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12 Jul 1999

Volume 75, Issue 2, pp. 151-304

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Electronic states at conducting polymer/conducting oxide interfaces observed using a low-energy photoelectron spectroscopic method

Naoki Nakanishi, Kazuya Tada, Mitsuyoshi Onoda, and Hiroshi Nakayama

Appl. Phys. Lett. 75, 226 (1999); http://dx.doi.org/10.1063/1.124330 (3 pages) | Cited 4 times

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We have observed the electronic states at conducting polymer/conducting oxide interfaces using a low-energy photoelectron spectroscopic method. The electronic states of conducting polymer/indium tin oxide (ITO) interfaces were different from those of conducting polymer/metal interfaces. The electron transfer from a conducting polymer to ITO occurred at the interfaces, and is not related to the difference of the ionization potential between conducting polymers and ITO. Although the origin of this electron transfer is not clear at this stage, we speculate that the surface states of ITO play a major role. Moreover, the electron transfer at the interfaces is enhanced at higher temperatures. Other conducting oxides such as indium oxide (In2O3) and tin oxide (SnO2) also show a similar tendency to that of ITO. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
73.61.Ph Polymers; organic compounds
79.60.Jv Interfaces; heterostructures; nanostructures

Effect of arsenic doping on {311} defect dissolution in silicon

Richard Brindos, Patrick Keys, Kevin S. Jones, and Mark E. Law

Appl. Phys. Lett. 75, 229 (1999); http://dx.doi.org/10.1063/1.124331 (3 pages) | Cited 13 times

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Si+ ions were implanted into silicon wafers with background concentrations of arsenic ranging from 1×1017 to 3×1019 cm−3 to study the interaction between arsenic atoms and excess self-interstitials. Samples were then annealed at 750 °C for a range of times between 15 and 60 min to nucleate and dissolve {311} defects. The concentration of trapped interstitials in these defects was measured using quantitative plan-view transmission electron microscopy. It is shown that, as the arsenic concentration increases, there is a reduction in the number and size of the {311} defects. This decrease in the {311} defect density with increasing arsenic well concentration is believed to be the result of interstitial trapping by the arsenic. Upon annealing, the trapped interstitial concentration in the {311} defects decreases as the defects dissolve. The time constant for the dissolution was calculated to be 33±5 min at 750 °C, and was independent of background concentration. This suggests that the arsenic traps some of the interstitials, and these traps are sufficiently stable that they do not affect the subsequent {311} dissolution at 750 °C. © 1999 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uf Ge and Si
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
81.05.Cy Elemental semiconductors

Depth and thermal stability of dry etch damage in GaN Schottky diodes

X. A. Cao, H. Cho, S. J. Pearton, G. T. Dang, A. P. Zhang, F. Ren, R. J. Shul, L. Zhang, R. Hickman, and J. M. Van Hove

Appl. Phys. Lett. 75, 232 (1999); http://dx.doi.org/10.1063/1.124332 (3 pages) | Cited 51 times

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GaN Schottky diodes were exposed to N2 or H2 inductively coupled plasmas prior to deposition of the rectifying contact. Subsequent annealing, wet photochemical etching, or (NH4)2S surface passivation treatments were examined for their effect on diode current–voltage (I–V) characteristics. We found that either annealing at 750 °C under N2, or removal of ∼500–600 Å of the surface essentially restored the initial I–V characteristics. There was no measurable improvement in the plasma-exposed diode behavior with (NH4)2S treatments. © 1999 American Institute of Physics.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
81.65.Rv Passivation

Growth and luminescence properties of self-organized ZnSe quantum dots

Takehiko Tawara, Satoru Tanaka, Hidekazu Kumano, and Ikuo Suemune

Appl. Phys. Lett. 75, 235 (1999); http://dx.doi.org/10.1063/1.124333 (3 pages) | Cited 24 times

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Self-organized ZnSe quantum dots (QDs) were grown on (100) ZnS/GaAs surfaces to study the relation of the size dispersion and luminescence. The exact dot sizes were obtained by measurements of atomic force microscope with its tip calibration and transmission electron microscope. The average dot size was 2.0 nm high and 11 nm in its diameter and the density was 1×1010 cm−2. Transition energies of ZnSe QDs were calculated using these measured dot sizes. These calculated peaks were in reasonable agreement with measured photoluminescence (PL) peaks. It was also revealed that the broadening of the PL spectra from ZnSe QDs were consistently explained by the dot size distribution. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Measurement of AlInAsSb/GaInAsSb heterojunction band offset by photoluminescence spectroscopy

