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We introduce an automated wavefunction-identification program to generate large-scale datasets for active-region (AR) design of quantum cascade lasers (QCLs) by using machine learning. Conventional QCL design methods rely on expert knowledge and extensive iterative testing; thus, they are inefficient AR design approaches. Our automated approach identifies crucial wavefunctions within a QCL band diagram rapidly and with high accuracy. Key wavefunctions in the optical-transition, injector-, and extractor-regions, which include, upper- and lower-laser levels, injecting levels, extractor levels, and high-energy leakage-path levels, are identified by using a refined k-means clustering algorithm and tailored probability formulas. We find that an accuracy of > 95 % can be achieved using this identification program. Leveraging our automated wavefunction identification program, we generated approximately 430 000 QCL structures, identified wavefunctions, and computed basic metrics such as energy differences between various levels. A nominally 8 μm-emitting QCL structure, with each stage comprising 24 layers and a fixed applied electric field of 40 kV/cm, which is expected to be close to that corresponding to the laser threshold, was used in the analysis. The compositions of InGaAs wells and AlInAs barriers were lattice-matched to InP, and only layer thicknesses were varied within empirically derived ranges. Using this dataset, we trained neural networks to map QCL structures to energy level differences and tested the performance. The promising results, with a coefficient of determination, R2, values around 90%, validate both the efficacy of our automated program for generating substantial, usable training data and the capability of our network for QCL-AR design. [ABSTRACT FROM AUTHOR]

Gradual switching between multiple resistance levels is desirable for analog in-memory computing using resistive random-access memory (RRAM). However, the filamentary switching of HfOx-based conventional RRAM often yields only two stable memory states instead of gradual switching between multiple resistance states. Here, we demonstrate that a thermal barrier of Ge2Sb2Te5 (GST) between HfOx and the bottom electrode (TiN) enables wider and weaker filaments, by promoting heat spreading laterally inside the HfOx. Scanning thermal microscopy suggests that HfOx + GST devices have a wider heating region than control devices with only HfOx, indicating the formation of a wider filament. Such wider filaments can have multiple stable conduction paths, resulting in a memory device with more gradual and linear switching. The thermally enhanced HfOx + GST devices also have higher on/off ratio (>103) than control devices (<102) and a median set voltage lower by approximately 1 V (∼35%), with a corresponding reduction of the switching power. Our HfOx + GST RRAM shows 2× gradual switching range using fast (∼ns) identical pulse trains with amplitude less than 2 V. [ABSTRACT FROM AUTHOR]

Magnetization switching induced by spin–orbit torque is of fundamental interest for developing spintronic devices with low-power consumption and nonvolatility. Here, we report on the spin–orbit torque induced magnetization switching behavior of (001) oriented tetragonal Heusler alloy D022-Mn3Ga films with an intrinsic ferrimagnetic spin structure grown on the GaAs(001) substrate by molecular-beam epitaxy. The out-of-plane hysteresis loop and anomalous Hall effect demonstrated a large perpendicular magnetic anisotropy and low saturation magnetization of D022-Mn3Ga thin films. The spin–orbit torque induced magnetization switching has been realized in D022-Mn3Ga/Pt heterostructure based Hall devices under an in-plane external field. It is found that the critical switching current density Jc is much smaller than that of the L10-MnGa/heavy metal system. Besides, both a dampinglike effective field HDL and a fieldlike effective field HFL are quantified by performing harmonic Hall voltage measurements. All these results indicate that ferrimagnetic D022-Mn3Ga can be a promising candidate material for realizing high-density and energy-efficient spintronic devices. [ABSTRACT FROM AUTHOR]

