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5 Aug 2002

Volume 81, Issue 6, pp. 951-1149

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Internal photoemission of electrons and holes from (100)Si into HfO2

V. V. Afanas’ev, A. Stesmans, F. Chen, X. Shi, and S. A. Campbell

Appl. Phys. Lett. 81, 1053 (2002); http://dx.doi.org/10.1063/1.1495088 (3 pages) | Cited 83 times

Online Publication Date: 30 July 2002

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The electron energy band alignment at the Si/HfO2 interfaces with different interlayers (Si3N4, SiON, and SiO2) is directly determined using internal photoemission of electrons and holes from Si into the Hf oxide. Irrespective of the interlayer type, the energy barrier for the Si valence electrons was found to be equal 3.1±0.1 eV, yielding the conduction band offset of 2.0±0.1 eV. Photoemission of holes is effectively suppressed by SiON and SiO2 interlayers, yet it is observed to occur across the Si3N4 interlayer with a barrier of 3.6±0.1 eV, which corresponds to a Si/HfO2 valence band offset of 2.5±0.1 eV. The HfO2 band gap width of 5.6 eV, thus derived from the band offsets, coincides with the bulk value obtained from the oxide photoconductivity spectra. © 2002 American Institute of Physics.
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79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.40.+w Photoconduction and photovoltaic effects

Ferroelastic phase in SrBi2Ta2O9 and study of the ferroelectric phase-transition dynamics

S. Kamba, J. Pokorný, V. Porokhonskyy, J. Petzelt, M. P. Moret, A. Garg, Z. H. Barber, and R. Zallen

Appl. Phys. Lett. 81, 1056 (2002); http://dx.doi.org/10.1063/1.1498005 (3 pages) | Cited 26 times

Online Publication Date: 30 July 2002

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Polarized microscope observation of ferroelastic domains in a SrBi2Ta2O9 (SBT) single crystal reveals the presence of domains up to Tc1 ≃ 770 K, which supports the ferroelasticity and Amam symmetry of the intermediate phase between ferroelectric and paraelectric phases. Far-infrared spectra of SBT ceramics, single crystal and thin films show a well underdamped optical soft mode at 28 cm−1, which partially softens to 21 cm−1 near the ferroelectric transition temperature (Tc2 ≅ 600 K). This softening does not explain the entire anomaly of low-frequency permittivity observed near Tc2. On the basis of high-frequency measurements, which do not show a significant dispersion, central-mode-type dispersion in the 10–100 GHz range is proposed as an explanation. So, the phase transition at Tc2 apparently shows a crossover behavior between the displacive and the order–disorder type. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
62.20.D- Elasticity
77.80.B- Phase transitions and Curie point
78.30.Hv Other nonmetallic inorganics
77.22.Ch Permittivity (dielectric function)
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Pyroelectric nanoporous films: Synthesis and properties

Ganesh Suyal, Andreas Seifert, and Nava Setter

Appl. Phys. Lett. 81, 1059 (2002); http://dx.doi.org/10.1063/1.1498008 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2002

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PbZrxTi1−xO3 (x = 0.45) and PbxCa1−xTiO3 (PCT) (x = 0.75) porous thin films were deposited on platinized silicon wafers by chemical solution deposition route using a polymer as a volatile phase. The introduction of pores creates a matrix-void composite resulting in a high figure of merit for pyroelectric applications. The figures of merit Fv and Fd for PCT films are shown to be as high as 4.8 and 250 μC/m2 K, respectively. © 2002 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
77.70.+a Pyroelectric and electrocaloric effects
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.05.Rm Porous materials; granular materials
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Epitaxial PbZr.52Ti.48O3 films on SrTiO3/(001)Si substrates deposited by sol–gel method

A. A. Talin, S. M. Smith, S. Voight, J. Finder, K. Eisenbeiser, D. Penunuri, Z. Yu, P. Fejes, T. Eschrich, J. Curless, D. Convey, and A. Hooper

Appl. Phys. Lett. 81, 1062 (2002); http://dx.doi.org/10.1063/1.1498006 (3 pages) | Cited 12 times

Online Publication Date: 30 July 2002

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We report on the sol–gel deposition and characterization of high-quality, epitaxial films of PbZr.52Ti.48O3 (PZT) on (001)Si substrates, with a thickness range of 400 Å to 1 μm. The epitaxial growth of PZT on (001)Si is achieved using a thin template layer of SrTiO3, grown by molecular-beam epitaxy. The sol–gel PZT films have a typical surface roughness of 5 Å and exhibit well defined reflective high-energy electron diffraction patterns characteristic of smooth, epitaxial films. Using high-resolution transmission electron microscopy and double-crystal x-ray diffraction, we find that the PZT films are oriented with the c axis normal to the (001)Si plane and with the a axis lying along 〈110〉Si direction. Finally, we measure the electromechanical coupling coefficients and the surface acoustic wave velocities for our films as a function of thickness and compare our experimental data to previously published theoretical values for this system. © 2002 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
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.A- Nucleation and growth
77.80.-e Ferroelectricity and antiferroelectricity
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
68.35.Iv Acoustical properties

HfO2 gate dielectric with 0.5 nm equivalent oxide thickness

H. Harris, K. Choi, N. Mehta, A. Chandolu, N. Biswas, G. Kipshidze, S. Nikishin, S. Gangopadhyay, and H. Temkin

Appl. Phys. Lett. 81, 1065 (2002); http://dx.doi.org/10.1063/1.1495882 (3 pages) | Cited 42 times

