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4 May 1998

Volume 72, Issue 18, pp. 2199-2342

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Wavelength dependence of carrier-type in reduced BaTiO3:Rh

J. Y. Chang, C. R. Chinjen, S. H. Duan, C. Y. Huang, and C. C. Sun

Appl. Phys. Lett. 72, 2199 (1998); http://dx.doi.org/10.1063/1.121321 (3 pages) | Cited 2 times

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We report that in BaTiO3:Rh the carrier-type depends not only on the postprocessing condition but also on the incident wavelength in two beam coupling. Carriers are the holes for the as-grown sample, and change to electrons for the sample reduced in the atmosphere of 10−14 atm oxygen partial pressure. However, for the sample reduced in the atmosphere of 10−10 atm oxygen partial pressure, the carrier is an electron for the incident wavelength of 514 nm, and a hole for 633 nm. Its absorption, photoinduced absorption, and two beam coupling are investigated and discussed. © 1998 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
78.20.-e Optical properties of bulk materials and thin films
42.70.Gi Light-sensitive materials

Optical properties of AlxGa1−xN/GaN heterostructures on sapphire by spectroscopic ellipsometry

G. Yu, H. Ishikawa, M. Umeno, T. Egawa, J. Watanabe, T. Jimbo, and T. Soga

Appl. Phys. Lett. 72, 2202 (1998); http://dx.doi.org/10.1063/1.121322 (3 pages) | Cited 25 times

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A method of analysis of spectroscopic ellipsometry (SE) measurement data is proposed for AlxGa1−xN/GaN heterostructures grown on sapphire substrates. The SE data measured at three angles of incidence, 40°, 50°, and 60°, are simultaneously fitted assuming the dielectric function to consist of a Sellmeir dispersion equation and a free-exciton absorption term. The refractive index n and the extinction coefficient k of undoped AlxGa1−xN films are determined in the spectral range of 1.5–4.13 eV of photon energy. The transition energy of the free exciton, which is in excellent agreement with the reported results for GaN in a previous paper, is found to vary from 3.44 to 3.95 eV when the composition x varies from 0 to 0.151. The refractive index n of AlxGa1−xN has also been compared with those reported results. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
71.35.-y Excitons and related phenomena
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High-finesse AlxOy/AlGaAs nonabsorbing optical cavity

Hyun-Eoi Shin, Young-Gu Ju, Hyun-Woo Song, Dae-Sung Song, Il-Young Han, Jung-Hoon Ser, Han-Youl Ryu, Yong-Hee Lee, and Hyo-Hoon Park

Appl. Phys. Lett. 72, 2205 (1998); http://dx.doi.org/10.1063/1.121323 (3 pages) | Cited 9 times

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We report the measured finesse value of ∼ 390 in nonabsorbing AlxOy/AlGaAs cavities. The nonabsorbing cavity consisting of a bottom AlxOy/AlGaAs distributed Bragg reflector (DBR), an AlxOy spacer layer, and a top AlxOy/AlGaAs DBR is prepared by a wet-oxidation process. The measured resonance linewidth agrees well with that of calculation, indicating very small overall losses in the cavity. The wet-oxidation process does not seem to degrade the interface of the epitaxial layers significantly. The lower bound of maximum achievable reflectivity from the AlxOy DBR is estimated to be >99.95%, assuming an average interface roughness of about 0.6 nm. The maximum achievable finesse of this type of cavity is expected to be larger than that of the all-epitaxial counterpart assuming the same roughness. © 1998 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes

Strongly enhanced soft x-ray emission at 8 nm from plasma on a neodymium-doped glass surface heated by femtosecond laser pulses

Hidetoshi Nakano, Tadashi Nishikawa, and Naoshi Uesugi

Appl. Phys. Lett. 72, 2208 (1998); http://dx.doi.org/10.1063/1.121324 (3 pages) | Cited 3 times