We report on the spontaneous perpendicular exchange bias effect in as-grown L10-MnGa/FeMn bilayers. An FeMn layer with different thicknesses is introduced as an antiferromagnetic layer to couple with single-crystalline ferromagnetic L10-MnGa, which is epitaxially grown on a GaAs (001) substrate by molecular-beam epitaxy. The perpendicular exchange bias shows a strong dependence on both the thickness of the FeMn layer and the measurement temperature. A large spontaneous perpendicular exchange bias up to 8.9 kOe is achieved in L10-MnGa/FeMn bilayers at 5K without any external magnetic treatment. The corresponding effective interfacial exchange energy Jeff is estimated to be 1.4 mJ/m². The spontaneous perpendicular exchange bias effect in the (001) textured L10-MnGa/FeMn bilayers paves the way for spintronic devices based on exchange biased perpendicularly magnetized materials. [ABSTRACT FROM AUTHOR]

Optical emission from atmospheric pressure micro-jet operating with pure argon (argon μAPPJ) flow has been detected with a moderate resolution spectrometer. Large broadening of the several argon (Ar) lines has been observed in the near infrared spectral region. This effect was attributed to resonance broadening of the s2 (Paschen notation) level in ³p54s configuration. In the present work, corresponding line profiles are suggested for plasma diagnostics. For this, a general case of resonance broadening coefficient of noble gases is discussed. As broadening reflects the Ar density, and the static gas pressure of the jet is in equilibrium with the ambient, the local gas temperature can be inferred. An estimation of gas temperature from the width of the 750 nm Ar line is in agreement with rotational temperature of OH radicals determined from the A²Σ+→X²ΠP (0, 0) band. At low temperatures (300-600 K) and at partial Ar pressure near atmospheric, the resonance width of the suggested lines is very sensitive to small temperature variations. High temperature sensitivity and large width make the resonance broadened lines very attractive for diagnostics of low temperature discharges at elevated pressure, e.g., as they are used in plasma-medicine. [ABSTRACT FROM AUTHOR]

Resonant coupling of the transverse-magnetic polarized (guided) optical mode of a quantum-cascade laser (QCL) to the antisymmetric surface-plasmon modes of 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antisymmetric-mode absorption. In turn, lasing in the symmetric mode, that is, surface emission in a single-lobe far-field beam pattern, is strongly favored over controllable ranges in grating duty cycle and tooth height. By using core-region characteristics of a published 4.6 lm-emitting QCL, grating-coupled surface-emitting (SE) QCLs are analyzed and optimized for highly efficient single-lobe operation. For infinite-length devices, it is found that when the antisymmetric mode is resonantly absorbed, the symmetric mode has negligible absorption loss (0.1 cm1) while still being efficiently outcoupled, through the substrate, by the DFB grating. For finite-length devices, 2nd-order distributed Bragg reflector (DBR) gratings are used on both sides of the DFB grating to prevent uncontrolled reflections from cleaved facets. Equations for the threshold-current density and the differential quantum efficiency of SE DFB/DBR QCLs are derived. For 7 mm-long, 8.0 lm-wide, 4.6 lm-emitting devices, with an Ag/InP grating of s39% duty cycle, and 0.22 lm tooth height, threshold currents as low as 0.45A are projected. Based on experimentally obtained internal efficiency values from high-performance QCLs, slope efficiencies as high as 3.4W/A are projected; thus, offering a solution for watt-range, single-lobe CW operation from SE, mid-infrared QCLs. [ABSTRACT FROM AUTHOR]

High-performance Y2O3/In2O3-based transparent thin-film transistors were processed featuring low thermal budget. The device shows a field-effect mobility of 43.5 cm2 V-1 s-1, a subthreshold swing of 0.28 V/decade, and an on/off current ratio of 108. These results are attributed to the high dielectric constant of Y2O3 and unique electronic structure of In2O3. Furthermore, the cubic phases of crystalline Y2O3 and In2O3 films have the identical crystal structure with a small lattice mismatch, which provides a well-defined dielectric/semiconductor interface for the optimal performance. [ABSTRACT FROM AUTHOR]

We report magnetoresistance (MR) measurements for structures with micrometer-thick regioregular, polythiophene (rr-P3HT) polymer layers between two ferromagnetic contacts. Hole spin transport through the polymer layer leads to a relative MR value in 300 mT fields of 0.3% at 300 K and increasing to 18% at 25 K. The inferred intrinsic spin lifetime and diffusion length are about 7 ms and 0.4 μm, respectively. The spin transport coherence length is enhanced by the electric field, leading to an enhancement in MR with increasing applied voltage. [ABSTRACT FROM AUTHOR]

