bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxide thickness dependence of interface trap generation in a metal-oxide-semiconductor structure during substrate hot-hole injection
Authors: Khosru Quazi Deen Mohd , Yasuda Naoki , Taniguchi Kenji , Hamaguchi Chihiro
Published: July 2002

Oxide thickness dependence of interface trap generation in a metal-oxide-semiconductor (MOS) structure is investigated using uniform hot-hole injection into the gate oxides of p-channel MOS transistors with very thin oxide thicknesses. Significant dependence of interface trap generation on oxide thickness (tox) is found for very thin oxides and the dependence disappears for tox≥8 nm. A universal relationship between hole trapping in the oxide bulk and interface trap generation at the Si/SiO2 interface is observed experimentally. The experimental results suggest that interface trap generation is a process involving hole trapping in the oxide bulk, rather than a pure interfacial process. No oxide thickness dependence of interface trap generation for thicker oxides (tox≥8 nm) is in agreement with previous reports and the overall dependence can consistently be explained with the help of the spatial distribution of trapped holes in the oxide. In contrast to the reports describing delayed interface trap formation, we observed oxide field-dependent annealing of the generated interface traps after the end of hole injection.
Possibility of dc drift reduction of Ti:LiNbO3 modulators via dry O2 annealing process
Authors: Nagata Hirotoshi , Ichikawa Junichiro , Kobayashi Masanobu , Hidaka Jun , Honda Hideki , Kiuchi Kazumasa , Sugamata Tohru
Published: July 2002

The possibility of the dc drift reduction of Ti:LiNbO3 optical modulators via the dry O2 annealing process of the wafer is investigated. In such modulators, the hydrogen impurities are reduced compared against those in the wet O2 annealed ones which exhibit large dc drifts. The dc drifts are observed to be less than 3 V for the dc bias application of 5 V at 80 °C through 60 h, but the dc drift in the second measurement of the same modulator is found to 5 V. After the bias application, the migration of H+ ions are observed in the Ti:LiNbO3.
Reactive ion etching of GaN using BCl3
Authors: Lin M. E. , Fan Z. F. , Ma Z. , Allen L. H. , Morkoç H.
Published: July 2002

Reactive ion etching with SiCl4 and BCl3 of high quality GaN films grown by plasma enhanced molecular beam epitaxy is reported. Factors such as gas chemistry, flow rate, and microwave power affecting the etching rate are discussed. The etch rate has been found to be larger with BCl3 than with SiCl4 plasma. An etch rate of 8.5 Å/s was obtained with the BCl3 plasma for a plasma power of 200 W, pressure of 10 mTorr, and flow rate of 40 sccm. Auger electron spectroscopy (AES) was used to investigate the surface of GaN films after etching. Oxygen contamination has been detected from the AES profiles of etched GaN samples.
Nonlinearity and inversion of femtosecond single- and two-photon photoelectric emission sensitivities from gold
Authors: Girardeau-Montaut J. P. , Girardeau-Montaut C. , Moustaizis S. D. , Fotakis C.
Published: July 2002

We report measurements of the two-photon photoemission sensitivity of gold at 496 nm, for three incidence angles of a p-polarized laser beam, with a 450-fs pulse duration, produced by a KrF pumped dye laser. The nonlinear growing of the photoelectric efficiency versus the laser peak intensity, in the range of 5–9 GW/cm2, is demonstrated to be consecutive to the thermal nonequilibrium between the electrons and the lattice at the surface of the metal. We also observe with a solid that the single-photon photoelectric sensitivity, measured by us previously, can be lower than the one for the two-photon process, when the incident laser intensity is high enough. The crossing point of respective sensitivities for 248- and 496-nm laser radiations is about 5.5×10−6 A/W and corresponds to a laser intensity of about 6.5 GW/cm2. This effect, which can be only observed with ultrashort laser pulses, represents a significant step towards the realization of very high brightness electron beams.
Enhanced damage accumulation in carbon implanted silicon
Authors: de Souza J. P. , Boudinov H. , Fichtner P. F. P.
Published: July 2002

The accumulation of damage in Si implanted with 12C+ was investigated experimentally using aligned Rutherford backscattering analysis. The damage profiles in Si implanted with 12C+ or 11B+ at 50 keV to the same doses and dose rate were compared. It was found that the damage accumulates at a noticeably higher rate by 12C+ implantation than by 11B+, especially for doses ≳2×1015 cm−2. In order to explain our results we suggest that self-interstitial Si atoms are captured by the implanted C atoms, forming complex defects which are stable at room temperature.
Phosphorus-induced positive charge in native oxide of silicon wafers
Authors: Shimizu Hirofumi , Munakata Chusuke
Published: July 2002

Alternating current surface photovoltage is enhanced in p-type silicon (Si) wafers, which are rinsed with a phosphorus (P)-contaminated water solution, whereas it is reduced in n-type Si wafers, indicating that the positive charge appears at wafer surfaces. This result suggests that P reacts with SiO2 in the form of (POSi)+ network, causing a positive charge in the native oxide.
Strain effects on the energy bands of ZnSe films grown on GaAs substrates by spectroscopic ellipsometry
Authors: Dahmani R. , Salamanca-Riba L. , Nguyen N. V. , Chandler-Horowitz D. , Jonker B. T.
Published: July 2002