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We have demonstrated efficient soft x-ray generation from femtosecond laser plasma created on a neodymium-doped glass target. Nd ions doped in glass target enhanced soft x-ray emission near 8 nm without broadening the soft x-ray pulse duration when there is no prepulse. A weak prepulse caused strong enhancement in soft x-ray intensity at 8 nm. By introducing a prepulse at 50 ns before the main pulse, 1% energy conversion efficiency from laser pulse into soft x-ray at 8±0.5 nm was achieved by using a neodymium-doped glass target. This value is 1.2 times as high as that for Nd metal target case. © 1998 American Institute of Physics.
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78.70.En X-ray emission spectra and fluorescence
78.47.-p Spectroscopy of solid state dynamics
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Generation of Q-switched Er:YAG laser pulses using evanescent wave absorption in ethanol

K. L. Vodopyanov, R. Shori, and O. M. Stafsudd

Appl. Phys. Lett. 72, 2211 (1998); http://dx.doi.org/10.1063/1.121325 (3 pages) | Cited 8 times

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We report on a technique of passively Q switching an Er:YAG laser operating at 2.94 μm. The Q switch consists of a high refractive index prism having one total internal reflection surface in contact with an absorbing liquid. The initial losses were achieved via attenuated total reflection. Using the above Q switch, pulses with up to 85 mJ having 130–140 ns pulse width were generated. The output was linearly polarized and the spacial beam profile was near TEM00. The laser was operated at 2 Hz repetition rate. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.79.Bh Lenses, prisms and mirrors

A multistate external cavity laser diode

A. P. Kanjamala and A. F. J. Levi

Appl. Phys. Lett. 72, 2214 (1998); http://dx.doi.org/10.1063/1.121326 (3 pages) | Cited 2 times

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A semiconductor laser diode in a photon cavity containing a mirror whose optical bandwidth is less than the classical cavity mode spacing can have multiple lasing states at the same bias current. The physics determining the behavior of this nonlinear multistate device is self-consistency between photon number, carrier number, and refractive index. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Dj Gratings
42.81.Wg Other fiber-optical devices

Electroluminescence of a novel terbium complex

X. C. Gao, Hong Cao, Chunhui Huang, Biaoguo Li, and Shigeo Umitani

Appl. Phys. Lett. 72, 2217 (1998); http://dx.doi.org/10.1063/1.121327 (3 pages) | Cited 44 times

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We describe efficient electroluminescence from a terbium complex, tris-(1-phenyl-3-methyl-4isobutyryl-5-pyrozolone)-bis(triphenyl phosphine oxide) terbium (PTT). The green-emitting material possesses much higher photoluminescence efficiency compared to the commonly used green light emitter, 8-hydroxyquinoline aluminum (ALQ). The rarely observed emission from the hole transport layer, N, N′-bis(3-methylphenyl)-N, N′-diphenyl-benzidine (TPD) of the device ITO/TPD/PTT/Al proves that PTT also is a good electron transporting material. The ITO/TPD/PTT/ALQ/Al device shows luminance up to 920cd/m2 at a drive voltage of 18 V and a luminous efficiency of 0.51 lm/W at a current density of 0.70 mA/cm2, which are up to now the highest among devices using rare-earth complex materials as emitters. © 1998 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Mid-infrared interband cascade lasers with quantum efficiencies >200%

B. H. Yang, D. Zhang, Rui Q. Yang, C.-H. Lin, S. J. Murry, and S. S. Pei

Appl. Phys. Lett. 72, 2220 (1998); http://dx.doi.org/10.1063/1.121265 (3 pages) | Cited 42 times

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An external differential quantum efficiency exceeding 200% has been observed from 4 μm InAs/InGaSb/AlSb interband cascade lasers under 1 μs pulses and 0.1% duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers >16 mW have been measured with 5 μs pulses at 10% duty cycle, the internal quantum efficiency and the internal loss are determined to be 220% and 14 cm−1, respectively. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Far-field emission narrowing effect of microdisk lasers

