APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

14 Apr 1997

Volume 70, Issue 15, pp. 1921-2056

Page 1 of 2 Pages Next Page | Jump to Page

Spatial gain profiles of a continuous wave radio-frequency pumped atomic xenon laser

S. N. Tskhai, F. J. Blok, Yu. B. Udalov, P. J. M. Peters, W. J. Witteman, and V. N. Ochkin

Appl. Phys. Lett. 70, 1921 (1997); http://dx.doi.org/10.1063/1.118779 (2 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Spatially dependent small signal gain measurements in a continuous wave rf excited Ar–He–Xe (59.5/40/0.5) gas discharge are presented. Maximum values for the small signal gain of the 2.03 and 2.65 μm xenon transitions of about 22% and 37%/cm, respectively, were obtained at a total pressure of 120 mbar, an input power per unit electrode area of 20 W/cm2 and at a rf driving frequency of 115 MHz. With a spatial resolution better than 0.5 mm, a strongly inhomogeneous gain distribution in the transverse direction was measured. © 1997 American Institute of Physics.
Show PACS
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Temperature sensitivity of repoling in strontium barium niobate near to the glassy transition

Peter G. R. Smith, Robert W. Eason, Paul T. Brown, and Graeme W. Ross

Appl. Phys. Lett. 70, 1923 (1997); http://dx.doi.org/10.1063/1.118780 (3 pages)

Full Text: | Download PDF

Show Abstract
We report the observation of an enhanced temperature sensitivity for transient repoling near to the domain freezing temperature in ferroelectric strontium barium niobate. This work has important consequences for the use of optical fields to control domain patterns in such materials. We model the repoling characteristics of the material using a Vogel–Fulcher type response and present results showing the degree of repoling as a function of field and temperature, for short duration repoling times. © 1997 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Light-emitting electrochemical cells from a blend of p- and n-type luminescent conjugated polymers

Yang Yang and Qibing Pei

Appl. Phys. Lett. 70, 1926 (1997); http://dx.doi.org/10.1063/1.118781 (3 pages) | Cited 21 times

Full Text: | Download PDF

Show Abstract
We demonstrate polymer light-emitting electrochemical cells (LECs) made of a blend of p- and n-type luminescent conjugated polymers. These two polymers, poly[9-(3,6,9-trioxadecyl)- carbazole-3,6-diyl] (TOD–PC, a p-type polymer) and poly[2,3-di(p-tolyl)–quinoxaline-5,8-diyl] (DT–PQX, a n-type polymer), are blue and blue–green emission polymers, respectively, both with high photoluminescent quantum efficiency. However, the photoluminescence of the polymer blend is completely quenched, due to the charge transfer between the two polymers. A new and faint orange–yellow photoluminescence emission, which has photonic energy consistent with the energy difference of the π band of TOD–PC and the π∗ and of DT–PQX, has been observed. LECs fabricated from this polymer blend show strong current injection and bright electroluminescence at this new emission color, which is believed to be due to the interpolymer radiative recombination of the electrons from the n-type polymer and holes from the p-type polymer. Such an independent p doping of TOD–PC and n doping of DT–PQX in the blend and interpolymer radiative recombination provide an interesting way of generating new emission colors in the LEC system. © 1997 American Institute of Physics.  
Show PACS
78.60.Fi Electroluminescence
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
78.66.Qn Polymers; organic compounds
78.40.Me Organic compounds and polymers

Thermal stability in oligomeric triphenylamine/tris(8-quinolinolato) aluminum electroluminescent devices

Shizuo Tokito, Hiromitsu Tanaka, Koji Noda, Akane Okada, and Yasunori Taga

Appl. Phys. Lett. 70, 1929 (1997); http://dx.doi.org/10.1063/1.118782 (3 pages) | Cited 129 times

Full Text: | Download PDF

Show Abstract
Thermal stability of the electroluminescent (EL) devices using various hole-transporting materials based on triphenylamine, and a typical emitting material, tris(8-quinolinolato) aluminum has been systematically studied. The thermal stability of the EL devices is clearly seen to depend on the glass transition temperature (Tg) of the hole-transporting material. The highest thermal stability up to 155 °C is obtained in the device using the pentamer of triphenylamine. It has been found that the linear linkage of triphenylamine is useful to attain high Tg rather than the branch linkage. © 1997 American Institute of Physics.
Show PACS
85.60.Jb Light-emitting devices
42.79.Kr Display devices, liquid-crystal devices
68.60.Dv Thermal stability; thermal effects
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Investigation of the electric-field distribution at the subwavelength aperture of a near-field scanning optical microscope

