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28 Oct 1996

Volume 69, Issue 18, pp. 2623-2782

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Control of field screening effects in GaInAs(P)/GaInAsP quantum‐confined Stark effect modulator structures

P. König, M. Geiger, D. Ottenwälder, F. Scholz, and A. Hangleiter

Appl. Phys. Lett. 69, 2698 (1996); http://dx.doi.org/10.1063/1.117682 (3 pages) | Cited 2 times

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We compare the field screening behavior of quantum‐confined Stark effect modulator structures where the GaInAsP/InP heterojunction is in the intrinsic (standard structure) or in the doped regions (modified structure) at working wavelengths of 1.55 and 1.3 μm. The modified structures are obtained by expanding the GaInAsP confinement layers into the p‐doped and n‐doped regions without changing the total intrinsic layer thickness. The effectiveness of the InP heterobarriers for the holes on the p‐side and for the electrons on the n‐side is thereby lowered. A significant reduction of field screening for the modified structures is achieved. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors

Solid phase immiscibility in GaInN

I‐hsiu Ho and G. B. Stringfellow

Appl. Phys. Lett. 69, 2701 (1996); http://dx.doi.org/10.1063/1.117683 (3 pages) | Cited 248 times

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The large difference in interatomic spacing between GaN and InN is found to give rise to a solid phase miscibility gap. The temperature dependence of the binodal and spinodal lines in the Ga1−xInxN system was calculated using a modified valence‐force‐field model where the lattice is allowed to relax beyond the first nearest neighbor. The strain energy is found to decrease until approximately the sixth nearest neighbor, but this approximation is suitable only in the dilute limit. Assuming a symmetric, regular‐solutionlike composition dependence of the enthalpy of mixing yields an interaction parameter of 5.98 kcal/mole. At a typical growth temperature of 800 °C, the solubility of In in GaN is calculated to be less than 6%. The miscibility gap is expected to represent a significant problem for the epitaxial growth of these alloys. © 1996 American Institute of Physics.
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64.75.-g Phase equilibria
68.60.-p Physical properties of thin films, nonelectronic
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations

Low temperature characterization of modulation doped SiGe grown on bonded silicon‐on‐insulator

D. J. Paul, N. Griffin, D. D. Arnone, M. Pepper, C. J. Emeleus, P. J. Phillips, and T. E. Whall

Appl. Phys. Lett. 69, 2704 (1996); http://dx.doi.org/10.1063/1.117684 (3 pages) | Cited 8 times

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Modulation doped pseudomorphic Si0.87Ge0.13 strained quantum wells were grown on bonded silicon‐on‐insulator (SOI) substrates. Comparison with similar structures grown on bulk Si(100) wafers shows that the SOI material has higher mobility at low temperatures with a maximum value of 16 810 cm 2/V s for 2.05×1011 cm−2 carries at 298 mK. Effective masses obtained from the temperature dependence of Shubnikov–de Haas oscillations have a value of (0.27±0.02) m0 compared to (0.23±0.02) m0 for quantum wells on Si(100) while the cyclotron resonance effective masses obtained at higher magnetic fields without consideration for nonparabolicity effects have values between 0.25 and 0.29 m0. Ratios of the transport and quantum lifetimes, τ/τq=2.13±0.10, were obtained for the SOI material that are, we believe, the highest reported for any pseudomorphic SiGe modulation doped structure and demonstrates that there is less interface roughness or charge scattering in the SOI material than in metal–oxide–semiconductor field effect transistors or other pseudomorphic SiGe modulation doped quantum wells. © 1996 American Institute of Physics.
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73.40.Ty Semiconductor-insulator-semiconductor structures
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

High p‐type conductivity in cubic GaN/GaAs(113)A by using Be as the acceptor and O as the codopant

Oliver Brandt, Hui Yang, Helmar Kostial, and Klaus H. Ploog

Appl. Phys. Lett. 69, 2707 (1996); http://dx.doi.org/10.1063/1.117685 (3 pages) | Cited 35 times