Room-temperature spectroscopic ellipsometry measurements were carried out on ZnSe thin films grown on (001)GaAs substrates by molecular-beam epitaxy for the study of the lattice mismatch-induced strain at the interface. The magnitude of the absorption coefficient at the E0+Δ0 critical point is very sensitive to the strain in the film. The variation in the magnitude of the absorption coefficient is used to estimate the critical thickness for the onset of dislocation generation. Almost complete relaxation of the films was obtained for thicknesses higher than 500 nm. Also, the strain-induced coupling between the valence subbands was found to cause additional shifting of the light-hole subband.
Spontaneous modulation of composition in Ta-Si films produced by pulsed laser deposition
Authors: Nevolin V. , Chubunova E. , Khabelashvili I. , Lebedinskii Yu. , Zenkevich A. , Uvarov O. B.
Published: July 2002

Ta-Si films with different composition ratio were prepared by the pulsed laser deposition technique on a Si3N4/Si(100) substrate at room temperature. Cross-sectional transmission electron spectroscopy (TEM) and Auger electron spectroscopy in combination with Rutherford backscattering spectroscopy were employed to investigate the deposited structures. As-deposited films were found to be spontaneously modulated with composition along the growth direction, the period of the structure depending upon Si/Ta average composition ratio, and is about 50 Å in thickness. Auger electron spectroscopy analysis confirms the codeposited Ta-Si layers reveal an oscillating character of the chemical bonding. The contrast analysis of cross-sectional TEM images and the study of electron-diffraction patterns identify amorphous state (up to the resolution of analytical technique) of the deposited layers. The observed effect is attributed to the nature of the depositing flux.
Influence of strain on interfacial recombination in AlGaInP/GaInP double heterostructures
Authors: Domen K. , Kondo M. , Tanahashi T.
Published: July 2002

Using time-resolved photoluminescence, we examined the carrier-recombination process in strained AlGaInP/GaInP double heterostructures grown by metal-organic vapor phase epitaxy. We found that interfacial recombination dominates the process at room temperature, and that the interfacial recombination is enhanced by tensile strain and reduced by compressive strain.
Hybrid Shubnikov–de Haas-photoluminescence analysis of two-dimensional electron density in strained quantum well structures with heavily doped contact layers
Authors: Lovejoy Michael L. , Simmons Jerry A. , Ho Pin , Martin Paul A.
Published: July 2002

A hybrid analysis technique is presented to accurately extract the two-dimensional (2D) electron density of PHEMT structures in which multiple subbands are occupied and severe parallel conduction by heavily doped contact layers occurs. Complications due to shorted Hall voltages by the parallel contact layer, which precludes simple Hall analysis, and to multiple subband occupation, which requires high magnetic-field sweeps in Shubnikov–de Haas (SdH) measurements, are eliminated by this hybrid analysis that combines SdH measurements with photoluminescence measurements to extract the total 2D density. Comparisons with other methods demonstrate the high accuracy of this new technique.
Field electron emission from hydrogenated amorphous silicon films on tungsten: Light-induced effects
Authors: Joag D. S. , Sharma A. K. , More M. A. , Dusane R. O. , Takwale M. G.
Published: July 2002

Field electron emission from a hydrogenated amorphous silicon deposited tungsten tip has been studied. The effect of prolonged (hourly) exposure to light on the field electron emission current has been investigated. The current-voltage characteristics of the as-deposited, light exposed, and annealed states of the emitter showed semiconducting behavior in accordance with the Fowler–Nordheim law. In case of an initially annealed emitter tip, the field emission current was found to increase monotonically with the light exposure, reversibly for shorter durations of a few minutes. The effect of long term (hourly) exposure of light resulted in the increase in the field emission current level nonlinearly with the exposure time. The current level did not come down to the original level even after switching off the light in contrast to the effect of short duration light exposure. The enhancement in the field emission current has been attributed to tunneling though the dangling bond states created by light exposure. The results have been discussed in light of the Staebler–Wronski effect.
Accurate fabrication of anamorphic microlenses and efficient collimation of tapered unstable-resonator diode lasers
Authors: Liau Z. L. , Walpole J. N. , Mull D. E. , Dennis C. L. , Missaggia L. J.
Published: July 2002

Highly precise f/0.9 refractive anamorphic microlenses have been fabricated in GaP substrates by mass-transport smoothing of etched multiple-mesa structures. Astigmatic outputs from tapered unstable-resonator lasers have been collimated to a nearly round beam of near diffraction-limited 0.43° divergence. Initial good efficiencies (as high as 35%) have been obtained in coupling the laser output into a single-mode fiber. These lenses are highly promising for realizing simple compact optical systems that exploit the high power capability of tapered lasers.
Running waveguide discharge for inner coating of metal tubes
Authors: Hytry R. , Möller W. , Wilhelm R.
Published: July 2002

A plasma-enhanced chemical vapor deposition process by means of the so-called running discharge has been developed. Amorphous hydrogenated carbon (C:H) films were deposited over a length of 2.5 m on the inner wall of an assembled waveguide system. The average deposition rate from a running discharge in methane was 0.27 Å/s. An increase of the average deposition rate to 2.6 Å/s was achieved using acetylene as process gas, while the H/C ratio in the C:H films remains nearly constant at one. The breakdown of a discharge in the metallic waveguide has been studied in argon plasmas depending on magnetic field, microwave power, and gas pressure. A sharp transition between a magnetically enhanced localized discharge and a running discharge was observed at increasing pressure in the range of some Pascal at a microwave power of 100 W. The running velocity (∼104 m/s) of the plasma package increases with increasing microwave power and increasing gas pressure. This plasma behavior has been further investigated by means of the power balance and plasma modeling in methane.
Direct bonding of organic materials
Authors: Spierings G. A. C. M. , Haisma J.
Published: July 2002

