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10 Aug 1992

Volume 61, Issue 6, pp. 621-731

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1‐kW, capacitively coupled radio frequency discharge excited CO laser with a closed‐cycle fast axial flow

Shunichi Sato and Manabu Taniwaki

Appl. Phys. Lett. 61, 621 (1992); http://dx.doi.org/10.1063/1.107854 (3 pages) | Cited 7 times

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A capacitively coupled transverse radio frequency discharge has been successfully applied to excite a CO laser with a closed‐cycle fast axial flow. The discharge and laser characteristics are described and the role of the O2 added to CO/N2/He mixtures is discussed. For a mixture of CO/N2/He/O2=7.5/12.5/80/0.8 an output of about 1 kW has been obtained at an entrance gas temperature of 160 K. Stable output with good beam quality has been demonstrated.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.-v Laser optical systems: design and operation
52.80.Pi High-frequency and RF discharges

Fe ions in proton‐exchanged LiNbO3 waveguides

J. Olivares, E. Diéguez, F. J. López, and J. M. Cabrera

Appl. Phys. Lett. 61, 624 (1992); http://dx.doi.org/10.1063/1.107855 (3 pages) | Cited 9 times

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The valence state of Fe in proton‐exchanged LiNbO3 optical waveguides is studied by electron paramagnetic resonance (EPR) and loss measurements. Starting from a fully reduced substrate showing no Fe3+ EPR signal, the exchange process induces a strong Fe2+→Fe3+ conversion within the guiding region. A new EPR line is also observed to peak at 1650 G for B perpendicular to C‐axis which is attributed to a new Fe3+ center. Losses (at 442 nm) are about forty times lower in the guide than in the reduced substrate.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Gn Optical waveguides and couplers
76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

High‐power coherent surface‐emitting antiguided diode laser arrays

S. S. Ou, D. Botez, L. J. Mawst, M. Jansen, M. Sergant, T. J. Roth, and J. J. Yang

Appl. Phys. Lett. 61, 627 (1992); http://dx.doi.org/10.1063/1.107828 (3 pages)

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High‐power coherent GaAs/GaAlAs surface‐emitting antiguided laser arrays with dry etched micromirrors have been demonstrated for the first time. Both the deflecting 45° and 90° micromirrors were fabricated by ion beam etching. Twice diffraction‐limited far‐field beam profiles were obtained to pulsed output powers as high as 550 mW, with 220 mW in the central lobe.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Room‐temperature diphenyl‐diacetylene liquid crystals

Shin‐Tson Wu, J. D. Margerum, H. B. Meng, L. R. Dalton, C.‐S. Hsu, and S.‐H. Lung

Appl. Phys. Lett. 61, 630 (1992); http://dx.doi.org/10.1063/1.107829 (3 pages) | Cited 46 times

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Thirty new asymmetric diphenyl‐diacetylene (PTTP) liquid‐crystal homologs are synthesized and their physical properties characterized. In addition to the observed high birefringence and relatively low viscosity, several dialkyl PTTP homologs also possess a low melting point, wide nematic range, and low heat of fusion enthalpy. These properties are highly desirable for forming eutectic mixtures with entirely PTTP components. A binary eutectic showing a nematic range from 10 to 98 °C is studied. These new liquid‐crystal compounds and mixtures should be particularly useful for infrared applications.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

21 W broad area near‐diffraction‐limited semiconductor amplifier

L. Goldberg and D. Mehuys

Appl. Phys. Lett. 61, 633 (1992); http://dx.doi.org/10.1063/1.107830 (3 pages) | Cited 11 times

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A 600 μm wide broad area single pass GaAlAs traveling wave amplifier emitted 21 W in pulsed operation. The far‐field was dominated by a near‐diffraction limited 0.08° wide lobe, with 16 W measured in a 0.9° angular aperture. Current dependent scattering of the output beam power to outside of the diffraction‐limited lobe was observed.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.45.+h Stimulated emission
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Two wavelength optically controlled latch and AND gate

