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1 Oct 1988

Volume 64, Issue 7, pp. 3341-3768

Page 2 of 4 Pages Previous Page Next Page | Jump to Page

The formation of hydrogen passivated silicon single‐crystal surfaces using ultraviolet cleaning and HF etching

T. Takahagi, I. Nagai, A. Ishitani, H. Kuroda, and Y. Nagasawa

J. Appl. Phys. 64, 3516 (1988); http://dx.doi.org/10.1063/1.341489 (6 pages) | Cited 220 times

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We have tried to develop a new procedure to prepare the clean surface of a silicon single crystal. We successfully prepared the contamination free bare silicon surface with ultraviolet cleaning followed by HF dipping with low concentration HF obtained by dilution by organic free ultrapure water, at room temperature under the atmospheric condition. X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet photoelectron spectroscopy measurements proved thus prepared surface has a hydrogen monoatomic layer terminating the dangling bonds of silicon. The hydrogen termination was found to have remarkable passivation effect against surface oxidation reaction. A silicon thin‐film epitaxially grown on the prepared surface was confirmed to have perfect crystal structure and high‐purity level by scanning electron microscopy, reflection high‐energy electron diffraction, Raman spectroscopy and secondary ion mass spectroscopy.
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81.65.-b Surface treatments
68.35.Dv Composition, segregation; defects and impurities
68.55.-a Thin film structure and morphology

Model for molecular‐beam‐epitaxy growth over nonplanar surfaces

Mitsuru Ohtsuka and Seiichi Miyazawa

J. Appl. Phys. 64, 3522 (1988); http://dx.doi.org/10.1063/1.341490 (6 pages) | Cited 12 times

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A model for molecular‐beam‐epitaxy growth is proposed to describe the morphology formed on a nonplanar, profiled surface that may consist of multifaceted crystal structures. Anisotropy of growth rate is introduced as a main factor for explaining the observed growth morphology. We show that on the nonplanar surface, the migration of adatoms modifies the growth rate at each point of the growing surface and thus affects the formation of the morphology within the range of migration length. The model can successfully describe the growth behavior including the development of sharp facet edges, since it is formulated in terms of a difference (rather than differential) equation which does not require the continuity of surface slope. The morphology simulated on the basis of this model agrees to experimental results of GaAs growth.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation

Measurement of electron diffusion lengths in ITO/p‐InP by surface photocurrents

Thomas Hanak and R. K. Ahrenkiel

J. Appl. Phys. 64, 3528 (1988); http://dx.doi.org/10.1063/1.341491 (4 pages) | Cited 1 time

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The electron diffusion length is deduced in n‐indium tin oxide/p‐InP heterojunctions by a short‐circuit photocurrent technique. The technique involved the nonlinear least‐squares fit of the photocurrent and junction capacitance to a simple model. The absorption coefficient of the monochromatic light is also produced by the fit. This produces an electron effective diffusion length in the p‐InP which varies from about 1.0 μm for highly absorbed light up to about 8.0 μm for deeply penetrating light.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects

Modifications in the one‐particle Monte Carlo method for solving the Boltzmann equation with changed variables

M. Nedjalkov and P. Vitanov

J. Appl. Phys. 64, 3532 (1988); http://dx.doi.org/10.1063/1.342470 (6 pages)

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Modifications in the one‐particle Monte Carlo method are described when it is more convenient to change the variables in the Boltzmann equation. The physical interpretation of the coefficients in the equation obtained is shown. An example under the condition of symmetry about the field is considered. The results are compared with those obtained by other methods solving the Boltzmann equation.
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72.20.Dp General theory, scattering mechanisms
02.60.Cb Numerical simulation; solution of equations
02.50.Ng Distribution theory and Monte Carlo studies