T.-D. Lee, P.-H. Cheng, J.-S. Pan, R.-S. Tsai, Y. Lai, and K. Tai

Appl. Phys. Lett. 72, 2223 (1998); http://dx.doi.org/10.1063/1.121328 (3 pages) | Cited 7 times

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Far-field intensity distribution of semiconductor microdisk lasers is experimentally measured and the emission angle is found to be much smaller than that of a planar source with the same near-field width. In fact the emission angle is determined mainly by the disk radius instead of the disk thickness. A scalar diffraction theory in the cylindrical coordinate is developed to explain such an emission-angle-narrowing phenomenon and numerical calculation based on a vectorial diffraction theory is carried out to explain the measured polarization state. © 1998 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.25.Ja Polarization
42.25.Fx Diffraction and scattering

Low voltage cathodoluminescence properties of blue emitting SrGa2S4:Ce3+ and ZnS:Ag,Cl phosphors

F.-L. Zhang, S. Yang, C. Stoffers, J. Penczek, P. N. Yocom, D. Zaremba, B. K. Wagner, and C. J. Summers

Appl. Phys. Lett. 72, 2226 (1998); http://dx.doi.org/10.1063/1.121266 (3 pages) | Cited 30 times

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The low voltage properties of ZnS:Ag and SrGa2S4:Ce3+ have been investigated for applications in field emission displays. It was observed that although ZnS:Ag,Cl has slightly better chromaticity than SrGa2S4:Ce3+, the high luminous efficiency, fast decay time, and better saturation behavior of the thiogallate potentially make it a very important blue phosphor. © 1998 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence

Temperature-dependent terahertz output from semi-insulating GaAs photoconductive switches

A. G. Markelz and E. J. Heilweil

Appl. Phys. Lett. 72, 2229 (1998); http://dx.doi.org/10.1063/1.121329 (3 pages) | Cited 11 times

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The temperature dependence of the terahertz (THz) output power and spectra from biased photoconductive switches was measured for several antenna gap widths and applied biases. The spectrally integrated THz output had a nonmonotonic temperature dependence in all cases with the value increasing by a factor of 3 from room temperature to 150 K for low biases and 100 K at high biases. An abrupt decrease in output power occurs below 90 K, and the spectrum shifts to lower frequencies as the temperature is lowered. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
85.60.-q Optoelectronic devices

On the lack of influence of disorder in Cr3+-doped LiSr0.8Ca0.2AlF6

Keith Holliday, D. L. Russell, J. F. H. Nicholls, B. Henderson, Mitsuo Yamaga, and Taturu Yosida

Appl. Phys. Lett. 72, 2232 (1998); http://dx.doi.org/10.1063/1.121330 (3 pages) | Cited 3 times

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Optical and electron spin resonance spectroscopies have been used to investigate the thermal stability of lasers based on Cr3+:LiSr0.8Ca0.2AlF6, a material in which the onset of critically inhibiting nonradiative decay at temperatures below 300 K might be expected based on results from other Cr3+-activated disordered gain media. The influence of disorder on the Cr3+ environment is shown to be very small in LiSr0.8Ca0.2AlF6 so that the 4T2→4A2 fluorescence transition is not broadened relative to that in LiSrAlF6 and the onset of significant nonradiative decay is also held above room temperature. © 1998 American Institute of Physics.
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76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)
78.55.Hx Other solid inorganic materials
42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
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Picosecond ultrasonics study of the modification of interfacial bonding by ion implantation

G. Tas, J. J. Loomis, H. J. Maris, A. A. Bailes, and L. E. Seiberling

Appl. Phys. Lett. 72, 2235 (1998); http://dx.doi.org/10.1063/1.121276 (3 pages) | Cited 26 times

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We report on experiments in which picosecond ultrasonic techniques are used to investigate the modification of interfacial bonding that results from ion implantation. The bonding is studied through measurements of the acoustic reflection coefficient at the interface. This method is nondestructive and can be used to create a map of the variation of the bonding over the area of the interface. © 1998 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
61.72.up Other materials
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
68.60.Bs Mechanical and acoustical properties