X. An, K. M. Geib, M. J. Hafich, T. E. Crumbaker, P. Silvestre, F. R. Beyette, S. A. Feld, G. Y. Robinson, and C. W. Wilmsen

Appl. Phys. Lett. 61, 636 (1992); http://dx.doi.org/10.1063/1.107831 (3 pages) | Cited 1 time

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A new optical device which functions either as a gated latch or an AND gate is demonstrated. This device utilizes two different wavelengths of input light and is composed of two heterojunction phototransistors (HPTs) vertically integrated with a light emitting diode. The collector‐base regions of the two HPTs are fabricated from different band‐gap materials and thus, respond to different wavelengths of input light. The device structure was fabricated from InGaAsP/InP epitaxial layers grown by gas source MBE. The gated latch and AND gate are shown to have an on/off contrast ratio of 12 and 6, respectively.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.Bq Design and performance testing of integrated-optical systems
85.60.Dw Photodiodes; phototransistors; photoresistors

Theoretical comparison of sensitivities of acoustic shear wave modes for (bio)chemical sensing in liquids

Günter Kovacs and Adrian Venema

Appl. Phys. Lett. 61, 639 (1992); http://dx.doi.org/10.1063/1.107807 (3 pages) | Cited 37 times

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A theoretical comparison of the sensitivities of various acoustic shear wave modes applied in (bio)chemical sensing in a liquid environment is presented. The sensitivity which is defined as the relative change of oscillation frequency due to mass adsorption in a (bio)chemical interface is obtained from perturbation theory. It is shown that the application of a Love wave mode for chemical compound sensing in liquids is very promising because of its high sensitivity.
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43.58.+z Acoustical measurements and instrumentation
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Microwave growth from the beam breakup instability in long‐pulse electron beam experiments

P. R. Menge, R. M. Gilgenbach, and R. A. Bosch

Appl. Phys. Lett. 61, 642 (1992); http://dx.doi.org/10.1063/1.107808 (3 pages) | Cited 3 times

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The beam breakup (BBU) instability has been investigated in high‐current, long‐pulse electron beams propagating through microwave cavities. Experiments are performed using a relativistic electron‐beam generator with diode parameters: 0.7–0.8 MV, 1–15 kA, and 0.5–1.5 μs. The magnitude of the solenoidal magnetic field places these experiments in an intermediate regime between strong focusing and weak focusing. The electron‐beam transport system consists of ten identical pillbox cavities each containing a small microwave loop antenna designed to detect the TM110 beam breakup mode. The TM110 microwave mode is primed in the first cavity by a magnetron tuned to the resonance frequency of 2.5 GHz. The BBU instability growth is measured through the amplification of the 2.5 GHz microwaves between the second and tenth cavities. Strong growth (25–38 dB) of the TM110 microwave signal is observed when the initial cavity is primed exactly on resonance, with a rapid decrease of the growth rate off‐resonance. The magnitude of microwave growth is consistent with the predictions of BBU theory.
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29.27.Bd Beam dynamics; collective effects and instabilities

Lateral motion of terrace width distributions during step‐flow growth

S. A. Chalmers, J. Y. Tsao, and A. C. Gossard

Appl. Phys. Lett. 61, 645 (1992); http://dx.doi.org/10.1063/1.107809 (3 pages) | Cited 15 times

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We have observed two phenomena that occur during (Al,Ga)Sb lateral superlattice (LSL) growth which have implications on our understanding of adatom/step edge interactions on vicinal surfaces: shifts of the lateral distribution of terrace widths in the direction of step propagation, and lateral variations in the superlattice tilt angle that are correlated with the terrace width distribution. Both phenomena can be explained with a model of step‐flow growth that includes both asymmetric adatom attachment at step edges and anisotropic adatom crossing over multiple step edges. A comparison between numerical simulations of this model and experimentally observed (Al,Ga)Sb LSL terrace width distributions leads to quantitative estimates of adatom migration characteristics. We find that at least one type of adatom, probably Ga, has a migration length equivalent to several terrace widths, and moves up and down step edges nearly isotropically. This method of determining adatom migration characteristics can be extended to any material that LSL layers can be grown above and below as terrace width markers.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation

Synchrotron topographic characterization of Fe‐doped flux‐grown potassium niobate tantalate

Z. W. Hu, S. S. Jiang, J. Y. Wang, J. Y. Zhao, J. H. Jiang, and D. Feng

Appl. Phys. Lett. 61, 648 (1992); http://dx.doi.org/10.1063/1.107810 (3 pages) | Cited 3 times

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The Fe‐doped flux‐grown KTa1−xNbxO3 (KTN) with composition on the margin of the cubic phase zone has been characterized by synchrotron topography. It is shown that growth bands in flux‐grown KTN are primary planar defects which lie along the [010] growth direction. A set of [100] oriented black‐white fringes revealed by anomalous scattering are ascertained to be 180° ferroelectric domains, which are caused by occurrence of the partial transition in the interior of KTN. The origins of occurrence of this partial ferroelectric transition and the growth characteristics in KTN are outlined
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61.72.-y Defects and impurities in crystals; microstructure
81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Novel measurements of high‐dynamic crystal strength by picosecond x‐ray diffraction

J. S. Wark, N. C. Woolsey, and R. R. Whitlock

Appl. Phys. Lett. 61, 651 (1992); http://dx.doi.org/10.1063/1.107811 (3 pages) | Cited 10 times

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The fracture strength of many brittle materials is known to increase with the cubed root of the strain rate. At ultrahigh strain rates, the strengths should approach the ideal fracture strength. We have made direct measurements of the dynamic tension in laser‐shocked silicon wafers at strain rates in excess of 108 s−1 by the use of picosecond x‐ray diffraction. The elastic strains observed (3.4%±0.2%) correspond to tensile stresses of the order of 70 kbar, and are comparable to the highest fracture strengths observed in static measurements.
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62.50.-p High-pressure effects in solids and liquids
62.20.M- Structural failure of materials

Ti/Ti‐N Hf/Hf‐N and W/W‐N multilayer films with high mechanical hardness

K. K. Shih and D. B. Dove

Appl. Phys. Lett. 61, 654 (1992); http://dx.doi.org/10.1063/1.107812 (3 pages) | Cited 44 times

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Ti/Ti‐N, Hf/Hf‐N, and W/W‐N multilayer films with very thin individual metal and metal‐nitride layers were developed, with hardness of the structure much higher than that of single‐layer nitride films. Hardnesses with value between 3500 and 5000 kg/mm2 or higher were observed in the multilayer films. This is an improvement over that of single‐layer metal‐nitride films where hardnesses between 2200 and 2800 kg/mm2 are typically achieved. The improvement is thought to be due to the fact that the grains are restricted to a very small size in the thin individual layers of the sandwich structure. The multilayer films, in general, have better adhesion and less defects than the single‐layer films. These films were prepared on room‐temperature substrates by a simple sputtering process and have potential applications, as in hard coatings.
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68.60.Bs Mechanical and acoustical properties
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Submicrometer modification of polymer surfaces with a surface force microscope

X. Jin and W. N. Unertl

Appl. Phys. Lett. 61, 657 (1992); http://dx.doi.org/10.1063/1.107813 (3 pages) | Cited 52 times

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We have used the sharp tip of a surface force microscope to make modifications with submicrometer dimensions on polymer surfaces. In this letter we show three examples: scribed grooves with widths less than 120 nm, raised areas with heights up to 1 nm above the original surface, and pits with depths of 6 nm. We also discuss possible sources of contrast in surface force microscope images that are not due to height variations in the surface topography. Because the surface force microscope can be used for both conducting and nonconducting materials, it has an advantage over the higher resolution scanning tunneling microscope.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

Time resolved nonequilibrium phonon dynamics in the nonradiative decay of photoexcited forsterite

S. G. Demos, J. M. Buchert, and R. R. Alfano

Appl. Phys. Lett. 61, 660 (1992); http://dx.doi.org/10.1063/1.107814 (3 pages) | Cited 8 times