J. R. Chang, Y. K. Su, C. L. Lin, K. M. Wu, W. C. Huang, Y. T. Lu, D. H. Jaw, W. L. Li, and S. M. Chen

Appl. Phys. Lett. 75, 238 (1999); http://dx.doi.org/10.1063/1.124334 (3 pages) | Cited 5 times

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We have grown unstrained Al0.66In0.34As0.85Sb0.15/Ga0.64In0.36As0.84Sb0.16 multiple-quantum-well (MQW) structures on InP substrates by metalorganic vapor phase epitaxy. Low-temperature photoluminescence was performed for these MQW structures. By comparing the luminescence peak energies with the theoretical calculations, we estimated the conduction-band offset ratio to be 0.75±0.10 for the Al0.66In0.34As0.85Sb0.15/Ga0.64In0.36As0.84Sb0.16 heterostructure. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

The impact of in situ photoexcitation on the formation of vacancy-type complexes in silicon implanted at 85 and 295 K

N. Yarykin, C. R. Cho, G. A. Rozgonyi, and R. A. Zuhr

Appl. Phys. Lett. 75, 241 (1999); http://dx.doi.org/10.1063/1.124335 (3 pages) | Cited 2 times

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Photoexcitation of silicon during low-fluence implantation with MeV Si and Ge ions is observed to suppress vacancy-type point-defect formation, as determined by in situ deep-level transient spectroscopy. The A-center formation after low-temperature implantation is extended over a wide temperature interval indicating that electrically inactive clusters, which emit vacancies during annealing, are formed in the end-of-range region during implantation at 85 K. The number of vacancies stored in these clusters is influenced by low-temperature in situ photoexcitation. © 1999 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si

Quantum-well width dependence of threshold current density in InGaN lasers

W. W. Chow, H. Amano, T. Takeuchi, and J. Han

Appl. Phys. Lett. 75, 244 (1999); http://dx.doi.org/10.1063/1.124336 (3 pages) | Cited 15 times

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The quantum-confined Stark effect was found to result in a strong quantum-well width dependence of threshold current density in strained group-III nitride quantum well lasers. For an In0.2Ga0.8N/GaN structure with quantum-well width in the neighborhood of 3.5 nm, our analysis shows that the reduction in spontaneous emission loss by the electron–hole spatial separation outweighs the corresponding reduction in gain to produce a threshold current-density minimum. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

High-performance (Al,Ga)N-based solar-blind ultraviolet p–i–n detectors on laterally epitaxially overgrown GaN

G. Parish, S. Keller, P. Kozodoy, J. P. Ibbetson, H. Marchand, P. T. Fini, S. B. Fleischer, S. P. DenBaars, U. K. Mishra, and E. J. Tarsa

Appl. Phys. Lett. 75, 247 (1999); http://dx.doi.org/10.1063/1.124337 (3 pages) | Cited 130 times

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Solar-blind ultraviolet photodiodes with a band-edge wavelength of 285 nm were fabricated on laterally epitaxially overgrown GaN grown by metalorganic chemical vapor deposition. Current–voltage measurements of the diodes exhibited dark current densities as low as 10 nA/cm2 at −5 V. Spectral response measurements revealed peak responsivities of up to 0.05 A/W. Response times for these diodes were measured to be as low as 4.5 ns for 90%-to-10% fall time. For comparison, diodes were fabricated using the same p–i–n structure deposited on dislocated GaN. These diodes had dark current densities many orders of magnitude higher, as well as a less sharp cutoff, and a significant slow tail under impulse excitation. © 1999 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
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Exchange-biasing asymmetric spin valves using a pulsed current

S. Sankar, R. S. Beach, and A. E. Berkowitz

Appl. Phys. Lett. 75, 250 (1999); http://dx.doi.org/10.1063/1.124338 (3 pages)

