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18 May 1998

Volume 72, Issue 20, pp. 2499-2618

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Nanosize diamond formation promoted by direct current glow discharge process: Synchrotron radiation and high resolution electron microscopy studies

I. Gouzman, A. Hoffman, G. Comtet, L. Hellner, G. Dujardin, and M. Petravic

Appl. Phys. Lett. 72, 2517 (1998); http://dx.doi.org/10.1063/1.121404 (3 pages) | Cited 20 times

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Diamond nucleation on Si(100) surfaces can be promoted by a dc-glow discharge process, using a CH4/H2 gas mixture. However, the phase composition and structure of the carbon film deposited during the dc-glow discharge pretreatment are still unclear. In the present work, we report on a combined study of near edge x-ray absorption fine structure (NEXAFS), and high resolution scanning electron microscopy (HR-SEM) of this film as a function of substrate temperature. NEXAFS measurements of the films deposited by the dc-glow discharge process render unambiguous evidence of diamond phase formation in the 880–900 °C substrate temperature range. It is determined from HR-SEM measurements that in this temperature range, nanosize diamond particles are formed. At lower and higher substrate temperatures the NEXAFS results indicate the predominant formation of graphitic carbon. The changes in the film composition as a function of substrate temperature during the dc-glow discharge process is expressed in terms of relative graphitic character (RGC) of the precursor film. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.70.Dm X-ray absorption spectra
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology

Photoluminescence and electronic density of states in a-C:H films

F. Giorgis, F. Giuliani, C. F. Pirri, A. Tagliaferro, and E. Tresso

Appl. Phys. Lett. 72, 2520 (1998); http://dx.doi.org/10.1063/1.121405 (3 pages) | Cited 22 times

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The density of states in the energy region near Fermi level for hydrogenated amorphous carbon thin films is presented. The different types of states are identified in their origin and the problem of their detection is considered. It is shown that only some of these states are accessible to detection by electron spin resonance. A quantitative correlation between their density and the quantum efficiency of the room temperature photoluminescence process is achieved. Such correlation applies to films having a wide range of physical properties deposited by different techniques. © 1998 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Hx Other solid inorganic materials
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Pressure dependence of the negative bias voltage for stabilization of cubic boron nitride thin films deposited by sputtering

Wilfredo Otaño-Rivera, Lawrence J. Pilione, and Russell Messier

Appl. Phys. Lett. 72, 2523 (1998); http://dx.doi.org/10.1063/1.121407 (3 pages) | Cited 8 times

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Thin films of boron nitride were deposited by unbalanced magnetron sputtering at pressures between 0.065 and 1.32 Pa in order to study the effects of pressure and negative substrate bias on the energy of the bombarding plasma ions and subsequent stabilization of the cubic phase. It was found that the threshold bias voltage for nucleation of films with a high percentage of the cubic phase increases with the product of the pressure and sheath thickness. This trend is explained in terms of the changes in the average energy of the particles bombarding the growing film produced by pressure-dependent charge-exchange collisions in the plasma/substrate sheath. This energy modification process has predictable consequences in complex deposition processes. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Piezoelectric actuator generating torsional displacement from piezoelectric d15 shear response

A. E. Glazounov, Q. M. Zhang, and C. Kim

Appl. Phys. Lett. 72, 2526 (1998); http://dx.doi.org/10.1063/1.121408 (3 pages) | Cited 7 times

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A torsional actuator generating angular displacement from piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (i) prove the proposed concept of the torsional actuator, (ii) show that the actuator functions well under the torque load, and (iii) demonstrate that it has superior characteristics compared to previously reported designs of torsional actuators. © 1998 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Studies of metallic species and oxygen incorporation during sputter-deposition of SrBi2Ta2O9 films, using mass spectroscopy of recoiled ions

J. Im, A. R. Krauss, A. M. Dhote, D. M. Gruen, O. Auciello, R. Ramesh, and R. P. H. Chang

Appl. Phys. Lett. 72, 2529 (1998); http://dx.doi.org/10.1063/1.121409 (3 pages) | Cited 9 times

