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21 Feb 2000

Volume 76, Issue 8, pp. 943-1075

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Atomic force microscope tip-surface behavior under continuous bias or pulsed voltages in noncontact mode

B. Legrand and D. Stiévenard

Appl. Phys. Lett. 76, 1018 (2000); http://dx.doi.org/10.1063/1.125925 (3 pages) | Cited 6 times

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The atomic force microscope is now widely used to oxidize a silicon surface with a continuous bias or pulsed voltages applied between the tip and the silicon surface. The aim of this letter is to study the induced electrostatic effect on the cantilever oscillation in noncontact mode when pulsed voltages are used for nanooxidation. Depending on the relative amplitudes between electrostatic and mechanical excitations, and also on the phase between the pulsed voltages and the mechanical excitation, the cantilever response can dramatically vary. We focus on the details of controlling the feedback loop and exposure conditions in noncontact mode. © 2000 American Institute of Physics.
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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)
81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
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

Optical absorption and anomalous photoconductivity in undoped n-type GaN

S. J. Chung, M. S. Jeong, O. H. Cha, C.-H. Hong, E.-K. Suh, H. J. Lee, Y. S. Kim, and B. H. Kim

Appl. Phys. Lett. 76, 1021 (2000); http://dx.doi.org/10.1063/1.125944 (3 pages) | Cited 18 times

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Photoconductivity and optical absorption measurements were employed to analyze deep levels in undoped n-type GaN films grown on sapphire substrate by metalorganic chemical vapor deposition. At room temperature, the photoconductivity measurement exhibits a broad level at around 1.90 eV. Similarly, the optical absorption spectrum shows a deep level located at 1.87 eV within the band gap, which is best described by a transition from a donor charge-transfer level to the conduction band, according to Lucovsky theory. A persistent photoconductivity whose behavior is distinctive from that of previously reported work for n- or p-type GaN epitaxial films was observed. The photocurrent quenching and decreased dark current in the persistent photoconductivity effect suggest that metastable electron states are formed in the band gap to trap electrons which tunnel out the potential barrier with long recovery time. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Determination of the concentration of hot-carrier-induced bulk defects in laser-recrystallized polysilicon thin film transistors

T. M. Brown and P. Migliorato

Appl. Phys. Lett. 76, 1024 (2000); http://dx.doi.org/10.1063/1.125926 (3 pages) | Cited 8 times

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We present a method to investigate hot carrier induced defects in laser recrystallized polysilicon thin film transistors, based on the use of a structure with front and back gate and the analysis of the off current. The maximum process temperature for these devices was 425 °C. We find that both positive and negative VGS produce similar degradation of the characteristics and the main effect is bulk, rather than interface, state creation. The changes in the I–V characteristics are accounted for by an increase of the dangling bond concentration, which is obtained as a fitting parameter, giving a good agreement between experiment and simulation. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
73.50.Fq High-field and nonlinear effects
73.61.Cw Elemental semiconductors

Intra-valence band photocurrent spectroscopy of self-assembled Ge dots in Si

C. Miesner, O. Röthig, K. Brunner, and G. Abstreiter

Appl. Phys. Lett. 76, 1027 (2000); http://dx.doi.org/10.1063/1.125927 (3 pages) | Cited 29 times

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Intra-valence band photocurrent investigations of self-assembled Ge dots in Si are reported. Boron-doped Ge dots of about 70 nm diameter and 6.5 nm height are deposited by molecular beam epitaxy in the Stranski–Krastanov growth mode within the intrinsic region of a p+-i-p+ Si structure. For a broad excitation wavelength range between about 2 μm (620 meV) and 6 μm (207 meV), interlevel photocurrent is observed in normal incidence and waveguide geometry. The absorption is attributed to transitions from hole states bound in the Ge dots to continuum states. The photocurrent can be measured up to T = 100 K without any significant decrease of the responsivity. © 2000 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Cy Elemental semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Electronic states and band alignment in GalnNAs/GaAs quantum-well structures with low nitrogen content

M. Hetterich, M. D. Dawson, A. Yu. Egorov, D. Bernklau, and H. Riechert

Appl. Phys. Lett. 76, 1030 (2000); http://dx.doi.org/10.1063/1.125928 (3 pages) | Cited 127 times