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Information on the nonequilibrium phonon dynamics of the 225 cm−1 and 335 cm−1 modes on forsterite has been obtained using time resolved Raman scattering. The observed nonequilibrium phonon population is associated with the overall complex nonradiative decay following the excitation of the impurity ion.
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63.20.-e Phonons in crystal lattices
78.30.Hv Other nonmetallic inorganics
78.47.-p Spectroscopy of solid state dynamics
42.70.Hj Laser materials

Focused ion beam imaging of grain growth in copper thin films

J. Gupta, J. M. E. Harper, J. L. Mauer IV, P. G. Blauner, and D. A. Smith

Appl. Phys. Lett. 61, 663 (1992); http://dx.doi.org/10.1063/1.107815 (3 pages) | Cited 21 times

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Scanning ion microscopy (SIM) employing focused ion beam (FIB) imaging was used to study the grain structure of thin copper films as a function of annealing temperature from 20 to 500 °C. Accurate measurement of grain size is obtained for grains as small as 60 nm, allowing the microstructure of copper to be analyzed on small‐grained samples which show poor contrast in scanning electron microscopy. Moreover, the short sample preparation time provides an advantage over transmission electron microscopy (TEM). The growth and coalescence of small (<100 nm) grains in the initially bimodal grain size distribution occurs in the temperature range of 250–350 °C in films of 1000 nm thickness. This grain growth takes place concurrently with the relaxation of compressive stress as observed by temperature‐ramped stress measurement. Also, temperature‐ramped in situ TEM examination confirms that coarsening of small grains is the dominant grain growth mechanism up to 500 °C.
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61.72.Mm Grain and twin boundaries
68.55.-a Thin film structure and morphology
68.37.Vj Field emission and field-ion microscopy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Two‐color GaAs/(AlGa)As quantum well infrared detector with voltage‐tunable spectral sensitivity at 3–5 and 8–12 μm

K. Kheng, M. Ramsteiner, H. Schneider, J. D. Ralston, F. Fuchs, and P. Koidl

Appl. Phys. Lett. 61, 666 (1992); http://dx.doi.org/10.1063/1.107816 (3 pages) | Cited 27 times

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We report on a novel GaAs:Si/(AlGa)As multiquantum well photodetector structure which exhibits photoresponse maxima in both the 8–12 and 3–5 μm spectral regions. The relative intensity of these maxima strongly depends on the bias voltage, demonstrating the potential of such a structure as a tunable two‐color intersubband detector.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Kinetics of selective epitaxial deposition of Si1−xGex

T. I. Kamins, D. W. Vook, P. K. Yu, and J. E. Turner

Appl. Phys. Lett. 61, 669 (1992); http://dx.doi.org/10.1063/1.107817 (3 pages) | Cited 20 times

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The kinetics of selective deposition of epitaxial Si1−xGex layers in an atmospheric‐pressure reactor have been examined. Adding HCl to the SiH2Cl2/GeH4/H2 system decreases the Si component of the deposition rate more than the Ge component, increasing the Ge fraction in the deposited layer. HCl addition also decreases boron incorporation. When deposited selectively on oxide‐patterned wafers, lateral transport of the depositing materials causes the deposition rate and the Ge fraction to be higher in small patterns than in large patterns and also to be higher near the edges of patterns than at their centers.
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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.)

Determination of the densities of gap states in hydrogenated polycrystalline Si and Si0.8Ge0.2 films

Min Cao, Tsu‐Jae King, and Krishna C. Saraswat

Appl. Phys. Lett. 61, 672 (1992); http://dx.doi.org/10.1063/1.107818 (3 pages) | Cited 16 times

