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1 Jan 2005

Volume 97, Issue 1, Articles (01xxxx)

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Strained Si, SiGe, and Ge channels for high-mobility metal-oxide-semiconductor field-effect transistors

Minjoo L. Lee, Eugene A. Fitzgerald, Mayank T. Bulsara, Matthew T. Currie, and Anthony Lochtefeld

J. Appl. Phys. 97, 011101 (2005); http://dx.doi.org/10.1063/1.1819976 (28 pages) | Cited 247 times

Online Publication Date: 9 December 2004

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This article reviews the history and current progress in high-mobility strained Si, SiGe, and Ge channel metal-oxide-semiconductor field-effect transistors (MOSFETs). We start by providing a chronological overview of important milestones and discoveries that have allowed heterostructures grown on Si substrates to transition from purely academic research in the 1980’s and 1990’s to the commercial development that is taking place today. We next provide a topical review of the various types of strain-engineered MOSFETs that can be integrated onto relaxed Si1−xGex, including surface-channel strained Si n- and p-MOSFETs, as well as double-heterostructure MOSFETs which combine a strained Si surface channel with a Ge-rich buried channel. In all cases, we will focus on the connections between layer structure, band structure, and MOS mobility characteristics. Although the surface and starting substrate are composed of pure Si, the use of strained Si still creates new challenges, and we shall also review the literature on short-channel device performance and process integration of strained Si. The review concludes with a global summary of the mobility enhancements available in the SiGe materials system and a discussion of implications for future technology generations.
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85.30.Tv Field effect devices
72.20.Ht High-field and nonlinear effects
01.30.Rr Surveys and tutorial papers; resource letters
73.20.At Surface states, band structure, electron density of states
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Pulse propagation in adiabatically coupled photonic crystal coupled cavity waveguides

P. Sanchis, J. García, A. Martínez, and J. Martí

J. Appl. Phys. 97, 013101 (2005); http://dx.doi.org/10.1063/1.1827345 (9 pages) | Cited 5 times

Online Publication Date: 13 December 2004

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A rigorous analysis of pulse propagation in planar photonic crystal (PhC) coupled cavity waveguides (CCWs) of finite length is reported. Conventional PhC waveguides, formed by a single line defect, are used at both interfaces of the CCW. An adiabatic taper based on progressively varying the radii of the spacing defects between cavities is used to achieve flat transmission bands with respect to the butt coupling case. The influence on the main parameters of the propagated pulse such as group delay, full width at half maximum and pulse attenuation are investigated for both the adiabatic and butt coupling cases. Furthermore, the Fabry-Perot formula has been used for modeling the pulse propagation along the CCW of finite length, which permits to analyze a large range of parameters avoiding the huge computation time requirements of finite-difference time-domain simulations.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Nondegenerate four-wave mixing in graded metallic films

J. P. Huang and K. W. Yu

J. Appl. Phys. 97, 013102 (2005); http://dx.doi.org/10.1063/1.1828610 (4 pages) | Cited 5 times

Online Publication Date: 15 December 2004

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The effective nondegenerate four-wave mixing (NDFM) susceptibility of graded metallic films with weak nonlinearity is exactly derived by invoking the local-field effects. It is found that the presence of gradation in metallic films can yield a broad resonant plasmon band in the optical region, which results in a large enhancement in the NDFM response and thus a large figure of merit.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.An Optical susceptibility, hyperpolarizability
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys
78.68.+m Optical properties of surfaces

Photoreactive phase conjugation strength in disperse red 1 doped poly(methylmethacrylate) thin films