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We investigate the electronic states in strained Ga0.62In0.38N0.015As0.985/GaAs multiple- quantum-well structures using photoluminescence and (polarized) photoluminescence excitation measurements at low temperature. From a theoretical fit to the experimental data, a type-I band alignment for the heavy holes with a strained conduction-band offset ratio of about 80% is obtained, while the light holes show an approximately flat band alignment. Additionally, our results suggest an increased effective electron mass in GaInNAs, possibly due to the interaction of the conduction band with nitrogen-related resonant states, an observation prospectively of benefit for GaInNAs-based diode lasers. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

An analysis of temperature dependent piezoelectric Franz–Keldysh effect in AlGaN

Y. T. Hou, K. L. Teo, M. F. Li, Kazuo Uchida, Hiroki Tokunaga, Nakao Akutsu, and Koh Matsumoto

Appl. Phys. Lett. 76, 1033 (2000); http://dx.doi.org/10.1063/1.125929 (3 pages) | Cited 12 times

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Strong Franz–Keldysh oscillations near the band gap of AlGaN are observed in the contactless electroreflectance (CER) studies of a GaN/InGaN/AlGaN multilayer structure. The line shape analysis of the CER spectra at different temperatures provides an accurate determination of the AlGaN band gap energies and the built-in electric fields. Using the existing data of the thermal expansion coefficients of GaN and sapphire, and the piezoelectric constants of AlGaN, the temperature dependence of the electric field is estimated and is in good agreement with the experimental results between 15 and 300 K. We attribute such electric field to the piezoelectric strain effect. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.20.Jq Electro-optical effects
65.40.De Thermal expansion; thermomechanical effects

Room-temperature observation of the Coulomb blockade effects in Al two-terminal diodes fabricated using a focused ion-beam nanoparticle process

T. W. Kim, S. O. Kang, D. C. Choo, and J. H. Shim

Appl. Phys. Lett. 76, 1036 (2000); http://dx.doi.org/10.1063/1.125930 (3 pages) | Cited 5 times

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Al two-terminal diodes were fabricated on a basis of an artificial pattern formation method using focused ion-beam (FIB) techniques. The results of current–voltage and conductance–voltage measurements at room temperature showed the Coulomb staircase and the Coulomb blockade effects, respectively. The Coulomb blockade effects originate from the many nanoparticles created by the defects due to the Ga+ ion beam. These results indicate that Al two-terminal diodes fabricated by using the FIB system hold promise for potential applications in single-electron transistors operating at room temperature. © 2000 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling

Temperature-dependent tunneling through thermally grown SiO2 on n-type 4H– and 6H–SiC

Richard Waters and Bart Van Zeghbroeck

Appl. Phys. Lett. 76, 1039 (2000); http://dx.doi.org/10.1063/1.125931 (3 pages) | Cited 7 times

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The temperature dependence of field emission through thermally grown silicon dioxide (SiO2) on n-type 4H and 6H silicon carbide (SiC) substrates is reported. Room-temperature SiO2/SiC barrier heights, ΦB, of 1.92 and 2.12 V are extracted for the 4H– and 6H–SiC samples, respectively, using a Fowler–Nordheim analysis. Barrier heights of 2.2 and 2.4 V along with a linear temperature-dependent barrier height lowering, ΔΦB/ΔT, of 2.4 and 2.0 mV/K for 4H– and 6H–SiC are extracted using an alternative analytical expression for tunneling from semiconducting substrates derived previously. In both analyses, the temperature-dependent flatband voltage, using the measured room-temperature value, was included. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Many-body effects on excitons properties in GaN/AlGaN quantum wells

Giampiero Traetta, Roberto Cingolani, Aldo Di Carlo, Fabio Della Sala, and Paolo Lugli

Appl. Phys. Lett. 76, 1042 (2000); http://dx.doi.org/10.1063/1.125932 (3 pages) | Cited 22 times

