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28 Jun 1999

Volume 74, Issue 26, pp. 3921-4070

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Clustering of ultra-low-energy implanted boron in silicon during postimplantation annealing

E. Schroer, V. Privitera, F. Priolo, E. Napolitani, and A. Carnera

Appl. Phys. Lett. 74, 3996 (1999); http://dx.doi.org/10.1063/1.123239 (3 pages) | Cited 13 times

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We report on the clustering behavior of ultra-low-energy (500 eV) implanted boron in silicon during the postimplantation activation annealing. The broadening of the boron concentration profile is found to be composed of a diffusing and a nondiffusing contribution. The nondiffusing part is attributed to clustered boron. The concentration of boron in clusters is found to be dependent on the annealing temperature and the annealing time. The amount of boron in clusters decreases with increasing annealing time. A dissolution time constant with an average activation energy of 2.3 eV is determined from this behavior. © 1999 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si

Ln3Au3Sb4: Thermoelectrics with low thermal conductivity

D. Young, K. Mastronardi, P. Khalifah, C.-C. Wang, R. J. Cava, and A. P. Ramirez

Appl. Phys. Lett. 74, 3999 (1999); http://dx.doi.org/10.1063/1.123240 (3 pages) | Cited 3 times

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The thermoelectric properties of intermetallic compounds with the Y3Au3Sb4 structure type, of formula Ln3Au3Sb4 for Ln=Gd, Nd, Ho, and Sm, are reported. The highest Seebeck coefficients are on the order of 100–200 μV/K, indicating that the dominant carriers are holes, and increase with increasing temperature. Variation of the Au:Sb ratio significantly affects the resistivities and Seebeck coefficients. Materials with mixtures of lanthanides on the large atom site show improved Seebeck coefficients without degradation of the electrical resistivity. The thermal conductivities are very low, even for the stoichiometric materials, and decrease in materials with mixed lanthanides. Band-structure calculations show a complex multivalley character for both valence and conduction bands. © 1999 American Institute of Physics.
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72.15.Jf Thermoelectric and thermomagnetic effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
81.05.Bx Metals, semimetals, and alloys

Acoustic field mapping on GaAs using microscopic reflectance and reflectance anisotropy

Paulo V. Santos

Appl. Phys. Lett. 74, 4002 (1999); http://dx.doi.org/10.1063/1.123241 (3 pages) | Cited 9 times

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The mapping of surface acoustic wave (SAW) fields by means of microscopic reflectance and reflectance anisotropy in GaAs-based structures is reported. The two techniques are complementary with the second being sensitive to the strain and the first both to the strain and to the surface modulation induced by the SAW. Their combination provides information about both the longitudinal and transverse components of the SAW particle displacement vector. © 1999 American Institute of Physics.
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77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
68.35.Gy Mechanical properties; surface strains
78.20.Jq Electro-optical effects
81.05.Ea III-V semiconductors

Theoretical modeling of thermoelectricity in Bi nanowires

X. Sun, Z. Zhang, and M. S. Dresselhaus

Appl. Phys. Lett. 74, 4005 (1999); http://dx.doi.org/10.1063/1.123242 (3 pages) | Cited 75 times

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A theoretical model based on the basic electronic band structure of bulk Bi is developed to predict the dependence of the band structure and thermoelectric properties on nanowire width. By carefully tailoring the Bi wire size and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire widths. © 1999 American Institute of Physics.
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73.50.Lw Thermoelectric effects
73.63.-b Electronic transport in nanoscale materials and structures
71.20.Gj Other metals and alloys
81.05.Bx Metals, semimetals, and alloys

Light-induced negative differential resistance in planar InP/InGaAs/InP double-heterojunction p-i-n photodiode

Chong-Long Ho, Meng-Chyi Wu, Wen-Jeng Ho, and Jy-Wang Liaw

Appl. Phys. Lett. 74, 4008 (1999); http://dx.doi.org/10.1063/1.123243 (3 pages) | Cited 5 times

