films were prepared by this method, and the average grain size of our films is about one order of magnitude larger than that of the polycrystalline films grown without Sb. The possible mechanism of the metal enhanced C60 single crystal growth has been discussed. © 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
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Studies of carbon nitride thin films synthesized by KrF excimer laser ablation of graphite in a nitrogen atmosphere

Y. F. Lu, Z. M. Ren, W. D. Song, D. S. H. Chan, T. S. Low, K. Gamani, G. Chen, and K. Li

J. Appl. Phys. 84, 2909 (1998); http://dx.doi.org/10.1063/1.368446 (4 pages) | Cited 24 times

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Carbon nitride thin films were deposited on silicon wafers by pulsed KrF excimer laser (wavelength 248 nm, duration 23 ns) ablation of graphite in a nitrogen atmosphere. Different excimer laser fluences and pressures of the nitrogen atmosphere were used in order to achieve a nitrogen content as high as possible in the deposited thin films. Fourier transform infrared and x-ray photoelectron spectroscopies were used to identify the binding structure and the content of the nitrogen species in the deposited thin films. The N/C ratio 0.42 was obtained at an excimer laser fluence of 0.8 J cm−2 at a repetition rate of 10 Hz under a nitrogen pressure of PN = 100 mTorr. A high content of C�N double bond instead of C�N triple band was indicated in the deposited thin films. Ellipsometry was used to analyze the optical properties of the deposited thin films. The carbon nitride thin films have amorphous-semiconductorlike characteristics with an optical band gap Eopt of 0.42 eV. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
61.66.Bi Elemental solids
61.66.Dk Alloys
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
79.60.Ht Disordered structures
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Processing factor dependence of resistivity parameters of ruthenate-based thick film resistors with low temperature coefficients

Gary M. Crosbie, F. Johnson, and W. Trela

J. Appl. Phys. 84, 2913 (1998); http://dx.doi.org/10.1063/1.368447 (7 pages) | Cited 3 times

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Many analog sensor and control circuits take advantage of the low (<100ppm/°C) temperature coefficient of resistance (TCR) of thick film resistors which are based on fired ruthenate-glass nanocomposites. To manufacture resistors with even smaller TCRs, a knowledge of the effects of processing on conduction mechanism parameters is of particular importance, because TCR is fixed in firing and cannot be trimmed later to a target value, as resistance can be. The peak firing temperature and time were varied, and a special four-probe dc design was used to minimize contact and printing nonuniformities. Corresponding to a greater energy level degeneracy in larger particles, the electrostatic charging energy decreased with the observed coarsening of the resistor microstructure. For the primary data set, the charging energy decreased (at >95% confidence) from 1.56 to 1.15 meV with increasing firing temperature (from 845 to 855 °C) and time (from 8 to 11 min). Model-based estimation of parameters is a means to provide quantitative understanding of how TCR and underlying conduction are controlled by process factors. © 1998 American Institute of Physics.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Mh Cermets, ceramic and refractory composites

Improvement of CdTe solar cell performance with discharge control during film deposition by magnetron sputtering

R. Wendt, A. Fischer, D. Grecu, and A. D. Compaan

J. Appl. Phys. 84, 2920 (1998); http://dx.doi.org/10.1063/1.368397 (6 pages) | Cited 3 times

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We have used a combination of rf and dc excitation to control the plasma density during planar magnetron sputter deposition of CdTe films and CdTe-based solar cells. While adding dc current we have adjusted the rf power to maintain a constant deposition rate. We find that the lower plasma density obtained with negative dc currents yields films with a more highly faceted surface, more columnar growth structure, and stronger photoluminescence. The solar cells prepared with rf sputtered CdS and with CdTe deposited at reduced rf power and −70 mA of dc current produce substantially higher performance. The results indicate advantages to reducing the ion bombardment energy and flux to the growing film by the addition of dc control during rf sputtering from highly insulating semiconductor targets. © 1998 American Institute of Physics.
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84.60.Jt Photoelectric conversion
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
81.15.Cd Deposition by sputtering

Mean energy required to produce an electron-hole pair in silicon for photons of energies between 50 and 1500 eV

F. Scholze, H. Rabus, and G. Ulm

J. Appl. Phys. 84, 2926 (1998); http://dx.doi.org/10.1063/1.368398 (14 pages) | Cited 28 times

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The photon energy dependence of the mean energy W required to produce an electron-hole pair in silicon for photons with energies between 50 and 1500 eV was determined from the spectral responsivity of selected silicon photodiodes. The spectral responsivity was measured with a relative uncertainty of less than 0.3% using monochromatized synchrotron radiation whose radiant power was measured with a cryogenic electrical substitution radiometer. In order to deduce W from the spectral responsivity of photodiodes with a relative uncertainty of about 1%, a method for the calculation of photon and electron escape losses from silicon photodiodes was developed and the model for the charge carrier recombination losses was improved. In contrast to recent theoretical and experimental results, a constant value W = (3.66±0.03) eV was obtained in the photon energy range from 50 to 1500 eV. The present experimental results are confirmed by calculation of the pair creation energy in silicon from data from the literature for the relevant material properties. The difference from previous theoretical work is due to different assumptions about the influence of the band structure of silicon. © 1998 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Cw Elemental semiconductors
85.60.Dw Photodiodes; phototransistors; photoresistors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Reliability of metal semiconductor field-effect transistor using GaN at high temperature