R. S. Decca, H. D. Drew, and K. L. Empson

Appl. Phys. Lett. 70, 1932 (1997); http://dx.doi.org/10.1063/1.118783 (3 pages) | Cited 19 times

Full Text: | Download PDF

Show Abstract
The reflectivity of a 9 nm AlAs layer embedded in a GaAs matrix was measured using a near-field scanning optical microscope. Results for freshly cleaved surfaced are understood considering the electrostatic nature of the electric field in the near field of a subwavelength aperture. The optical contrast arises from the different index of refraction of AlAs and GaAs, with topography associated effects playing no role. While keeping the wavelength of the incident radiation and the aperture dimensions fixed, ∣E∣ was mapped on planes perpendicular to the tip axis, as a function of the height of the tip above the sample. The results were compared with a finite element calculation for the scattered light. In the analysis, we model the sample with a position dependent dielectric constant. Good agreement between the model and the experimental data was found. © 1997 American Institute of Physics.
Show PACS
07.79.Fc Near-field scanning optical microscopes
78.66.Fd III-V semiconductors
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.60.Hv Refractometers and reflectometers

Electric field effect on luminescence efficiency in 8-hydroxyquinoline aluminum (Alq3) thin films

W. Stampor, J. Kalinowski, P. Di Marco, and V. Fattori

Appl. Phys. Lett. 70, 1935 (1997); http://dx.doi.org/10.1063/1.118784 (3 pages) | Cited 51 times

Full Text: | Download PDF

Show Abstract
Electric field-induced luminescence quenching in thin films made from common organic electroluminescent material of aluminum (III) 8-hydroxyquinoline (Alq3) is reported. The dependence of luminescence quenching on excitation wavelength and electric field is attributed to field-assisted hopping separation of charge in localized excited states. The effect extrapolated to high electric fields can reduce the luminescence yield by as much as 60% limiting electroluminescence quantum efficiency in high-field-driven light emitting diodes based on the Alq3 emitter. © 1997 American Institute of Physics.
Show PACS
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
71.55.Jv Disordered structures; amorphous and glassy solids
85.60.Jb Light-emitting devices

Theory of mode-locked semiconductor lasers with finite absorber relaxation times

J. L. A. Dubbeldam, J. A. Leegwater, and D. Lenstra

Appl. Phys. Lett. 70, 1938 (1997); http://dx.doi.org/10.1063/1.118785 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
We investigate the influence of a finite absorber relaxation time on passively mode-locked semiconductor lasers. We find that the mode-locking mechanism of Haus is surprisingly susceptible to small perturbations and small changes in the parameters. Even when the absorber relaxation time is much larger than the pulse duration, it typically is still short enough to be a crucial part of the physics of mode-locking. Allowing for a finite absorber relaxation time, we find that stable operation of a mode-locked semiconductor is possible over a wide range of parameters. We argue that the pulse duration is inversely proportional to the square root of the pulse energy. © 1997 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Frequency doubling in two-component self-assembled chromophoric waveguide structures

P. M. Lundquist, W. Lin, H. Zhou, D. N. Hahn, S. Yitzchaik, T. J. Marks, and G. K. Wong

Appl. Phys. Lett. 70, 1941 (1997); http://dx.doi.org/10.1063/1.118786 (3 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Self-assembled chromophoric multilayers having large second-order optical nonlinearities can be combined with linear guiding materials such as polymethylmethacrylate to produce two-component frequency doubling waveguides. This approach introduces considerable flexibility in optimizing the trade-off between the overlap of waveguide mode profiles and linear absorption. Extremely low waveguide propagation losses can be achieved because electric field poling and the accompanying poling-induced optical scattering are obviated. © 1997 American Institute of Physics.
Show PACS
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.70.Jk Polymers and organics
42.25.Fx Diffraction and scattering