Sean Liu, Wei Lin Wang, Chien Cheng Fang, Tzer-Hsiang Huang, and Chia Chen Hsu

J. Appl. Phys. 97, 013103 (2005); http://dx.doi.org/10.1063/1.1829786 (10 pages) | Cited 3 times

Online Publication Date: 15 December 2004

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Near-resonant optical pumping was used to modulate third-order susceptibility χ(3) in disperse red 1 doped poly(methylmethacrylate) thin films. An optically pumped degenerate four-wave mixing (DFWM) experiment was conducted to examine the photoreactive phase conjugation (PC) signals. Experimental results indicated a large anisotropy in PC signals arising from ∣χ3333(3)∣2, and almost isotropic PC signals from ∣χ1331(3)∣2 under s-polarized and p-polarized pump fields. Additionally, a dynamic microscopic model, based on the theory developed by Sekkat et al.[Synth. Met. 54, 373 (1993) ; J. Phys. Chem. B 106, 12407 (2002) ; Opt. Commun. 229, 291 (2004) ] was presented to describe the observed optical nonlinear responses. Results from the model were generally consistent with those of the optically pumped DFWM experiment.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.An Optical susceptibility, hyperpolarizability
82.30.Qt Isomerization and rearrangement
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Generation of uniform plasmas by crossed internal oscillating current sheets: Key concepts and experimental verification

E. L. Tsakadze, K. Ostrikov, Z. L. Tsakadze, and S. Xu

J. Appl. Phys. 97, 013301 (2005); http://dx.doi.org/10.1063/1.1826214 (10 pages) | Cited 1 time

Online Publication Date: 9 December 2004

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The results of comprehensive experimental studies of the operation, stability, and plasma parameters of the low-frequency (0.46 MHz) inductively coupled plasmas sustained by the internal oscillating rf current are reported. The rf plasma is generated by using a custom-designed configuration of the internal rf coil that comprises two perpendicular sets of eight currents in each direction. Various diagnostic tools, such as magnetic probes, optical emission spectroscopy, and an rf-compensated Langmuir probe were used to investigate the electromagnetic, optical, and global properties of the argon plasma in wide ranges of the applied rf power and gas feedstock pressure. It is found that the uniformity of the electromagnetic field inside the plasma reactor is improved as compared to the conventional sources of inductively coupled plasmas with the external flat coil configuration. A reasonable agreement between the experimental data and computed electromagnetic field topography inside the chamber is reported. The Langmuir probe measurements reveal that the spatial profiles of the electron density, the effective electron temperature, plasma potential, and electron energy distribution/probability functions feature a high degree of the radial and axial uniformity and a weak azimuthal dependence, which is consistent with the earlier theoretical predictions. As the input rf power increases, the azimuthal dependence of the global plasma parameters vanishes. The obtained results demonstrate that by introducing the internal oscillated rf currents one can noticeably improve the uniformity of electromagnetic field topography, rf power deposition, and the plasma density in the reactor.
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52.50.Dg Plasma sources
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.-b Plasma properties
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.70.Ds Electric and magnetic measurements
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides

Nitrogen oxide γ-band emission from primary and secondary streamers in pulsed positive corona discharge

Ryo Ono and Tetsuji Oda

J. Appl. Phys. 97, 013302 (2005); http://dx.doi.org/10.1063/1.1829371 (4 pages) | Cited 11 times

Online Publication Date: 15 December 2004

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Nitrogen oxide γ-band emissions (A2 Σ+→X2 Π) from primary and secondary streamers are observed in O2/N2 and NO/N2 pulsed positive corona discharges with the aim of investigating the production of NO molecules and N2(A3 Σu+) metastables in these primary and secondary streamers. The spatial distribution of the NO‐γ emission shows that the NO‐γ emission is mostly observed in the secondary streamer propagation area of the O2/N2 discharge. That is, NO molecules are mainly produced in the secondary streamer in the O2/N2 discharge. On the other hand, in the NO/N2 discharge, the NO‐γ emission is observed in the primary streamer propagation area. This result indicates that N2(A3 Σu+) metastables are mostly produced in the primary streamer because the NO‐γ emission is observed following the process NO(X2 Π)+N2(A3 Σu+)→NO(A2 Σ+)+N2(X2 Σg), where NO(X2 Π) is distributed uniformly in the background gas in the NO/N2 discharge.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Kinetics of image formation in the equipotential semiconductor-thermoplastic system