An experimental study on buckling of graphene/epoxy nanocomposite beam structures is presented. Significant increase (up to 52%) in critical buckling load is observed with addition of only 0.1% weight fraction of graphene platelets into the epoxy matrix. Based on the classical Euler-buckling model, the buckling load is predicted to increase by ∼32%. The over 50% increase in buckling load observed in our testing suggests a significant enhancement in load transfer effectiveness between the matrix and the graphene platelets under compressive load. Such nanocomposites with high buckling stability show potential as lightweight and buckling-resistant structural elements in aeronautical and space applications. [ABSTRACT FROM AUTHOR]

Reflection high energy electron diffraction, atomic force microscopy, and theoretical studies based on classical nucleation theory have been used to interpret the morphology, orientation relationship, and stability of Cu2O nanoclusters on SrTiO3 (100) (STO). We propose that the competing interfacial and elastic energies facilitate an in-plane rotation of the Cu2O clusters by 45° with respect to the STO substrate and stabilize Cu2O clusters on STO(100) with an orientation relationship of (001)Cu2O//(001)SrTiO3 and <100>Cu2O//<110>SrTiO3. Our preliminary theoretical analysis also suggests that this particular orientation results in smaller critical nucleus sizes and lower nucleation barriers and also indicates a chemical potential (growth rate) dependence of the orientation relationship. [ABSTRACT FROM AUTHOR]

p-type conduction has been observed in unintentional carbon-doped ZnO thin films grown by metal organic chemical vapor deposition through postgrowth annealing treatment. The existence of carbon, which has been verified by secondary ion mass spectrometry and x-ray photoelectron spectroscopy, was predicted to immobilize the oxygen in the interstitial site in ZnO thin films after annealing. Using first principles calculations, the formation of carbon-oxygen cluster defect in ZnO was found to be favorable and acts as a shallow acceptor. The cryogenic photoluminescence of the p-type carbon-doped ZnO thin films shows an additional peak located at 3.3564 eV, which was attributed to the acceptor (carbon-oxygen cluster defect) bound exciton emission. [ABSTRACT FROM AUTHOR]

Epitaxial LaAlO3 films have been grown on Si (001) by molecular beam epitaxy with an ultrathin SrTiO3 seed layer. High resolution x-ray diffraction and transmission electron microscopy show the high quality epitaxial structure of LaAlO3 films, and the epitaxial relationship of LaAlO3 with Si is LaAlO3(001)∥Si(001) and LaAlO3[100]∥Si[110]. The band gap of epitaxial LaAlO3 films was measured to be 6.5±0.1 eV from O 1s loss spectra. Band offsets between crystalline LaAlO3 films and Si were determined to be partitioned equally with 2.86±0.05 eV for valence-band offset and 2.52±0.1 eV for conduction-band offset by using x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

We measure the small signal, 1 GHz source-drain dynamical conductance of a back-gated single-walled carbon nanotube field effect transistor at both low and high dc bias voltages. At all bias voltages, the intrinsic device dynamical conductance at 1 GHz is identical to the low frequency dynamical conductance, consistent with the prediction of a cutoff frequency much higher than 1 GHz. This work represents a significant step towards a full characterization of a nanotube transistor for rf and microwave amplifiers. [ABSTRACT FROM AUTHOR]

