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20 Jul 1998

Volume 73, Issue 3, pp. 279-419

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Electron trapping process in ferroelectric lead–zirconate–titanate thin-film capacitors

Hong-ming Chen and Joseph Ya-min Lee

Appl. Phys. Lett. 73, 309 (1998); http://dx.doi.org/10.1063/1.121818 (3 pages) | Cited 8 times

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The effects of constant voltage stress on ferroelectric lead–zirconate–titanate (PZT) thin-film capacitors have been studied. Two stress effects are observed in the PZT capacitance–voltage (C–V) characteristics. The first is that the capacitance is reduced, and the second is a voltage shift of the C–V curve. These effects are found to depend on the stress electric field and the injected charge fluence. A correlation between the stress effects and the electron trapping inside the films is established. The injected charge fluence can be calculated from the leakage current. The trapping efficiency, electron capture cross section, and the trap density are obtained from the measured injected charge influence and the C–V voltage shift. The calculated value of the electron capture cross-section σT is 1.89×10−19 cm2 and the neutral electron trap density NT is 1.20×1013 cm−2. © 1998 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Enhanced thermal stability of C49 TiSi2 in the presence of aluminum

S.-L. Zhang, F. M. d’Heurle, C. Lavoie, C. Cabral, and J. M. E. Harper

Appl. Phys. Lett. 73, 312 (1998); http://dx.doi.org/10.1063/1.121853 (3 pages) | Cited 14 times

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The introduction of a thin layer of Al at the interface between Ti films and Si substrates enhances the formation of C49 TiSi2 and retards the transition from C49 to C54. An Al interlayer, 0.64 nm thick, reduces the time required to form C49 TiSi2 isothermally at 500 °C from 14 to 7 min. The C49–C54 transformation temperature is increased from 767 to 853 °C, when heating the samples at a constant ramp rate of 3 K/s. Most of the Al is found toward the interface between a Ti-rich silicide at the surface and TiSi2, rather than at the interface between TiSi2 and the Si substrate. The grain size of the C49 TiSi2 formed in the presence of Al is about five times smaller than that formed on a control sample with pure Ti, indicating that the increased density of grain boundaries in C49 TiSi2 in the presence of Al does not help the C49–C54 transformation. Therefore, the improved thermal stability of C49 TiSi2 is likely to be caused by other factors such as a reduced electron/atom ratio when replacing Si with Al in the disilicide. © 1998 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.60.Dv Thermal stability; thermal effects
61.72.Mm Grain and twin boundaries
66.30.Ny Chemical interdiffusion; diffusion barriers
73.40.Ns Metal-nonmetal contacts
64.70.K- Solid-solid transitions

The complex formation of ripples during depth profiling of Si with low energy, grazing oxygen beams

Z. X. Jiang and P. F. A. Alkemade

Appl. Phys. Lett. 73, 315 (1998); http://dx.doi.org/10.1063/1.121819 (3 pages) | Cited 45 times

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Surface roughening of Si under low-energy (0.5–2.0 keV) O2+ bombardment at incidence angles between 45° and 80° has been studied. Surface roughening occurred already at an erosion depth of only a few tens of nanometers. It was found that there were distinctly two angular ranges for sub-keV beams where roughening was strong, and two ranges where it was insignificant. The transition between the different ranges can be very sharp. These observations cannot be explained by the current models for surface roughening. Instead, it is believed that it is the combined sputtering rate dependence on both the surface topography and the oxygen content that determines the occurrence of roughening. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Vacancy defects in (Pb, La)(Zr, Ti)O3 capacitors observed by positron annihilation

D. J. Keeble, B. Nielsen, A. Krishnan, K. G. Lynn, S. Madhukar, R. Ramesh, and C. F. Young

Appl. Phys. Lett. 73, 318 (1998); http://dx.doi.org/10.1063/1.121820 (3 pages) | Cited 32 times

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A study of vacancy-related defects in ferroelectric capacitors was performed using a variable energy positron beam (VEPB). Heterostructures of (Pb0.9La0.1)(Zr0.2Ti0.8)O3 (PLZT) ferroelectric with La0.5Sr0.5CoO3 (LSCO) electrodes were deposited by pulsed laser deposition and the effects of oxygen deficiency studied using structures grown with 760 and 1×10−5 Torr oxygen. The VEPB depth profile showed an increase in vacancy-related defects with increased oxygen nonstoichiometry. A study of LSCO and PLZT thin films was also performed. The formation of vacancy clusters in the LSCO top electrode, and VPb−VO defects in the PLZT layer, with increased oxygen deficiency is inferred. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.32.Tt Capacitors
81.15.Fg Pulsed laser ablation deposition
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation

Conduction of heat in inhomogeneous solids

M. D. Dramićanin, Z. D. Ristovski, V. Djoković, and S. Galović

Appl. Phys. Lett. 73, 321 (1998); http://dx.doi.org/10.1063/1.121821 (3 pages) | Cited 11 times

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In this letter we present a method for calculation of linear heat flow in inhomogeneous solids. The method is based on the evaluation of transfer matrices for each layer in a multilayered structure from the Laplace transformation of the partial differential equation of heat conduction. The multilayered structure is then described by a matrix obtained as a chain of products of individual layer transfer matrices and corresponding boundary thermal resistivity matrices. The analytic expression for the nth power of the multilayered transfer matrix is found, describing a periodic multilayered structure composed of n equal multilayered structures. The application of the presented method for calculation of photothermal signals is also shown. Dispersion relation for the thermal waves in inhomogeneous solids is obtained from the matrix elements of the transfer matrix. Finally, from the dispersion relation explicit expressions for the effective values of thermal diffusivity and conductivity of both the discontinuously and continuously inhomogeneous solids are evaluated. © 1998 American Institute of Physics.
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44.30.+v Heat flow in porous media
05.70.Ce Thermodynamic functions and equations of state

Oxidation resistance of tantalum–ruthenium dioxide diffusion barrier for memory capacitor bottom electrodes

Dong-Soo Yoon, Hong Koo Baik, Sung-Man Lee, Chang-Soo Park, and Sang-In Lee

Appl. Phys. Lett. 73, 324 (1998); http://dx.doi.org/10.1063/1.121822 (3 pages) | Cited 17 times

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The effect of the RuO2 addition into a Ta film on the oxidation resistance of a diffusion barrier for the Ta+RuO2/Si system was investigated. The Ta+RuO2/Si system was sustained up to 800 °C without an increase in resistivity, while the Ta/Si structure completely degraded after annealing at 450 °C. The Ta+RuO2 diffusion barrier showed an amorphous microstructure for an as-deposited state and formed a conductive RuO2 phase after annealing. Ta was sufficiently bound to oxygen of RuO2 for an as-deposited state, but RuO2 was divided into Ru and Ru–O binding states. Ta–O bonds showed a little change compared to the as-deposited state with increasing annealing temperature, whereas Ru–O bonds significantly increased. Therefore, the Ta layer deposited by the RuO2 addition effectively prevented the indiffusion of oxygen up to 800 °C and its oxidation resistance was superior to those of polycrystalline nitride (TiN, TaN) and ternary amorphous (TaSiN) barriers reported by others. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
81.65.Mq Oxidation
81.65.Kn Corrosion protection
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Cg Contact resistance, contact potential
81.40.Gh Other heat and thermomechanical treatments

Charge transport, optical transparency, microstructure, and processing relationships in transparent conductive indium–zinc oxide films grown by low-pressure metal-organic chemical vapor deposition

Anchuan Wang, Jiyan Dai, Jizhi Cheng, Michael P. Chudzik, Tobin J. Marks, Robert P. H. Chang, and Carl R. Kannewurf

Appl. Phys. Lett. 73, 327 (1998); http://dx.doi.org/10.1063/1.121823 (3 pages) | Cited 44 times

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Indium–zinc oxide films (ZnxInyOx+1.5y), with x/y = 0.08–12.0, are grown by low-pressure metal-organic chemical vapor deposition using the volatile metal–organic precursors In(TMHD)3 and Zn(TMHD)2 (TMHD = 2,2,6,6–tetramethyl–3,5–heptanedionato). Films are smooth (rms roughness = 40–50 Å) with complex microstructures which vary with composition. The highest conductivity is found at x/y = 0.33, with σ = 1000 S/cm (n-type; carrier density=3.7×1020 cm3; mobility=18.6 cm2/V s; dσ/dT<0). The optical transmission window of such films is broader than Sn-doped In2O3, and the absolute transparency rivals or exceeds that of the most transparent conductive oxides. X-ray diffraction, high resolution transmission electron microscopy, microdiffraction, and high resolution energy dispersive X-ray analysis show that such films are composed of a layered ZnkIn2O3+k phase precipitated in a cubic In2O3:Zn matrix. © 1998 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
72.80.Jc Other crystalline inorganic semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Hd Other semiconductors
78.66.Li Other semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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