Valerii I. Anikin and Igor L. Zhurminsky

J. Appl. Phys. 97, 013303 (2005); http://dx.doi.org/10.1063/1.1829146 (5 pages)

Online Publication Date: 15 December 2004

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The redistribution of corona current in regions with a low potential has been experimentally shown. This led to the equipotentiality of the semiconductor-thermoplastic system at charging in the field of corona discharge. The self-coordinated model of kinetics formation of electrostatic contrast in a corona discharge is proposed. The model takes into consideration a nonlinearity of current–voltage characteristics of the semiconductor, and thermoplastic and deformation of the thermoplastic layer. The moment of deformation appearance is set at random from experimental data.
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42.30.Va Image forming and processing
72.40.+w Photoconduction and photovoltaic effects
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Measurement of the spatiotemporal surface charge distribution in an ac plasma display cell using Pockels effect

D. C. Jeong, H. S. Bae, and K. W. Whang

J. Appl. Phys. 97, 013304 (2005); http://dx.doi.org/10.1063/1.1821637 (8 pages) | Cited 16 times

Online Publication Date: 15 December 2004

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We measured the surface charge distribution in a coplanar type alternating current plasma display panel cell by the longitudinal electro-optic amplitude modulation method with BSO (Bi12SiO20) single crystal. The effects of the initialization condition were investigated to take care of the errors coming from the charge relaxation phenomena of the BSO crystal. Using BSO single crystal as the dielectric layer, the two-dimensional spatiotemporal surface charge distribution was successfully measured in a discharge cell with a discharge gas of neon and xenon 4% at the pressure of 100 torr driven by square-type sustaining pulses. The temporal behavior of the surface charge is compared with the simulated result and the measurement of the infrared light emission from the discharge. The positive and negative surface charges show somewhat different spatiotemporal characteristics.
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85.60.Pg Display systems
78.20.Jq Electro-optical effects
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Time-resolved and time-integrated photoluminescence analysis of state filling and quantum confinement of silicon quantum dots

Lap Van Dao, Xiaoming Wen, My Tra Thi Do, Peter Hannaford, Eun-Chel Cho, Young H. Cho, and Yidan Huang

J. Appl. Phys. 97, 013501 (2005); http://dx.doi.org/10.1063/1.1823027 (5 pages) | Cited 17 times

Online Publication Date: 13 December 2004

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In this paper we report studies of the optical properties of silicon quantum dot structures. From time-resolved and time-integrated photoluminescence measurements we investigate the state-filling effect and carrier lifetime, and discuss the parabolic confinement of quantum dot structures and the large energy splitting between quantum dot levels. The photoluminescence intensities for different quantum dot levels decay with a stretched exponential function and the decay times are in the range 2–100 μs depending on the observation wavelength and the dot size.
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78.67.Hc Quantum dots
78.47.-p Spectroscopy of solid state dynamics
78.55.Ap Elemental semiconductors

Detailed analysis of inverse Fourier transform techniques to uniquely infer second-order nonlinearity profile of thin films

Aydogan Ozcan, Michel J. F. Digonnet, and Gordon S. Kino

J. Appl. Phys. 97, 013502 (2005); http://dx.doi.org/10.1063/1.1826216 (16 pages) | Cited 4 times

Online Publication Date: 13 December 2004

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The mathematical details of a family of inverse Fourier transform techniques to uniquely recover the second-order optical nonlinearity profile of thin films are discussed both theoretically and numerically. These methods are all based on the Maker-fringe technique, i.e., they involve focusing a fundamental laser beam onto a nonlinear film and measuring the generated second-harmonic power as a function of the incidence angle of the fundamental beam. It is shown that each method can be treated as a special case of a general theory. An error analysis for the recovery of theoretical nonlinearity profiles is also illustrated with numerical examples.
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42.70.Ce Glasses, quartz
42.30.Kq Fourier optics
42.65.An Optical susceptibility, hyperpolarizability