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The asymmetric spin valve features a quiescent state in which the two ferromagnetic layers are antiparallel for any spacer thickness. It consists of AFM/FM/spacer/FM/AFM, where AFM is an antiferromagnet and FM is a ferromagnet. By cooling through the Néel temperature (TN) with a large current flowing, the FM layers are exchange biased in antiparallel directions. Current along is found to be sufficient to heat the device above TN. Devices with a 45 Å spacer layer were exchanged biased using a steady dc current which is turned down after T>TN; devices with thinner spacer layers (20 and 30 Å) were destroyed by a steady dc current due to excessive heating. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.80.+q Magnetomechanical effects, magnetostriction

Evidence of strong flux pinning in melt-processed ternary (Nd–Eu–Gd)Ba2Cu3Oy superconductors

A. K. Pradhan, M. Muralidhar, M. R. Koblischka, M. Murakami, K. Nakao, and N. Koshizuka

Appl. Phys. Lett. 75, 253 (1999); http://dx.doi.org/10.1063/1.124339 (3 pages) | Cited 21 times

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The flux pinning behavior of ternary melt-processed (Nd–Eu–Gd)Ba2Cu3Oy superconductors is studied with varying defect concentrations using magnetotransport and magnetization measurements. A huge field-induced bump feature in the resistivity with increasing defect density, field-induced magnetization kink and linear voltage-current (V-I) characteristics over the whole transition temperature regime favor the phenomenon of vortex entanglement in the liquid phase. The Nd/Ba substitution sites along with the fine second-phase particles are one of the possible reasons for the vortex entanglement and these defects give rise to high critical current density and reduced dissipation at low temperature with significant enhancement in pinning. © 1999 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
61.72.-y Defects and impurities in crystals; microstructure
72.20.My Galvanomagnetic and other magnetotransport effects
74.25.Sv Critical currents
74.25.F- Transport properties
74.25.Ha Magnetic properties including vortex structures and related phenomena

High exchange bias field induced in ferrimagnetic bilayers of amorphous rare earth–transition-metal alloys

R. Sbiaa and H. Le Gall

Appl. Phys. Lett. 75, 256 (1999); http://dx.doi.org/10.1063/1.124340 (3 pages) | Cited 3 times

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The magnetic reversal processes of exchange-coupled double layers (ECDL) and corresponding single layers of rare-earth–transition metal were studied by magneto-optical Faraday rotation (FR). The dependence of FR on the temperature shows a transition of DyFeCo/TbFeCo ECDL from one type to another near the compensation temperature of single layers. Minor and major hysteresis loops allowed us to measure the exchange bias field induced by DyFeCo, which has also been calculated with an analytical model. We have also observed that an unusual hystersis loop appears few celsius degrees before this transition occurs. In this letter, we analyze and describe different magnetization states, and various kinds of magnetization processes, including the usual and unusual FR loops, are explained in detail. © 1999 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Gg Ferrimagnetics
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.66.Bz Metals and metallic alloys

Enhanced flux pinning in (Nd0.33Sm0.67)Ba2Cu3O7−δ melt-processed superconductors by Ar postannealing

A. Hu, P. Schätzle, W. Bieger, P. Verges, G. Fuchs, and G. Krabbes

Appl. Phys. Lett. 75, 259 (1999); http://dx.doi.org/10.1063/1.124341 (3 pages) | Cited 22 times

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High-quality binary (Nd0.33Sm0.67)Ba2Cu3O7−δ monodomain superconductors were fabricated by the combination of a compositional-controlled melt-processing technique in air and postannealing in Ar. Critical current densities over the whole field range were observed strongly dependent on Ar postannealing while holding superconducting transition temperatures as high as 96 K. The suppressed chemical variation between the rare-earth element (RE: Nd, Sm) and Ba associated with disperse RE2BaCuOy (RE211) precipitate due to the decomposition occurring in Ar postannealing was attributed to the modified flux pinning. This makes Ar postannealing promising to process superconductors with desired properties for various applications. © 1999 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.10.+v Occurrence, potential candidates
74.62.Dh Effects of crystal defects, doping and substitution
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents

Direct writing of low Tc superconductor-normal metal-superconductor junctions using a focused ion beam

R. W. Moseley, W. E. Booij, E. J. Tarte, and M. G. Blamire

Appl. Phys. Lett. 75, 262 (1999); http://dx.doi.org/10.1063/1.124342 (3 pages) | Cited 18 times