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The many-body effects on excitons properties in GaN/AlGaN quantum wells are theoretically investigated by using a Green’s function model and the electron and hole wave functions calculated either in the envelope function approximation or in the frame of a self-consistent tight-binding model. We show that the built-in field induced by the piezoelectric and spontaneous polarization charge causes a reduction of the exciton binding energy and of the absorption coefficient well below the values expected for the quantum well with flat band. At high carrier concentrations, the many-body screening prevails over the screening of the built-in electric field, causing complete exciton bleaching at typical densities of the order of 1012 cm−2. © 2000 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Gg Exciton-mediated interactions
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Investigation of vertical transport in n-GaN films grown by molecular beam epitaxy using Schottky barrier diodes

M. Misra, A. V. Sampath, and T. D. Moustakas

Appl. Phys. Lett. 76, 1045 (2000); http://dx.doi.org/10.1063/1.125933 (3 pages) | Cited 19 times

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In this letter, the lateral and vertical transport in lightly doped n−-GaN films, grown by plasma assisted molecular beam epitaxy, were investigated in order to explore the role of electron scattering by charged dislocations. Lateral transport constants were determined by Hall effect measurements on n−-GaN films. The doping concentration and mobility of the investigated films was 1–2×1017 cm−3 and 150–200 cm2/V s, respectively. Vertical transport was studied by etching mesa structures and forming Schottky barrier diodes. The diodes exhibit near ideal forward current–voltage characteristics with reverse saturation current densities in the 1–10×10−9  A cm−2 range. The doping concentrations as well as the barrier height of the diodes were determined from capacitance–voltage measurements to be 8–9×1016 cm−3 and 0.95–1.0 V, respectively. The analysis of the reverse saturation current, using the diffusion theory, leads to vertical mobility values of 950 cm2/V s. The significant increase in mobility for vertical transport is attributed to reduction in scattering by charged dislocations. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.Kk Junction diodes
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Bk General theory, scattering mechanisms
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.65.Cf Surface cleaning, etching, patterning
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Strongly reduced bias dependence in spin–tunnel junctions obtained by ultraviolet light assisted oxidation

H. Boeve, E. Girgis, J. Schelten, J. De Boeck, and G. Borghs

Appl. Phys. Lett. 76, 1048 (2000); http://dx.doi.org/10.1063/1.125934 (3 pages) | Cited 24 times

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For future implementation of ferromagnetic tunnel junctions, we need a better understanding of the influence of the insulating barrier preparation method on the junction resistance, tunnel magnetoresistance (TMR), and its voltage bias dependence. In this letter, we focus on the bias dependence of junctions (Co–Al2O3–Ni80Fe20) prepared by ultraviolet light assisted in situ oxidation in an O2 ambient. For an initial Al thickness of 1.3 nm, the resistance times area product of the junctions is 60 kΩ μm2, while showing up to 20% TMR at 5 mV bias. The decrease of TMR with bias voltage up to 1 V is remarkably small leading to V1/2, for which half of the low-bias TMR remains, well over 0.6 V. © 2000 American Institute of Physics.
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73.40.Rw Metal-insulator-metal structures
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.65.Mq Oxidation
81.05.Bx Metals, semimetals, and alloys
75.50.Bb Fe and its alloys
75.47.De Giant magnetoresistance
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Bg Metals and alloys
82.50.-m Photochemistry
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Oxygen-deficiency-activated charge ordering in La2/3Sr1/3MnO3−δ thin films

J. Li, C. K. Ong, J.-M. Liu, Q. Huang, and S. J. Wang

Appl. Phys. Lett. 76, 1051 (2000); http://dx.doi.org/10.1063/1.125935 (3 pages) | Cited 33 times

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The oxygen-deficiency-activated charge ordering (CO) transition has been observed in C-oriented La2/3Sr1/3MnO3−δ thin films prepared by pulsed laser deposition on LaAlO3 substrates. A rapid growth of the sample resistivity at temperatures below TC is observed, while significant thermal hysteresis and electrical field induced transition from the insulator CO state to metallic-like state are recorded. Such a CO state can also be partially melted under a magnetic field of 0.4 T, resulting in enhanced magnetoresistance at low temperatures. Magnetic properties of the films can be well understood as the coexistence of the ferromagnetic state and the CO state. The CO state in oxygen deficient thin films is explained in terms of the Mn–O octahedral distortion or the narrowness of the conduction bandwidth of the eg carriers. © 2000 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
71.30.+h Metal-insulator transitions and other electronic transitions
81.15.Fg Pulsed laser ablation deposition
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Melt-spun precipitation-hardened Sm2(Co, Cu, Fe, Zr)17 magnets with abnormal temperature dependence of coercivity