Direct bonding of polymethylmethacrylate (PMMA) is described as an example of the applicability of direct bonding to organic materials such as polymers. Direct bonding of a PMMA wafer to itself and to silicon and fused silica wafers is realized. At room temperature, the value of the bond energy indicates the presence of weak chemical interactions at the bonded interface. Heating a bonded PMMA/PMMA wafer pair to the glass transition temperature of PMMA (105 °C) and higher temperatures causes the two surfaces to fuse and the interface to become bridged by polymer chains.
Effects of dual spectral sources on the curing of polyimide films by rapid isothermal processing
Authors: Wait M. A. , Mavoori J. , Singh R. , Harriss J. E. , Poole K. F. , Kolis J. W. , Thakur R. P. S. , Ogale A. A.
Published: July 2002

There are fundamental differences between conventional furnace processing (CFP) and rapid isothermal processing (RIP). The radiation spectrum of a conventional furnace consists of photons in the infrared and longer wavelength regions, whereas the spectrum of the incoherent light sources used in RIP consists of some UV, visible, and infrared photons. As compared to CFP, the photophysical and photochemical effects associated with RIP provide the capability of lower temperature processing. However, a further reduction in processing temperature can be achieved by the use of vacuum ultraviolet (VUV) and UV light sources in conjunction with a single spectral source RIP. We provide experimental results for the dual spectral source curing of polyimide dielectric films. Our findings indicate that simultaneous exposure of polyimide samples to both VUV and conventional RIP sources during processing cured the polyimide more rapidly and at lower temperatures than did single spectral source RIP alone. These results may be of great importance for the RIP of the future generation of semiconductor devices.
Single-domain layers formed in heat-treated LiTaO3
Authors: Åhlfeldt Henrik
Published: July 2002

Ferroelectric single-domain surface layers are formed in z-cut LiTaO3 following heat treatment above the Curie temperature. The polarity of the layers is the same as the polarity of the previously observed domain-inverted layers formed in heat-treated LiNbO3. The physical mechanisms behind these two phenomena are believed to be closely related.
Tunable dual-wavelength operation of a diode array with an external grating-loaded cavity
Authors: Wang Chi-Luen , Pan Ci-Ling
Published: July 2002

A novel grazing-incidence grating cavity has been developed for simultaneous generation of laser output at two wavelengths. The gain section is a commercial laser diode array. By moving vertically with respect to the optical axis V-shaped double slit at the end mirror, we demonstrate tuning of the spectral separation of the dual-wavelength laser output from 3.52 to 11.29 nm. The side-mode suppression ratio is 10–20 dB. Examination of the far-field patterns reveal that the laser mode at the two wavelengths corresponds to a different order of the array modes.
Abnormal diffusion behavior of Yb+ and Er+ implanted in KTiOPO4
Authors: Wang Ke-Ming , Ding Pei-Jun , Wang Wei , Lanford W. A. , Li Yi , Li Ju-Sheng , Liu Yao-Gang
Published: July 2002

400 keV Yb+ and 300 keV Er+ were implanted into potassium titanyl phosphate (KTiOPO4 or KTP) with doses of 3×1015 and 1×1015 ions/cm2, respectively. The samples were annealed in the temperature range 600 to 800 °C in Ar ambient. The diffusion behaviors of implanted Yb+ and Er+ in KTiOPO4 were investigated by Rutherford backscattering of 2.0 MeV He ions. The results show that no obvious diffusion of Yb+ and Er+ in KTiOPO4 is detected at 600 °C annealing, but there are three and two peaks of implanted rare-earth ion distribution after 800 °C annealing for the case of Yb+ and Er+, respectively. An explanation of these phenomena is suggested.
Anomalous diffusion of lightly implanted As into Si substrate during N2 annealing
Authors: Aoki Nobutoshi , Kanemura Takahisa , Mizushima Ichiro
Published: July 2002

We observe the anomalous diffusion of lightly implanted As into Si substrate during conventional furnace anneal in nitrogen ambient. The anomalous behavior shows two conspicuous features in the near-surface region and in the tail region. In the near-surface region reaching about 30–50 nm from the interface, a large number of As atoms moves toward the oxide/Si interface, and occasionally accumulates in a narrow region about 10–20 nm from the interface. Retarded diffusion is observed in the tail region. The diffusivity in the tail region increases with the increase of annealing time.
Externally deposited phase-compensating dielectric mirrors for asymmetric Fabry–Perot cavity tuning
Authors: Karim Z. , Kyriakakis C. , Tanguay A. R. , Hu K. , Chen L. , Madhukar A.
Published: July 2002

The wavelength dispersion of the phase shift on reflection that is inherent in dielectric Bragg mirrors can be used to phase compensate resonant-cavity-based devices such as multiple quantum well asymmetric Fabry–Perot spatial light modulators and vertical cavity surface-emitting lasers. We demonstrate the post-growth ability to accurately fine-tune the location of the Fabry–Perot minima in a resonant cavity by employing either a normal or inverted dielectric mirror configuration. The dielectric multilayer mirrors are composed of alternating quarter-wave layers of MgF2 and Sb2S3, and exhibit broadband reflectivities.
Deposition of tungsten films by pulsed excimer laser ablation technique
Authors: Dhote A. M. , Ogale S. B.
Published: July 2002

Laser ablation deposition technique using a KrF (248 nm) excimer laser has been employed to deposit W films on Si(100) and SiO2 from W(CO)6 with high growth rate. The influence of substrate temperature on the film growth rate and resistivity has been investigated in a broad temperature range (20–500 °C) at laser fluence of 0.4 J cm−2. Film resistivities within a factor of 3 of the bulk value have been observed in the substrate temperature range of 300–500 °C. The crystal structure of the film deposited in this temperature range corresponds specifically to the α-W phase. Optical emissions from the plasma generated during the pulsed excimer laser ablation of W(CO)6 are also examined by an optical multichannel analyzer.
Josephson broadband spectroscopy to 1 THz
Authors: Edstam J. , Olsson H. K.
Published: July 2002