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Negative differential resistance (NDR) was observed in the dc photocurrent-reverse bias characteristics at 1.55 μm wavelength of a planar InP/InGaAs/InP double-heterojunction p-i-n photodiode, which is designed for high-speed operation. In the bias range of measurements, two NDR regions can be observed, which are suggested to be mainly caused by the drop of average electron velocities in both the InGaAs absorption and InP buffer layers, i.e., the transferred electron effect. For providing evidence, power dependence of these NDR regions was investigated. Besides, another high-responsivity p-i-n photodiode was fabricated and characterized for comparison. © 1999 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
78.66.Fd III-V semiconductors
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Variable sample temperature scanning superconducting quantum interference device microscope

J. R. Kirtley, C. C. Tsuei, K. A. Moler, V. G. Kogan, J. R. Clem, and A. J. Turberfield

Appl. Phys. Lett. 74, 4011 (1999); http://dx.doi.org/10.1063/1.123244 (3 pages) | Cited 25 times

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We demonstrate a design for a scanning superconducting quantum interference device (SQUID) microscope in which the sample temperature can be varied over a large range. In this design, both sample and SQUID are in the same vacuum space, separated by a few microns. By firmly anchoring the SQUID to a low-temperature bath, the sample temperature can be changed while the SQUID remains superconducting. This allows magnetic imaging at varying sample temperatures with micron-scale spatial resolution and the sensitivity of a low-Tc SQUID. We demonstrate this approach by imaging the temperature dependence of Abrikosov vortices in thin films of the high-temperature superconductor YBa2Cu3O7−δ. We extract the in-plane penetration depth λab(T) in our samples from these measurements. © 1999 American Institute of Physics.
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07.55.Ge Magnetometers for magnetic field measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Enhanced field sensitivity close to percolation in magnetoresistive La2/3Sr1/3MnO3/CeO2 composites

Ll. Balcells, A. E. Carrillo, B. Martínez, and J. Fontcuberta

Appl. Phys. Lett. 74, 4014 (1999); http://dx.doi.org/10.1063/1.123245 (3 pages) | Cited 130 times

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The magnetoresistance of La2/3Sr1/3MnO3/CeO2 composites is explored as a function of the metal/insulator composition, temperature, and magnetic field. An important enhancement of the low-field magnetoresistance is observed for samples close to metallic percolation threshold. The improved field sensitivity is still fairly large at room temperature. Manganese perovskites composites may constitute a new alternative for the development of magnetoresistive devices. © 1999 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials

Large magnetoresistance in tunnel junctions with an iron oxide electrode

P. Seneor, A. Fert, J.-L. Maurice, F. Montaigne, F. Petroff, and A. Vaurès

Appl. Phys. Lett. 74, 4017 (1999); http://dx.doi.org/10.1063/1.123246 (3 pages) | Cited 80 times

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We report on the fabrication and properties of (cobalt/alumina/iron oxide) tunnel junctions. We observe magnetoresistance (MR) effects reaching 43% at 4.2 K and 13% at room temperature. This large MR is ascribed to the presence of a Fe3−xO4 (close to half-metallic magnetite) phase identified by electron diffraction. At low temperature, the MR drops sharply when the bias voltage is smaller than 10 mV, which suggests that the magnetoresistance originates from the activation of tunneling channels through spin polarized states below and above the Fermi level in the iron oxide. © 1999 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Gk Tunneling

Structure and magnetic properties of Gd3(Fe1−xCox)25Cr4 compounds

Dong Yang, Jianli Wang, Ning Tang, Yuping Shen, and Fuming Yang

Appl. Phys. Lett. 74, 4020 (1999); http://dx.doi.org/10.1063/1.123247 (3 pages) | Cited 14 times

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The structural and magnetic properties of Gd3(Fe1−xCox)25Cr4 compounds with x = 0–0.6 have been investigated. The structures of all the compounds investigated are found to possess monoclinic symmetry and belong to the A2/m space group. Substitution of Co for Fe leads to a clear contraction of the unit-cell volume. The Curie temperature increases from 492 K for x = 0 to 762 K for x = 0.6. The composition dependence of the saturation magnetization at 5 K reaches a maximum around x = 0.3. It is noteworthy that substitution of Co for Fe results in a significant change of the magnetocrystalline anisotropy of the Co sublattice, and changes the easy magnetization direction of Gd3(Fe1−xCox)25Cr4 compounds from basal plane to easy axis. © 1999 American Institute of Physics.
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75.50.Ww Permanent magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
61.05.cp X-ray diffraction