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P‐type room‐temperature conductivities as high as 50/Ω cm are achieved in cubic GaN layers by the concept of reactive codoping. We use Be as the acceptor species and O as the reactive donor to render isolated Coulomb scatterers into dipole scatterers. This concept allows us to achieve high hole mobilities and thus p‐type conductivities. © 1996 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Structure and formation mechanisms of AlGaAs V‐groove vertical quantum wells grown by low pressure organometallic chemical vapor deposition

G. Biasiol, F. Reinhardt, A. Gustafsson, E. Martinet, and E. Kapon

Appl. Phys. Lett. 69, 2710 (1996); http://dx.doi.org/10.1063/1.117686 (3 pages) | Cited 18 times

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The structure of AlGaAs vertical quantum well (VQW) structures grown by low‐pressure organometallic chemical vapor deposition on V‐grooved GaAs substrates was analyzed as a function of growth temperature and Al mole fraction using transmission electron microscopy and atomic force microscopy (AFM). The low‐pressure growth yields several, extremely narrow (a few nm wide) branches of Ga‐enriched VQWs at the bottom of the grooves. The variation in Al content across the VQW was evaluated by measuring the AlGaAs oxide thickness on a cleaved edge of the structure using AFM in air. The transmission electron microscopy analysis demonstrates that the different VQW branches originate from distinct nanofacets that self‐order at the bottom of the V‐groove, probably due to facet‐induced segregation of group III species. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, 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.Fx Diffusion; interface formation

High resolution ion scattering study of silicon oxynitridation

H. C. Lu, E. P. Gusev, T. Gustafsson, E. Garfunkel, M. L. Green, D. Brasen, and L. C. Feldman

Appl. Phys. Lett. 69, 2713 (1996); http://dx.doi.org/10.1063/1.117687 (3 pages) | Cited 47 times

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High resolution medium energy ion scattering was used to characterize the nitrogen distribution in ultrathin silicon oxynitrides with sub‐nm‐accuracy. We show that nitrogen does not incorporate into the subsurface region of the substrate after oxidation of Si(100) in NO. Core‐level photoemission experiments show two bonding configurations of nitrogen near the interface. Oxynitridation in N2O results in a lower concentration and a broader distribution of nitrogen than in the NO case. © 1996 American Institute of Physics.
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81.65.-b Surface treatments
61.72.S- Impurities in crystals
68.55.Nq Composition and phase identification
61.82.Fk Semiconductors

Properties of GaN grown at high rates on sapphire and on 6H–SiC

S. Fischer, C. Wetzel, W. L. Hansen, E. D. Bourret‐Courchesne, B. K. Meyer, and E. E. Haller

Appl. Phys. Lett. 69, 2716 (1996); http://dx.doi.org/10.1063/1.117688 (3 pages) | Cited 7 times

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Thick GaN films were deposited with growth rates as high as 250 μm/h by the direct reaction of ammonia and gallium vapor at 1240 °C. The characteristics of our films are comparable to those of typical thin films grown by metal organic chemical vapor deposition or molecular beam epitaxy. Grown under identical conditions, films on (0001) sapphire and on (0001) 6H–SiC were compared in terms of their structural and optical properties. Considering x‐ray rocking curve full width at half‐maximum (FWHM: 420 arcsec), photoluminescence linewidths of the excitons (FWHM: 3 meV at 6 K and 100 meV at 300 K), free electron concentration, defect related luminescence, and the homogeneity of these properties, we find superior values for films grown on SiC. For both substrate materials we find an optimum growth rate window of 40–80 μm/h. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Valence band splittings and band offsets of AlN, GaN, and InN

Su‐Huai Wei and Alex Zunger

Appl. Phys. Lett. 69, 2719 (1996); http://dx.doi.org/10.1063/1.117689 (3 pages) | Cited 135 times

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First‐principles electronic structure calculations on wurtzite AlN, GaN, and InN reveal crystal‐field splitting parameters ΔCF of −217, 42, and 41 meV, respectively, and spin–orbit splitting parameters Δ0 of 19, 13, and 1 meV, respectively. In the zinc blende structure ΔCF≡0 and Δ0 are 19, 15, and 6 meV, respectively. The unstrained AlN/GaN, GaN/InN, and AlN/InN valence band offsets for the wurtzite (zinc blende) materials are 0.81 (0.84), 0.48 (0.26), and 1.25 (1.04) eV, respectively. The trends in these spectroscopic quantities are discussed and recent experimental findings are analyzed in light of these predictions. © 1996 American Institute of Physics.
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71.70.Ch Crystal and ligand fields
71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Optical characteristics of p‐type GaN films grown by plasma‐assisted molecular beam epitaxy