We demonstrate the operation of a ‘‘Josephson Broadband Spectrometer’’ (JOBS) with a frequency range and bandwidth of 1 THz. The JOBS uses the inherent frequency tuning of the Josephson oscillations (f=2 eV/h) as a probe of the complex impedance environment, ZL(f), of the Josephson junction. Spectra taken of microstrip resonators (YBa2Cu3O7/SiO/Au) display up to nine harmonic resonances corresponding to a bandwidth of 1000 GHz. We find the surface resistance of YBa2Cu3O7 to scale as f2 over this frequency range, whereas the London penetration depth is frequency independent. The upper frequency limit of the measurement is set by the resonator loss whereas the JOBS presumably has an even larger intrinsic bandwidth.
Back side Raman measurements on Ge/Pd/n-GaAs ohmic contact structures
Authors: Wuyts K. , Watté J. , Silverans R. E. , Van Hove M. , Borghs G. , Palmstro/m C. J. , Florez L. T. , Münder H.
Published: July 2002

Back side Raman measurements were performed on Ge/Pd/n-GaAs ohmic contacts. The analysis was carried out on as-deposited and annealed Ge/Pd/60 nm GaAs structures, and complemented by measurements on isolated 60 nm GaAs slabs. Ohmic behavior is found to coincide with the presence of a confined, highly doped (∼1–3×1019/cm3) region in the GaAs surface layers. This result can be interpreted as giving direct experimental evidence for the importance of doping in the ohmic behavior for this contact.
Threshold dose for ion-induced intermixing in InGaAs/GaAs quantum wells
Authors: Allard L. B. , Aers G. C. , Piva P. G. , Poole P. J. , Buchanan M. , Templeton I. M. , Jackman T. E. , Charbonneau S. , Akano U. , Mitchell I. V.
Published: July 2002

We have determined the threshold dose for 8 MeV Bi+ ions to induce intermixing of GaAs quantum wells in AlGaAs and InGaAs quantum wells in GaAs after rapid thermal annealing at 850 °C. Our measured threshold for the GaAs/AlGaAs system agrees well with previous work. The threshold for the InGaAs/GaAs system is much lower and explains, at least in part, earlier difficulties in the lateral patterning of nanostructures by focused-ion-beam lithography.
Photoluminescence lifetime of GaP/AlP superlattices grown by gas-source molecular-beam epitaxy
Authors: Asami Kumiko , Asahi Hajime , Kim Song Gang , Kim Joon Hong , Ishida Akito , Takamuku Setsuo , Gonda Shun-ichi
Published: July 2002

The photoluminescence lifetimes of GaP/AlP short-period superlattices (GaP)11/(AlP)3 and (GaP)9/(AlP)5, grown on GaP(001) by gas-source molecular-beam epitaxy are studied by a time-correlated single photon counting method at 4.2 and 298 K. Two components of the photoluminescence lifetime are found for each sample. The fast component is about 2 ns accompanied by a slow component of about 20 ns. Discussion of the possible explanations of the two components includes the co-existence of direct- and indirect-band-gap transitions in the superlattice, which was fabricated from the indirect-band-gap constituents.
Measurement of small distances between light spots by domain wall displacements
Authors: Hauser H. , Haberl F. , Hochreiter J. , Gaugitsch M.
Published: July 2002

Two laser beams are focused onto a thin permalloy film. By changing the direction of the magnetization of the permalloy film, the Kerr effect is exploited to either rotate the plane of polarization or modulate the amplitude of the reflected light. First, the film is characterized for our application by measuring the velocity of the domain wall displacements by two focused beams with known distances. By measuring the delay between the modulation of the reflected beams, it is possible to accurately determine the beam separation under the condition of reproducible wall movements. Therefore, a moving domain wall acts like a high-speed modulator. The method could be used for many applications, e.g., refraction measurements or rapid quality control of magnetic materials.
Oxide-semiconductor interface roughness and electrical properties of polycrystalline silicon thin-film transistors
Authors: Takahashi Hiroshi , Kojima Yoshikazu
Published: July 2002

Polycrystalline silicon thin-film transistors (TFTs) have been fabricated with a smooth oxide-semiconductor interface. Device characteristics are found to be improved with the interface smoothness. The channel mobility is especially improved to about 2 times larger than that of conventional poly-Si TFTs. The topography of the oxide-semiconductor interface was analyzed using nanometer resolution atomic force microscopy. The roughness of the oxide-semiconductor interface and the electrical properties of poly-Si TFTs are found to have a strong relationship.l
Low frequency noise properties of all-thin film superconducting point contacts
Authors: Hatle M. , Hamasaki K. , Kojima K.
Published: July 2002

We report the results of low frequency voltage noise measurements of an all-thin film superconducting point contact (SPC). The SPC is prepared in liquid helium by application of a voltage pulse to a Nb-MgO-NbN edge sandwich. Increasing the amplitude of the pulse we may observe a gradual transition of a junction from the tunneling to metallic transport regime. We study the magnitude of low frequency noise during this transition and find that noise decreases quickly with decreasing ratio of subgap-to-supergap resistance. This result is contrasted with an opposite finding of C. T. Rogers and R. A. Buhrman [IEEE Trans. Magn. MAG-21, 126 (1985)] for the limit of a ‘‘leaky’’ tunnel junction. This comparison suggests that the excess subgap conductivity observed in our samples is caused by an Andreev reflection.
Oxygen pressure dependence of in situ growth of NdCeCuO thin films by laser ablation
Authors: Lin Wen-Tai , Chen Yung-Fu
Published: July 2002