Nonlinear inductive response of high temperature superconducting films measured by the mutual inductance technique

J. H. Claassen, James C. Booth, J. A. Beall, D. A. Rudman, L. R. Vale, and R. H. Ono

Appl. Phys. Lett. 74, 4023 (1999); http://dx.doi.org/10.1063/1.123248 (3 pages) | Cited 11 times

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The dependence of the penetration depth λ on current density J in an unpatterned superconducting film can be measured with a pair of small coaxial coils positioned on opposite sides of the film. Mutual inductance measurements in this configuration with a direct-current (dc) current component in one of the coils provide a means to determine λ(J). It is possible to separate out the effects of heating by initially trapping a persistent current in the film. The nonlinear (current-dependent) coefficients of λ(J) measured by this “dc” technique agree well with those measured by third harmonic generation in coplanar waveguide transmission lines at 5 GHz. This nondestructure technique could be used to screen films before incorporating them into circuits sensitive to nonlinear effects.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.N- Response to electromagnetic fields

Magnetoresistance and planar Hall effects in submicron exchange-coupled NiO/Fe19Ni81 wires

A. Nemoto, Y. Otani, S. G. Kim, K. Fukamichi, O. Kitakami, and Y. Shimada

Appl. Phys. Lett. 74, 4026 (1999); http://dx.doi.org/10.1063/1.123249 (3 pages) | Cited 25 times

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Magnetization reversal processes of submicron NiO/Fe19Ni81 exchange-coupled Hall cross with a variable width in the range from 0.2 to 0.4 μm were studied by the magnetoresistivity and the planar Hall effect measurements. The magnetization reversal was found to take place via a coherent rotation in the Hall cross, suggesting that the size of the antiferromagnetic domain is regulated by the wire width. The magnitude of the exchange coupling field Hex varied in proportion to the inverse wire width. © 1999 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Et Exchange and superexchange interactions
75.60.Ch Domain walls and domain structure
75.50.Ee Antiferromagnetics
73.61.-r Electrical properties of specific thin films
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Rapid cooling and magnetic field-induced cooperative effect for the metastable quintet state in a spin crossover complex

Z. Yu, K. Liu, J. Q. Tao, Z. J. Zhong, X. Z. You, and G. G. Siu

Appl. Phys. Lett. 74, 4029 (1999); http://dx.doi.org/10.1063/1.123250 (3 pages) | Cited 9 times

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Our study shows that metastable quintet state of spin crossover complex [Fe(dpp)2(NCS)2]⋅py (dpp=dipyrido[3,2-a:2′,3′-c] phenazine, py=pyridine) at low temperatures may be realized by a rapid cooling. The relaxation from quintet state to singlet spin at low temperatures depends on the both of time and previous history of the sample. The U-shaped dents of the magnetic effective moment depending on the temperature after initial rapid zero-field cooling indicate an obvious affection of magnetic field to the realization of singlet state in the transition range. The observations for this sample are indeed consistent with the fact that cooperative effects play a very important role in the spin transition. © 1999 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities

Ferroelectric fatigue of Pb(Zr,Ti)O3 thin films measured in atmospheres of varying oxygen concentration

M. Brazier, S. Mansour, and M. McElfresh

Appl. Phys. Lett. 74, 4032 (1999); http://dx.doi.org/10.1063/1.123251 (2 pages) | Cited 35 times

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Ferroelectric fatigue in Pb(Zr,Ti)O3 films was found to be remarkably sensitive to the oxygen partial pressure of the atmosphere above the film during measurement. Films with Zr/Ti ratios of 55/45 and 75/25 were subjected to ferroelectric fatigue testing at room temperature in atmospheres of various oxygen partial pressure, or pO2. The number of switching cycles at which the onset of fatigue occurred was found to be sharply peaked with respect to the oxygen partial pressure surrounding the sample. Such a striking dependence on the oxygen concentration strongly supports current theories for fatigue that involve oxygen vacancy migration. © 1999 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
81.65.Mq Oxidation