Creation of a monoenergetic pulsed positron beam

S. J. Gilbert, C. Kurz, R. G. Greaves, and C. M. Surko

Appl. Phys. Lett. 70, 1944 (1997); http://dx.doi.org/10.1063/1.118787 (3 pages) | Cited 49 times

Full Text: | Download PDF

Show Abstract
We have developed a versatile, pulsed source of cold (ΔE = 0.018 eV), low-energy positrons (E≈0–9 eV). Multiple pulses of 105 positrons, each 10 μs in duration, are extracted from a thermalized, room temperature positron plasma stored in a Penning trap. The frequency, duration, and amplitude of the pulses can be varied over a wide range. © 1997 American Institute of Physics.
Show PACS
29.25.Bx Electron sources
07.77.Ka Charged-particle beam sources and detectors

Effect of bumps on the wafer on ion distribution functions in high-density argon and argon-chlorine discharges

J. R. Woodworth, B. P. Aragon, and T. W. Hamilton

Appl. Phys. Lett. 70, 1947 (1997); http://dx.doi.org/10.1063/1.118814 (3 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
The presence of bumps on or near the wafer in plasma processing reactors can significantly affect plasma parameters. We have used a gridded energy analyzer to measure ion fluxes, energy distributions, and angular distributions near such bumps on a grounded electrode in an inductively coupled discharge in a Gaseous Electronics Conference Reference Cell. We find that the bumps affect the ion energy distributions only slightly, lower the ion fluxes by more than a factor of 2 and dramatically alter the ion angular distributions. © 1997 American Institute of Physics.
Show PACS
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.)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Ion energy control in an insulating inductively coupled discharge reactor

Brian A. Smith and Lawrence J. Overzet

Appl. Phys. Lett. 70, 1950 (1997); http://dx.doi.org/10.1063/1.118788 (3 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
An electrically insulating plasma reactor with a Faraday shielded inductive source antenna permits direct control of the dc plasma potential of the discharge. This control may be used to provide a tailored ion energy distribution at a substrate of fixed potential or to fix the plasma potential at a chosen value. With a reactor constructed from Pyrex tubing and a Faraday shielded inductive source coil, all that is required to control the plasma potential is a small electrostatic probe in contact with the plasma. By applying a stairstep potential to the probe, it is possible to create an ion energy distribution possessing virtually any desired shape. Insulating reactors could provide a novel way to control ion production and ion energy separately without the need for direct substrate biasing. They may also provide a way to maintain a consistent plasma potential in a processing reactor in situations where the reactor walls are easily contaminated by the process. © 1997 American Institute of Physics.
Show PACS
52.75.-d Plasma devices
52.58.Qv Electrostatic and high-frequency confinement
52.70.Ds Electric and magnetic measurements
52.80.Hc Glow; corona
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides

Guiding and confinement of a laser produced plasma by a curved magnetic field

Y. Y. Tsui, D. Vick, and R. Fedosejevs

Appl. Phys. Lett. 70, 1953 (1997); http://dx.doi.org/10.1063/1.118789 (3 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
An axial magnetic field with a maximum strength of 2.2 kG was used to confine and guide a laser produced carbon plasma around a 30 deg bend. The plasma was produced by a 25 ns KrF laser pulse at a peak intensity of 1×109 W cm−2. An array of Faraday cups positioned at the exit of the guide field was used to determine that approximately 20% of the original plasma was confined by the magnetic field and guided along a 15 cm trajectory to a 5 cm2 area. © 1997 American Institute of Physics.
Show PACS
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps

The role of the dielectric loss of dispersed material in the electrorheological effect

Tian Hao

Appl. Phys. Lett. 70, 1956 (1997); http://dx.doi.org/10.1063/1.118790 (3 pages) | Cited 13 times