J. M. Myoung, K. H. Shim, C. Kim, O. Gluschenkov, K. Kim, S. Kim, D. A. Turnbull, and S. G. Bishop

Appl. Phys. Lett. 69, 2722 (1996); http://dx.doi.org/10.1063/1.117690 (3 pages) | Cited 27 times

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Using a molecular beam epitaxy system equipped with an inductively coupled radio frequency nitrogen plasma source, p‐type GaN films were grown on sapphire substrates with no postgrowth treatment. Uniformity of the surface morphology and spatial homogeneity of the luminescence of the films were investigated using scanning electron microscopy and cathodoluminescence (CL) imaging, respectively. By examining the dependence of photoluminescence on the excitation laser power density at 6 and 300 K, three different emissions having different origins were identified. A blue emission at ∼3.25 eV is associated with shallow Mg impurities, while two different lower‐energy emissions at ∼2.43 and ∼2.87 eV are associated with deep Mg complexes. The spatial distributions of the shallow and deep Mg impurities dominating the optical properties of the p‐type GaN films were also examined along the growth direction by low‐ and room‐temperature CL using an electron beam with a range of penetration depths © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Influence of N2O oxidation of silicon on point defect injection kinetics in the high temperature regime

C. Tsamis, D. N. Kouvatsos, and D. Tsoukalas

Appl. Phys. Lett. 69, 2725 (1996); http://dx.doi.org/10.1063/1.117691 (3 pages) | Cited 4 times

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In this work we investigate the influence of N2O oxidation on the kinetics of point defects at high temperatures. The interstitials that are injected during the oxidation process are monitored by the growth of preexisting oxidation stacking faults. We show that at high temperatures (1050–1150 °C), the supersaturation of self‐interstitials in the silicon substrate is enhanced when oxidation is performed in a N2O ambient compared to 100% dry oxidation. This behavior is attributed to the presence of nitrogen at the oxidizing interface. However, at lower temperatures this phenomenon is reversed and oxidation in N2O ambient leads to reduced supersaturation ratios. © 1996 American Institute of Physics.
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81.65.Mq Oxidation
68.35.Dv Composition, segregation; defects and impurities
61.72.J- Point defects and defect clusters

Direct extraction of the electron tunneling effective mass in ultrathin SiO2

B. Brar, G. D. Wilk, and A. C. Seabaugh

Appl. Phys. Lett. 69, 2728 (1996); http://dx.doi.org/10.1063/1.117692 (3 pages) | Cited 106 times

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Electron transport in ultrathin (tox<40 Å) Al/SiO2/n−Si structures is dominated by direct tunneling of electrons across the SiO2 barrier. By analyzing the tunneling currents as a function of the SiO2 layer thickness for a comprehensive set of otherwise identical samples, we are able to extract an effective mass for the tunneling electron in the SiO2 layer. Oxide films 16–35 Å thick were thermally grown in situ in a dry oxygen ambient. The oxide thicknesses were determined by capacitance–voltage measurements and by spectroscopic ellipsometry. The tunneling effective mass was extracted from the thickness dependence of the direct tunneling current between an applied voltage of 0 and 2 V, a bias range that has not been previously explored. Employing both a parabolic and a nonparabolic assumption of the E−κ relationship in the oxide forbidden gap, we found the SiO2 electron mass to be mP∗=0.30±0.02me, and mNP∗=0.41±0.01me, respectively, independent of bias. Because this method is based on a large sample set, the uncertainty in the mass determination is significantly reduced over prior current‐voltage fitting methods. © 1996 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling

The effect of atomic hydrogen on the growth of gallium nitride by molecular beam epitaxy

Zhonghai Yu, S. L. Buczkowski, N. C. Giles, T. H. Myers, and M. R. Richards‐Babb

Appl. Phys. Lett. 69, 2731 (1996); http://dx.doi.org/10.1063/1.117693 (3 pages) | Cited 29 times