Oxide degradation during selective epitaxial growth of silicon

J. A. Friedrich and G. W. Neudeck

J. Appl. Phys. 64, 3538 (1988); http://dx.doi.org/10.1063/1.341492 (4 pages) | Cited 8 times

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A derivative of selective epitaxial growth and epitaxial lateral overgrowth, has been devised to create single‐crystal silicon on insulator structures. The effect of conditions present in selective epitaxial growth and epitaxial lateral overgrowth on the electrical characteristics of the insulating masking oxides has been studied. It was determined that thin (<150 nm) oxides were attacked by the ambient employed in selective epitaxy. The rate of degradation increased with decreasing oxide thickness and with the addition of silicon‐containing species to the gas phase. The observed defect formation may be related to the oxide decomposition during annealing in oxygen‐free ambients and the undercutting of masking oxide at the Si‐SiO2 interface during the in situ preclean step used in epitaxial processes.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Formation and properties of In‐doped high‐conductivity CdS film

Toshiya Hayashi, Takehiro Nishikura, Tatsuro Suzuki, and Yoshinori Ema

J. Appl. Phys. 64, 3542 (1988); http://dx.doi.org/10.1063/1.341493 (9 pages) | Cited 16 times

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High dark‐conductivity CdS films have been prepared by coevaporation of CdS and In and the physical properties of the films were investigated. The dark conductivity of the films prepared at room ranged from 10−1 to 103 S cm−1. Analyzing the film structure by x‐ray analysis, it was found that the In atoms were doped substitutionally into the Cd site of a CdS crystallite at a low concentration In doping stage and then doped interstitially into the CdS crystallite at a high concentration In doping stage. In the carrier density versus the doped In concentration relation, the n‐type characteristic was found. This was explained by the two In doping processes described above. Further, the negative temperature dependence of the carrier density was detected in the very high‐concentration In‐doped samples. We used an explanation similar to the one given by Hung and Gliessman [Phys. Rev. 96, 1226 (1954)], that is, by using a tentative model in which the substitutionally doped low concentration In atoms form a shallow discrete donor level and the interstitially doped high‐concentration In atoms form an impurity band in the forbidden band.
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72.40.+w Photoconduction and photovoltaic effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
72.20.-i Conductivity phenomena in semiconductors and insulators

Electron‐spin‐resonance study of radiation‐induced paramagnetic defects in oxides grown on (100) silicon substrates

Yong Yun Kim and P. M. Lenahan

J. Appl. Phys. 64, 3551 (1988); http://dx.doi.org/10.1063/1.341494 (7 pages) | Cited 67 times

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We have used electron‐spin resonance to investigate radiation‐induced point defects in Si/SiO2 structures with (100) silicon substrates. We find that the radiation‐induced point defects are quite similar to defects generated in Si/SiO2 structures grown on (111) silicon substrates. In both cases, an oxygen‐deficient silicon center, the E′ defect, appears to be responsible for trapped positive charge. In both cases trivalent silicon (Pb centers) defects are primarily responsible for radiation‐induced interface states. In earlier electron‐spin‐resonance studies of unirradiated (100) substrate capacitors two types of Pb centers were observed; in oxides prepared in three different ways only one of these centers, the Pb0 defect, is generated in large numbers by ionizing radiation.
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61.80.Fe Electron and positron radiation effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.35.Dv Composition, segregation; defects and impurities
76.30.Mi Color centers and other defects

Electrically active point defects in amorphous silicon nitride: An illumination and charge injection study