D. Goll, I. Kleinschroth, W. Sigle, and H. Kronmüller

Appl. Phys. Lett. 76, 1054 (2000); http://dx.doi.org/10.1063/1.125936 (3 pages) | Cited 39 times

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Rapidly quenched Sm(CobalCu0.08Fe0.22Zr0.02)8.5 (Cu-/Fe-rich) and Sm(CobalCu0.05Fe0.10Zr0.03)8.5 (Cu-/Fe-poor) ribbons have been prepared by means of the melt-spinning technique. By applying an appropriate annealing procedure a microstructure similar to that of sintered magnets can be obtained. The energy dispersive x-ray microanalysis of the compositional dependence near the cell boundaries suggests a model for the profile of the crystal anisotropy constants responsible for the magnetic hardening. The Cu-/Fe-rich alloy shows a normal temperature dependence of coercivity with a negative temperature coefficient, but the Cu-/Fe-poor ribbons show a positive temperature coefficient in the temperature range from 400–700 K. The different temperature coefficients are discussed in terms of a pinning model. © 2000 American Institute of Physics.
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75.50.Ww Permanent magnets
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.05.Bx Metals, semimetals, and alloys
75.50.Vv High coercivity materials
61.72.Cc Kinetics of defect formation and annealing
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Bx Phase diagrams of metals, alloys, and oxides

Suppression of exchange bias by ion irradiation

T. Mewes, R. Lopusnik, J. Fassbender, B. Hillebrands, M. Jung, D. Engel, A. Ehresmann, and H. Schmoranzer

Appl. Phys. Lett. 76, 1057 (2000); http://dx.doi.org/10.1063/1.125937 (3 pages) | Cited 57 times

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The exchange bias effect in ferromagnetic/antiferromagnetic sandwich structures is generally believed to be sensitive on the interface exchange interaction, the magnetization, and the thickness of the ferromagnetic layer. Also the interface structure plays a crucial role. We show that, by irradiating samples with He ions, we can manipulate the exchange bias field in a controlled manner. Depending on the dose (1014–1017 ions/cm2) and the acceleration voltage (10–35 kV) of the ions, the shift of the hysteresis can be reduced or even fully suppressed. Potential applications of this effect for magnetic patterning on the nanoscale will be discussed. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Ct Interface structure and roughness
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
61.80.Jh Ion radiation effects
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A model for fatigue in ferroelectric perovskite thin films

Matthew Dawber and J. F. Scott

Appl. Phys. Lett. 76, 1060 (2000); http://dx.doi.org/10.1063/1.125938 (3 pages) | Cited 183 times

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An analytic expression in closed form is given for “fatigue,” the dependence of P(N), the switched charge per unit area P versus switching event number N, in ABO3 perovskite structure ferroelectric thin films is given. The analysis is based upon Arlt’s model for fatigue in bulk perovskites, which involves preferential electromigration of oxygen vacancies to sites parallel to the electrode–ferroelectric interface plane, together with some arguments by Brennan on the effectiveness of such defect planes in pinning domain walls. The model is applied to PZT/Pt with no adjustable parameters and yields in complete agreement with experimental data the dependence of P(N) at different frequencies, different voltages, and different temperatures. Notably, unlike other proposals in the literature, the model does not involve any charge injection from the electrodes. © 2000 American Institute of Physics.
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77.80.Fm Switching phenomena
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
77.80.Dj Domain structure; hysteresis
66.30.Qa Electromigration
61.72.J- Point defects and defect clusters

Compositionally step-varied (Pb, Ca)TiO3 thin films with enhanced dielectric and ferroelectric properties

Dinghua Bao, Liangying Zhang, and Xi Yao

Appl. Phys. Lett. 76, 1063 (2000); http://dx.doi.org/10.1063/1.125939 (3 pages) | Cited 18 times