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GaN was grown by molecular beam epitaxy using an rf plasma source. Growth under gallium‐rich conditions at 730 °C was required to produce high quality layers as indicated by photoluminescence, Hall effect, atomic force microscopy, and x‐ray diffraction measurements. Atomic hydrogen has a significant effect for Ga‐rich growth, increasing growth rates by as much as a factor of 2. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Boron redistribution in a shallow δ‐doped Si structure after solid phase epitaxial growth

M. B. Huang and I. V. Mitchell

Appl. Phys. Lett. 69, 2734 (1996); http://dx.doi.org/10.1063/1.117694 (3 pages)

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A combination of nuclear reaction analysis, high‐resolution sectioning methods, and time‐resolved reflectivity have been used to study the boron redistribution from a shallow δ‐doped layer in silicon, following deep amorphization and subsequent solid phase epitaxial growth (SPEG). A significant fraction of the boron was found to move into the top 20 nm undoped Si cap layer after SPEG. Over the temperature range of 550–600 °C, the fraction of boron accumulating in the cap layer is increased with the SPEG temperatures. Boron redistribution was enhanced in the sample which was etched in HF prior to SPEG. Possible contributing factors are discussed. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
81.15.Np Solid phase epitaxy; growth from solid phases
68.60.Dv Thermal stability; thermal effects
66.30.J- Diffusion of impurities

Nonalloyed Ti/Al Ohmic contacts to n‐type GaN using high‐temperature premetallization anneal

L. F. Lester, J. M. Brown, J. C. Ramer, L. Zhang, S. D. Hersee, and J. C. Zolper

Appl. Phys. Lett. 69, 2737 (1996); http://dx.doi.org/10.1063/1.117695 (3 pages) | Cited 33 times

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On Si‐implanted n‐type GaN, a nonalloyed Ti/Al metallization has been found to form an Ohmic contact that has a specific contact resistance as low as 1.0×10−5 Ω cm2. The Ohmic character is believed to be caused by the 1120 °C implant activation anneal which generates nitrogen vacancies that leave the surface heavily n type. This theory is indirectly confirmed on unimplanted n‐type GaN by comparing the rc of nonalloyed Ti/Al on unannealed GaN with that of nonalloyed Ti/Al on 1120 °C annealed GaN. The former has rectifying electrical characteristics, while the latter forms an Ohmic contact with an rc=1.3×10−3 Ω cm2. © 1996 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts

Influence of carrier flow on the temperature‐dependent capacitance‐voltage profiles of heterojunction structures

S. D. Kwon, H. Lim, H. K. Shin, and Byung‐Doo Choe

Appl. Phys. Lett. 69, 2740 (1996); http://dx.doi.org/10.1063/1.117696 (3 pages) | Cited 6 times

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We suggest a model which can explain the shifting of carrier concentration peaks in the temperature‐dependent capacitance‐voltage carrier profiles of heterojunction (HJ) structures. The shift of concentration peaks, which was frequently observed in the inverted isotype HJs was previously attributed to the traps at the heterointerface. The main feature of our model is the role of band offset as a limiter to the test signal current. The model can explain the difference of the peak shift in the carrier profiles of the normal and inverted type HJs. According to this model, the peak shifts at low temperatures occur naturally for the inverted type HJs. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling

c‐axis tunneling in multilayers NdBa2Cu3O7−δ junctions with PrBa2Cu3O7−δ barriers

G. A. Alvarez, T. Utagawa, and Y. Enomoto

Appl. Phys. Lett. 69, 2743 (1996); http://dx.doi.org/10.1063/1.117697 (3 pages) | Cited 8 times

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This letter reports c‐axis tunneling spectroscopy investigations of high quality junctions fabricated from c‐axis oriented NdBa2Cu3O7−δ/PrBa2Cu3O7−δ/NdBa2Cu3O7−δ multilayers deposited by pulsed laser deposition. The conductance spectra as a function of temperature show a smooth crossover from tunneling to metallic junction behavior. A temperature dependent BCS‐like gap giving 2Δ/kBTc=6 was observed. The current–voltage characteristics exhibit supercurrent and quasiparticle tunneling that is commonly observed for superconductor–insulator–superconductor junctions. © 1996 American Institute of Physics.
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74.78.Fk Multilayers, superlattices, heterostructures
74.50.+r Tunneling phenomena; Josephson effects