Hetero-epitaxy of single-crystal perovskite SrTiO3 on GaAs(001) was achieved using molecular beam epitaxy. The growth was accomplished by deposition of a submonolayer of titanium on GaAs(001), followed by the co-deposition of strontium and titanium initiated at a low-temperature, low-oxygen-pressure condition. X-ray photoelectron spectroscopy showed that the Ti prelayer reacted with As and formed TiAs-like species on the As terminated GaAs(001) surface. Reflection-high-energy-electron diffraction showed that SrTiO3 grew coherently on the GaAs(001) at early stage of growth. This coherent behavior began to degrade when SrTiO3 thickness exceeded 20 Å. Cross-sectional transmission electron microscopy revealed an abrupt interface between SrTiO3 and GaAs and good crystallinity of the SrTiO3 film. An epitaxial relationship between SrTiO3 and GaAs was further confirmed by x-ray diffraction. The success of growth of SrTiO3 on GaAs paves the way for integration of various functional perovskite oxides with GaAs. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWNTs) have been grown via chemical vapor deposition on high-κ dielectric SrTiO[sub 3]/Si substrates, and high-performance semiconducting SWNT field-effect transistors have been fabricated using the thin SrTiO[sub 3] as gate dielectric and Si as gate electrode. The transconductance per channel width is 8900 μS/μm. The high transconductance cannot be explained by the increased gate capacitance; it is proposed that the increased electric field at the nanotube–electrode interface due to the high-κ SrTiO[sub 3] decreases or eliminates the nanotube-electrode Schottky barrier. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Optical amplification and electroluminescence at 1.5 μm is reported in Er-doped Zn[sub 2]Si[sub 0.5]Ge[sub 0.5]O[sub 4] (ZSG:Er) on silicon. ZSG:Er films were deposited by rf sputtering from a composite target in Ar/O[sub 2] mixtures. Channel waveguides were fabricated by plasma etching with Cl/Ar. The refractive index of ZSG:Er was found to be 1.75 at 1.54 μm. Signal enhancement greater than 13 dB and an internal gain of ∼2 dB have been achieved by optically pumping a 4.7 cm ZSG:Er amplifier. Electroluminescence at 1.5 μm was achieved using an ac device structure with a ZSG:Er central layer and upper and lower dielectric layers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Bipolar transistors with a ferromagnetic base are shown theoretically to have the potential to generate almost 100% spin-polarized current injection into nonmagnetic semiconductors. Optical control of ferromagnetism and spin splitting in the base can lead to either long-lived or ultrafast switching behavior. Fringe field control of the base magnetization could be used for information transfer between metallic magnetoelectronics and conventional semiconducting electronics. [ABSTRACT FROM AUTHOR]

We report effusive evaporation of Ga[sub 2]O[sub 3] thin films on GaAs(001) substrates in a production-type molecular-beam epitaxy system. A polycrystalline Ga[sub 2]O[sub 3] charge heated in a high-temperature effusion cell is used as the evaporation source. The Ga[sub 2]O[sub 3]-GaAs structures are characterized by atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), ellipsometry, and transmission electron microscopy (TEM). The Ga[sub 2]O[sub 3] films are amorphous and stoichiometric by transmission electron diffraction and RBS, respectively. Under optimal growth conditions, the Ga[sub 2]O[sub 3] film surface has a typical roughness of 2-3 Å as revealed by AFM, while the Ga[sub 2]O[sub 3]-GaAs interface is atomically abrupt as confirmed by the cross-sectional TEM. Such amorphous and stoichiometric Ga[sub 2]O[sub 3] oxide paves the way for GaAs gate dielectrics applications. [ABSTRACT FROM AUTHOR]

Amorphous Ga[sub 2]O[sub 3] films are deposited onto the GaAs(001) surface using effusive evaporation from a high-purity polycrystalline Ga[sub 2]O[sub 3] source. The Ga[sub 2]O[sub 3]-GaAs structure is characterized by cross-sectional transmission electron microscopy, electron diffraction, and photoluminescence intensity measurements. As-deposited Ga[sub 2]O[sub 3] films are found to be amorphous forming an atomically abrupt interface of low interface state density D[sub it] with GaAs. For oxide films with a thickness t[sub ox] ≥ 127 Å, rapid thermal annealing above a critical temperature T[sub c]=720 °C induces Ga[sub 2]O[sub 3] bulk crystallization resulting in structural deformation of the Ga[sub 2]O[sub 3]-GaAs interface and complete destruction of its low D[sub it] character. Preliminary data suggest that the critical temperature T[sub c] may increase in the limit of very thin Ga[sub 2]O[sub 3] films. [ABSTRACT FROM AUTHOR]