Online Publication Date: 30 July 2002

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Hafnium dioxide films have been deposited using reactive electron beam evaporation in oxygen on hydrogenated Si(100) surfaces. The capacitance–voltage curves of as-deposited metal(Ti)–insulator–semiconductor structures exhibited large hysteresis and frequency dispersion. With post-deposition annealing in hydrogen at 300 °C, the frequency dispersion decreased to less than 1%/decade, while the hysteresis was reduced to 20 mV at flatband. An equivalent oxide thickness of 0.5 nm was achieved for HfO2 thickness of 3.0 nm. We attribute this result to a combination of pristine hydrogen saturated silicon surfaces, room temperature dielectric deposition, and low temperature hydrogen annealing. © 2002 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing

Stress-induced polarization-graded ferroelectrics

Joseph V. Mantese, Norman W. Schubring, Adolph L. Micheli, Margarita P. Thompson, Ratna Naik, Gregory W. Auner, I. Burc Misirlioglu, and S. Pamir Alpay

Appl. Phys. Lett. 81, 1068 (2002); http://dx.doi.org/10.1063/1.1498506 (3 pages) | Cited 33 times

Online Publication Date: 30 July 2002

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Polarization-graded ferroelectrics and their electrically active embodiments, graded ferroelectric devices and transpacitors, have been formed from a variety of material systems, both by grading the composition of the ferroelectric and by imposing temperature gradients normal to the electrode surfaces. In this letter, we show how these same devices can be formed from homogeneous ferroelectric films of lead strontium titanate by imposing stress gradients on the material normal to their electrode surfaces. © 2002 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
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.65.Ly Strain-induced piezoelectric fields
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
68.60.Bs Mechanical and acoustical properties

Dielectric characteristics of Al2O3–HfO2 nanolaminates on Si(100)

M.-H. Cho, Y. S. Roh, C. N. Whang, K. Jeong, H. J. Choi, S. W. Nam, D.-H. Ko, J. H. Lee, N. I. Lee, and K. Fujihara

Appl. Phys. Lett. 81, 1071 (2002); http://dx.doi.org/10.1063/1.1499223 (3 pages) | Cited 63 times

Online Publication Date: 30 July 2002

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The structural characteristics and the chemical state of a HfO2–Al2O3 nanolaminate structure, depending on the postannealing temperature, were examined by x-ray diffraction and x-ray photoelectron spectroscopy. The structural stability is significantly enhanced up to 870 °C and so is able to sustain its amorphous and laminate structure. However, the laminate structure is drastically broken at the annealing temperature of 920 °C and the crystallization is locally generated. In particular, the formation of the interfacial layer during the postannealing treatment is effectively suppressed in the nanolaminated structure. The dielectric constant of the nanolaminate structure calculated from the accumulation capacitance increases from ∼10 to ∼17 as the annealing temperature increases. This change is closely related to the degree of the mixture composed by Al2O3 and HfO2. © 2002 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
61.46.-w Structure of nanoscale materials
79.60.Jv Interfaces; heterostructures; nanostructures

Boron penetration studies from p+ polycrystalline Si through HfSixOy

M. A. Quevedo-Lopez, M. El-Bouanani, M. J. Kim, B. E. Gnade, R. M. Wallace, M. R. Visokay, A. LiFatou, M. J. Bevan, and L. Colombo

Appl. Phys. Lett. 81, 1074 (2002); http://dx.doi.org/10.1063/1.1498872 (3 pages) | Cited 31 times

Online Publication Date: 30 July 2002

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We present detailed B penetration studies from B-doped polysilicon through alternate gate dielectric candidate HfSixOy films. No detectible B penetration is observed for annealing times as long as 20 s after 950 °C. Considerable B incorporation into the Si substrate is observed for annealing temperatures higher than 950 °C. By modeling the B depth profiles, we calculated the B diffusivities through HfSixOy to be higher than the corresponding diffusivities for SiO2. B diffusion through grain boundaries after HfSixOy crystallization is proposed to be responsible for the enhanced B diffusivity observed. © 2002 American Institute of Physics.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.05.Cy Elemental semiconductors
61.72.Mm Grain and twin boundaries

Field-induced effects in the relaxor ferroelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 studied by micro-Brillouin scattering

Jae-Hyeon Ko and Seiji Kojima

Appl. Phys. Lett. 81, 1077 (2002); http://dx.doi.org/10.1063/1.1496136 (3 pages) | Cited 7 times

Online Publication Date: 30 July 2002

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Field-induced changes of Brillouin scattering spectra in a relaxor-based ferroelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystal have been examined under an electric field oriented along the pseudocubic [001] direction. A complete cycle of the Brillouin shift-electric field loop shows that sound velocities of one longitudinal and two transverse modes are softened during the polarization reversal. In particular, one transverse mode, which corresponds to the (c11−c12)/2 elastic stiffness coefficient, becomes markedly soft from 18.6 to 14 GHz and then restores its initial value at two distinct electric fields. In addition, two peaks have also been observed in the field dependence of the full width at half maximum of this mode. It implies that, at least two kinds of polarization rotation process are involved in the switching process, which seems to be related with the existence of intermediate monoclinic symmetry during the field-induced phase transition from rhombohedral to tetragonal phase. © 2002 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
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
77.22.Ej Polarization and depolarization
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
77.80.B- Phase transitions and Curie point
62.65.+k Acoustical properties of solids
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