Superconducting complementary output switching logic operating at 5–10 Gb/s

Mark Jeffery, Willem Perold, and T. Van Duzer

Appl. Phys. Lett. 69, 2746 (1996); http://dx.doi.org/10.1063/1.117698 (3 pages) | Cited 6 times

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We present experimental results of superconducting voltage‐state complementary output switching logic gates operating 10 Gb/s and 2‐bit encoder circuits clocked at 5–8 Gb/s. The logic gates and circuits were designed using a Monte Carlo optimization process so that they have a high theoretical yield at 5–10 Gb/s in spite of existing Josephson junction process variations. © 1996 American Institute of Physics.
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85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.40.Dc Microwave circuits

Biomagnetic measurements with an integrated YBa2Cu3O7 magnetometer in a hand‐held cryostat

M. Schilling, S. Krey, and R. Scharnweber

Appl. Phys. Lett. 69, 2749 (1996); http://dx.doi.org/10.1063/1.117699 (3 pages) | Cited 4 times

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With low‐noise magnetometers made from high‐temperature superconductors, mobile applications of superconducting quantum interference device (SQUID) magnetometry become possible. Due to the high volume heat of evaporation of liquid nitrogen, a SQUID magnetometer can be operated in a small size cryostat for some hours. For the first time biomagnetic measurements are presented using an integrated YBa2Cu3O7 magnetometer mounted in a hand‐held cryostat with a content of 100 cm3 of liquid nitrogen. These measurements and the noise properties are compared to those made in a conventional cryostat. The low‐noise magnetometer consists of a multiloop pick‐up coil coupled inductively to a dc SQUID based on ramp‐type Josephson junctions with PrBa2Cu3O7 barriers. © 1996 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors
87.50.C- Static and low-frequency electric and magnetic fields effects

A novel multilayer circuit process using YBa2Cu3Ox/SrTiO3 thin films patterned by wet etching and ion milling

H. Q. Li, R. H. Ono, L. R. Vale, D. A. Rudman, and S. H. Liou

Appl. Phys. Lett. 69, 2752 (1996); http://dx.doi.org/10.1063/1.117700 (3 pages) | Cited 5 times

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A process combining hydrofluoric acid (HF) and Ar+ ion milling has been used to make YBa2Cu3Ox/SrTiO3/YBa2Cu3Ox(YBCO/STO/YBCO) multilayer test circuits. Low‐angle steps can be readily etched in STO and YBCO films with this process. YBCO lines crossing 5° steps have about the same critical temperature Tc (89–90 K) and critical current density Jc (≳1×106 A/cm2 at 86 K) as lines on planar surfaces. Via connections have the same Tc as other circuit components and adequate critical currents for most circuit designs. © 1996 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits

A high sensitivity, wide dynamic range magnetometer designed on a xylophone resonator

R. B. Givens, J. C. Murphy, R. Osiander, T. J. Kistenmacher, and D. K. Wickenden

Appl. Phys. Lett. 69, 2755 (1996); http://dx.doi.org/10.1063/1.117665 (3 pages) | Cited 8 times

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A novel magnetometer based on a classical xylophone resonator is described. The device consists of an aluminum bar supported by two wires placed at the nodal points of the fundamental resonance frequency. The wires also supply current of this frequency to the bar. In the presence of a magnetic field, the Lorentz force causes the resonator to vibrate. The amplitude of this vibration is proportional to a vector component of the magnetic field. The device is intrinsically linear, and by altering the drive current the sensitivity can range from nanoteslas to teslas. © 1996 American Institute of Physics.
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07.55.Ge Magnetometers for magnetic field measurements
07.64.+z Acoustic instruments and equipment
43.40.Cw Vibrations of strings, rods, and beams

Nanostructured magnetic networks

J. A. Barnard, H. Fujiwara, V. R. Inturi, J. D. Jarratt, T. W. Scharf, and J. L. Weston

Appl. Phys. Lett. 69, 2758 (1996); http://dx.doi.org/10.1063/1.117666 (3 pages) | Cited 26 times