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The densities of gap states are determined using the field‐effect conductance method for hydrogenated polycrystalline Si0.8Ge0.2 for the first time, and also for polycrystalline Si. The polycrystalline films were hydrogenated by high dose H+ implantation and subsequent low‐temperature anneal. The density of states is found to be higher in hydrogenated Si0.8Ge0.2 than in hydrogenated Si, for the low‐pressure chemical vapor deposited films used in this work. The Si0.8Ge0.2 film is slightly n‐type whereas the Si film is slightly p‐type. The polycrystalline Si density of states shows the characteristic hump associated with silicon dangling bonds. These dangling bond states are located 0.63 eV below the conduction band. In the case of polycrystalline Si0.8Ge0.2, the dangling bond states are more complicated.
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71.20.-b Electron density of states and band structure of crystalline solids
71.55.Jv Disordered structures; amorphous and glassy solids
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Role of stress in irradiation‐then‐anneal technique used for improving radiation hardness of metal‐insulator‐semiconductor devices

Kuei Shu, Chang Liao, and Jenn‐Gwo Hwu

Appl. Phys. Lett. 61, 675 (1992); http://dx.doi.org/10.1063/1.107819 (3 pages) | Cited 6 times

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The improvement efficiencies of the newly reported irradiation‐then‐anneal (ITA) treatments applied to improve the radiation hardness of metal‐insulator‐semiconductor (MIS) devices with various interfacial stresses were studied. Each ITA treatment includes an irradiation of Co‐60 with a total dose of 106 rads (SiO2) and an anneal in N2 at 400 °C for 10 min, successively. It is found that the efficiency of improvement strongly depends on the number of ITA treatments and especially on the interfacial stress of device. These dependencies should be explained by the possible release of SiO2/Si interfacial stress by ITA treatments.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Fe Electron and positron radiation effects

Differences between light induced and native midgap states in intrinsic hydrogenated amorphous silicon obtained from detailed modeling of photoconductivities and subband‐gap absorption

Mehmet Gunes and Christopher R. Wronski

Appl. Phys. Lett. 61, 678 (1992); http://dx.doi.org/10.1063/1.107820 (3 pages) | Cited 14 times

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The nature and densities of states near‐midgap of intrinsic hydrogenated amorphous silicon (a‐Si:H) were derived from detailed numerical analysis of magnitudes and intensity dependence of both subband‐gap absorption and steady‐state photoconductivities. Self‐consistent results were obtained for a wide range of intensities only with the introduction of defects states above midgap which are different from those in the annealed state. These states, which are not detected by CPM, have densities and electron capture cross sections which are greater than those of the nativelike defects associated with the dangling bond. This is consistent with the rapid decreases in photoconductivity that occur upon initial light soaking and previously reported evidence for two types of SWE defects.
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71.55.Ht Other nonmetals
73.50.Pz Photoconduction and photovoltaic effects
71.23.-k Electronic structure of disordered solids

Intervalence‐subband transition in SiGe/Si multiple quantum wells−normal incident detection

J. S. Park, R. P. G. Karunasiri, and K. L. Wang

Appl. Phys. Lett. 61, 681 (1992); http://dx.doi.org/10.1063/1.107821 (3 pages) | Cited 39 times

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Normal incident infrared absorption is observed in intervalence‐subband transition of Si1−xGex/Si multiple quantum wells for the first time. The observed absorption peak wavelength, strength, and broadness are shown to be strongly dependent on the Ge content in the well. The intervalence‐subband absorption peak shows up at a shorter wavelength with the beam polarized parallel to the growth plane (normal incidence), compared with the previously reported intersubband transition between two heavy hole subbands, which occurs when the optical field is polarized along the growth direction. The dependence of the absorption peak height with the Ge composition and thus the direct gap energy in the quantum well indicates that the origin of this transition is due to the intervalence‐subband transition from the heavy hole ground state to another valence subband. The normal incident detection suggests the convenient fabrication of focal plane infrared detector arrays using Si1−xGex/Si multiple quantum wells.
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78.66.-w Optical properties of specific thin films
78.30.Hv Other nonmetallic inorganics

Generation of positive charge in SiO2 thin films during electron irradiation

A. J. de Castro, M. Fernández, J. L. Sacedón, and J. V. Anguita

Appl. Phys. Lett. 61, 684 (1992); http://dx.doi.org/10.1063/1.108473 (3 pages) | Cited 3 times