D. T. Krick, P. M. Lenahan, and J. Kanicki

J. Appl. Phys. 64, 3558 (1988); http://dx.doi.org/10.1063/1.341499 (6 pages) | Cited 78 times

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We observe a strong correlation between changes in the density of paramagnetic silicon ‘‘dangling‐bond’’ centers and changes in the space‐charge density in amorphous silicon nitride films subjected alternately to illumination and both positive‐ and negative‐charge injection. We demonstrate that ultraviolet illumination annihilates space charge and creates stable paramagnetic centers in silicon nitride. These centers can be passivated with a 1‐h anneal at 250 °C. Our results provide the first direct experimental evidence associating a specific point defect with the trapping phenomena in amorphous silicon nitride. We also demonstrate both directly and for the first time the amphoteric nature of the silicon nitride dangling‐bond center. Furthermore, our ability to cycle the defect between its paramagnetic neutral state and both its charged diamagnetic states suggests that the optical generation of dangling bonds in amorphous silicon nitride involves no complex structural rearrangement, but simply changes in the charge and spin states of the defect.
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73.61.Ng Insulators
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
76.30.Mi Color centers and other defects

Time‐dependent modeling of resonant‐tunneling diodes from direct solution of the Schrödinger equation

R. K. Mains and G. I. Haddad

J. Appl. Phys. 64, 3564 (1988); http://dx.doi.org/10.1063/1.341500 (6 pages) | Cited 41 times

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Numerical solution of the time‐dependent Schrödinger equation for resonant‐tunneling diodes has been impeded by the difficulty in handling open‐system boundary conditions. This paper presents a boundary condition method to simulate the interaction with ideal particle reservoirs at the device boundaries. A switching transient is calculated where the device is switched from the peak current state to the valley current state. In addition, this method was used to develop a small‐signal analysis of resonant‐tunneling diodes. Results for the small‐signal equivalent circuit of a particular device versus frequency are presented.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Gk Tunneling

A high‐sensitivity torsional magnetometer for two‐dimensional electron systems

I. M. Templeton

J. Appl. Phys. 64, 3570 (1988); http://dx.doi.org/10.1063/1.341417 (4 pages) | Cited 17 times

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A dc torsional magnetometer for use in high magnetic fields is described. It provides several significant advantages over an earlier device, both by its increased sensitivity and better damping, and also, in particular, because its design allows a torque to be introduced electrostatically. This makes it possible to compensate for monotonic background signals, and to provide a ‘‘transfer standard’’ between calibration and operating conditions. An example is given of its use in the study of the de Haas–van Alphen effect in a single‐quantum‐well two‐dimensional electron system.
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07.55.-w Magnetic instruments and components
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Influence of microstructure on the resistivity of MoSi2 thin films

A. H. van Ommen, A. H. Reader, and J. W. C. de Vries

J. Appl. Phys. 64, 3574 (1988); http://dx.doi.org/10.1063/1.341418 (7 pages) | Cited 11 times

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A study of electrical transport properties in MoSi2 thin films revealed a large resistivity difference of 57 vs 157 μΩ cm at room temperature between films formed from a codeposited Mo/Si structure and layers formed by reaction of deposited Mo with Si. The resistivity difference was found to be temperature independent. The Hall effect in the films formed from deposited Mo was a factor of four larger than in films formed from a codeposited alloy. The temperature dependencies of the Hall effect were also found to be different. Analyses of the films by Rutherford backscattering and transmission electron microscopy revealed no significant differences in thickness or grain size of the layers. The only microstructural difference is the stacking fault density, which is very high in the high‐ohmic films. The mechanism by which the stacking faults influence the electrical properties of MoSi2 and other refractory metal silicides is discussed, and relations are established between the method of deposition, the microstructure of the films, and the electrical transport properties.
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73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Self‐consistent calculations of tunneling currents in n+‐GaAs/i‐ AlxGa1−xAs/n+‐GaAs structures and comparison with measurements