Ba(1−x)SrxTiO3 thin films by off-axis cosputtering BaTiO3 and SrTiO3

E. J. Cukauskas, Steven W. Kirchoefer, William J. DeSisto, and Jeffrey M. Pond

Appl. Phys. Lett. 74, 4034 (1999); http://dx.doi.org/10.1063/1.123252 (3 pages) | Cited 22 times

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Thin films of Ba(1−x)SrxTiO3 (BST) have been deposited by off-axis cosputtering targets of SrTiO3 (STO) and BaTiO3 (BTO). The films were grown on (100) MgO and LaAlO3 substrates at 550 °C at an argon/oxygen gas pressure of 20 Pa. Reaction of the sputtered species in the plasma resulted in the growth of BST films. The film composition was set by the relative power levels of the STO and BTO targets. X-ray diffractometry indicated the as-deposited films were predominantly (h00) oriented. The calculated lattice parameter was 3.955±0.01 Å, slightly larger than bulk Ba0.5Sr0.5TiO3. Postannealing the films in flowing O2 at 780 °C resulted in greater peak heights and no change in orientation. Capacitance–voltage characteristics measured at 10 GHz yielded Q’s of 65 with nearly 14% tuning for BST on LAO and Q>1000 with a 2% tuning for films on MgO.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Two-step two-color recording in a photorefractive praseodymium-doped La3Ga5SiO14 crystal

T. Nikolajsen, P. M. Johansen, X. Yue, D. Kip, and E. Krätzig

Appl. Phys. Lett. 74, 4037 (1999); http://dx.doi.org/10.1063/1.123253 (3 pages) | Cited 5 times

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Two-step two-color recording is demonstrated in a photorefractive La3Ga5SiO14:Pr3+ crystal using cw laser radiation. The 488 nm line from an Ar-ion laser is used for gating and gratings are written using a Ti:sapphire laser operating in the range from 788 to 840 nm. The dependence of holographic recording on grating and writing intensity is investigated. A saturation of the sensitivity is found for 2 W/cm2 of grating intensity. A threshold photon energy of 1.53 eV for the second excitation step is observed. © 1999 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.40.Ht Hologram recording and readout methods
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Ternary single electron tunneling phase logic element

F. Y. Liu, F.-T. An, and R. A. Kiehl

Appl. Phys. Lett. 74, 4040 (1999); http://dx.doi.org/10.1063/1.123254 (3 pages) | Cited 2 times

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An analysis of a ternary single electron tunneling phase logic element is presented. The analysis is based on Monte Carlo simulations and an analytical treatment of a resistively loaded tunneling junction at low temperatures. We show that tristable operation can be obtained over a 19% dc bias operating range by optimizing the pump frequency and amplitude. For large ac frequencies, our optimizations also show that simple linear relationships exist between the optimal parameters (the optimal dc bias and pump amplitude) and frequency. Finally, we show that the ternary phase state of a clocked element can be controlled by an input signal provided that the clock turn-on is not too abrupt. The results should be of use in the design of ternary and other multilevel tunneling phase logic families. © 1999 American Institute of Physics.
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85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
84.30.Sk Pulse and digital circuits
02.70.Rr General statistical methods
85.25.Am Superconducting device characterization, design, and modeling

Superconducting multiplexer for arrays of transition edge sensors

J. A. Chervenak, K. D. Irwin, E. N. Grossman, John M. Martinis, C. D. Reintsema, and M. E. Huber

Appl. Phys. Lett. 74, 4043 (1999); http://dx.doi.org/10.1063/1.123255 (3 pages) | Cited 72 times

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We report the design and testing of an analog superconducting time-division multiplexer to instrument large format arrays of low-temperature bolometers and microcalorimeters. The circuit is designed to multiplex an array of superconducting quantum interference devices, thereby simplifying wiring and room temperature electronics. We have fabricated a prototype 8×1 multiplexer chip and show a switching rate of 1 MHz. We calculate that a 32×32 array or larger is feasible. © 1999 American Institute of Physics.
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85.25.Am Superconducting device characterization, design, and modeling
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Selective H atom sensors using ultrathin Ag/Si Schottky diodes