Full Text: | Download PDF

Show Abstract
A set of electrorheological (ER) suspensions composed of solid materials with different dielectric losses and dielectric constants were examined by means of dielectric and rheological methods. We found that the dielectric loss of dispersed material, which was only slightly stressed in previous works, plays a considerable role in ER response; a large dielectric loss value is necessary for a clear ER effect. Two processes, the turning of randomly distributed microparticles toward the direction of an applied external electric field, probed recently by an x-ray diffraction method, and a coalescing of ordered microparticles, widely observed in ER fluids under a microscope, are suggested for understanding the ER mechanism. The first process is dominated by the dielectric loss of dispersed material, and the second one by the dielectric constant. Our result can be used to understand why certain materials of high dielectric constant but low dielectric loss would have shown an obvious ER effect according to the polarization and the conduction models, yet only displays weak or even no detectable ER effect experimentally. Our findings help to further understand the ER mechanism and also offer a clear implication on how to design high performance ER fluids. © 1997 American Institute of Physics.
Show PACS
83.80.Gv Electro- and magnetorheological fluids
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
47.55.Kf Particle-laden flows
82.70.Kj Emulsions and suspensions
83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams

Elastic constants and crystal anisotropy of titanium diboride

P. S. Spoor, J. D. Maynard, M. J. Pan, D. J. Green, J. R. Hellmann, and T. Tanaka

Appl. Phys. Lett. 70, 1959 (1997); http://dx.doi.org/10.1063/1.118791 (3 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
In this study, the elastic constants of a titanium diboride (TiB2) single crystal were measured using resonant ultrasound spectroscopy. In contrast to previous work, the current results are consistent with the measured elastic constants of TiB2 polycrystals. In addition, the crystal anisotropy of TiB2 was examined. The current data show that the elastic properties of TiB2 are much more isotropic than previously considered. © 1997 American Institute of Physics.
Show PACS
62.20.D- Elasticity
62.65.+k Acoustical properties of solids

Control of the growth and domain structure of epitaxial SrRuO3 thin films by vicinal (001) SrTiO3 substrates

Q. Gan, R. A. Rao, and C. B. Eom

Appl. Phys. Lett. 70, 1962 (1997); http://dx.doi.org/10.1063/1.118792 (3 pages) | Cited 67 times

Full Text: | Download PDF

Show Abstract
We report the effect of both miscut angle (α) and miscut direction (β) of vicinal substrates on the epitaxial growth and domain structure of isotropic metallic oxide SrRuO3 thin films. The thin films have been grown on vicinal (001) SrTiO3 substrates with α up to 4.1° and β up to 37° away from the in-plane [010] axis. Single-crystal epitaxial (110)o SrRuO3 thin films were obtained on vicinal SrTiO3 substrates with a large miscut angle (α=1.9°, 2.1°, and 4.1°) and miscut direction close to the [010] axis. Decreasing the substrate miscut angle or aligning the miscut direction close to the [110] axis (β=45°) resulted in an increase of 90° domains in the plane. The films grown on vicinal substrates displayed a significant improvement in crystalline quality and in-plane epitaxial alignment as compared to the films grown on exact (001) SrTiO3 substrates. Atomic force microscopy revealed that the growth mechanism changed from two-dimensional nucleation to step flow growth as the miscut angle increased. © 1997 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Cd Deposition by sputtering

Textured diamond films growth on (100) silicon via electron-assisted hot filament chemical vapor deposition

G. S. Fu, X. H. Wang, W. Yu, L. Han, L. F. Dong, and X. W. Li

Appl. Phys. Lett. 70, 1965 (1997); http://dx.doi.org/10.1063/1.118793 (3 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Textured (100) diamond films are successfully grown on single-crystalline (100) silicon substrate by electron assisted hot filament chemical vapor deposition from a gas mixture of methane and hydrogen. The effects of various parameters have been studied. The optimal growth conditions are obtained and the oriental growth character is discussed. © 1997 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
72.80.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Decomposition of amorphous Zr41Ti14Cu12.5Ni10Be22.5 alloy: As investigated by small angle neutron scattering

Jun-Ming Liu

Appl. Phys. Lett. 70, 1968 (1997); http://dx.doi.org/10.1063/1.118794 (3 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
In situ small angle neutron scattering has been applied to investigate in details the structural relaxation of amorphous Zr41Ti14Cu12.5Ni10Be22.5 alloy between 620 and 673 K and its effect on subsequent crystallization at 673 K. We demonstrate that crystallization in the decomposed alloy is significantly suppressed. It is revealed that spinodal decomposition of the alloy generates a second supercooled liquid phase embedded in the similarly disordered matrix. The second phase achieves a volume fraction of about 10% and exhibits a barlike pattern. Anomalous kinetics of the microstructural coarsening is observed.© 1997 American Institute of Physics.
Show PACS
61.43.Dq Amorphous semiconductors, metals, and alloys
81.30.Bx Phase diagrams of metals, alloys, and oxides
81.05.Bx Metals, semimetals, and alloys