The formation of interfacial layers between silicon and the overgrown epitaxial SrTiO[sub 3] as a function of the growth temperature has been studied in detail using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. Models for the chemical compositions and atomic bonding states have been established. With a good understanding of the mechanisms of the interfacial layer formations, the molecular-beam epitaxy growth process can be well controlled to form high-quality, single-crystalline oxide films, as well as a desired interface between the grown oxide and silicon substrate. The epitaxial relationship has been found to be SrTiO[sub 3] (001) Si(001), and SrTiO[sub 3] 〈100〉Si〈ll0〉. [ABSTRACT FROM AUTHOR]

We report on the out-of-plane piezoelectric response (d[SUB33]), measured via piezoresponse scanning force microscopy, of submicron capacitors fabricated from epitaxial PbZr[SUBx]Ti[SUB1-x]O[SUB3] thin films. Investigations on 1 μm[SUP2] and smaller capacitors show that the substrate-induced constraint is dramatically reduced by nanostructuring. At zero field, the experimentally measured values of d[SUB33] for clamped as well as submicron capacitors are in good agreement with the predictions from thermodynamic theory. The theory also describes very well the field dependence of the piezoresponse of clamped capacitors of key compositions on the tetragonal side of the PbZr[SUBx]Ti[SUB1-x]O[SUB3] phase diagram as well as the behavior of submicron PbZr[SUB0.2]Ti[SUB0.8]O[SUB3] (hard ferroelectric) capacitors. However, the field-dependent piezoresponse of submicron capacitors in compositions closer to the morphotropic phase boundary (soft ferroelectrics) is different from the behavior predicted by the theoretical calculations. [ABSTRACT FROM AUTHOR]

We report on the sol-gel deposition and characterization of high-quality, epitaxial films of PbZr[sub .52]Ti[sub .48]O[sub 3] (PZT) on (001)Si substrates, with a thickness range of 400 Å to 1 µm. The epitaxial growth of PZT on (001)Si is achieved using a thin template layer of SrTiO[sub 3], grown by molecular-beam epitaxy. The sol-gel PZT films have a typical surface roughness of 5 Å and exhibit well defined reflective high-energy electron diffraction patterns characteristic of smooth, epitaxial films. Using high-resolution transmission electron microscopy and double-crystal x-ray diffraction, we find that the PZT films are oriented with the c axis normal to the (001)Si plane and with the a axis lying along 〈110〉Si direction. Finally, we measure the electromechanical coupling coefficients and the surface acoustic wave velocities for our films as a function of thickness and compare our experimental data to previously published theoretical values for this system. [ABSTRACT FROM AUTHOR]

The stability of epitaxially grown single crystal SrTiO[sub 3](001) thin films on Si(100) substrates was studied as a function of temperature under vacuum and oxygen-rich environments using Rutherford backscattering spectrometry in channeling geometry, nuclear reaction analysis, and x-ray photoelectron spectroscopy. During vacuum annealing, it was found that interfacial silica formed due to diffusion of oxygen from the film to Si. This was further accompanied by the atomic disordering of Sr, Ti, and O sublattices in the film due to reduction reactions. Although the interfacial degradation process is similar during heating in oxygen environment, no disordering of the film was observed. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this letter, we report on the integration of epitaxial ferroelectric Pb(Zr, Ti)O[sub 3] (PZT) thin films on Si [100] substrates using a SrTiO[sub 3] (STO) template layer and a conducting perovskite (La[sub 0.5]Sr[sub 0.5])CoO[sub 3] electrode. X-ray diffraction studies reveal both in-plane and out-of-plane alignment of the heterostructure. The epitaxial films show extremely high remnant polarization as well as piezoelectric d[sub 33] coefficients compared to textured and untextured polycrystalline films. [ABSTRACT FROM AUTHOR]

Studies rapid cooling and magnetic field-induced cooperative effect for the metastable quintet state in a spin crossover complex. Background on the study of the spin transition phenomenon; Use of a superconducting quantum interface device for magnetic measurements.