Yellow and infrared self-frequency conversions in GdAl3(BO3)4:Nd3+

Alain Brenier, Chaoyang Tu, Zhaojie Zhu, Jianfu Li, and Baichang Wu

J. Appl. Phys. 97, 013503 (2005); http://dx.doi.org/10.1063/1.1823023 (4 pages) | Cited 10 times

Online Publication Date: 7 December 2004

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We have demonstrated two self-frequency conversions from the bifunctional laser and optical nonlinear GdAl3(BO3)4:Nd3+ crystal. For the first one, the laser operated in a dual-wavelength mode in the math→math (at 1062 nm) and math→math (at 1338 nm) channels, under a fixed wavelength pumping (at 747.7 nm) and with a fixed crystal orientation (28.5°). Then the self-sum frequency mixing 1/1062+1/1338→1/592 process occurred, leading to a weak yellow beam at 592 nm. In the second self-frequency conversion, the Nd3+:GdAl3(BO3)4 laser operated in a single wavelength mode at 1062 nm. Then the self-difference frequency mixing process 1/λP−1/1062 = 1/λI occurred at a 29.9° phase matching angle. The idler wavelength λI was tunable in the 2450–2600 nm range, due to the tunability of the λP pump wavelength. The highest yield was 0.12%. New Sellmeier formulas valid at least up to 2600 nm have been established.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Local strain, defects, and crystallographic tilt in GaN(0001) layers grown by maskless pendeo-epitaxy from x-ray microdiffraction

R. I. Barabash, G. E. Ice, W. Liu, S. Einfeldt, A. M. Roskowski, and R. F. Davis

J. Appl. Phys. 97, 013504 (2005); http://dx.doi.org/10.1063/1.1825614 (5 pages) | Cited 4 times

Online Publication Date: 7 December 2004

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Polychromatic x-ray microdiffraction, high-resolution monochromatic x-ray diffraction, and finite element simulations have been used to determine the distribution of strain, defects, and crystallographic tilt in uncoalesced GaN layers grown by maskless pendeo-epitaxy. An important materials parameter was the width-to-height ratio of the etched columns of GaN from which occurred the lateral growth of the wings. Tilt boundaries formed at the column/wing interface for samples with a large ratio. Formation of the tilt boundary can be avoided by using smaller ratios. The strain and tilt across the stripe increased with the width-to-height ratio. The wings were tilted upward at room temperature.
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42.70.Hj Laser materials
68.49.−h
68.55.-a Thin film structure and morphology

Antimony orthophosphate glasses with large nonlinear refractive indices, low two-photon absorption coefficients, and ultrafast response

E. L. Falcão-Filho, Cid B. de Araújo, C. A. C. Bosco, G. S. Maciel, L. H. Acioli, M. Nalin, and Y. Messaddeq

J. Appl. Phys. 97, 013505 (2005); http://dx.doi.org/10.1063/1.1828216 (5 pages) | Cited 10 times

Online Publication Date: 7 December 2004

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Antimony glasses based on the composition Sb2O3–SbPO4 were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n2, of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n2 was observed by adding lead oxide to the Sb2O3–SbPO4 composition. Large values of n2 ≈ 10−14 cm2/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.
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42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
81.05.Kf Glasses (including metallic glasses)
42.65.-k Nonlinear optics

Thermally induced diffusion in GaInNAs/GaAs and GaInAs/GaAs quantum wells grown by solid source molecular beam epitaxy

T. K. Ng, H. S. Djie, S. F. Yoon, and T. Mei

J. Appl. Phys. 97, 013506 (2005); http://dx.doi.org/10.1063/1.1825632 (8 pages) | Cited 5 times

Online Publication Date: 7 December 2004

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The effects of the thermal annealing induced diffusion on the photoluminescence (PL) of a GaAs/GaInAs/GaAs/GaInNAs/GaAs quantum well (QW) structure grown by solid source molecular beam epitaxy are studied. The PL experimental results in conjunction with the numerical quantum-mechanical modeling that predicts the changes in the QW confining potential with group-III atomic diffusion, have been used to obtain the values for diffusion coefficient. The activation energies of GaInAs/GaAs QW (ED,GIA) were found to be between 0.49 to 0.51 eV, while that of GaInNAs/GaAs QW (ED,GINA) showed comparable values of between 0.6 to a 0.67 eV, as annealing time increases from 10 to 30 s. The ED,GIA and ED,GINA values are attributed to the same interstitial diffusion mechanism.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
78.67.De Quantum wells
68.65.Fg Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
66.30.Dn Theory of diffusion and ionic conduction in solids
61.72.J- Point defects and defect clusters