A phase stability diagram of the NdCeCuO (NCCO) films grown by in situ laser ablation in O2 is demonstrated. The superconducting NCCO films can be grown under the deposition conditions below and close to the CuO/Cu2O transition line without vacuum annealing. On post-deposition cooling in an oxygen pressure lower than the deposition pressure, the superconductivity of the in situ NCCO films can be significantly improved without vacuum annealing. This process may shorten the reduction step and mitigate the over-reduction of the superconducting films. A film grown at 680 °C in 300 mTorr and then cooled down in 0.5 mTorr shows Tc(onset) of 21 K and Tc(zero) of 18 K.
Temporal response of a lithium nitrate electrohydrodynamic ion source
Authors: Blount Mark , Panitz J. A.
Published: July 2002

The first measurements of electrohydrodynamic (EHD) ion emission from thin films of molten lithium nitrate under pulsed field conditions are presented. Pulse widths from ∼20 ns to 50 μs were used to initiate ion emission from the apex of a stainless-steel field emitter tip coated with molten lithium nitrate. Current densities ≳100 A/cm2 were obtained from a single emission site. As the pulse width was increased from 20 ns to several microseconds the electric field required to initiate ion emission decreased and asymptotically approached the electric field value characteristic of dc operation. In contrast to dc operation, Li+ was the dominant species (≳90%) for pulse durations less than 1 μs. The abundance of Li+ was independent of pressure between 10−3 and 10−8 Torr of water vapor. The use of a lithium nitrate EHD ion source for the production of intense lithium ion beams in light-ion inertial confinement fusion reactors is foreseen.
Photoluminescence determination of the Fermi energy in heavily doped strained Si1−xGex layers
Authors: Líbezný M. , Jain S. C. , Poortmans J. , Caymax M. , Nijs J. , Mertens R. , Werner K. , Balk P.
Published: July 2002

Photoluminescence (PL) measurements of strained Si1−xGex heavily doped p-type layers with different Ge fraction x are reported in this letter. UHV chemical-vapor-deposition-grown samples with x=0.08, 0.12, and 0.16 and doped with 4×1018 cm−3 boron atoms are studied. No-phonon and TO-phonon replicas corresponding to free-electron band-to-band transitions are observed. Values of the band-gap narrowing and Fermi level EF are determined from the PL curves. The earlier theoretical predictions that EF should increase (because of the decrease of the effective density of states) with increasing Ge fraction, are confirmed by PL experiments.
Determination of localized-state distributions in amorphous semiconductors from transient photoconductivity
Authors: Naito Hiroyoshi , Ding Jinli , Okuda Masahiro
Published: July 2002

A method has been proposed for the determination of localized-state distributions in amorphous semiconductors from transient photoconductivity using Laplace transforms. The method is valid in both pre- and post-recombination regimes of transient photoconductivity. The applicability of the method is demonstrated in amorphous arsenic triselenide.
Continuous-wave LiB3O5 optical parametric oscillator pumped by a tunable Ti:sapphire laser
Authors: Colville F. G. , Ebrahimzadeh M. , Sibbett W. , Dunn M. H.
Published: July 2002

We have demonstrated a continuous-wave optical parametric oscillator that uses lithium triborate as the nonlinear material and a tunable Ti:sapphire laser as the pump source. By exploiting type I noncritical phase matching and a combination of temperature and pump frequency tuning, we have generated widely tunable radiation from 1.49 to 1.70 μm, limited by the bandwidth of the optical coatings. Total output powers of 30 mW and pump depletions of 40% have been obtained at two times the oscillation threshold of 360 mW. We discuss the application of this nonlinear frequency conversion process to several recently proposed experiments.
Pressure dependence of deep level transitions in AgGaSe2
Authors: Choi In-Hwan , Yu Peter Y.
Published: July 2002

Polarized optical absorption in single crystals of AgGaSe2 has been measured as a function of hydrostatic pressure. Two polarized absorption peaks due to defects are reported. The pressure dependence of these peaks suggests that they are due to deep centers. These deep center absorption peaks merged into the fundamental absorption edge under high pressure.
Reduced phosphorus loss from InP surface during hydrogen plasma treatment
Authors: Balasubramanian Sathya , Kumar Vikram , Balasubramanian N.
Published: July 2002

A new method for plasma hydrogenation of InP with a reduced phosphorus loss is reported. The loss of P from InP surface is suppressed by the use of a sacrificial InP wafer kept directly in the plasma while the test sample is kept away from it in a downstream geometry. It is shown using photoluminescence that the P vacancy related transitions are considerably reduced for InP hydrogenated in the presence of a sacrificial wafer when compared to the one hydrogenated without it. The results suggest the utility of the sacrificial InP wafer in providing a P overpressure during H plasma exposure.
Film thickness reduction of thermally annealed hydrogenated amorphous silicon prepared with plasma-enhanced chemical vapor deposition
Authors: Yang Y.-K , Shin J.-S. , Hsieh R.-G. , Gan J.-Y.
Published: July 2002

The structural change of thermally annealed hydrogenated amorphous silicon films prepared with plasma-enhanced chemical vapor deposition has been examined in this study. At 615 °C, a significant amount of microvoids can be annealed out of the silicon films. The annihilation of microvoids mainly causes the reduction of film thickness while the surface smoothness is largely retained. During annealing, the thickness of silicon films has been reduced by 220 Å from the initial thickness of 1200 Å. Evaluated with the thickness reduction alone, the void fraction of the as-deposited films must be higher than 16%. The film thickness reduction starts at the very early stage of annealing and has almost completed within 30 min. Our results also have shown that the reduction of film thickness cannot be the result of crystallization, instead, it is more likely accompanied with the hydrogen effusion.
Improved characteristics of a Cherenkov laser loaded with a Kerr-like medium
Authors: Shiozawa T. , Sato T. , Horinouchi K.
Published: July 2002