A piezoelectric pseudoshear multilayer actuator

Qing-Ming Wang and L. E. Cross

Appl. Phys. Lett. 72, 2238 (1998); http://dx.doi.org/10.1063/1.121331 (3 pages) | Cited 3 times

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A type of high strain piezoelectric ceramic actuator, namely, pseudoshear multilayer actuator, is described. In this structure, a stack of prepoled rectangular piezoelectric transducer ceramic sheets are conductively bonded at alternate ends, while the bottom layer bonded on a fixed base. When driven, alternate layers elongate or shrink in the same direction through converse piezoelectric effect, which results in the actuator structure developing a strong shear motion about the face perpendicular to the bonding direction. Experimental results indicate that more than 50 μm displacement can be achieved from the top layer for an actuator consisting of 18 layers with dimensions of 25.57 mm×4.02 mm×0.51 mm (1×w×t). By reducing ceramic sheet thickness and using more layers, even large displacement can be obtained, and driving voltage can also be reduced while keeping the same field level. Nonlinear piezoelectric response under high driving field further enhances the displacement level. © 1998 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Anisotropic modulated structures upon annealing of epitaxial AuNi ultrathin films on Au(001)

C. Dressler, G. Abadias, P. Bayle-Guillemaud, A. Marty, I. Schuster, J. Thibault, and B. Gilles

Appl. Phys. Lett. 72, 2241 (1998); http://dx.doi.org/10.1063/1.121267 (3 pages) | Cited 6 times

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This letter presents experimental evidence of an anisotropic compositional modulation upon annealing in (Ni/Au)n multilayers and Au–Ni alloy ultrathin films embedded in Au layers. These materials were grown by molecular beam epitaxy, on a (001)Au buffer layer. The influence of temperature, local composition, and strain has been investigated by high-resolution electron microscopy and x-ray diffraction. © 1998 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology

Electron emission induced modifications in amorphous tetrahedral diamondlike carbon

T. W. Mercer, N. J. DiNardo, J. B. Rothman, M. P. Siegal, T. A. Friedmann, and L. J. Martinez-Miranda

Appl. Phys. Lett. 72, 2244 (1998); http://dx.doi.org/10.1063/1.121332 (3 pages) | Cited 32 times

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The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by “conditioning” where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination. © 1998 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.43.Er Other amorphous solids
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.At Surface states, band structure, electron density of states
79.20.Kz Other electron-impact emission phenomena

Scanning capacitance microscopy imaging of threading dislocations in GaN films grown on (0001) sapphire by metalorganic chemical vapor deposition

P. J. Hansen, Y. E. Strausser, A. N. Erickson, E. J. Tarsa, P. Kozodoy, E. G. Brazel, J. P. Ibbetson, U. Mishra, V. Narayanamurti, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 72, 2247 (1998); http://dx.doi.org/10.1063/1.121268 (3 pages) | Cited 138 times

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A combination of atomic force microscopy and scanning capacitance microscopy was used to investigate the relationship between the surface morphology and the near-surface electrical properties of GaN films grown on c-axis sapphire substrates by metalorganic chemical vapor deposition. Local regions surrounding the surface termination of threading dislocations displayed a reduced change in capacitance with applied voltage relative to regions that contained no dislocations. Capacitance–voltage characteristics obtained from these regions indicated the presence of negative charge in the vicinity of dislocations. © 1998 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.61.Ey III-V semiconductors
07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
61.72.Lk Linear defects: dislocations, disclinations
71.55.Eq III-V semiconductors
73.25.+i Surface conductivity and carrier phenomena
73.20.Hb Impurity and defect levels; energy states of adsorbed species
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Measurements of thermal transport in low stress silicon nitride films

W. Holmes, J. M. Gildemeister, P. L. Richards, and V. Kotsubo

Appl. Phys. Lett. 72, 2250 (1998); http://dx.doi.org/10.1063/1.121269 (3 pages) | Cited 45 times