Shock wave compression of the ferroelectric ceramic Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3: Depoling currents

Robert E. Setchell

J. Appl. Phys. 97, 013507 (2005); http://dx.doi.org/10.1063/1.1828215 (16 pages) | Cited 18 times

Online Publication Date: 7 December 2004

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Shock wave compression of poled Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 (PZT 95/5-2Nb) results in rapid depoling and release of bound charge. In the current study, planar-impact experiments with this material were conducted on a gas-gun facility to determine Hugoniot states, to examine constitutive mechanical properties during shock propagation, and to investigate shock-induced depoling characteristics. A previous article summarized results from the first two of these areas, and this article summarizes the depoling studies. A baseline material, similar to materials used in previous studies, was examined in detail. More limited experiments were conducted with other materials to investigate the effects of different porous microstructures. Experiments were conducted over a wide range of conditions in order to examine the effects of varying shock strength, poling orientation, input wave shape, electric field strength, porous microstructure at a fixed density, and initial density. Depoling currents were recorded in an external circuit under either short-circuit or high-field conditions, and provide a convenient means of examining the kinetics associated with the ferroelectric–to–antiferroelectric phase transition. For sufficiently strong shock waves, the measured short-circuit currents indicate that the phase transition is very rapid and essentially complete. As shock strengths are reduced, short-circuit currents show increasing rise times and decreasing final levels at the end of shock transit. These features indicate that the transition kinetics can be characterized in terms of both a transition rate and a limiting degree of transition achieved in a given shock experiment. The presence of a strong electric field does not appear to have a significant effect on transition kinetics at high shock stresses, but has a strong effect at low stresses. As was found for constitutive mechanical properties, only small effects on measured currents resulted from differences in the porous microstructure of common-density materials, but large effects were observed when initial density was varied. To examine transition kinetics in more detail, short-circuit currents obtained with the baseline material and several approximate methods were used to estimate values for the rate and degree of transition as functions of shock properties. Differences between these currents and currents measured in high-field experiments using the same impact conditions were used to examine field effects on transition kinetics and corresponding dielectric properties.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
62.50.-p High-pressure effects in solids and liquids
77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)

Amorphization and decomposition of scandium molybdate at high pressure

Akhilesh K. Arora, Takehiko Yagi, Nobuyoshi Miyajima, and T. A. Mary

J. Appl. Phys. 97, 013508 (2005); http://dx.doi.org/10.1063/1.1819975 (8 pages) | Cited 15 times

Online Publication Date: 13 December 2004

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The behavior of negative thermal-expansion material scandium molybdate Sc2(MoO4)3 is investigated at high pressure (HP) and high temperature (HT) using x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The compound exhibits unusually high compressibility (bulk modulus ∼ 6 GPa) and undergoes amorphization at 12 GPa. On the other hand, in situ laser heating of amorphous samples inside the diamond-anvil cell is found to result in crystalline diffraction pattern and Raman spectrum different from those of the original compound. Upon release of the pressure subsequent to laser heating, the Raman spectrum and the diffraction pattern remain unchanged. Matching of several of the diffraction lines and Raman peaks in the laser-heated samples with those of MoO3 suggests a solid-state decomposition of the parent compound under HP-HT conditions into MoO3 and other compounds. Other diffraction lines are found to correspond to Sc2Mo2O9, Sc2O3, and the parent compound. Quantitative analysis of the characteristic x-ray emission from different regions of the sample during scanning electron microscopic observations is used for obtaining the compositions of the daughter compounds. The stoichiometries of two main phases are found to be close to those of MoO3 and Sc2Mo2O9. These results support the model that the pressure-induced amorphization occurred in this system because a pressure-induced decomposition was kinetically constrained.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
64.75.-g Phase equilibria
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.66.Bi Elemental solids
61.66.Dk Alloys
78.30.Hv Other nonmetallic inorganics
78.70.En X-ray emission spectra and fluorescence
62.20.D- Elasticity