Electric-field-induced commensurate phase in ZrTiO4

Yung Park and Ho-Gi Kim

Appl. Phys. Lett. 70, 1971 (1997); http://dx.doi.org/10.1063/1.118795 (3 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
With the use of x-ray diffraction, the creation of a new commensurate phase with modulation wave-vector qo = 26/50a∗ by the application of a dc electric field along the a axis in ZrTiO4 is demonstrated. The temperature range over which this induced phase exists (12 K at E = 8 KV/cm), increases with the increasing dc electric field. © 1997 American Institute of Physics.
Show PACS
64.70.Rh Commensurate-incommensurate transitions
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)

Dynamic growth effects during low-pressure deposition of diamond films

Donald R. Gilbert, Rajiv Singh, Roy Clarke, and S. Murugkar

Appl. Phys. Lett. 70, 1974 (1997); http://dx.doi.org/10.1063/1.118796 (3 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
Diamond films were deposited in a modified electron–cyclotron-resonance plasma system operating at pressures between 1.0 and 2.0 Torr. This system provides the advantage of efficient plasma generation due to magnetic enhancement and high diffusion rates due to relatively low-pressure operation. Films were formed from preexisting seed layers providing high “nucleation” densities to promote rapid coalescence. Raman analysis of grown films showed a quality dependence on both deposition pressure and nucleation density. We speculate that the increased presence of amorphous carbon and larger film stresses is the result of grain-boundary impurity effects in the seeded films. Oxygen addition improved film quality by reducing nondiamond carbon incorporation. © 1997 American Institute of Physics.
Show PACS
81.05.ub Fullerenes and related materials
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.)
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.Bs Mechanical and acoustical properties
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
61.72.Mm Grain and twin boundaries

Viscous drag effect on imaging of linearized plasmid deoxyribonucleic acid in liquid medium with the atomic force microscope

O. Teschke, R. A. Douglas, and T. A. Prolla

Appl. Phys. Lett. 70, 1977 (1997); http://dx.doi.org/10.1063/1.118797 (3 pages) | Cited 15 times

Full Text: | Download PDF

Show Abstract
In many attempts to image biomolecules like deoxyribonucleic acid with the atomic force microscope, the apparent width of the molecules exceeds the expected width as obtained by x-ray diffraction. This increase in size was explained by a geometrical tip convolution, but the increased width seems to persist despite improvements to the tip. Experimental evidence is shown that part of this increase is due to the liquid drag force when molecules are imaged under liquid. The liquid drag force is calculated using standard fluid dynamics where the tip motion in the liquid is modeled by the relative motion of a cylinder through a constant velocity fluid. The Reynold’s number for the experimental configuration is smaller than 1, characterizing a laminar flow and the calculated drag force is 80 pN, which is in agreement with the experimentally measured force for ethanol and relative tip velocity of 100 μm/s. Both the viscous drag force and the apparent width increase may be modeled by a vk dependence, where v is the sample velocity relative to the tip, and k is a constant independent of the liquid and the tip–sample geometry and is equal to 0.53. An apparent molecular width increase of ∼30 nm for a ∼2 nm diam molecule for a 150 μm/s scanning velocity was observed. © 1997 American Institute of Physics.
Show PACS
87.64.Dz Scanning tunneling and atomic force microscopy
87.80.-y Biophysical techniques (research methods)
87.19.-j Properties of higher organisms
87.15.-v Biomolecules: structure and physical properties

Direct observation of sp3 bonding in tetrahedral amorphous carbon using ultraviolet Raman spectroscopy

K. W. R. Gilkes, H. S. Sands, D. N. Batchelder, J. Robertson, and W. I. Milne

Appl. Phys. Lett. 70, 1980 (1997); http://dx.doi.org/10.1063/1.118798 (3 pages) | Cited 111 times