The amplification characteristics of a Cherenkov laser loaded with a Kerr-like medium are investigated on the basis of the fluid model for an electron beam. The numerical simulation with the aid of the finite element method shows that the amplification characteristics are greatly improved by the proper choice of the nonlinear parameter for a Kerr-like medium. The enhanced characteristics are due to the improved velocity matching between the electron beam and the electromagnetic wave, and to the self-focusing effect of a Kerr-like medium.
Experimental realization of millimeter-wave amplification by a sheet beam free electron laser
Authors: Zhang Ze-Xiang , Destler W. W. , Granatstein V. L. , Antonsen T. M. , Levush B. , Rodgers J. , Cheng S.
Published: July 2002

We report an observation of millimeter-wave (94 GHz) amplification in a sheet beam, short period, planar wiggler, free electron laser amplifier. The observed gain is about 5 dB for a 530 keV, 4 A beam through a 54 cm wiggler. Wave energy absorption was also observed when the beam energy is off-resonance. Experimental results are in good agreement with numerical simulation. This amplifier configuration has potential for producing equally high output power but at relatively low voltage compared with longer period free electron lasers.
Characteristics of Ag-Au alloy sheathed Bi-Pb-Sr-Ca-Cu-O superconducting tapes for current leads
Authors: Sasaoka T. , Nomura K. , Sato J. , Kuma S. , Fujishiro H. , Ikebe M. , Noto K.
Published: July 2002

Oxide superconductor tape with Ag-Au sheath was studied for current leads. A 100-cm-long current lead of 1000 A with 0.2 W/kA heat leakage was designed using Ag-11 at. % Au alloy sheath with low thermal conductivity. The overall current density of the superconducting tape is required to be 350–770 A/cm2 at 77 K when the superconductor cross-section ratio in the tape is 0.35–0.7. Bi-Pb-Sr-Ca-Cu-O superconducting tape with Ag-11 at. % Au alloy sheath was fabricated and the critical current density Jc was measured. The overall-Jc was 1700 A/cm2 at 77 K under 0 T. The possibility of the current lead of 1000 A under 0.28 T with 0.2 W/kA was made clear.
Lateral p-n junctions in metal-organic vapor-phase epitaxy of AlGaAs lasers on GaAs substrates having [011] etched ridges
Authors: Wang T. Y.
Published: July 2002

AlGaAs lasers with a current-blocking layer have been grown on GaAs substrates having [011] etched ridges using metal-organic vapor-phase epitaxy. Conducting channels are formed over the ridges due to the diffusion of Se dopant atoms on the (311)B facets during the nonplanar growth. The formation of lateral p-n junctions at the substrate interface is evidenced by measuring the electron-beam-induced junction current from the front facet of a bonded diode. This result is useful in the single-step fabrication of laser structures with a novel current-blocking scheme.
Growth behavior and surface morphology of homoepitaxial YBa2Cu3O7−δ thin films on flux-grown single crystals
Authors: Shimizu Takashi , Hirayama Fuminori , Oka Kunihiko , Nonaka Hidehiko , Matsuda Mizushi , Arai Kazuo
Published: July 2002

Atomically flat terraces and steps with a height of one c-axis lattice parameter have been observed with atomic force microscopy (AFM) on the surface of a flux-grown YBa2Cu3O7−δ (YBCO) single crystal. Homoepitaxial growth of YBCO on the flux-grown single crystal has been investigated using reflection high-energy electron diffraction (RHEED). Initial stage of the RHEED intensity oscillation without anomalous peaks usually observed in heteroepitaxial growth suggests epitaxial growth of YBCO on the substrate surface from the beginning of deposition. A surface image of AFM for the homoepitaxial film reveals coalescent step-like structures and two-dimensional islands of one c-axis height on the growing surface of YBCO. The observed RHEED oscillation and AFM image are consistent with the two-dimensional nucleation growth of the film.
High power coherent two-dimensional semiconductor laser array
Authors: Sanders Steve , Waarts Robert , Nam Derek , Welch David , Scifres Don , Ehlert John C. , Cassarly Wiliam J. , Finlan J. Michael , Flood Kevin M.
Published: July 2002

Diffraction limited 1.4 W pulsed output power is demonstrated from a two-dimensional 144 element surface emitting laser array placed in an external Talbot cavity. Phase locking of the array is achieved with a parallel phase sensing and control system based on phase contrast imaging used in combination with a liquid crystal array in the laser cavity. Diffraction limited cw operation is also demonstrated.
Characterization of Ca+ ion-implanted GaAs by photoluminescence
Authors: Shen Hong-Lie , Makita Yunosuke , Kimura Shinji , Tanoue Hisao , Yamada Akimasa , Shibata Hajime , Obara Akira , Sakuragi Shiro
Published: July 2002

Optical properties of Ca+ ion-implanted GaAs were characterized by photoluminescence measurements at 2 K. Four new emissions denoted by (Ca0,X), gCa, SM, and (e,Ca) were found to be produced by Ca incorporation into GaAs. By changing the Ca dopant concentration and excitation intensity, it was revealed that the (Ca0, X) emission is due to excitons bound to a neutral shallow Ca acceptor, and SM probably originates from excitons bound to a Ca impurity in a deep energy level. In addition, in an impure GaAs substrate, Ca could also form a shallow emission gCa, despite the fact that the g emission for well-known shallow acceptors such as C, Be, and Mg was usually found only in ultrapure GaAs. It was demonstrated that Ca is a shallow acceptor impurity in GaAs with a binding energy of 28.4 meV.
A nonmechanical laser scanner based on electron-beam pumped AlGaInP-GaInP semiconductor structures
Authors: Cornelissen Hugo J. , Savert C. J. , Niesten M. J. H. , Vrijssen G. A. H. M. , Valster A. , van der Poel C. J.
Published: July 2002