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Using a focused ion beam, we have produced superconductor-normal metal-superconductor junctions by controllably removing a portion of the top layer of a patterned superconductor-normal metal thin film. The high-quality junctions showed Josephson coupling which scaled qualitatively with barrier properties and temperature as expected. The largest product of a junction’s critical current and the normal state resistance measured is 98 μV at 4.2 K. The method has good reproducibility and could be exploited in a number of superconducting electronics applications. © 1999 American Institute of Physics.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.50.+r Tunneling phenomena; Josephson effects
81.65.Cf Surface cleaning, etching, patterning
81.05.Bx Metals, semimetals, and alloys
74.25.Sv Critical currents

Excitation of bright and dark microwave magnetic envelope solitons in a resonant ring

Boris A. Kalinikos, Nikolai G. Kovshikov, and Carl E. Patton

Appl. Phys. Lett. 75, 265 (1999); http://dx.doi.org/10.1063/1.124343 (3 pages) | Cited 8 times

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The excitation of both bright and dark microwave magnetic envelope solitons has been realized for one and the same resonant ring containing a yttrium–iron–garnet film magnetostatic wave (MSW) delay line. The resonant ring modifies the MSW character to produce a series of frequency intervals with alternating regions of positive and negative dispersion. These alternating regions support bright and dark soliton production, respectively. © 1999 American Institute of Physics.
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75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Ds Spin waves
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Self-assembling ferroelectric Na0.5K0.5NbO3 thin films by pulsed-laser deposition

Choong-Rae Cho and Alex Grishin

Appl. Phys. Lett. 75, 268 (1999); http://dx.doi.org/10.1063/1.124344 (3 pages) | Cited 65 times

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Highly [100]-axis oriented single-phase Na0.5K0.5NbO3 (NKN) thin films have been grown on polycrystalline Pt80Ir20 (Pt) and SiO2 (native oxide)/Si (111) substrates using KrF excimer laser ablation of a stoichiometric ceramic target. X-ray diffraction θ–2θ scan and rocking curve data are evidence of the strong effect of film self-assembling along the [100] direction regardless of the substrate texture. Furthermore, multiple-cell structuring along the polar axis has been observed in NKN films grown onto the Pt substrate. Ferroelectric measurements yield remnant polarization Pr of 10 μC/cm2 and spontaneous polarization Ps of 17.5 μC/cm2 at 80 kV/cm. The electrical resistivity of the Na0.5K0.5NbO3 film was in the order of 1010 Ω cm at 10 kV/cm. Dielectric permittivity ϵ′ and dissipation factor tan δ have been found to vary 480–440 and 0.028–0.024, respectively, in the frequency range 0.4–100 kHz. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
73.61.-r Electrical properties of specific thin films
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Chirp dependence in InGaAs/InAlAs multiple quantum well electro-absorptive modulators near polarization-independent conditions

M. Pamplona Pires, B. Yavich, and P. L. Souza

Appl. Phys. Lett. 75, 271 (1999); http://dx.doi.org/10.1063/1.124345 (3 pages) | Cited 8 times

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We study the dependence of the chirp parameter on heavy- and light-hole energy splitting by analyzing the change in the absorption curve of different InGaAs/InAlAs p-i-n multiple quantum well structures designed for use in amplitude modulators. We observe, for the transverse electric mode, a high chirp parameter for the sample whose fundamental transition involves the light hole, whereas for samples whose fundamental transition involves the heavy hole, the more polarization sensitive the samples are, the smaller the chirp parameter is. This indicates that it is not possible to have tensile strained InGaAs/InAlAs multiple quantum well structures for electro-absorptive modulators which are simultaneously chirp-free and polarization independent. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.20.Jq Electro-optical effects
42.79.Hp Optical processors, correlators, and modulators
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Tunable, narrow, and directional luminescence from porous silicon light emitting devices

Selena Chan and Philippe M. Fauchet

Appl. Phys. Lett. 75, 274 (1999); http://dx.doi.org/10.1063/1.124346 (3 pages) | Cited 45 times