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We have measured the thermal conductance, G, of ≈ 1 μm thick low stress silicon nitride membranes over the temperature range, 0.06<T<6 K, as a function of surface condition. For T>4 K, G is independent of surface condition indicating that the thermal transport is determined by bulk scattering. For T<4 K, scattering from membrane surfaces becomes significant. Membranes which have submicron sized Ag particles glued to the surface or are micromachined into narrow strips have a G that is reduced by a factor as large as 5 compared with that of clean, solid membranes with the same ratio of cross section to length. © 1998 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.60.Dv Thermal stability; thermal effects
05.70.Ce Thermodynamic functions and equations of state
61.43.Er Other amorphous solids
63.50.-x Vibrational states in disordered systems
68.35.Ja Surface and interface dynamics and vibrations
68.55.-a Thin film structure and morphology

A method for the formation of polymer walls in liquid crystal/polymer mixtures

Yoan Kim, Jim Francl, Bahman Taheri, and John L. West

Appl. Phys. Lett. 72, 2253 (1998); http://dx.doi.org/10.1063/1.121333 (3 pages) | Cited 49 times

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We have investigated the formation of polymer walls for high polymer content liquid crystal (LC) formulations, using a patterned electric field to induce phase separation. The effect of this field on the phase separation temperature of a LC/monomer mixture is studied as a function of the photopolymerizable monomer concentration. The phase separation temperature increases with the patterned field strength. The application of a patterned field results in segregation of the LC molecules in the high electric field regions, i.e., pixels, whereas the monomers segregate in the low-field regions, i.e., interpixels. Subsequent photopolymerization results in the formation of polymer walls around the pixels. The structure of the polymer walls was investigated using scanning electron microscopy. © 1998 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
64.75.-g Phase equilibria
82.35.-x Polymers: properties; reactions; polymerization

Current–voltage characteristics of metal-insulator-semiconductor structures via quantum mechanical tunneling

Jihad M. Mohaidat and Riyad N. Ahmad-Bitar

Appl. Phys. Lett. 72, 2256 (1998); http://dx.doi.org/10.1063/1.121270 (3 pages) | Cited 4 times

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The current–voltage (I-V) characteristics for a metal-insulator-heavily-doped semiconductor structure are computed numerically by solving the time-dependent Schrödinger equation. The Fowler–Nordheim tunneling expression was found to be inappropriate to estimate the barrier potential nor found to fit the experimental results at both high and low applied fields. It is shown also that the computed I–V characteristic curves agree well with the recently published experimental data for Ta-Sn-O and Ta2O5 films at the high as well as low fields.© 1998 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
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Observation of a Cole–Davidson type complex conductivity in the limit of very low carrier densities in doped silicon

Tae-In Jeon and D. Grischkowsky

Appl. Phys. Lett. 72, 2259 (1998); http://dx.doi.org/10.1063/1.121271 (3 pages) | Cited 23 times

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Using THz time-domain spectroscopy to measure the complex conductivity of doped silicon from low frequencies to frequencies higher than the THz plasma frequency and the carrier damping rate, we were able to show in the limit of extremely low carrier densities N<1013/cm3, that the Cole–Davidson (C–D) type complex conductivity accurately describes the conductivity of doped silicon. In the low N limit the C–D parameter β converges to 0.83 for n-type and 0.70 for p-type silicon. In addition, we have observed a new absorption line at 1.9 THz from an unidentified defect in some of our Czochralski, single-crystal, low-N silicon samples. © 1998 American Institute of Physics.
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72.80.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.30.+q High-frequency effects; plasma effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Si/SiGe quantum wells grown on vicinal Si(001) substrates: Morphology, dislocation dynamics, and transport properties

P. Waltereit, J. M. Fernández, S. Kaya, and T. J. Thornton

Appl. Phys. Lett. 72, 2262 (1998); http://dx.doi.org/10.1063/1.121272 (3 pages) | Cited 14 times