An AlGaInP-GaInP strained-layer quantum well laser structure emitting at 670 nm is pumped by a 7–20 keV scanning electron beam. At room temperature, a threshold power density as low as 57 W/mm2 is obtained, which is only 3.8× the value for diode laser operation. More than 250 points are resolved on a 5 mm bar. They are scanned at a speed of 1000 m/s at an output level of 20 mW.
Auger electron spectroscopy study of the interaction of NO2 with Si(100)
Authors: Bhat M. , Kamath A. , Kwong D. L. , Sun Y. M. , White J. M.
Published: July 2002

The nitridation of clean Si(100)-2×1 with NO2 has been studied using Auger electron spectroscopy (AES). In this letter we demonstrate that the interaction of Si(100) with NO2 leads to the efficient incorporation of nitrogen (N) and oxygen (O) in single crystal Si as opposed to the case of N2O on Si(100). A comparative study of the incorporation efficiency of N and O by the reaction of NO2 and N2O with Si(100) over a wide temperature range has been performed. It is observed that only a few Langmuirs (L) of NO2 is required to saturate the Si surface while reaction with N2O is not as favorable. At temperatures ranging from room temperature to 1000 °C, varying proportions of N and O are incorporated into the Si by NO2. Repeated dosing and annealing cycles indicate that continued incorporation of N and O is possible even through a nitrogen-rich Si layer.
Intracavity laser spectroscopy of RF plasmas of methane and benzene used in depositing diamondlike carbon films
Authors: Lipp M. J. , O’Brien J. J.
Published: July 2002

Spatially resolved concentrations of excited atomic hydrogen (n=2), generated from 13.56 MHz RF hydrocarbon discharges, are determined during film formation using intracavity laser spectroscopy. Self-bias voltages and pressures of methane (25 and 100 mTorr) and benzene (25 mTorr) are selected so that diamondlike carbon films are deposited. In all cases, the minimum concentration occurs at the power electrode. Benzene produces the least amount of excited atomic hydrogen overall. The results may have implications concerning the proposed impact induced fragmentation of hydrocarbon molecules during film growth.
Extended and localized vibrational modes in (1-3) Penrose-like piezocomposites
Authors: Montero de Espinosa F. , Torres M.
Published: July 2002

Acoustic vibrational modes of piezocomposites with ceramic bars arranged at the vertices of both perfect Penrose tilings and random Penrose tilings have directly been observed by recording the corresponding standing vibration amplitude pattern. The random Penrose tiling exhibits similar although smoother spectrum than the perfect Penrose one. For both structures, the existence of extended and localized modes is shown. Resonances frequencies at the edges of the spectrum pseudogap correspond to localized and highly entropic modes. As expected, the modes are more localized in the random Penrose tiling case.
Spiral growth of InP by metalorganic vapor phase epitaxy
Authors: Hsu C. C. , Xu J. B. , Wilson I. H.
Published: July 2002

Spirals were observed on InP grown by metalorganic vapor phase epitaxy. Atomic force microscopy is the technique used. The growth took place on a vicinal surface and the growth mechanism is according to the classical Burton–Cabrera–Frank theory. Spirals originate from screw dislocations. Successive turns of steps are sent out by the dislocations. These steps are generally of monolayer height (0.29 nm) except close to the dislocation emergence points where they are submonolayers. It is predicted that spiral growth will become the dominant mechanism if the vicinal steps are eliminated.
Photorefractive effect in Bi12SiO20:Cr crystals at 633 nm
Authors: Yeh T. S. , Lin W. J. , Lin I. N. , Hu L. J. , Lin S. P. , Tu S. L. , Lin C. H. , Hsu S. E.
Published: July 2002

Pure and Cr2O3-doped Bi12SiO20 (BSO) single crystals have been successfully grown using Czochralski technique. Doping 30 ppm of Cr2O3 into BSO single crystals has lowered the transmittance and increased the photochromic effect of the materials significantly. Although the overall diffraction efficiency of photorefractive effect in response to 633 nm laser beam has not been increased, the intrinsic diffraction efficiency (ηi) and the response time constant (τ) have been improved markedly. The applicability of the BSO crystals in the red light regime is thus increased.
Control of chaos in a CO2 laser
Authors: Perez J. M. , Steinshnider J. , Stallcup R. E. , Aviles A. F.
Published: July 2002

We report the experimental control of chaos in an optically modulated CO2 laser. The CO2 laser was driven into chaos by injecting a feedback beam modulated by an electro-optical modulator. Control of chaos was achieved using a modified proportional feedback technique in which the control pulses were delayed by approximately one relaxation period. Using this technique, it was possible to control unstable periodic orbits up to period 6.
Nonlinear mechanisms in microwave photodetectors operated with high intrinsic region electric fields
Authors: Williams Keith J.
Published: July 2002

Measurements and simulations to determine the contributing nonlinear mechanisms in microwave photodetectors operated with high intrinsic region electric fields are presented. An important component of the nonlinear behavior is attributed to absorption in undepleted material adjacent to the depletion region, limiting the attainable device linearity. With as little as 10 nm of undepleted absorbing material, the second harmonic of a 5 GHz fundamental frequency at 1 mA of average detector current can be −60 dBc. Linearity improvements up to 50 dB should be possible if photodetectors can be fabricated with strictly depleted absorbing regions.
Grain size reduction in Nb3Sn wire using composite powder metallurgy filaments with Cu(Sn) artificial pinning centers
Authors: Thieme C. L. H. , Rodrigues D. , Foner S.
Published: July 2002