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Controlled room-temperature photoluminescence (PL) and electroluminescence (EL) from porous silicon (PSi) multilayer structures are achieved. The basic structure is composed of two PSi multilayer mirrors sandwiching a highly luminescent PSi film. This creates an active microcavity resonator, in which a significant PL and EL line narrowing is observed. EL from a microcavity resonator is shown to have a high angular concentration of the output emission (30° around the normal axis). A tunable and narrow EL device, from an all-PSi microcavity resonator is presented, which offers the possibility for high spectral purity, flat-panel displays. © 1999 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.05.Rm Porous materials; granular materials
78.60.Fi Electroluminescence
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.
85.60.Jb Light-emitting devices

A deep semiconductor defect with continuously variable activation energy and capture cross section

M. A. Lourenço, Wai Lek Ng, K. P. Homewood, and K. Durose

Appl. Phys. Lett. 75, 277 (1999); http://dx.doi.org/10.1063/1.124347 (3 pages) | Cited 3 times

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A deep level with a continuously varying activation energy and capture cross section has been observed in CdS/CdTe thin-film solar cells. Given that the activation energy and capture cross section of a level are usually considered to be a unique identifier or signature for a particular deep level, this has important implications for the application of deep-level transient spectroscopy and related techniques for the characterization of deep levels in this and similar systems. We believe this phenomenon explains the well-known but poorly understood efficacy of CdCl2 treatment for CdS/CdTe thin solar cells. © 1999 American Institute of Physics.
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71.55.Gs II-VI semiconductors
84.60.Jt Photoelectric conversion
73.61.Ga II-VI semiconductors

Proton-induced disorder in InP-based resonant tunneling diodes

E. M. Jackson, B. D. Weaver, A. C. Seabaugh, J. P. A. Van der Wagt, and E. A. Beam

Appl. Phys. Lett. 75, 280 (1999); http://dx.doi.org/10.1063/1.124348 (3 pages) | Cited 5 times

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We have fabricated arrays of resonant tunneling diodes based on InP substrates for exposure at room temperature with fluences of 3 MeV protons up to 7×1014 H+/cm2. Proton fluences below about 1×1013 cm−2 have little effect on the resonant tunneling diode but higher fluences decrease the peak current and increase the valley current. We find that proton-induced changes in the operating parameters are qualitatively similar to the effects of doping the wells. © 1999 American Institute of Physics.
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85.30.Kk Junction diodes
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
73.61.Ey III-V semiconductors

Ballistic-electron-emission-spectroscopy detection of monolayer thickness fluctuations in a semiconductor heterostructure

D. K. Guthrie, P. N. First, T. K. Gaylord, E. N. Glytsis, and R. E. Leibenguth

Appl. Phys. Lett. 75, 283 (1999); http://dx.doi.org/10.1063/1.124349 (3 pages)

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Ballistic-electron-emission spectroscopy (BEES) is used to measure fluctuations in the thickness of buried Ga0.8Al0.2As layers. The device under measurement is a half-electron-wavelength Fabry–Perot filter that has been designed to have two quasibound states. By performing BEES at several different spatial locations and by utilizing the relationship between the thicknesses of the device layers and the location (in energy) of the quasibound states, single-monolayer variations are detected in the thicknesses of both the GaAs quantum well and the surrounding Ga0.8Al0.2As barriers. The lateral resolution is shown to be better than 20 nm. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
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High-sensitivity quantitative Kelvin probe microscopy by noncontact ultra-high-vacuum atomic force microscopy

Ch. Sommerhalter, Th. W. Matthes, Th. Glatzel, A. Jäger-Waldau, and M. Ch. Lux-Steiner

Appl. Phys. Lett. 75, 286 (1999); http://dx.doi.org/10.1063/1.124357 (3 pages) | Cited 93 times

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We present quantitative measurements of the work function of semiconductor and metal surfaces prepared in ultrahigh vacuum (UHV) using a combination of UHV noncontact atomic force microscopy and Kelvin probe force microscopy. High energetic and lateral resolution is achieved by using the second resonance frequency of the cantilever to measure the electrostatic forces, while the first resonance frequency is used to simultaneously obtain topographic images by the frequency modulation technique. Spatially resolved work-function measurements reveal a reduced work function in the vicinity of steps on highly oriented pyrolytic graphite. On the GaAs(110) surface it could be demonstrated that defect states in the forbidden band gap cause a local pinning of the Fermi level along monolayer steps. On p-WSe2(0001) work-function variations due to the Coulomb potential of single dopant sites were resolved. © 1999 American Institute of Physics.
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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
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