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The positive shifts in the energy position of the Si(L2,3VV) Auger peak produced by 1–3 kV electron irradiation of SiO2 thin films have been quantitatively explained as related to the electron trapped charge distribution. However, the electron beam also induces negative Auger shifts for certain experimental conditions. This result is interpreted in terms of a buildup of positive charge, associated to the bond breaking processes in the oxide bulk, with a formation cross section σf+≊10−17 cm2. The centroid of the spatial positive charge distribution depends on the primary beam energy, and it is not necessarily located at the SiO2/Si interface.
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61.80.Fe Electron and positron radiation effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ng Insulators

Ambipolar lifetimes in GaAs/AlGaAs self‐electro‐optic‐effect devices

V. Swaminathan, J. M. Freund, M. W. Focht, G. D. Guth, G. J. Przybylek, L. E. Smith, R. E. Leibenguth, and L. A. D’Asaro

Appl. Phys. Lett. 61, 687 (1992); http://dx.doi.org/10.1063/1.107822 (3 pages)

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We have used an electrical technique to determine the ambipolar lifetime in p‐i‐n GaAs/AlGaAs self‐electro‐optic‐effect devices in which the i region consists of a multiple quantum well structure (MQW). From an analysis of the voltage drop in the i region obtained from the forward current‐voltage characteristics, values for the ambipolar lifetimes are derived for diodes with different MQW. A value of 80–90 ps is determined for the ambipolar lifetime which is found not to change significantly when the AlxGa1−xAs barrier thickness or composition is reduced from 65 to 35 Å or x∼0.3 to 0.2, respectively, in the MQW. Since these changes in the barrier have previously been shown to improve photoresponse efficiency of the p‐i‐n diode, it is inferred that the carrier escape and collection times are smaller than 80–90 ps in devices with thin (35 Å) or low (x∼0.2) AlxGa1−xAs barrier.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects
85.60.-q Optoelectronic devices

Luminescence origins in molecular beam epitaxial Si1−xGex

J.‐P. Noël, N. L. Rowell, D. C. Houghton, A. Wang, and D. D. Perovic

Appl. Phys. Lett. 61, 690 (1992); http://dx.doi.org/10.1063/1.107823 (3 pages) | Cited 51 times

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Interstitial‐type features smaller than ∼1.5 nm and in areal densities up to 7×108 cm−2 have been identified as the origin of a broad photoluminescence (PL) band from thick, fully strained layers of Si1−xGex alloys grown by molecular beam epitaxy. The strong PL band was predominant when the alloy layer thickness was greater than 4–10 nm, depending on x and the growth temperature. Thinner alloy layers exhibited phonon‐resolved transitions originating from shallow dopant bound excitons, similar to bulk material but shifted in energy due to strain and hole quantum confinement.
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78.55.Hx Other solid inorganic materials
78.66.-w Optical properties of specific thin films
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Characterization of SiO2/Si(100) interface structure of ultrathin SiO2 films using spatially resolved electron energy loss spectroscopy

Hisashi Fukuda, Makoto Yasuda, and Toshiyuki Iwabuchi

Appl. Phys. Lett. 61, 693 (1992); http://dx.doi.org/10.1063/1.107824 (3 pages) | Cited 20 times

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High‐resolution transmission electron microscopy (HRTEM) with 0.3‐nm resolution, scanning transmission electron microscopy using transmission electron diffraction and electron energy loss spectroscopy (EELS) with 0.7‐nm resolution have been employed to characterize the SiO2/Si(100) interface structure of ultrathin (5–12 nm) SiO2 films grown by rapid thermal oxidation (RTO) at 1100 °C. In the HRTEM image, the SiO2/Si(100) interface of ultrathin SiO2 film grown by RTO in dry oxygen ambient seems to be uniform. The TED patterns also showed that the atomic structure abruptly changes from the crystalline silicon to amorphous oxide network across the SiO2/Si interface. The EELS plasmon‐loss spectra showed that for 5‐nm‐thick SiO2 an intermediate oxide composition indicating a plasmon energy between Si (17.0 eV) and SiO2 (22.5 eV) is present, whereas it disappears for 12‐nm‐thick SiO2 film.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
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