Cu(Sn) artificial pinning centers (APCs) were introduced into multifilamentary Nb3Sn wire using powder metallurgy Nb+Cu rods. In the composite Nb+Cu filaments the Cu ribbons had a thickness of either 20 or 5 nm before reaction. During the 600 °C anneal the APCs enhanced the reaction rate and reduced the Nb3Sn grain size to <20 nm. The Cu concentration in the filaments decreased. In 20% Cu-20 nm APC wires the critical current density over the A15 area was 2250 A/mm2 at 12 T and 4.2 K. Flux pinning increased strongly with decreasing field.
Ultra-wide-band pulse generation and radiation using a high T
c superconductor opening switch
Authors: Lai Y. S. , Funk E. E. , Cao W. L. , Lee Chi H. , Shen Zhi-Yuan , Pang Philip , Kountz Dennis J. , Holstein William L.
Published: July 2002

A new method of generating ultra-wide-band electromagnetic pulses using a Tl2Ba2CaCu2O8 high Tc superconductor as a fast laser activated opening switch is presented. The superconductor is used as an opening switch with a current charged transmission line pulse forming network to produce jitter-free triggered square pulses which are radiated by an ultra-wide-band conical antenna. We report radiation and reception of pulses with center frequencies near 3.5 GHz and a bandwidth in excess of 80%. We also discuss how this technique can be used to assess various wide-band antenna designs.
Angular limitations of polymer-based waveguide holograms for 1-to-many V-shaped surface-normal optical interconnects
Authors: Li Maggie M. , Chen Ray T. , Tang Suning , Gerold Dave
Published: July 2002

Experimental results of 1-to-2 intraplane and of 1-to-32 interplane V-shaped fanouts are delineated. Coupling efficiencies of 48% for surface-normal and of 45% for near-surface-normal interplane fanout beams are theoretically and experimentally confirmed. The influence of the angular fluctuation of a device having two multiplexed waveguide holograms with film thickness of 15 μm and index modulation of 0.04 is studied. The angle between the two grating vectors is determined to be less than 26° to keep the near-surface-normal fanout beams.
Misfit dislocations in ZnSe grown on vicinal Si(001) substrates
Authors: Romano L. T. , Knall J. , Bringans R. D. , Biegelsen D. K.
Published: July 2002

High resolution electron microscopy (HREM) has been used to study misfit dislocations of ZnSe films grown on vicinal Si(001) substrates tilted 4° towards the [11̄0] axis. In images taken with the electron beam parallel to the [11̄0] direction, 60° dislocations were found to predominate whereas mostly Lomer dislocations or closely spaced 60° dislocations (separated by <2 nm) were observed in images taken in the orthogonal direction. A model is presented here to explain the formation of the asymmetric dislocation structure on the basis of mechanisms for propagation and formation of misfit dislocations.
On the bamboo structure as the salvation of thin film metallization for deep submicron device technologies
Authors: Fu Kuan-Yu
Published: July 2002

The recently proposed Dreyer-Fu-Varker (DFV) model [J. Appl. Phys. 73, 4894 (1993) and 1993 Int. Rel. Phys. Proc. 304 (1993)] for predicting electromigration lifetime has been extended to include the shape factor (normally referred to as the standard deviation). An experiment has been conducted to verify the validity of this extension. Excellent agreement between the model prediction and the experimental data has been obtained. It is found that a significant portion of the increase in the shape factor with the decrease in line width can be attributed to the increase in the temperature standard deviation for narrower lines. Based on this newly expanded DFV model coupled with the experimental observations it is shown that the maximum allowable current density, for meeting the reliability specification of electromigration, suffers a steep drop with line width in the deep submicron region. As a result, the bamboo structure cannot salvage thin film metallization from electromigration susceptibility for deep submicron microchip technologies.
Transport superconducting properties of grain boundaries in Tl1Ba2Ca2Cu3Ox thin films
Authors: Nabatame T. , Koike S. , Hyun O. B. , Hirabayashi I. , Suhara H. , Nakamura K.
Published: July 2002

In order to investigate weak link properties in the Tl1Ba2Ca2Cu3Ox[Tl-(1223)] system, we measured the transport properties of artificially grown grain boundaries in Tl-(1223) films. Epitaxial thin films were grown on SrTiO3 bicrystal substrates with five tilt angles of 5°, 10°, 15°, 24°, and 36.8°. We found that the grain boundaries Jc (Jcg.b.) of large tilt angles (θ≥15°) at 77 and 5 K were substantially less than intragrain Jc(Jcg) and limited by a weak link. However, the Jcg.b./Jcg values for low tilt angle grain boundaries (θ≤10°) were almost unity. Moreover, magnetic-field history dependent Jc values for low tilt angle grain boundaries were not observed in a low magnetic field (<0.1 T). These data indicate that the low tilt angle grain boundaries do not work as a weak link and retain high Jc.
Conversion of fullerenes to diamond under high pressure and high temperature
Authors: Ma Yanzhang , Zou Guangtian , Yang Haibin , Meng Jinfang
Published: July 2002

Fullerenes have been converted to diamond crystals with the size of 0.1 mm at 5.0–5.5 GPa and 1400 °C, using NiMnCo catalyst. They are similar to graphite in the growing phenomena. They are transformed into diamond directly without being graphitized first.