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Nanostructured contiguous networks of Fe well suited to fundamental studies of the effects of confinement are described. The Fe networks are prepared by sputter deposition onto the surface of nanochannel alumina. One of the most obvious consequences of confining the magnetic material to a nanostructured network is a dramatic enhancement in the coercivity when compared to a continuous Fe film of the same thickness. © 1996 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
81.07.-b Nanoscale materials and structures: fabrication and characterization

Co‐doped ferrite single domains and the effect of metallic nanoinclusions

M. Multigner, S. Läkamp, G. Pourroy, A. Hernando, and R. Valenzuela

Appl. Phys. Lett. 69, 2761 (1996); http://dx.doi.org/10.1063/1.117667 (3 pages) | Cited 1 time

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Magnetic properties measurements were performed on metal–ferrite composites prepared by coprecipitation of Co and Fe chlorides at various Co/Fe ratios. The microstructure can be described as octahedrally shaped ferrite particles with nanometric CoFe alloy inclusions. Upon elimination of the metallic fraction, and increase in coercive field Hc and a decrease in saturation magnetization Ms were observed. Scanning electron microscopy observations revealed that ferrite particles were in micron range, with a narrow size distribution. The composite magnetic properties can be interpreted in terms of a nanostructured exchanged‐coupled system, while the ferrite‐only magnetic behavior is close to a single‐domain, Stoner–Wohlfarth system. © 1996 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

A novel procedure for measuring the absolute current density profile of a focused gallium‐ion beam

J. B. Wang and Y. L. Wang

Appl. Phys. Lett. 69, 2764 (1996); http://dx.doi.org/10.1063/1.117668 (3 pages) | Cited 3 times

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A simple and sensitive method has been developed for measuring the absolute current density profile of a focused gallium‐ion beam down to six orders of magnitude below its peak intensity. This method exploits both physical sputtering and a chemical etch‐stop mechanism that occurs on Si(100) substrates after Ga‐ion implantation. Sputtering creates craters on the substrate while the ion implanted area becomes insoluble in aqueous NaOH. This etch‐stop layer can be used as negative resistance for creating hillocks on the substrate. By measuring the topographs of sputtered craters and etched hillocks using atomic force microscopy, the absolute current density profile of the focused ion beam is deduced. © 1996 American Institute of Physics.
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41.75.Ak Positive-ion beams
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.uf Ge and Si

Low‐stiffness silicon cantilevers for thermal writing and piezoresistive readback with the atomic force microscope

B. W. Chui, T. D. Stowe, T. W. Kenny, H. J. Mamin, B. D. Terris, and D. Rugar

Appl. Phys. Lett. 69, 2767 (1996); http://dx.doi.org/10.1063/1.117669 (3 pages) | Cited 33 times

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Low‐stiffness silicon cantilevers have been developed for proposed data storage devices based on the atomic force microscope, in particular thermomechanical recording. The cantilevers combine a sharp tip with an integrated piezoresistive sensor for data readback from a rotating polycarbonate disk. A novel process was developed to make shallow piezoresistors in cantilevers 1 μm thick, significantly thinner and therefore softer than previously possible. Readback was demonstrated at linear velocities up to 120 mm/s. Separate cantilevers with resistively heated tips were fabricated for writing data marks on polycarbonate, with measured thermal time constants of 30 μs. © 1996 American Institute of Physics.
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07.79.Lh Atomic force microscopes
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
07.10.Cm Micromechanical devices and systems

Effects of a series resistor on electron emission from a field emitter

J. W. Luginsland, A. Valfells, and Y. Y. Lau

Appl. Phys. Lett. 69, 2770 (1996); http://dx.doi.org/10.1063/1.117670 (3 pages) | Cited 5 times

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Universal curves are constructed that provide an immediate determination of the effect of a series resistor on the electron emission from a field emitter. These curves are applicable to both the low current and high current regime. The effects of space charge and of the series resistor are apparent from these curves, which are applicable to a large class of materials. An example is given to illustrate their use. © 1996 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters
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