Modifications of ZnO thin films under dense electronic excitation

P. M. Ratheesh Kumar, C. Sudha Kartha, K. P. Vijayakumar, F. Singh, D. K. Avasthi, T. Abe, Y. Kashiwaba, G. S. Okram, M. Kumar, and Sarvesh Kumar

J. Appl. Phys. 97, 013509 (2005); http://dx.doi.org/10.1063/1.1823574 (6 pages) | Cited 18 times

Online Publication Date: 13 December 2004

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Spray pyrolyzed ZnO films prepared using solution containing ethanol and water (volume ratio 1:1), exhibited optical transmission of 85% in the visible range and electrical resistivity of 78 Ω cm. These samples were irradiated using 120 MeV Au ion beam and then characterized using optical absorption and transmission, x-ray diffraction (XRD), electrical resistivity measurements, x-ray photoelectron spectroscopy (XPS), and photoluminescence studies. It appears that irradiation does not affect absorption edge while optical transmittance was slightly reduced. But intensities of peaks of XRD and photoluminescence were found to decrease continuously with increasing ion fluence. Electrical resistivity of the films decreased considerably (from 78 to 0.71 Ω cm) with increase in ion fluence. Atomic concentration from XPS analysis showed that Zn/O ratio is getting increased due to ion beam irradiation. Variations in carrier concentration were also measured using Hall measurements.
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81.05.Dz II-VI semiconductors
61.82.Fk Semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
79.60.Dp Adsorbed layers and thin films
61.80.Jh Ion radiation effects
81.15.Rs Spray coating techniques
73.61.Ga II-VI semiconductors
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors

Downconversion and upconversion dynamics in Pr-doped Y3Al5O12 crystals

G. Özen, O. Forte, and B. Di Bartolo

J. Appl. Phys. 97, 013510 (2005); http://dx.doi.org/10.1063/1.1823577 (5 pages) | Cited 14 times

Online Publication Date: 13 December 2004

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We have investigated the spectroscopic properties of praseodymium ion in a Y3Al5O12 sample. We obtained the luminescence spectra by exciting selectively the sample at 460 and 599 nm, resulting in the excitation of the math and math levels, respectively. With excitation in the math level we obtained emission from this level and from the math level. We used time resolved spectra and decay pattern inspection to assign spectral lines to specific radiative transitions. With excitation in the math level we observed luminescence emitted by the same level and upconverted emission from the math level and the (4f5d) band. The experimental data indicate that the mechanism responsible for the upconversion processes is excited state absorption. We found the upconverted emission from math and the (4f5d) band to be proportional to the square of the excitation energy and to the cube of the excitation energy, respectively.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Lm Parametric down conversion and production of entangled photons
71.55.Ht Other nonmetals
78.47.-p Spectroscopy of solid state dynamics
78.40.Ha Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials

Growth of vacuum evaporated ultraporous silicon studied with spectroscopic ellipsometry and scanning electron microscopy

Kate Kaminska, Aram Amassian, Ludvik Martinu, and Kevin Robbie

J. Appl. Phys. 97, 013511 (2005); http://dx.doi.org/10.1063/1.1823029 (8 pages) | Cited 26 times

Online Publication Date: 13 December 2004

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Using a combination of variable-angle spectroscopic ellipsometry and scanning electron microscopy, we investigated the scaling behavior of uniaxially anisotropic, ultraporous silicon manufactured with glancing angle deposition. We found that both the diameter of the nanocolumns and the spacing between them increase with film thickness according to a power-law relationship consistent with self-affine fractal growth. An ellipsometric model is proposed to fit the optical properties of the anisotropic silicon films employing an effective medium approximation mixture of Tauc-Lorentz oscillator and void. This study shows that the optical response of silicon films made at glancing incidence differs significantly from that of amorphous silicon prepared by other methods due to highly oriented nanocolumn formation and power-law scaling.
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81.05.Cy Elemental semiconductors
81.05.Rm Porous materials; granular materials
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.66.Db Elemental semiconductors and insulators
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Enhanced bulk metallic glass formability by combining chemical compatibility and atomic size effects