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Compositionally graded, strain relaxed Si0.72Ge0.28 buffers were grown on vicinal Si(001) substrates by gas source molecular beam epitaxy. Misfit dislocations are shown to run along intersections of the {111} glide planes with the (11n) interface. X-ray diffraction studies demonstrate a relative tilt of the epilayer to the substrate in a direction which depends on the interplay between substrate orientation related preferential dislocation nucleation rates and surface contamination induced heterogeneous nucleation. Atomic force microscopy (AFM) images reveal an anisotropy in surface roughness on the μm scale related to reduced growth rates on vicinal surfaces. Transport properties at 0.4 K in two dimensional electron gases grown on these relaxed SiGe buffers show anisotropic scattering times similar to interface roughness scattering which can be correlated to terrace configurations in the nm range determined by AFM. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Cw Elemental semiconductors
73.61.Le Other inorganic semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness

Atomic structure of faceted planes of three-dimensional InAs islands on GaAs(001) studied by scanning tunneling microscope

Y. Hasegawa, H. Kiyama, Q. K. Xue, and T. Sakurai

Appl. Phys. Lett. 72, 2265 (1998); http://dx.doi.org/10.1063/1.121273 (3 pages) | Cited 51 times

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The three-dimensional (3D) island structure was prepared by molecular beam epitaxy for the lattice mismatched InAs/GaAs(001) system and its images showing atomic structure on faceted planes were taken in situ by ultrahigh vacuum scanning tunneling microscopy (STM). The (113), (114), and (215) faceted planes are observed for the 3D islands. Based on the STM images, atomic structural models are proposed for the faceted surfaces. The surface structure of the (113) faceted planes we propose is different from those observed on the flat GaAs(113) surface. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)

Behavior of Al–Al2O3–Al single-electron transistors from 85 mK to 5 K

M. Kenyon, A. Amar, D. Song, C. J. Lobb, and F. C. Wellstood

Appl. Phys. Lett. 72, 2268 (1998); http://dx.doi.org/10.1063/1.121334 (3 pages) | Cited 3 times

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Using e-beam lithography and conventional double-angle evaporation, we have fabricated Al–Al2O3–Al single-electron transistors and studied their behavior from 85 mK to about 5 K. The total island capacitance CΣ of the devices ranges from 120 to 200 aF, with typical estimated junction overlaps of about 30 nm×30 nm. At 4.2 K, our devices display well-behaved periodic I–Vg characteristics with the maximum charge-transfer function ∂I/∂Q0 ranging from 4 to 130 pA/e. The electrical characteristics of these devices agree well with the predictions of the Orthodox Theory, with current modulation being observed up to a temperature T ≃ e2/(2CΣkB). Below 1 K small deviations occur, which are partly due to island self-heating effects. © 1998 American Institute of Physics.
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85.35.Gv Single electron devices
85.40.Hp Lithography, masks and pattern transfer

Hydrogen-induced thermal interface degradation in (111) Si/SiO2 revealed by electron-spin resonance

A. Stesmans and V. V. Afanas’ev

Appl. Phys. Lett. 72, 2271 (1998); http://dx.doi.org/10.1063/1.121335 (3 pages) | Cited 20 times

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Electron-spin resonance (ESR) experiments show that the interface degradation induced in thermal (111) Si/SiO2 by postoxidation annealing (POA) in vacuum—previously isolated by ESR as a permanent creation of Pb (∘Si ≡ Si3) interface defects—is strongly enhanced ( ∼ 6 times) when performed in H2 ambient. It, thus, appears that the H2 POA step, standardly applied to passivate interface states (preexisting Pbs) naturally introduced during oxidation, effectively creates additional defect entities; the process initiates from ∼ 550 °C onward vis-à-vis ∼ 640 °C for vacuum. The results unveil the atomic nature of one of the mechanisms of the electrically long-known H-induced POA generation of adverse interface states. © 1998 American Institute of Physics.
Show PACS
81.05.Cy Elemental semiconductors
81.65.Mq Oxidation
73.20.Hb Impurity and defect levels; energy states of adsorbed species
76.30.Mi Color centers and other defects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.40.Gh Other heat and thermomechanical treatments
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