Hermann Nienhaus, Howard S. Bergh, Brian Gergen, Arun Majumdar, W. Henry Weinberg, and Eric W. McFarland

Appl. Phys. Lett. 74, 4046 (1999); http://dx.doi.org/10.1063/1.123256 (3 pages) | Cited 21 times

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Schottky diodes with ultrathin silver films on n-Si(111) are used for selective detection of atomic hydrogen. The exothermic adsorption of H atoms on the Ag surface creates hot electrons which may travel ballistically through the metal film and traverse the Schottky barrier. The chemically induced current is measurable ( ≈ 0.001 electrons/H atom) as a chemicurrent. After saturation of the adsorption sites, this chemicurrent achieves a steady-state value due to a balance of removal of adsorbed hydrogen and readsorption. The detection limit of the sensors is approximately 1010 H atoms cm−2 s−1. The detectors are completely insensitive to H2 molecules. © 1999 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
85.30.Hi Surface barrier, boundary, and point contact devices

Nanooxidation of silicon with an atomic force microscope: A pulsed voltage technique

B. Legrand and D. Stievenard

Appl. Phys. Lett. 74, 4049 (1999); http://dx.doi.org/10.1063/1.123257 (3 pages) | Cited 44 times

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The use of an atomic force microscope (AFM) as an active tool to realize silicon nanolithography is now well known, using a continuous voltage applied between the AFM tip and the surface. The main drawback of this technique is the poor reliability of the tip due to the strong tip-surface interaction. An original way which both increases the reliability and improves the nanolithography resolution is the use of pulsed voltages instead of continuous polarization. In such a case, the interaction time of the tip with the surface under electric field decreases. The frequency oscillation (in noncontact mode) of the cantilever is taken as a reference, and pulsed voltages with variable phase and duty cycle are used. We show that the variation of the phase allows a 100% modulation of the oxide width. Finally, combining this lithography technique with wet etching, a 17.5 nm wide and 5.5 nm height nanowire has been obtained starting from a silicon-on-insulator substrate. © 1999 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
07.79.Lh Atomic force microscopes

Charge sensitivity of radio frequency single-electron transistor

Alexander N. Korotkov and Mikko A. Paalanen

Appl. Phys. Lett. 74, 4052 (1999); http://dx.doi.org/10.1063/1.123258 (3 pages) | Cited 31 times

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A theoretical analysis of the charge sensitivity of the radio frequency single-electron transistor (rf-SET) is presented. We use the “orthodox” approach and consider the case when the carrier frequency is much less than I/e where I is the typical current through rf-SET. The optimized noise-limited sensitivity is determined by the temperature T, and at low T it is only 1.4 times worse than the sensitivity of conventional single-electron transistor. © 1999 American Institute of Physics.
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85.35.Gv Single electron devices
85.25.Am Superconducting device characterization, design, and modeling
85.30.De Semiconductor-device characterization, design, and modeling

Light invariant, efficient, multiple band gap AlGaAs/Si/metal hydride solar cell

S. Licht, B. Wang, T. Soga, and M. Umeno

Appl. Phys. Lett. 74, 4055 (1999); http://dx.doi.org/10.1063/1.123259 (3 pages) | Cited 7 times

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Electronic and ionic charge transfer provides a basis for composite semiconductor/electrolyte systems featuring simultaneous solar/electrical conversion and solar energy storage. This cell contains both multiple band gap and electrochemical storage, and provides a nearly constant energetic output in illuminated or dark conditions. Multiple semiconductor band gaps can enhance the energetics of this interaction. The cell combines bipolar AlGaAs (Eg = 1.6 eV) and Si (Eg = 1.1 eV) and AB5 metal hydride/NiOOH storage, and generates a light variation insensitive potential of 1.2–1.3 V at total (including storage losses) solar/electrical energy conversion efficiency of 18.1%. © 1999 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.40.Mr Semiconductor-electrolyte contacts
82.47.-a Applied electrochemistry

Molecular-beam epitaxial regrowth on oxygen-implanted GaAs substrates for device integration