F. Q. Guo, S. J. Poon, and G. J. Shiflet

J. Appl. Phys. 97, 013512 (2005); http://dx.doi.org/10.1063/1.1839221 (6 pages) | Cited 19 times

Online Publication Date: 13 December 2004

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The glass formability (GFA) of Y- and Ca-based alloys is enhanced by inserting elements that yield a more uniform separation in the atomic sizes, as well as a wider atomic size distribution range, in agreement with the analytical findings of Miracle, Senkov, and others. The degree of the GFA improvement depends on the chemical compatibility of the addition elements with the existing components. By combining this observation with similar results noted in other alloys that form large-size bulk metallic glasses, the importance of the atomic size effect and chemical compatibility in glass forming alloys is revealed. The atomic size effect and chemical compatibility are discussed along with other glass forming factors.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
82.60.Fa Heat capacities and heats of phase transitions

Electron-irradiation effects on CdSe thin films investigated by thermally stimulated current method

L. Ion and S. Antohe

J. Appl. Phys. 97, 013513 (2005); http://dx.doi.org/10.1063/1.1830090 (4 pages) | Cited 1 time

Online Publication Date: 13 December 2004

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Defects determining the electrical properties of CdSe thin films, before and after irradiation with high-energy electrons, have been investigated by thermally stimulated current technique. Thin films of CdSe, 30 μm thick, prepared by thermal-vacuum evaporation on glass substrate at a temperature of 220 °C were subjected to irradiation with 6-MeV electrons to a fluency of 5×1013 e/cm2. The main defect (D1), controlling the electrical properties of the films both before and after irradiation, is located at 0.38 eV below the conduction-band edge. Some other defects existing in lower densities and having lower ionization energies (0.24 eV, D2; 0.17 eV, D3; and 0.14 eV, D4) were also identified. Electron irradiation induces in significant increase in the peaks associated with the defects D1, D2, and D3, especially in the first one. The parameters characterizing all the detected traps were determined.
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61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects
73.61.Ga II-VI semiconductors
61.72.J- Point defects and defect clusters
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.55.Gs II-VI semiconductors

Formation of a hydroxide thin film by laser ablation and conversion to an oxide film with topotaxy

Shiro Kambe, Kenji Sato, Kazuhide Morita, Fumiaki Sato, and Osamu Ishii

J. Appl. Phys. 97, 013514 (2005); http://dx.doi.org/10.1063/1.1828218 (7 pages)

Online Publication Date: 13 December 2004

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It is important to control the crystallographic orientation of oxide films for application in electronic devices. In the case of oxide superconductors, the orientation of epitaxial films has been controlled by varying the substrate temperature and the partial pressure of oxygen. To fix the orientation irrespective of the substrate temperature and the pressure of oxygen, the metal layer of the deposited film should be parallel to the substrate, and the formation of the oxide film by heat treatment should preserve this orientation. Hydroxides are one of the promising compounds that satisfy the above condition. By heating the hydroxide to achieve dehydration, oxides will be formed with the atomic arrangement preserved, that is, topotaxially. The purpose of this study is to form a completely oriented [001] Ca(OH)2 thin film, to form a perfectly [111] oriented CaO film after topotaxial dehydration, and to demonstrate formation of Ca(OH)2 and CaO films in vacuum. The [001] oriented Ca(OH)2 film was formed on a MgO substrate by laser ablation, indicating that the Ca layer of the film was parallel to the substrate. Pole figure measurements showed that the planar orientation of the Ca(OH)2 was random. This is due to the mismatch between the film and the substrate. By heating the Ca(OH)2 film at 600–800 °C to achieve dehydration, a [111] oriented CaO film was formed. Pole figure measurements showed that the CaO film is randomly oriented in the plane. This is because the mismatch between the CaO and the MgO is as large as 23%. It is to be noted that a [100] oriented film tends to be formed when the CaO film is deposited directly from a CaO target. The change of the orientation from [001] to [111] is discussed in connection with the topotaxy mechanism. These results show a possibility of “hydrogen bond epitaxy,” that is, formation of an atomically controlled oxide film through a hydroxide.
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81.15.−z
81.15.Fg Pulsed laser ablation deposition