B. Zimmermann, E. Marclay, M. Ilegems, and P. Guéret

J. Appl. Phys. 64, 3581 (1988); http://dx.doi.org/10.1063/1.342488 (8 pages) | Cited 6 times

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We present calculations and measurements of current as a function of voltage I(V), and conductivity at low voltage as a function of temperature, G(T), for n+ ‐GaAs/i‐ Alx Ga1−x As/n+ ‐GaAs single‐barrier tunneling structures. The current is modeled by its tunneling and thermionic emission components. The shape of the conduction‐band edge is obtained by solving Poisson’s equation self‐consistently, together with two different models for the charge density. In the first model, the electron density is evaluated semiclassically, and in the second, the electron density is calculated from the electronic wave functions. Good agreement is obtained with both models between the experimental and the calculated I(V) and G(T) characteristics over the 4.2–200 K temperature range. The fits obtained are very sensitive to small variations (1%) in barrier width and effective barrier height, which allows one to determine these parameters within a narrower uncertainty range.
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73.40.Gk Tunneling
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Doping effects of 3D metal on single‐phase YBa2Cu3O7−δ

Z. H. He, Z. Y. Chen, J. S. Xia, G. Q. Pan, Y. T. Qian, and Q. R. Zhang

J. Appl. Phys. 64, 3589 (1988); http://dx.doi.org/10.1063/1.341393 (4 pages) | Cited 5 times

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The measurements of x‐ray diffraction, the temperature dependence of the dc resistance and the ac susceptibility have been performed for the single‐phase 3D‐metal doping systems YBa2 Cu3−x Mx Oy (M=Fe, Co, and Ni; x=0.025, 0.05, 0.075, 0.10, 0.25, and 0.50 for Ni and Co and 0.05, 0.075, 0.10, 0.15, and 0.20 for Fe). With an increase of impurity content, two structural transitions were observed for the Co and Fe dopants but only one for the Ni dopant. The resistivity in the normal state changes from metallic to semiconductinglike behavior and the depression of Tc is linear with the impurity concentration (x) when x<0.10. A weak Curie–Weiss type paramagnetism, which is enhanced with impurity content, exists in the samples studied. Incorporating other work on oxygen defects, we suggest that a change of oxygen content induced by doping was the dominant effect on superconductivity in these samples.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates
74.10.+v Occurrence, potential candidates
61.72.up Other materials

Structural and microstructural characterization of a high‐Tc superconducting YBaSrCu3O7−δ compound

J. M. Liang, L. Chang, H. M. Sung, P. T. Wu, and L. J. Chen

J. Appl. Phys. 64, 3593 (1988); http://dx.doi.org/10.1063/1.341394 (5 pages) | Cited 3 times

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Transmission electron microscopy (TEM), energy dispersive analysis of x ray (EDS), x‐ray diffraction, electrical resistance, and magnetic susceptibility measurements were applied to characterize the structure and microstructures of a high‐Tc superconducting YBaSrCu3O7−δ compound. The sintered samples were found to be predominantly of a single phase with a modified perovskite structure. Combined EDS/TEM and high‐resolution lattice imaging with computed image simulation data showed that the atomic ratio of Sr and Ba atoms is about unity and Ba sites in YBa2Cu3O7−δ compound were partially substituted by Sr atoms in the three‐layer perovskite structure, in agreement with the results of a previous neutron diffraction study. It was also found that the marked contrast difference in high‐resolution images along [100] and [010] directions of the high‐Tc oxygen‐deficient superconducting crystals can be used to advantage to distinguish [100] and [010] directions of the modified perovskite structure in TEM. Lattice defects such as twins and dislocations were observed and analyzed.
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61.66.Fn Inorganic compounds
74.70.-b Superconducting materials other than cuprates
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
74.25.-q Properties of superconductors

Correlation of superconducting properties and oxygen concentration in Y1Ba2Cu3O7−δ films via Raman spectroscopy