C. L. Chen, L. J. Mahoney, S. D. Calawa, K. M. Molvar, P. A. Maki, R. H. Mathews, J. P. Sage, and T. C. L. G. Sollner

Appl. Phys. Lett. 74, 4058 (1999); http://dx.doi.org/10.1063/1.123260 (3 pages)

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Device-quality layers were regrown on GaAs wafers by molecular-beam epitaxy over conductive pregrown areas and on selectively patterned high-resistivity areas formed by oxygen implantation. The regrowth over both areas resulted in comparable device-quality GaAs. The high resistivity of the oxygen-implanted area was maintained after the regrowth and no oxygen incorporation was observed in the regrown layer. The cutoff frequency of a 1.5-μm-gate metal-semiconductor field-effect transistor fabricated on the regrown layer over the high-resistivity areas is 7 GHz. This demonstration shows that planar technology can be used in epitaxial regrowth, simplifying the integration of vastly different devices into monolithic circuits. © 1999 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
85.30.Tv Field effect devices
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Carbon-nanotube tips for scanning probe microscopy: Preparation by a controlled process and observation of deoxyribonucleic acid

Hidehiro Nishijima, Satsuki Kamo, Seiji Akita, Yoshikazu Nakayama, Ken I. Hohmura, Shige H. Yoshimura, and Kunio Takeyasu

Appl. Phys. Lett. 74, 4061 (1999); http://dx.doi.org/10.1063/1.123261 (3 pages) | Cited 144 times

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We report a controlled process to make carbon-nanotube tips for scanning probe microscopes. The process consists of three steps: (1) purification and alignment of carbon nanotubes using electrophoresis, (2) transfer of a single aligned nanotube onto a conventional Si tip under the view of a scanning electron microscope, and (3) attachment of the nanotube on the Si tip by carbon deposition. Nanotube tips fabricated using this procedure exhibit strong adhesion and are mechanically robust. Finally, the performance of these tips is demonstrated by imaging the fine structure of twinned deoxyribonucleic acid with tapping-mode atomic force microscopy in air. © 1999 American Institute of Physics.
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81.05.ub Fullerenes and related materials
07.79.Lh Atomic force microscopes
87.14.G- Nucleic acids
87.15.B- Structure of biomolecules
87.80.-y Biophysical techniques (research methods)

Resolution of polymethyl methacrylate: Molecular weights of 950 000 vs 50 000

Elizabeth A. Dobisz, Susan L. Brandow, Robert Bass, and Loretta M. Shirey

Appl. Phys. Lett. 74, 4064 (1999); http://dx.doi.org/10.1063/1.123262 (3 pages) | Cited 6 times

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The work examines the resolution and line-to-line resolution of two molecular weights of polymethyl methacrylate (PMMA), developed in 25%–50% solutions of methylisobutyl ketone in isopropanol. Both PMMA’s exhibited similar minimum linewidths of 15–18 nm. Measured linespread functions showed primary Gaussian standard deviations of 11.7 and 28 nm for the 950 and 50 K molecular weight PMMAs, respectively. Developer strength produced ⩽1 nm difference in the width of the linespread function. Atomic force microscope images of latent grating patterns show the same line-to-line resolution for the two undeveloped resists. Developed gratings show the 950 K PMMA to have superior line-to-line resolution. The results are analyzed through integration of the measured linespread functions. © 1999 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
42.70.Jk Polymers and organics

Independent control of ion energy and flux in plasma-enhanced diamond growth

Kungen Teii

Appl. Phys. Lett. 74, 4067 (1999); http://dx.doi.org/10.1063/1.123263 (3 pages) | Cited 13 times

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Ion energy and flux incident upon a positively biased substrate in an inductively coupled plasma (ICP) have been analyzed during diamond growth at a pressure of 20 mTorr. An electrically floated characteristic of the ICP source allowed a shift up of the plasma potential by the biasing. For the substrate bias (Vb) above 20 V, the ion energy remained constant, while the ion flux was shown to decrease with increasing Vb. The diamond film grown with a high ion flux was composed of well-coalesced large scale islands as compared to that with a low ion flux. The results provide a way to control ion energy and flux independently and its advantage for ion-assisted diamond growth. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
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