Examines the high resolution of emission spectra from zinc selenide-based blue-green laser diodes. Use of metalorganic chemical vapor deposition and molecular beam epitaxy; Implication of the growth of high-vapor pressure II-VI compounds; Structural components of a typical blue-green laser device.

A wide area vacuum ultraviolet (VUV) lamp employs a ring-shaped cold cathode to produce an electron beam excited plasma of disk geometry. When excited by the soft vacuum electron beam, molecular hydrogen, nitrogen, and atomic helium emit strong atomic resonance radiation at 121.6, 120, and 58 nm, respectively. The VUV optical power emitted on the atomic resonance line is typically 6–10% of the total applied discharge power. The spatial uniformity of the VUV emission intensity at a discharge input power level of 30 W approaches 6% across the entire disk diameter, up to a maximum of 20 cm. [ABSTRACT FROM AUTHOR]

A windowless helium lamp is employed to assist chemical vapor deposition of hydrogenated amorphous silicon from disilane feedstock gas at a film growth rate greater than 200 Å/min. Material properties in this preliminary study are comparable to the best hydrogenated amorphous silicon (a-Si:H) films produced by conventional bulk plasma CVD techniques. The amount of photoconductivity degradation under long-time illumination is more than plasma-deposited a-Si-H thin films. Photoconductivity as high as σp =4×10-4 (Ω cm)-1 has been obtained. [ABSTRACT FROM AUTHOR]

We employ a well-confined hydrogen plasma of disk shape both as a vacuum ultraviolet (VUV) lamp operating primarily at 121.5 nm and as a source of atomic hydrogen radicals. Both VUV photons and atomic hydrogen act to dissociate feedstock gases used in low-temperature (<400 °C) metalorganic chemical vapor deposition (MOCVD). Thin films have been deposited both with the confined hydrogen plasma and with an excimer laser operating at 193 nm in order to compare the two methods. Preliminary chemical and electrical properties of the films deposited via the two methods indicate the superiority of the atomic hydrogen assisted MOCVD technique. [ABSTRACT FROM AUTHOR]

Presents high-brightness blue and green light-emitting diodes (LED) based on II-VI heterostructures grown by molecular beam epitaxy on zinc selenide substrates. Components of the LED structure; Fabrication of mesa diode structure; Degradation of light output in II-VI laser diodes and LED.

The downstream region of a near afterglow plasma (Δt=100 μs) has been used to decompose trimethylgallium (TMGa) and the products analyzed using a mass spectrometer. The major TMGa dissociation products with a hydrogen plasma were identified as methane and ethane while with a helium plasma ethane, ethylene, and acetylene were the main dissociation species. Time-resolved optical emission originating from the downstream reaction zone shows that decomposition of TMGa occurs primarily via photodissociation with the hydrogen plasma while both photon and metastable species (He 21 S and 23 S) contributed to the TMGa decomposition with the helium plasma. VUV transmitting and VUV absorbing windows placed between the upstream hydrogen plasma and the downstream TMGa source provided further direct evidence of the role of VUV photodissociation in the TMGa decomposition. [ABSTRACT FROM AUTHOR]

A silicon surface covered with ∼150 Å of strontium titanium oxide was exposed to both atomic and molecular hydrogen at temperatures between 20 and 300 °C. A rf probe was used to continuously monitor changes in charge-carrier recombination centers at the SrTiO[sub 3]/Si interface by following the steady-state photogenerated carrier concentration in the silicon. Independent passivation of interfacial defects was observed by both atomic and molecular hydrogen. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An experimental investigation of picosecond laser propagation in a submillimeter liquid-core waveguide is presented. It is observed that the pump is spectrally broadened towards its Stokes frequency upon passing through the waveguide and the spectral bandwidth is further extended by stimulated raman scattering. This stable ultrafast broadband radiation is shown to be enhanced due to the use of the waveguide. [ABSTRACT FROM AUTHOR]