High-sensitivity piezoresistive cantilevers under 1000 Å thick

J. A. Harley and T. W. Kenny

Appl. Phys. Lett. 75, 289 (1999); http://dx.doi.org/10.1063/1.124350 (3 pages) | Cited 62 times

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Ultrathin, high-sensitivity piezoresistive cantilevers were constructed using vapor-phase epitaxy to grow the conducting layer. A fourfold reduction in thickness was achieved over the thinnest implanted piezoresistive cantilevers, allowing improved force or displacement sensitivity and increased bandwidth. In cantilevers 890 Å thick, the dopant is well confined to the surface, and the sensitivity is 70% of the theoretical maximum. A cantilever fabricated for high force resolution has a minimum detectable force of 8.6 fN/math in air. Additionally, the 1/f noise is shown to follow the relation proposed by Hooge [Phys. Lett A 29, 139 (1969)], increasing in inverse proportion to the number of carriers. © 1999 American Institute of Physics.
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77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
81.15.Kk Vapor phase epitaxy; growth from vapor phase
07.79.Lh Atomic force microscopes
73.50.Td Noise processes and phenomena

Direct nanometer-scale patterning by the cantilever oscillation of an atomic force microscope

C. K. Hyon, S. C. Choi, S. W. Hwang, D. Ahn, Yong Kim, and E. K. Kim

Appl. Phys. Lett. 75, 292 (1999); http://dx.doi.org/10.1063/1.124351 (3 pages) | Cited 21 times

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A resistless nanostructure patterning technique using tip oscillation of an atomic force microscope (AFM) was systematically investigated. Commercial AFM cantilevers are used to successfully generate patterns as narrow as 10 nm on a GaAs surface, without further sharpening of the tips. Reliable patterns with fully controlled width and depth are achieved by adjusting the feedback gain and the scan speed. This process allows nanometer-scale patterning to be performed simply, and is well suited for nanodevice fabrication. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.79.Lh Atomic force microscopes
81.05.Ea III-V semiconductors

Measurement of fluid properties with a near-field acoustic sensor

R. Patois, P. Vairac, and B. Cretin

Appl. Phys. Lett. 75, 295 (1999); http://dx.doi.org/10.1063/1.124352 (3 pages) | Cited 9 times

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The proposed microsensor is derived from the electromechanical resonator of our ac force microscope: the scanning microdeformation microscope (SMM). A submillimetric spherical probe immersed in the fluid sample replaces the tip usually used in SMM. This sphere is connected to a cantilever, which is excited at the resonance frequency. The measurement of the resonance frequency and of the damping enables the quantitative characterization of the investigated fluid. A theoretical approach allows to model the system behavior. The model takes into account two aspects: the mechanical vibration of the cantilever and the fluid mechanics. The values predicted by the model are in good agreement with the experimental measurements performed for various viscous media. © 1999 American Institute of Physics.
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07.64.+z Acoustic instruments and equipment
07.79.-v Scanning probe microscopes and components
06.30.Dr Mass and density
47.80.-v Instrumentation and measurement methods in fluid dynamics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems

Statistical modeling of pulse height spectrum of gamma-ray spectrometers limited by incomplete charge collection

Y. Nemirovsky

Appl. Phys. Lett. 75, 298 (1999); http://dx.doi.org/10.1063/1.124353 (3 pages) | Cited 6 times

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This letter presents an analytic approach to the calculation of the pulse height spectrum, using a statistical model, which simultaneously considers a random point of photon absorption (i.e., nonuniform absorption) and a random drift time for each carrier. The pulse height spectrum of gamma-ray spectrometers is calculated as a function of photon energy, electron and hole mobility-lifetime products and applied electric field. For spectrometers with a uniform electric field the pulse height spectrum is obtained by a single numerical integration of an analytical expression. © 1999 American Institute of Physics.
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07.85.Nc X-ray and γ-ray spectrometers
29.30.Kv X- and γ-ray spectroscopy
29.40.Wk Solid-state detectors
07.05.Tp Computer modeling and simulation
02.50.-r Probability theory, stochastic processes, and statistics
05.10.-a Computational methods in statistical physics and nonlinear dynamics
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
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