Y. Liu, G. Pangilinan, R. Sooryakumar, Michael J. Sumner, and Thomas R. Lemberger

J. Appl. Phys. 64, 3598 (1988); http://dx.doi.org/10.1063/1.341395 (4 pages) | Cited 5 times

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We report Raman scattering and resistance measurements on a YBa2Cu3O7−δ film in which δ is varied by repeated annealing in oxygen or argon. As oxygen is removed, the resistance rises, the transition moves to lower temperature and broadens, and ‘‘forbidden’’ Raman modes are observed. Group theory, the Raman activity of another oxygen rich (δ∼0) film of different orientation, and comparison with results on single crystals allow us to assign each Raman phonon. We hence demonstrate that several ‘‘forbidden’’ Raman peaks are associated with depletion of oxygen chain sites. Our results establish that the oxygen concentration δ, and hence the superconducting properties, can be varied reversibly by reannealing in oxygen or argon with the Raman spectra providing a useful microscopic probe of the lattice.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
78.30.-j Infrared and Raman spectra
81.40.Rs Electrical and magnetic properties related to treatment conditions

Magnetic bubble collapse in the presence of a microwave field

J. L. Dong, J. O. Artman, and S. H. Charap

J. Appl. Phys. 64, 3602 (1988); http://dx.doi.org/10.1063/1.341396 (8 pages)

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A bubble collapse experiment has been done on a garnet sample with the composition Y1.92Sm0.1Ca0.98Fe4.02Ge0.98O12 both with and without an applied local microwave field. To explain the experimental results, the analysis of bubble domain wall motion by Callen and Josephs has been modified by introducing a nonlinear velocity‐drive characteristic. In the case of no microwave excitation, a good fit between the theory and the experimental data is then obtained. A bubble collapse model in the presence of a microwave field which includes contributions from microwave‐produced ‘‘dipolar pressure’’ and ‘‘intrinsic pressure’’ has been made. While some discrepancies exist between theory and experiment, nevertheless these results may be helpful in understanding the observations of microwave bubble generation reported by a number of research groups.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
78.70.Gq Microwave and radio-frequency interactions

Surface and volume anisotropy from dipole‐dipole interactions in ultrathin ferromagnetic films

H. J. G. Draaisma and W. J. M. de Jonge

J. Appl. Phys. 64, 3610 (1988); http://dx.doi.org/10.1063/1.341397 (4 pages) | Cited 48 times

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At the boundary of a ferromagnetic material, the local change in the surroundings of the atomic magnetic moments induces an additional magnetic anisotropy. The dipole‐dipole interaction, responsible for the form‐dependent demagnetizing field inside the ferromagnet, differs for magnetic moments at the boundary and magnetic moments inside the bulk material. By calculation it is shown that the demagnetization factor for an ultrathin ferromagnetic film is thickness dependent. However, the anisotropy resulting from the dipole‐dipole interaction can be interpreted as a surface and a volume anisotropy which depend on the crystalline structure and orientation of the film, but are independent of the thickness of the film.
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75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films

Annealing temperature dependence of TC of thin‐film Gd grown on a glass substrate

O. Nakamura, K. Baba, H. Ishii, and T. Takeda

J. Appl. Phys. 64, 3614 (1988); http://dx.doi.org/10.1063/1.341398 (6 pages) | Cited 7 times

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Thin films of Gd were grown on a glass substrate with a sputtering technique. Measurements of x‐ray diffraction, magnetization, and electrical resistance were carried out for different samples that were annealed at various temperatures after the deposition. The deposited films are polycrystalline of hcp structure with preferred orientation, with the (100) plane parallel to the sample surface. The estimated Curie temperature TC of these films changes between 273 and 293 K, depending on the annealing temperature. It is found that this variation of TC is correlated with the relaxation of lattice imperfections.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.70.Ak Magnetic properties of monolayers and thin films

Stress‐induced changes in the magnetic properties of some nickel‐copper and nickel‐cobalt alloys