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We have recently developed a mass spectroscopy of recoiled ions technique which is suitable for monolayer-specific surface analysis of thin films during growth. We present initial results using this technique to study the effect of different bottom electrode layers on metallic species and oxygen incorporation in the early stages of SrBi2Ta2O3 (SBT) film growth via ion beam-sputter deposition. The work discussed here has been focused on studying the incorporation of Sr, Bi, and Ta during growth of SBT on Pt/Ti/SiO2/Si, Pt/MgO, Ti, and Si substrates. We found that the incorporation of Bi in sputter-deposited SBT films depends critically on the bottom electrode surface composition and the growth temperature. © 1998 American Institute of Physics.
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81.15.Cd Deposition by sputtering
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.35.Fx Diffusion; interface formation

Stress development during deposition of CNx thin films

E. Broitman, W. T. Zheng, H. Sjöström, I. Ivanov, J. E. Greene, and J.-E. Sundgren

Appl. Phys. Lett. 72, 2532 (1998); http://dx.doi.org/10.1063/1.121410 (3 pages) | Cited 30 times

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We have investigated the influence of deposition parameters on stress generation in CNx (0.3<x<0.5) thin films deposited onto Si(001) substrates by reactive magnetron sputtering of C in pure N2 discharges. Film stress, σ, which in all cases is compressive, decreases with an increase in the N2 pressure, PN2, due to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. The film stress σ is also a function of the film growth temperature, Ts, and exhibits a maximum value of ∼ 5 GPa at 350 °C. Under these conditions, the films have a distorted microstructure consisting of a three-dimensional, primarily sp2 bonded, network. In contrast, films deposited at Ts<200 °C with a low stress are amorphous. At 350 °C<Ts<600 °C, σ gradually decreases as Ts is increased and the microstructure becomes more graphitic and contains fewer defects. Nanoindentation measurements show that the films grown at 350 °C exhibit the highest hardness and elasticity. © 1998 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
61.43.Er Other amorphous solids
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Long-range ferroelectric interactions in KTaO3/KNbO3 superlattice structures

H.-M. Christen, E. D. Specht, D. P. Norton, M. F. Chisholm, and L. A. Boatner

Appl. Phys. Lett. 72, 2535 (1998); http://dx.doi.org/10.1063/1.121411 (3 pages) | Cited 53 times

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Symmetric superlattice structures consisting of alternating atomic-scale layers of KTaO3 and KNbO3 with variable periodicity were grown on KTaO3 substrates by pulsed laser deposition. The in-plane structure of KNbO3 closely matches that of the KTaO3 substrate, resulting in KTaO3/KNbO3 heterostructures that are uniformly strained in-plane without misfit dislocations. This strain imposes an in-plane KNbO3 lattice spacing identical to that of the KTaO3 substrate for the temperature range 30 °C<T<700 °C, and a tetragonal-to-tetragonal transition is observed whose phase transition temperature Tc depends on the KNbO3 layer thickness. The in-plane strain results in a significant increase in this ferroelectric-paraelectric Tc for superlattices with relatively thick KNbO3 layers (Tc = 535 °C for a 17 nm thick layer, as compared to 435 °C for bulk KNbO3) and for K(Nb0.5Ta0.5)O3 random-alloy thin films. As the superlattice period decreases, a reduction of Tc is observed. For superlattices with periodicities of 50 Å or less, the Curie temperature is identical to that of the K(Ta0.5Nb0.5)O3 random-alloy film, indicating significant long-range ferroelectric coupling across the KTaO3 layers. © 1998 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.B- Phase transitions and Curie point
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Fg Pulsed laser ablation deposition

Oxygen and the thermal stability of thin CoSi2 layers

R. T. Tung

Appl. Phys. Lett. 72, 2538 (1998); http://dx.doi.org/10.1063/1.120625 (3 pages) | Cited 10 times

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The thermal stability of thin CoSi2 layers is demonstrated to improve with the use of oxygen-containing annealing ambients. Pinhole formation observed in 11–27 nm thick CoSi2 layers after anneals at 800 °C in nitrogen and vacuum is found to be eliminated when oxygen is used as the annealing ambient. A thin SiO2 layer grown during oxygen anneals, which curbs surface diffusion and reduces the rates of kinetic processes, is thought to be the primary reason for the retardation of layer agglomeration. The beneficial effect of air exposure and wet etches to the integrity of thin CoSi2 layers is also shown. These findings suggest the inclusion of oxygen in certain Co salicide processing steps.
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68.60.Dv Thermal stability; thermal effects
73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Cc Kinetics of defect formation and annealing
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