Full Text: | Download PDF

Show Abstract
The vibrational modes of the sp3 sites in tetrahedral amorphous carbon (ta-C) thin films are revealed directly using ultraviolet Raman spectroscopy at 244 nm excitation and are shown to produce a Raman peak centered around 1100 cm−1. In addition, the main Raman peak associated with sp2 vibrational modes is shifted upward in frequency by 100 cm−1 relative to its position in spectra excited at 514 nm. The spectra are interpreted in terms of the bonding in ta-C. © 1997 American Institute of Physics.
Show PACS
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
78.40.Pg Disordered solids
61.43.Er Other amorphous solids

Deep levels and persistent photoconductivity in GaN thin films

C. H. Qiu and J. I. Pankove

Appl. Phys. Lett. 70, 1983 (1997); http://dx.doi.org/10.1063/1.118799 (3 pages) | Cited 92 times

Full Text: | Download PDF

Show Abstract
Photocurrent decay in GaN thin films was studied in the time span from a few seconds to several days. The persistent photoconductivity (PPC) behavior was observed not only in Mg-doped p-type GaN films but also in undoped n-type GaN films. The photoconductivity spectra and the photocurrent response time were measured using a weak probe light at several times after the samples had been kept in the dark. During the relaxation, the photocurrent due to the subband-gap probe light decreased more than the photocurrent due to the UV probe light. It is suggested that metastable centers at 1.1, 1.40, and 2.04 eV above the valence band edge are responsible for the PPC behavior in Mg-doped GaN, and that Ga vacancy is the candidate for PPC effect in n-type GaN. © 1997 American Institute of Physics.
Show PACS
71.55.Eq III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Tunneling spectroscopy for quantum well excitons

H. Cao, G. Klimovitch, G. Björk, S. Pau, and Y. Yamamoto

Appl. Phys. Lett. 70, 1986 (1997); http://dx.doi.org/10.1063/1.118800 (3 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
We have demonstrated a technique of directly measuring the exciton binding energy and the valence band split in the quantum well through a tunneling process. We have also measured the emission efficiency of quantum well heavy-hole excitons and light-hole excitons into the normal direction. © 1997 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.15.Nc Total energy and cohesive energy calculations
73.20.At Surface states, band structure, electron density of states
71.35.-y Excitons and related phenomena

Silicon quantum well as passivation barrier on GaAs surface

Z. H. Lu and J.-M. Baribeau

Appl. Phys. Lett. 70, 1989 (1997); http://dx.doi.org/10.1063/1.118801 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Synchrotron radiation Si L-edge absorption spectroscopy is used to study the band structure of thin silicon passivation films on GaAs(100) surface. The measurements show that the Si L-edge, which measures the conduction band minimum (CBM), is shifted drastically to a higher energy as the Si film thickness is reduced to below 2.5 nm. This shift in the CBM is found to scale with the Si layer thickness L as 1/L1.7, indicating that the electronic states within the Si layer are quantum confined. Within a confined quantum well, the energy levels of all states including localized gap states will be shifted to higher energy. Quantum confinement effects in the thin Si layer is found responsible for its successful use for passivation of GaAs surfaces.© 1997 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Ea III-V semiconductors
81.65.Rv Passivation
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
78.70.Dm X-ray absorption spectra
73.20.At Surface states, band structure, electron density of states
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Very low dark current metal–semiconductor–metal ultraviolet photodetectors fabricated on single-crystal GaN epitaxial layers

J. C. Carrano, P. A. Grudowski, C. J. Eiting, R. D. Dupuis, and J. C. Campbell

Appl. Phys. Lett. 70, 1992 (1997); http://dx.doi.org/10.1063/1.118777 (3 pages) | Cited 55 times

Full Text: | Download PDF

Show Abstract
We report a very low dark current (∼57 pA at 10 V reverse bias) metal–semiconductor–metal photodetectors fabricated on GaN epitaxial layers grown by low-pressure metalorganic chemical vapor deposition. The photodetectors exhibit the typical sharp band-edge cutoff, with good responsivity. There is indication of a photoconductive gain mechanism. We also performed a Medici simulation to establish an effective area for current density calculations. © 1997 American Institute of Physics.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.40.Sx Metal-semiconductor-metal structures
85.30.De Semiconductor-device characterization, design, and modeling
72.40.+w Photoconduction and photovoltaic effects
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
Page 1 of 2 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close