D. C. Jiles, T. T. Chang, D. R. Hougen, and R. Ranjan

J. Appl. Phys. 64, 3620 (1988); http://dx.doi.org/10.1063/1.341399 (9 pages) | Cited 11 times

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This paper presents results on the magnetic properties of NiCu and NiCo alloys with compositions in the range 70%–100% Ni. Measurements include coercivity initial susceptibility, maximum differential susceptibility, magnetostriction, and Barkhausen effect emissions. Results revealed a surprising increase in the magnetostriction as a function of magnetic induction B as the copper content increased. The saturation magnetostriction λs was nevertheless found to decrease with copper content. The addition of cobalt reduced the magnitude of the magnetostriction resulting in a change of sign from negative to positive at between 20% and 30% cobalt. Coercivity was found to be little affected by elastic stress, but strongly affected by plastic deformation such as occurs, for example, in cold working. A similar result was true for initial susceptibility. Maximum differential susceptibility was, however, found to be strongly dependent on elastic stress. Results were interpreted in terms of stress induced uniaxial anisotropy. As the tensile stress increased the magnetization became more reversible, but the susceptibility decreased.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Properties of cobalt in FZ and CZ silicon studied by Mössbauer spectroscopy

J. Utzig

J. Appl. Phys. 64, 3629 (1988); http://dx.doi.org/10.1063/1.341400 (5 pages) | Cited 8 times

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Mössbauer effect investigations were performed on the Co system in n‐ and p‐type silicon [floating zone (FZ) and Czochralski (CZ)]. The samples were saturated with Co‐57 between 1080 and 1100 °C and quenched and annealed isochronically up to 600 °C and isothermally for times up to 22 h. In n‐type material, a transformation of a quadrupole doublet into a single line with increasing annealing temperature is observed, independent of the P and O concentrations. In p‐type samples, three quadrupole doublets are found after quenching, which are attributed to different CoB pairs following an interpretation given by Bergholz [Physica, 116B, 312 (1983)]. These quadrupole doublets transform during annealing at first into the quadrupole doublet and then into the single line found in n‐type silicon. This transformation is interpreted as the decomposition of the CoB pairs followed by the precipitation of the interstitial Co. The transformation observed in n‐type Si is interpreted as a morphological change of the CoSi2 precipitate.
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61.72.Bb Theories and models of crystal defects
66.30.Lw Diffusion of other defects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.72.jd Vacancies
61.72.jj Interstitials

Study of molecular‐beam epitaxially grown GexSi1−x/Si layers by Raman scattering

S. J. Chang, M. A. Kallel, K. L. Wang, R. C. Bowman, and Peter Chow

J. Appl. Phys. 64, 3634 (1988); http://dx.doi.org/10.1063/1.341401 (3 pages) | Cited 4 times

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The strain distribution of a GexSi1−x/Si strained layer superlattice (SLS) as a function of the distance from the superlattice/substrate interface has been studied by Raman spectroscopy. A small‐angle bevel was made by angle lapping on a given thick GexSi1−x/Si SLS so that it is possible to probe the structure at different thicknesses. The Raman spectrum as a function of the distance from interface is then obtained. The results indicate that, as we move away from the substrate interface, the compression strain in the alloy layers decreases while the tensile strain in the Si layers increases. From linewidth measurement of the Raman peaks, it appears that there is an improved crystal quality and a lower concentration of defects going away from the substrate interface.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.30.Fs III-V and II-VI semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Fourier transform infrared spectroscopy studies at low temperatures of MPX3 layered compounds

M. Jouanne and C. Julien

J. Appl. Phys. 64, 3637 (1988); http://dx.doi.org/10.1063/1.341402 (4 pages) | Cited 4 times

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In this work experimental results in infrared absorption at low temperatures on the layered compounds of the MPX3 (M=Fe,Ni and X=S,Se) family are reported. The absorption spectra in the far infrared (between 50 and 500 cm−1) recorded on thin slabs of these compounds (10 μm thick) are compared with the corresponding Raman spectra and this comparison confirms the hypothesis of the phonon branches folding in the antiferromagnetic phase of FePS3 below the Néel transition at 118 K. In the midinfrared (between 700 and 4000 cm−1), broad bands have been observed at low temperatures for the iron phosphorus trichalcogenide compounds. These absorption bands are attributed to electronic transitions for both FePS3 and FePSe3 lamellars, which are mainly due to the splitting of the 3d‐metal levels by the pseudooctahedral field created by the nearest‐neighbor sulfur atoms.
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78.66.-w Optical properties of specific thin films
78.30.-j Infrared and Raman spectra
71.70.-d Level splitting and interactions
75.50.Ee Antiferromagnetics