The axial composition profiles in two-component alloy semiconductor nanowires are theoretically studied based on a comprehensive transient growth model which accounts for both surface diffusion and direct impingement of atoms to catalyst. The composition variation derives from the different growth rates contributed by each component. Our simulations reveal that the component with larger (smaller) diffusivity will segregate near the bottom (top) of the nanowire. In the presence (absence) of direct deposition on nanowire sidewalls, the steady state alloy composition is determined by the ratio of effective diffusion lengths (impingement rates to the catalyst). [ABSTRACT FROM AUTHOR]

Effects of perimeters of induced shielding current loops (ISCL) on a levitation force have been investigated for a single-domain YBa[sub 2]Cu[sub 3]O[sub 7-x] sample. The sample was prepared by a top-seeded melt–growth process. The levitation force of the sample decreases monotonously with the increasing perimeters of ISCL while the depth of the cutting slot increases along its diameter from one side to another. The maximum levitation force of the sample without any cutting slot is about 1.68 times higher than that of the sample bisected. A simple physical model is afforded to interpret the experimental results. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have used photoemission methods to directly measure the valence and conduction band offsets at SrTiO[sub 3]/Si(001) interfaces, as prepared by molecular-beam epitaxy. Within experimental error, the measured values are the same for growth on n- and p-Si, with the entire band discontinuity occurring at the valence band edge. In addition, band bending is much larger at the p-Si heterojunction than at the n-type heterojunction. Previously published threshold voltage behavior for these interfaces can now be understood in light of the present results. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A constant amount of Ge was deposited on strained Ge[sub x]Si[sub 1-x] layers of approximately the same thickness but with different alloy compositions, ranging from x=0.06 to x=0.19. From their atomic-force-microscopy images, we found that both the size and density of Ge islands increased with the Ge composition of the strained layer. By conservation of mass, this implies that these islands must incorporate material from the underlying strained layer. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

SrTiO[sub 3] has been grown epitaxially by molecular beam epitaxy on Si. The capacitance of this 110 Å dielectric film is electrically equivalent to less than 10 Å of SiO[sub 2]. This structure has been used to make capacitors and metal oxide semiconductor field effect transistors. The interface trap density between the SrTiO[sub 3] and the Si is 6.4x10[sup 10] states/cm[sup 2] eV and the inversion layer mobility is 221 and 62 cm2/V s for n- and p-channel devices, respectively. The gate leakage in these devices is two orders of magnitude smaller than a similar SiO[sub 2] gate dielectric field effect transistor. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

GaAs homointerfaces have been grown by molecular beam epitaxy using the steps of GaAs growth, As cap deposition, wafer storage, thermal desorption of the As cap, and GaAs overgrowth. As cap layers with a thickness of up to 7.8 μm were deposited and the wafers were stored for 3–7 days in ultrahigh vacuum (UHV) or under atmospheric conditions. Nonradiative recombination originating from the GaAs homointerface of wafers stored in UHV could not be detected (interface recombination velocity S<1000 cm/s), however, significant nonradiative recombination (S=10[sup 4]–10[sup 5] cm/s) was found for all GaAs homointerfaces where wafer storage occurred under atmospheric conditions. This result demonstrates that the As cap deposition/removal process is inadequate for GaAs surface protection in a fabrication facility. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The structure, magnetic properties and polar Kerr effects of Fe[sub 100-x]Si[sub x] (0≤x≤70) alloy films prepared by ion-beam co-sputtering were studied. We find that the saturation magnetization of these films decreases with increasing x, and a plateau of constant magnetization occurs as 22≤x≤28. Their polar Kerr rotation θ[sub k] decreases with increasing x as x≤16.2 and x>=30, but increases with increasing x as 20≤x≤28. In the measuring wavelength range of 400–800 nm, the θ[sub k] of Fe[sub 72]Si[sub 28] film is 40% to 50% larger than that of pure Fe film. We think that amorphization may play an important role in enlarging the polar Kerr rotation of these films. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]