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Compositionally step-varied (Pb, Ca)TiO3 thin films were prepared on platinum-coated silicon substrates by a monoethanolamine-modified sol-gel technique. The dielectric constant and dissipation factor were found to be 342 and 0.019, respectively, for thin films of 0.6μm in thickness annealed at 550 °C for 60 min. The remanent polarization and coercive field were 37.7 μC/cm2 and 60.4 kV/cm, respectively. The leakage current was 1.31×10−7 A/cm2 at the voltage of 5 V. The compositionally step-varied (Pb, Ca)TiO3 thin films had enhanced dielectric and ferroelectric properties which were suitable for various device applications. © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.Nq Composition and phase identification

Comparison of memory effect between YMnO3 and SrBi2Ta2O9 ferroelectric thin films deposited on Si substrates

Ho Nyung Lee, Yong Tae Kim, and Sung Ho Choh

Appl. Phys. Lett. 76, 1066 (2000); http://dx.doi.org/10.1063/1.125940 (3 pages) | Cited 30 times

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For the ferroelectric gate-type capacitors, we have fabricated Pt/YMnO3(YMO)/Si and Pt/SrBi2Ta2O9(SBT)/Si structures. We have used the highly c-axis oriented hexagonal YMO thin films (ϵr ≈ 19) and the polycrystalline SBT thin films (ϵr ≈ 150) with a dominant (115) orientation, respectively. The memory effect resulting from the ferroelectric switching properties is investigated as a function of the dielectric constant of ferroelectric thin films with 150 nm in thickness. About 3 times wider memory window is obtained by using a relatively low dielectric constant of YMO than that using a relatively high dielectric constant of SBT. Typical memory windows of the Pt/YMO/Si and the Pt/SBT/Si capacitors are 1.24 and 0.34 V, respectively, at a gate voltage of 5 V. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
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Stable avalanche-photodiode operation of ZnSe-based p+–n structure blue-ultraviolet photodetectors

Hitoshi Ishikura, Tomoki Abe, Nariyuki Fukuda, Hirofumi Kasada, and Koshi Ando

Appl. Phys. Lett. 76, 1069 (2000); http://dx.doi.org/10.1063/1.125941 (3 pages) | Cited 15 times

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A high-field operation of p+–n structure blue-ultraviolet photodetectors has been studied using ZnSe-based II–VI wide-band-gap compound semiconductors grown by molecular-beam epitaxy (MBE). With an improved crystal quality on macrodefects (dislocations and stacking faults) during an initial MBE growth as well as an optimized device structure including a complete superlattice ohmic-contact layer, a stable high electric-field operation up to 8×105 V/cm is established. It is demonstrated that the p+–n ZnSe photodiodes have shown a stable avalanche-photodiode operation with a large avalanche gain of G = 60 in the blue-ultraviolet region at room temperature. © 2000 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
72.20.Ht High-field and nonlinear effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Nn Stacking faults and other planar or extended defects
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Microvolume field-effect pH sensor for the scanning probe microscope

S. R. Manalis, E. B. Cooper, P. F. Indermuhle, P. Kernen, P. Wagner, D. G. Hafeman, S. C. Minne, and C. F. Quate

Appl. Phys. Lett. 76, 1072 (2000); http://dx.doi.org/10.1063/1.125942 (3 pages) | Cited 9 times

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A pH sensitive scanning probe is realized by integrating a micron-sized field-effect sensor onto a cantilever designed for an atomic force microscope. The hybrid device, called a scanning probe potentiometer (SPP), is capable of measuring pH gradients over a sample surface. The device was used to profile the pH across a reservoir of laminar streams created by fluid flow in an array of microfluidic channels of varying pH. When a single SPP scanned, a 1.5 mm reservoir in a 10-channel array, the pH profile was measured in less than 1 min with a spatial resolution of 10 μm and sensitivity of less than 0.01 pH units. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis
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FREE

Erratum: “High-Tc second-order gradiometer for magnetocardiography in an unshielded environment” [Appl. Phys. Lett. 75, 1979 (1999)]

K. A. Kouznetsov, J. Borgmann, and John Clarke

Appl. Phys. Lett. 76, 1075 (2000); http://dx.doi.org/10.1063/1.125943 (1 page)

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Abstract Unavailable
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87.63.-d Non-ionizing radiation equipment and techniques
87.19.Hh Cardiac dynamics
07.55.Ge Magnetometers for magnetic field measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures
99.10.Cd Errata
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