Signature of a silver phase percolation threshold in microscopically phase separated ternary Ge0.15Se0.85−xAgx (0 ⩽ x ⩽ 0.20) glasses

Pulok Pattanayak and S. Asokan

J. Appl. Phys. 97, 013515 (2005); http://dx.doi.org/10.1063/1.1827341 (4 pages) | Cited 6 times

Online Publication Date: 13 December 2004

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Temperature modulated alternating differential scanning calorimetric studies show that Se rich Ge0.15Se0.85−xAgx (0 ⩽ x ⩽ 0.20) glasses are microscopically phase separated, containing Ag2Se phases embedded in a Ge0.15Se0.85 backbone. With increasing silver concentration, Ag2Se phase percolates in the Ge–Se matrix, with a well-defined percolation threshold at x = 0.10. A signature of this percolation transition is shown up in the thermal behavior, as the appearance of two exothermic crystallization peaks. Density, molar volume, and microhardness measurements, undertaken in the present study, also strongly support this view of percolation transition. The superionic conduction observed earlier in these glasses at higher silver proportions is likely to be connected with the silver phase percolation.
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81.05.Kf Glasses (including metallic glasses)
64.60.A- Specific approaches applied to studies of phase transitions
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis
62.20.Qp Friction, tribology, and hardness

Characterization of epitaxial (Y,Bi)3(Fe,Ga)5O12 thin films grown by metal-organic decomposition method

Takayuki Ishibashi, Aiko Mizusawa, Masataka Nagai, Shinichiro Shimizu, Katsuaki Sato, Naoto Togashi, Takayuki Mogi, Michio Houchido, Hiroaki Sano, and Kazuo Kuriyama

J. Appl. Phys. 97, 013516 (2005); http://dx.doi.org/10.1063/1.1827339 (4 pages) | Cited 12 times

Online Publication Date: 13 December 2004

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Epitaxial (Y,Bi)3(Fe,Ga)5O12 garnet thin films have been prepared on Gd3Ga5O12 (111) substrates by a metal-organic decomposition (MOD) method using carboxylic acids. The chemical compositions of the films prepared in this study are Y2BiFe5O12 (YBFO), Y3Fe4GaO12 (YFGO), and Y2BiFe4GaO12 (YBFGO). Epitaxy of these films was confirmed by x-ray diffraction and Rutherford backscattering (RBS) measurements. Full width of half maximum values of the 444 diffraction peaks of YFGO and YBFGO were 0.4° and 0.04°, respectively. RBS channeling was clearly observed for the YFGO film with a minimum yield χmin along the [111] direction of ∼ 7.5%. These garnet films could also be reproducibly obtained by the MOD method without any deterioration in the MOD solutions over two years.
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75.50.Gg Ferrimagnetics
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.20.Ls Magneto-optical effects
64.75.-g Phase equilibria
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Structural characteristics and lattice parameters of hydride vapor phase epitaxial GaN free-standing quasisubstrates

V. Darakchieva, T. Paskova, P. P. Paskov, B. Monemar, N. Ashkenov, and M. Schubert

J. Appl. Phys. 97, 013517 (2005); http://dx.doi.org/10.1063/1.1823024 (7 pages) | Cited 16 times

Online Publication Date: 13 December 2004

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We have studied the lattice parameters of hydride vapor phase epitaxy (HVPE)-GaN quasisubstrates in relation to their structural properties. Layers grown on single-layer metalorganic vapor phase epitaxy (MOVPE) templates and on epitaxial lateral overgrown MOVPE templates are characterized by Raman scattering, high-resolution x-ray diffraction, and reciprocal space mapping. The strain relaxation in the films versus their thickness was found to proceed similarly in the GaN samples grown using the two types of templates but the strain saturates at different nonzero levels. The lattice parameters of relatively thin HVPE-GaN free-standing quasisubstrates indicate that no total strain relaxation is achieved after the sapphire removal. The lattice parameters of the thick quasisubstrates grown on different templates are not affected by the separation process and are found to have values very close to the reference strain-free lattice parameters of GaN powder.
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81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
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