Temperature dependence of nonlinear absorption in InP doping superlattices

H. Kobayashi, Y. Yamauchi, H. Ando, and K. Takahei

J. Appl. Phys. 64, 3641 (1988); http://dx.doi.org/10.1063/1.341403 (6 pages) | Cited 2 times

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Absorptive optical nonlinearity in InP doping superlattices grown by vapor‐phase epitaxy is investigated in a 2–300 K temperature range. The absorption spectra have tails below InP band‐gap energy, caused by the Franz–Keldysh effect due to the internal electric field. The absorption tail is almost temperature independent. This means that the periodic electric potential in the doping superlattice, responsible for the nonlinearity, is unchanged across this temperature range. Nonlinear absorption is evaluated by the pump‐probe method. The large reduction in absorption coefficient is obtained even with a weak excitation light intensity. This enhancement in nonlinearity is due to prolongation of the excited‐carrier lifetime. Nonlinear absorption increases as temperature decreases. This is due to the temperature dependence of the carrier lifetime.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
42.65.-k Nonlinear optics

Some remarks on excitation spectra versus photoluminescence spectra for the evaluation of quantum wells

Robert C. Miller and Rajaram Bhat

J. Appl. Phys. 64, 3647 (1988); http://dx.doi.org/10.1063/1.341404 (3 pages) | Cited 7 times

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Several GaAs/AlxGa1−xAs single‐quantum‐well samples are examined via photoluminescence and excitation spectra to emphasize that in many cases there is a poor correlation between the perceived qualities of quantum wells as deduced from each of the two different kinds of spectra.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Excitation process of the Tb emission center in a ZnS:Tb,F thin‐film electroluminescent device

Akiyoshi Mikami, Takashi Ogura, Koji Taniguchi, Masaru Yoshida, and Shigeo Nakajima

J. Appl. Phys. 64, 3650 (1988); http://dx.doi.org/10.1063/1.341405 (8 pages) | Cited 11 times

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The excitation spectrum for terbium (Tb) emission in a ZnS:Tb,F film varies sensitively with Tb concentration, the amount of fluorine (F) relative to Tb, post‐deposition annealing, and the temperature of measurement. There are at least three kinds of channels for the excitation of Tb3+ ions; namely, resonant energy transfer from the recombination of an electron‐hole pair, direct transitions between the 4f 8 configuration states of a Tb3+ ion, and the indirect excitation via lattice defects. A rapid quenching of photoluminescence (PL) is observed above 0.2 at. % of the Tb concentration in the case of indirect excitation of energy transfer. The PL intensity additionally reduced in the presence of F− ions, even at the same Tb concentration. In contrast, when the Tb3+ ions are directly excited to the 5D3 energy state, the PL intensity increases proportionally up to a maximum of about 2 at. %. The luminance of the electroluminescent device behaves in the same way. Another excitation band is found in an energy region slightly below the band gap of ZnS, and is identified as due to Tb‐related complexes associated with sulfur interstitials. The PL characteristics obtained with three excitation channels are also compared with the electroluminescence (EL) characteristics, concerning the effects of post‐deposition annealing and measurement temperature. The excitation mechanism of electroluminescence can be explained on the basis of the direct impact model, and the real nature of the energy transfer process is also discussed.
Show PACS
78.60.Fi Electroluminescence
78.55.Et II-VI semiconductors
79.20.Kz Other electron-impact emission phenomena
85.60.Jb Light-emitting devices
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