Seikoh Yoshida and Joe Suzuki

J. Appl. Phys. 84, 2940 (1998); http://dx.doi.org/10.1063/1.368448 (3 pages) | Cited 19 times

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The reliability of a GaN metal semiconductor field-effect transistor (MESFET) was investigated. We used Au/Pt as a Schottky gate and Ti/Al as a source drain of a GaN MESFET. The thermal stress test of the GaN MESFET at high temperature was investigated. It was found that no change of FET characteristics was observed even after the device was heated at 400 °C for 1000 h. Furthermore, using a GaN MESFET which was heated at 400 °C for 1000 h, a life of FET at 350 °C was examined by a continuously current injection at 350 °C. We confirmed that the FET performance did not change at 350 °C for 150 h. No degradation of metal–semiconductor interface was observed by secondary ion mass spectrometry and a transmission electron microscope. The reliability of the GaN MESFET as a high-temperature operation transistor was fully demonstrated. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
73.61.Ey III-V semiconductors

Reliability of metal–oxide–semiconductor capacitors on nitrogen implanted 4H-silicon carbide

M. Treu, E. P. Burte, R. Schörner, P. Friedrichs, D. Stephani, and H. Ryssel

J. Appl. Phys. 84, 2943 (1998); http://dx.doi.org/10.1063/1.368399 (6 pages) | Cited 6 times

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4H-SiC epitaxial layers were implanted with nitrogen up to doses of 1×1015 cm−2 and annealed at different temperatures. Atomic force microscopy revealed that the roughness of the SiC surface increased with the annealing temperature. It was shown that the oxide grows thicker on substrates with doping levels exceeding 1×1018 cm−3. The barrier height at the SiC/SiO2 interface, determined by voltage ramping on metal–oxide–semiconductor capacitors, decreased with increasing implantation dose. This decrease was attributed to residual implantation damage. Constant current injection experiments revealed an opposite charge buildup at the SiC/SiO2 interface for the highest implantation dose compared to samples with no implantation. It was shown that the breakdown behavior can be improved by annealing at 1700 °C compared to 1450 °C despite a higher surface roughness. © 1998 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices
84.32.Tt Capacitors
61.72.up Other materials
85.40.Ry Impurity doping, diffusion and ion implantation technology

Store–restore operation of flux quanta in coplanar type high Tc superconductive quantum interference devices

Hiroyuki Fuke, Kazuo Saitoh, Tadashi Utagawa, and Youichi Enomoto

J. Appl. Phys. 84, 2949 (1998); http://dx.doi.org/10.1063/1.368400 (4 pages) | Cited 1 time

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For a superconductive quantum interference device (SQUID) with rather large loop inductance for a single flux quantum, store–restore operation of flux quanta has been examined by external current pulses. To sense the stored flux quanta, the device includes another directly coupled SQUID as a magnetometer. Both of the coplanar type dc SQUIDs have been composed of Josephson junctions made by the narrow-focused ion beam irradiation technique in single-layer NdBa2Cu3O7−δ superconducting films. The SQUID has a critical current of 375 μA and an inductive parameter (βL) of 32. The number of stored flux quanta is controlled by the pulse signal height and the input terminal, but not by the number of pulses. © 1998 American Institute of Physics.
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85.25.Cp Josephson devices
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures
74.50.+r Tunneling phenomena; Josephson effects
74.72.-h Cuprate superconductors
74.25.Sv Critical currents

Characterization of breakdown phenomena in light emitting silicon n+p diodes

Lukas W. Snyman, Herzl Aharoni, and Monuko du Plessis

J. Appl. Phys. 84, 2953 (1998); http://dx.doi.org/10.1063/1.368401 (7 pages) | Cited 6 times

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A 10 kV, 10−10 A focused electron beam was used to map localized charge multiplication, and localized avalanche breakdown sites in the depletion region of light emitting silicon n+p junctions. It was observed that the localized avalanche breakdown sites led to the formation of large densities of extremely small current filaments in the junction. The dimension of each filament was well into the submicron range (100–150 nm in diameter) and the densities of the filaments varied laterally across the junction between 4×108 and 4×1010 cm−2. Accurate and high resolution maps of the current filaments could be obtained. The formation of the individual current filaments (microavalanche sites) at a submicron level are apparently related to localized defect and materials effects. The distribution of the current filaments at the micron level relates to the strength and distribution of electric field at the junction interface. Direct evidence has been obtained that the nonuniformities in the light emission patterns on a larger scale (10–100) microns are controlled by dopant striations on the lower doped p-side of the diode junction. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Cw Elemental semiconductors
73.50.Fq High-field and nonlinear effects
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